A Christmas Present from the HD Channel!
Post categories: hdtv
| 13:17 UK time, Wednesday, 17 December 2008
So, the channel is just over a year old - and what a year it's been! After looking back at some of the blogs and posts I can see how much we've done and worry about how much there's still to do.
Many of you have been asking for a test signal to help line up your own HD TVs, we have been listening but it's taken a while to get it sorted.
From this week the HD promo has two test signals and I want to talk about how to find them and how to use them to line up and check your home systems. I also wanted to share a fascinating mathematical proof that some people (Heroes style) can change the flow of time!
As many of you have noticed BBC test card has been going out for a couple of weeks, this has now been joined by an Audio/Video Sync test signal. The test card seems to have been given the name "Test Card X" but not by us, it is in fact a modified high definition version of test card W (named because it was widescreen!) and for those interested in the history of test cards, there is an interesting "romp" through it here - it even includes the current incarnation!
The HD version uses the very famous picture of Carole (George Hersee's daughter) re-scanned in high definition and added to an HD version of Richard Russell's well known widescreen test card.
Now for the purists there's a bit of a disappointment coming. No, not the fact the test card's only there for 90 seconds every two hours! Talking of that, I was with a group of people looking at the promo last week when the test card came up - they all said "does this have to up for so long" and "what's that noise on the sound track" I did attempt to explain how much it was wanted but it just made things worse! I said I had wanted 5 minutes and many of the posts had asked for up to 30 minutes - at that point I felt like I came from another planet and decided to get on with other things! But there is a test card going out and I hope we can all celebrate its reappearance after many years!
The disappointment is a technical one. I am going to admit I have doctored the test card - much to the disgust of many of my Research colleagues. Why? Two reasons actually. A high quality test signal like the HD test card is a very valuable asset and unlike the SD transmission chain the HD one is quite good and quite capable in the being "purloined"! Already some of the posts on digital spy have already gone into great detail with the exact measurements of the card.
This version of the test card can be easily identified as it's the only version with the HD DOG logo at the bottom. Now, I want no DOG posts in this blog, I will ignore them as the DOG debate goes on elsewhere.
What have I done and how useful is this version of the test card? First, white level has been reduced so the peak white box is not 100% (level 235 or 0.7v). The super white spot is now 
100% and the linearity of the grey scale is now slightly inaccurate. However no domestic displays have the level of adjustment we expect a broadcast monitor to have, so I this does not affect the usefulness of the test card to help you line up a "normal" TV. Also the colour bars are slightly lower in colour level. My apologies go out to people like Richard Russell and all the others who made these test charts possible - but this does protect the value of the work.
The second reason is to help protect screens from burn in. The full level test card will burn a screen in quite a short period so please heed this warning:
DO NOT leave the test card on screen for more than 2 minutes if your screen is less than three months old or more than 5 minutes on older screens. Make sure you go back to the promo for several minutes before using the test card again.
If you want more detail of the changes there is a very good post on Digital Spy. If you do have a broadcast style display at home it is quite easy to calculate the offsets to apply to a colorimeter to make sure the readings are correct.
Now for a bit of an explanation about the test card and how to use it to line up your TV, I have done this at home so can say it does work. But before you start to line your set up please take note of the following:
1. Make sure you have the user manual and know where the controls are.
2. Do not do this if you are unsure of any of the controls or there effect on your television picture.
3. It is best to do this in a darkened room, it doesn't need to be completely dark but if it's too bright or there is a lot of light falling on the screen the results will not be good.
4. Many modern flat screen televisions have presets for sound and picture. Write down which one you use so if you get lost you can always go back and start again.
5. If you have a PVR it would be a good idea to record the test card section of the promo. Most of the line up can be carried out on a freeze frame of the test card. If you do this please be mindful of the warning above about screen burn.
6. If your TV has it, change the picture settings mode to "manual" or the equivalent, so any inactive controls become active allowing you to change the settings on the TV.
7. Turn the sharpness setting to off or zero. If there are any picture enhancing options, make sure they are turned off or to zero (if you can). Remember, on some TVs the sharpness control has a centre zero allowing you to soften pictures - please don't do that!
So to start:
BRIGHTNESS AND CONTRAST
There is a GREY SCALE to the left of the picture on the test card. It's there to show the correct black and white levels of the picture. Broadcast displays have the ability to adjust the grey level independently so there is a linear grey scale between the black and white blocks. I am not going into how to use this here if you are interested start with this.
The top white block has two spots. As I said earlier, usually the white block is peak white with the right spot higher (super white) and the left spot slightly lower. On our test card, the levels are slightly reduced.
The bottom black bock has two spots, the right hand one is below black level (sub black) and the left is slightly above black. The modifications to the test card have not change these levels.
BRIGHTNESS
To set the brightness:
1. Turn your brightness control up until you can see both spots.
2. Turn the brightness down until the sub-black spot disappears but make sure you can still see the left slightly brighter spot.
CONTRAST
When a broadcast monitor is lined-up properly, we use a meter to check the white level however on a domestic television contrast is more a matter of personal choice and will be different on different types of display (LCD, Plasma, Projector etc.)
Adjust the contrast until you like the overall look of the test card while you are doing this, keep an eye on the spots in the top white block to make sure you can still see the left hand one. It doesn't matter if you cannot see the super white spot so don't worry if it's not there.
COLOUR
Again colour level is very much down to personal taste but most TVs have too much of it! Too much colour makes pictures look very odd. It will also make some colours bleed into each other or appear to move so the colour smears over the edge of the object - in other words someone wearing bright colours clothes may have the colour slightly off to one side! The best bit of the test card to use to set colour is the picture of Carole.
The centre of the test card has all you need to get the colour right. Carole's face should look natural and the primary colours in the picture (red dress and green and blue of the clown) should not be very bright. Colour is a subjective setting so just make sure you like it. Remember, if your colour setting was previously set very high you may not like the correct level until you get used to it!
One of the experts at BBC Research suggested another way to adjust colour level.
Get some Lee Lighting Filters No.181 Congo Blue and place it over the screen. This has the same effect as turning off the Green and Red leaving the Blue component of the picture. Looking at the colour bars around the edge to the test card, adjust the colour control until they all look the same brightness. There are some commercially available line up DVDs that use this method.
When you have adjusted the BRIGHTNESS, CONTRAST and COLOUR have a look at the promo again to see what you think. Watch it for some time so you get used to the new settings and see several different type of programme.
SHARPNESS
I have the sharpness control on my TV set to zero but some of you may want to add a little bit if the picture looks very soft.
To the right of the picture of Carole is a set of "frequency gratings" The frequencies are:
1. 5MHz
2. 10MHz
3. 15MHz
4. 20MHz
5. 25MHz
6. 30MHz
The BBC HD transmission system will pass frequencies 1 - 4. Most domestic displays will show 1-3 correctly but the 4th might not look quite right. A 50' 1080p display should be able to resolve the 4th grating satisfactorily.
PICTURE SIZE AND POSITION
Not all TVs offer menu setting that allow you to change picture size and position. Even if your TV does allow you to adjust size and position, it's not a good idea not to make anything but small changes unless you know what you are doing. Make a note of the current setting BEFORE you change anything!
Most displays lose a small amount of picture all round. This is called "overscan", it is perfectly normal and programmes have always been made taking this into account.
Some flat screens do have the option to either turn overscan off or reduce the picture size.
It is perfectly safe to use the "overscan off" option on you TV but you should not use the picture size controls for anything more than small changes.
The full test card should look like this, with the diamond points just touching the edge of the screen all the way round.
As a mater of interest, the cross on the Noughts and Crosses game is the centre of the picture!
You should now have a picture that looks fairly close to the one we see before transmission. Again watch some of the promo to get used to the new settings. Also if you have turned overscan off, you might want to look at some SD channels to make sure you don't see extra bit of the picture you don't like. You may see some white lines at the top of the screen on some News programmes for example. This happens when signals are brought back that don't fully meet the broadcast standards, but have to go to air too quickly (if not live) so it isn't possible to correct them.
AUDIO VIDEO SYNC
The second test signal is there to help you check and adjust audio/video synchronisation. AV sync has been the bane of my life ever since the test channel started. Remember we have rebuilt the HD Channel infrastructure round a service running 24 hours a day, 7 days a week so occasionally we have had to put new sections into service without being able to fully test them.
A couple of months ago, Rowan stated working with me to try and clear up our surround sound and AV sync problems. It has been a joy watching him dive headlong into the issues and some of you may have visited Rowan's blog to see how his work is progressing.
The last time I saw him, he was waist deep in diagrams of installations and programme signal routes to see if each video process had a suitable audio delay and each Dolby process had an appropriate video delay in circuit. The idea audio processing "takes time" is relatively new to television and we have to remind people to compensate for processing delay in the appropriate place so we can make sure everything is correct it if anything needs to be changed - I hope the message is getting through!
However even when we get it completely correct, some home setups can cause A/V sync problems of their own. The second test signal should help you check and adjust the sync timing of your AV system. This does not work on audio fed through the HDMI cable to the televisions own speakers. Any delays in that situation should be compensated for inside the TV. A/V sync is only adjustable when you use a AV systems connected by the optical/SPDIF output of a set top box or for AV amps that can us the HDMI output and have their own delay controls.
As some systems could have two ways to adjust AV sync - the set top boxes will have an audio delay option in the set up menus and good AV amplifiers may also have audio delay options, you need to start by setting all delays to zero. Again, please make a note of the settings BEFORE you start.
Why is there a need for A/V sync adjustment now? Most flat screen displays introduce a delay while they process the picture before it's displayed. Inside the TV the audio is delayed to match the processing delay but if you connect your set top box to an external audio system, the sound can be one or two frames ahead of the picture. In nature this is not normal and we can detect sound ahead of vision very quickly and it is "just not right"!
Our transmission system can also introduce delay to both audio and video signals. Some of the delay is obvious e.g. if we send the audio through a Dolby E decode/recode process, the sound is delayed by 2 frames so we must add a 2 frame video delay. Other process aren't so easy to check as the delay occurs inside a device that's processing audio and video together so the reason the A/V sync signal was not transmitted two weeks ago was to allow us time to test our whole system to make sure what we send you is actually in sync!
So it's time to introduce the BBC Research sync check signal...
The audio is actually two blocks of wood being banged once a second - nothing to beat the real thing! The video is made up from three components:
1. A travelling bar marked in frames starting 12 frames before the audio clap and going on for 12 more frames after. 2. Three Sync Flash Lines. 3. A sync "plunger" or "clapper bar" (acting like a clapper board)
Before I tell you how to use the signal, you might like to know what we did to make sure the signal itself was synchronised and the transmission system did not put it out of sync. We - or I should say Rowan - have been measuring the signal at every point in the chain to make sure it is as accurate as possible when it arrives at your set top box.
This is the task I set Rowan to about three weeks ago!
Why so complex? I needed to make sure the signal followed the routes many of our programmes do through post production and audio mixing, playout and transmission.
What is sync though? If you think about the speed of light vs. the speed of sound it's fairly obvious that sound arrives a lot later that the image of the "thing" making it. A rough rule is audio takes slightly less than 3ms to travel 1 metre so if you sit 2 and a half metres from your TV the audio takes nearly 7.5ms to reach you - nearly a quarter of a frame.
The effect of AV sync has been measured and tested quite extensively by the international broadcast standards bodies and we usually work to a tolerance of +20ms to -40ms (+half to - 1 frame) for a programme delivered to the BBC. This tolerance has been well tested in SD but there has not been enough work done to see if it's still OK in HD. To make sure there were no major surprises we have tightened the delivery specification to +10ms to -20ms while we do more tests.
In one of my previous blogs I explained that during the trial we found sync varied during a programme, especially live programmes, depending on how hard some of the early equipment was working. Now we are a lot more stable and have had a chance to go through the system from end to end to make sure it's sync. We have just finished testing the chain with an "off air" test of the signal and have a timing error of 0.86ms or 0.0125 of a frame!
Those of you who work or have worked in the business know the phrase "it's alright leaving me". A translation of that is "I'm OK, it's your problem"! To make sure you can use the signal to check your home system, we have gone one step further and made sure the signal is "alright arriving at you", not just "alright leaving me".
The final measurements of the off-air signal were made by looking at the digital signal from the transmitter - or in this case, the one received from the satellite.
This is what the test signal looks like in the transport stream from the satellite.
Rowan has a more detailed explanation of how and why we did this in his blog.
Part 1: Don't forget the kitchen sync
Part 2: Testing the test
How do you use the signal to check audio/video (AV) sync?
Remember this only works if you are connected to an external AV system. Check the audio delay setting in the set top box is 0ms and if your AV amplifier has a delay check that is set to zero.
Method 1
Look at the travelling bar at a point before the centre - look say at 10 on the left of screen. Listen to the clap and see if you think the bar has passed this point before you hear the sound. You might want to mask the right side with a bit of paper or put your finger on the number to help.
If the audio seems to happen after the bar has passed, move on a number and repeat until you think the audio and the point the bar passes your maker coincide. The sync point could be between two numbers but most devices only make corrections in half frame increments you will have to decide if you think it's closer to a number or closer to a half way position.
You should still be on the "video late" side of the zero mark. Read the number (or closest half number) and multiply by 40.
If your number is 3, the audio delay you need is 3 x 40 = 120ms. If your number is 1 and a half, the audio delay you need is 1.5 x 40 = 60ms
If your sync point is on the right hand side of the zero mark, I'm sorry to say there is nothing we can do to help. Before panicking - check you have no audio delay set then wait for the test signal to come round again.
Method 2
For those who like a challenge there is an electronic method. The white lines flash for 1 frame at the start of the audio waveform.
I am sure you can think of many ways to use this information to measure AV sync accurately, but here is a simple option for all of you with a dual beam oscilloscope, a photocell and a microphone lying around!
If you place the photocell over the top sync flash line and the microphone on one of your front speakers, connect them to separate input of the scope (with any amplification devices needed to boost or power them) you will get two spikes. Make sure your scope is configured to display the two traces at the same time and measure the difference in ms. Apply this delay to either the set top box or the AV system. If you have a very good AV system you may be able to get this exactly right instead of the nearest 20ms.
If you can't decide between two settings, it is always better to make the audio slightly late than have it in front of the pictures.
Why are there three sets of white flashes? The top line is the reference line, i.e. 0ms A/V offset when measured on an HD CRT. However sometime it is difficult to accurately measure the very top of active picture, possibly because the TV's casing gets in the way of the photocell. The second line is 1ms later (as measured on a CRT) and is usually easier to get an accurate reading from. The third line is in the centre of the active picture so should read 10ms A/V offset on a CRT.
On the various LCD and plasma displays we have tried this on, some show a difference between the three lines and some don't - not much help to you, but I would go for the second line if you can and minimise the delay there!
Please let me know how you get on.
How to record the BBC HD test signals
The HD test card is just over 1 hour into the promo and the AV sync signal is 50 minutes later. To record both signals, check the time the last programme finishes and add 1 hour. So if the last programme ends at 01:30 set your PVR to record from 02:25 to 02:45 for the test card and 03:15 to 03:35 for the AV sync signal.
My last thoughts this time are around phenomena I have discovered that manifests itself around my daughter and what used to be my phone. When she is on the phone I have discovered time slows down!
How do I know this? Simple maths!
Let's take a telephone billing period - call it Tm. A Tm can only have 4 values 28, 29 (every fourth year) 30 or 31. Each Tm is made up from telephone charging units, let's call them Tu.
Each Tu is charged at various rates but I am going to use the maximum UK rate £UK (premium numbers etc are barred).
So my maximum phone bill can only be Tu x £UK. As the Tm can have four values the total bill can vary between each Tm. So why have my bills been consistently two to three times this amount?
My thought are, as the rate £UK is fixed in any Tm (but in general is always rising) and the periods of charging Tm are fixed to one of four values the only thing that can change is the Tu! As this is measured in time, I can only conclude time around my daughter changes as she uses the phone. Oh! I forgot to say, we are on the free weekends and evenings tariff so this time dilation effects occurs in the brief period between the end of school and 18:00!
I think Douglas Adams spotted this change to the laws of maths in the Hitch Hikers Guide - other explanations welcome!
Have a very merry, in sync and well lined-up Christmas and we will speak again in the New Year.
Andy
P.S. When she is on the phone to us each Tu is very long period of time of course.
Andy Quested is Principal Technologist, HD, BBC Future Media and Technology.
© MMIX~RS~q~RS~~RS~z~RS~47~RS~)
Comments
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Thank you for the post Andy.
Can you rephrase that and label each of them left top spot, top right spot and bottom left spot and bottom right spot.
2. Turn the brightness down until the sub-black spot disappears but make sure you can still see the left spot above black spot.
Thanks.
As for your phone bill how about an unlimited phone package, it would most likely cost you less to upgrade than the cost of the calls before 6 through the year.
Have a good Christmas and New Years.
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It should read , could you please rephrase what is written below.
It's a shame there is no option to edit blogs.
Also from a technical point of view often when the BBC has a link to extra sport streams it pops up on BBC1 and 2 as a link through the digitial text system.
Would it not be possible to do this for HD as well to alert viewers to when a HD version is being broadcast.
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Dear Andrew
Have just noticed two images are missing to go with the Brightness paras. Have asked for them to go back in
Andy
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Andrew
Images are back in the brightness section and the second point re-worded. Thanks for the feedback. During proof reading I was getting grief about going Christmas shopping and I will let you guess from whom!
I have some bad news re the sub black spot - I watched it go out at 17:00 and it was missing. We are going to track its progress after programmes finish tomorrow morning but if we can't I will have to use the alternate version for 1 black spot only!!!
As for the phone bill... We have issued the "you are grounded Teddy Phone" to replace the mobile. This month it took 8 days to use all the credit!
Andy
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Thanks Andy!
Appreciate your team's persistence.
I hope this will enable many more to get the best out of their HD video and 5.1 sound investment.
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Thanks Bill
Has anyone seen the sync test signal? The first outing was around 17:45 today. I would be interested in your thoughts
Andy
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Yes, recorded it.
Works very well. When played back I could easily see that my error was sub 1 frame (video late) and looked like 20 ms.
This makes sense as my video processor automatically accounts for it's delay, but I have made no adjustment for the plasmas own delay (being fed with 50p).
Will be building a light sensor just for fun!
Will be interesting to try this a few times to see what the tolerence of the Sat box is.
Thanks Andy (and team)!
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Merry Christmas to you, all.
Great work, just what we have been waiting for! The test card will probably be the best thing on telly over Christmas!
Just a couple of additions. Some Flat panel displays may not clip 100% white when adjusting the contrast. The next best thing is to turn the contrast up until white becomes impure, may be accompanied by a pinkish hue. Back off the contrast until the image regains a natural white balance.
Sharpness controls. Zero setting may not necessarily be the neutral on all sets. Look at the test card and adjust for minimum ringing, without reducing it so much that the edges become too soft.
5.1 sounds...I've yet to hear a decent home surround sound system that can fully immerse the viewer. I get better results using 2 speakers. Besides I don’t really want to be immersed in an episode of Eastenders with vases and plates flying across my head!
All the best for the New Year!
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Strange, as I'm reading this the sound has just dropped out on BBC HD (Virgin Media). Hows that for timing!
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Excellent post Andy. Really enjoyed reading it and will be recording the audio/video sync tomorow.
Virgin Media made a software change to their V+ boxes a few weeks ago and one of the side-effects was a considerable drop in volume and audio/video sync changes. I've gone from 30ms to 60ms overnight but will use the new test signal to test just how accurate my eyes/ears really are!
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Good and informative part of the post on sync.
I would like to say that Oceans was pleasantly acceptable picture quality and production techniques.
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Excellent Blog!
Will TV ever get to the stage of auto-setup as with AV surround systems or will it always rely on human senses, like tuning a piano?
Can a pc system with webcam and mic help set up TVs?
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Dear _marko
Interesting idea. Anything that can show the relative timing of two triggers can be used as long as you can calibrate the measurement device i.e. you know what zero timing actually is.
The trouble with the web cam would be getting an accurate reading from a device that may only be polled by the pc every few frames.
Strange thing to say but the output of your TV is analogue and the simplest measurement tools will have analogue front ends.
Andy
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What a fascinating post. I've often wondered why we don't have something similar on FreeView. Surely a static image and an explanatory voice over wouldn't take up too much bandwidth?
Can you imagine - going round to relatives' houses and not seeing some horrific 4:3 zoomed, over saturated picture....
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TerenceEden:
Try this on your Freeview receiver:
Select channel 105
Wait for Welcome screen
Press Yellow
Tune to another channel, say BBC2
Select 105 again
Wait for Welcome screen
Press Green
Wait up to 30 seconds for text 'status screen'
Press Green
Wait up to 30 seconds...
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@Andrew Knight
There are 7 interactive video streams reserved for the the Sports Multiscreen service, 6 for sporting events and one for the multiscreen menu.
These are all standard definition streams, there aren't any in high definition. High profile sporting events (the Olympics, Wimbledon, etc) are carried on the HD channel and the events are editorially selected, often mirroring BBC One. The same stream is replicated for non-HD viewers on the interactive service.
Regarding notifications of when something is available in HD, currently on the Freesat service we provide a direct "jump" from the BBC Home page when you press red and this is to support users who wish to jump straight to the HD channel if they were prompted to press red after a comment in the programme.
We're also exploring other ways of using the digital text service to better highlight when programmes are also available on BBC HD.
Si, BBC Red Button
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For those interested in recording the audio/video sync test, it follows:
Natural World - Mountains of the Monsoon
BBC Four Sessions - K.D.Lang
Sunshine
Survivors
Blazing Saddles
Raven
* Audio/Video Sync. Test *
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My setup was already spot on at 60ms but this sync test makes setup much quicker.
BTW Just how stunning does Natural World - Mountains of the Monsoon look? Those frogs/snakes look TRULY real. Amazing!
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@ si_lumb
The digital text indicator for BBC currently has "christmas baubles" displayed with the red button (at least via Virgin Media) so adding an "available in HD now" message when appropriate shouldn't be too hard should it?
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Yes - great blog - lot's of useful stuff.
And 'BikeNutt' I agree those closeups of frogs looked stunning.
I hope the BBC are now realizing that there are a large number of viewers that take picture quality seriously.
At the back of our minds is that even 'average' HD pictures can look much better than many Freeview channels - and that the 'bean counters' will want to keep dropping the quality to 'just better' than SD to squeese in more channels.
These blogs show us that there are people at the BBC who also care about these things.
Well Done! daveac
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@BikeNutt
Thanks for the reply. You're right, the same technology behind the Christmas "trigger" would be the mechanism by which we could alert viewers to the fact a programme is available in HD. It's the same technology that invites you to join in quizzes or to watch alternate sports.
The key thing is that there are 3 platforms that currently carry BBC HD: Sky, Virgin and Freesat. Each has different "middleware" that runs our digital text service, meaning that the trigger mechanism has to be developed individually for each one. To add in the ability to schedule a prompt to jump straight to a programme on the BBC HD channel is a simple desire and tricky to realise. For example, Freesat currently doesn't have the scheduling ability yet (it's on the roadmap), even though it can do the jump. Our Sky offering will need some tweaks to make the jump "nice" (see the BBCi labs blog later for talk of how channel jumps work). We also need to work with Virgin engineers to support it on their platform. We have spoken about it in the team and it is something we'd like to offer, and the fact it has surfaced here suggests it would be valued.
When we're sure that we can offer it or a feature like it on all the platforms that carry BBC HD then the proposal will get prioritised against other Red Button enhancements. Right now we're working on some new features on the Sport Multiscreen to enhance the Six Nations.
Hope that answers your question.
Happy Christmas!
Si, BBC Red Button
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Thanks for the audio sync test it is realy good.
Are you sure the Lee Lighting Filters No.181 Congo Blue is the right. I have been using Lee 47B tri-blue for years and a quick google sugests the 47B is the correct one.
I was not aware of a burnin problem on flat screens. Does this apply to LCD or only plasma.
It would easier to set the colour with a colour bar test card is there any chance of adding that.
Thanks
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@ si_lumb
Thank you for your post.
A jump link feature would be great when you have the time and resources.
You mention working on the 6 nations interactive service.
At some point would it be possible to add alternate commentory audio streams on the HD service for events like the 6 nations or if the BBC F1 coverage decides to have more than 1 audio stream.
@ Andy Quested
Thanks for the rewording. Is the black sub spot issued resolved now?
Perhaps it would be wise on the promo loop to broadcast a brief warning message telling viewers along the same lines as your blog, the chances without a disclaimer damage could happen.
There are so many settings to change a viewer could easly find the perfect settings and then find the screen is ruined, which wouldn't be good as they would miss the BBC HD lineup over the next two weeks waiting for a replacement TV.
Thanks to those who have scheduled in some Planet Earth episodes.
P.S If the teddy phone punishment hasn't been enough I think posting it on this blog should hopefully mean the credit lasts the whole month next month.
Happy Christmas and Happy New Years to all at the BBC.
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Dear trevorjharris and Andrew Knight
Thanks for the comment.
The sub black spot is there!
I will check again about the filter but on domestic sets I don't think it's that critical!! Colour bars, a full grey scale, a frequency sweep and several other signals would have been good but... At least I have managed 2 x 90 second signals for the first time in about 10 years!
We thought about an on screen warning but decided no one would read it so it's in the instructions and as you actually have to "do something extra" to keep the card up for longer than 90 seconds we thought this was deterrent enough.
A full level test card will burn LCDs after a while and a Plamsa quite quickly. The reduced level card will still cause problems if left on too long - but so will the radio banner if you leave that too long while listening to a radio channel.
It is more likely the card will leave a residual image than a true burn in. A residual image will fade if you just watch moving picture for a while
Andy
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trevorjharris:
With regards the issues of the colour filters. They will not always comply with the primaries of the phosphors or LCD blue filter used for your display (Not to mention decoder errors!). Therefore, you will always end up with some discrepancies.
The Filter is there only as guidance, as even if you adjust the blue to this setting, you may find yourself with 'red push' giving poor flesh tones
If you have a 'Blue only mode' on your TV then use this for a more accurate setting. Otherwise, use the blue filter and then eyeball the colour settings.
BTW, I have seen SMPTE colour bars on freesat. However, it appears they have now stopped broadcasting them.
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Thank you Andy and Team for the work you've put in on the test card and its transmission.
You've especially validated my thoughts on colour saturation and luminance levels. I've directed critics of my 'under coloured' display to this blog! One can only watch flourescent pictures for so long...
Now to complain elsewhere about varying black levels, poor gamma 'correction' (Nechricolor) and active line length!
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Very useful to be able to check shadow and highlight levels to retain detail in both, thank you. As for audio sync, I find the problem is variation in sync rather than a constant difference, so I am pleased you are addressing the question. Another problem in audio is the loudness difference between SD and HD - using Sky HD box - (HD requires turning up considerably on all HD channels). It has been suggested that this is because different compression is used, true or not?
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Dear dtwayland
There is a level difference issue between the two different type of audio used. SD channel use PCM audio while HD use AC3 (Dolby Digital). At the moment we are working to make sure the level across the channel is constant but we hope the level difference between HD and SD channels will be satisfactorily corrected soon
Andy
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Delphiplasma -
4:3 colour bars on EB1: 11343 V 27500 2/3, tagged as 55205.
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Thanks giftfinger.
Using the broadcasted SMPTE colour bars and Test card has given me terrific HD image quality. However, the SD images are looking stunning as well!!!
I adjusted the greyscale\gamma using professional calibrating tools for the input that I run the Freesat box on, as you require 10% windows for plasma displays.
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Again Andy, another thankyou. At some point in the new year, I'll have a look to see how my THX calibration results compare with ones from this method.
181 was always referred to by a different name when I was a lampy!
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All very good and much appreciated but when is the trust going to start setting some meaningful Audio Standards for channels on Freesat?
eg. Most BBC HD programmes are transmitted in AC2.0 NOT Dolby Digital as promised.
Most other channels are transmitting films in Stereo only.
This is simply unacceptable to most Freesat users.
Many people these days have surround sound systems. So its unacceptable to have stereo on films.
If I switch to analogue, I can watch a film in Dolby Pro Logic. In fact practically every terrestrial film is transmitted in pro Logic Surround throughout all of the terrestrial channels. Pro Logic might be old technology but at least its surround.
If I use Freesat Digital, then practically every film is transmitted in Stereo - a technology developed in 1925!!!
A brand new state of the art platform using 84 year old 2 dimensional sound technology at a time when all films have been recorded in 3D surround for over 30 years and when Pro Logic has been used on the old analogue platform for years!!!
Isn't it time the trust laid down some minimum audio standards of Dolby Pro Logic for films and Dolby Digital for anything on HD for mot only their own concerns but all Freesat channel providers?
At the moment, Freesat users are being cheated with audio standards worse than on analogue.
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Christmas over, it's now or never - I'm aiming to buy my wife a very large TV. In the shop, the pictures (often from blu-ray boxes) look superb, but the dealer says we must not expect such quality from Freesat or terrestrial digital. Specifically he says we are likely to see 'artefacts' on detailed moving images, because of spectrum compromises, just as we hear a rough edge to DAB radio. Is he right? I do indeed notice weird effects on many digital pictures, and I guess that a big screen will magnify them.
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Alsone,
AC3 is actually another name for dolby digital.
See here:-
http://en.wikipedia.org/wiki/Dolby_Digital
BBCHD transmits prgrams in either 2 channel DD or 5.1 DD.
Pro logic is matrix encoded into the 2 stereo channels and you can set your amp to decode this way when bbchd is transmitting a stereo program.
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PS
IMHO the DD in 2.0 or 5.1 scarried on bbchd sounds better than the audio carried on SD channels.
But, yes I would also like to see ALL films broadcast in 5.1 No excuse really as they will have been made with a 5.1 soundtrack.
All new drama should commisioned in 5.1 but you will always get the reason "it costs more".
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Happy New Year Andy and all involved in BBC HD.
Was there any Technical reason why BBC HD did not show the
"Live from Musikverein in Vienna, the Vienna Philharmonic Orchestra perform their traditional New Year's Day concert" shown live on BBC2.
I am assuming that it was available from the EBU in HD and 5.1 sound. I am watching the BBC live broadcast and am disappointed in the picture quality, even for SD. Normally BBC SD is good, but there are times that digital artefacts, possibly due to poor compression, produce poor picture quality.
I have asked Danielle to consider it for BBC HD next year.
Do you mind me using this communication method? As also allows others to comment as well.
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The HD test card is great. Thanks for that.
Its just a shame that the channel still looks awful in terms of picture quality. I really hope heads start rolling because people need to start loosing their jobs if the quality continues.
Over cristmas we had shows such as Gavin and stacey, The Royal Family, A Strictly christmas special and on new years eve we had the Jools holland show.
All of the shows mentioned looked very very poor and never been true HD in my view.
I taped Jools Holland expecting it to look half decent and it looked awful. The picture looked just as good if not better on the SD channel.
The Royal family was just a total waste of budget due to the production choices. Why spend money on this in HD when your production is so bad and you have poor encoders and low bandwith??
I dont like to see people loose their jobs but if the people in charge are not producing the goods then its time to ship them out. If the powers that be dont increase the bandwith back up to 20 mbps as it was on the launch or purchase same encoders as sky then action must be taken.
The BBC HD Channel at the moment is a total laughing stock.
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re: wednesday83's comment - have you set up your tv correctly? To say that SD picture is better than the HD picture suggests to me that you may have not. Do you have a scart connection between your HD box and TV? If so remove it. Set all your picture adjustments to 'normal', i.e. no enhancements etc.
An example of poor HD picture quality was CH4's Peter Kay 'Talent' show. Poor studio lighting being the culprit i think.
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You know what? There seems to be quite a lot of criticism aimed at HD production quality. However, it must be said that SD production has never always been consistently great.
Just watched SD Jonathan Creek last night. It was awful!! (Never been a Jonathan Creek fan, I was forced to watch it. So no idea if this is the norm? I don't think the poor image quality was deliberate) the story line, however, was good.
I see HDTV as a standard to bring back the great (and c**p) SD images we were use to on our CRT TVs, with a lot more detail. If the production quality of a program sucks then you will just have to suffer it and hope the scripting is good (Or should we? Queue licence fee screams!).
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lol of course have my TV set up properly. No scart, just really good HD on most sky channels. The only let down of course is BBC HD. I know quite a few people at work with HD and all say the same - HD is great except the bbc.
The people who blame just production on the beeb are having a laugh. Why was the bbc HD channel stunning when it was using around 20mpbs????? Are we to believe they have changed all their production methods??? NO CHANCE.
Why are the same programmes looking awful as soon as the bitrate is lowered????
The people who constantly blame production need to find some recordings of shows when the bbc ran at 20mpbs. It was the best channel of the lot.
Now the beeb are trying to run the channel at a low budget its awful.
BBC 1 SD also seems to have suffered a bitrate decrease in the last 6 months. An attempt to make people think the HD channel is better than it is??
Its time people stopped accepting the rubbish thrown at us by the bbc.
The BBC HD ratings shows how good the channel is - POOR|.
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Forgot to mention as well that my tv settings was set up with the aid of the BBC HD test card. So before people blame my tv settings....
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www.bbc.co.uk/complaints
www.bbc.co.uk/watchdog
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Just found your fascinating blog. It may prove to be a bit overwhelming.
Count me as one of those BBC viewers who are very serious about their picture quality.
We're reading buddies
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Dear wednesday83
I am sorry to read you found many of the programmes over Christmas to be poor quality. Can I point you at one of my other blogs dealing with picture quality though?
http://www.bbc.co.uk/blogs/bbcinternet/2008/11/bbc_hd_picture_quality_and_dol.html
I'm afraid I cannot agree with your comments because the quality of the majority of programmes this Christmas was outstanding. It may be that you do not like certain production styles?
I will be looking into a few issues and areas I was not happy with, but in general the quality of th BBC HD Channel matched and often exceeded other channels. The HD Test Signals have also demonstrated the transmission system is working well too.
We are always looking at ways to improve the quality of the transmitted images. I hope we will soon be able to further reduce the errors caused by noise on some pictures and as compression technology improves some of the more challenging images will start to look better too.
Andy
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Maybe Andy you should start at looking to up the Bitrate back up to the 19/20 mpbs mark when the channel looked stunning. I know you claim the channel looks stunning but it simply is not.
The encoders and bandwith used cannott cope with any dark scenes and any scenes with movement. Did you watch the olympics??? The swimming sessions looked awful yet on Eurosport HD looked very decent.
I know you wont like to admit it but I think it would be a good start to actually admit the channel quality has dropped hugely since the days it was using 19/20mpbs of bandwith.
Its excuses after excuses at BBC HD.
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Andy, just out of curiosity, why is it that the HD Preview can't be (easily) recorded on sky+? I know it can be done by a Manual Recording, but the simple method of hitting record won't work. Is there some special flag on the transmission, and if so why?
This had me confused recently when on the phone to Sky to set up my new box. "We've enabled recording for you" "well it still doesn't work..."
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Dear DavidJRob
Unfortunately you are correct, there is no easy way to record the HD Chanel Preview loop! It's not actually a programme so not listed as an "EPG Event" and can only be recorded using the manual option on a Sky HD box.
The instant record function will not work because there is no real end time for the Preview. It's length varies depending on how long there is between the end of the last programme and the start of the next day's scheduled programmes. The variable length also means the Preview could look like one long event so could easily fill a large chunk of disk space, deleting other watched then un-watched programmes that haven't been tagged to keep - something that would rather annoy me!!
Andy
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My post is about sound not picture. I watched and listened to the Jools Holland program on New Year's Eve. I was very disappointed with the sound. I do not have an AV system, I just connected the sound output from my TV to a high quality stereo amplifier and speakers and the sound I heard was just mono. I am using a Virgin media V+ box connected to my TV via an HDMI cable. What do i need to do to get stereo sound from HD TV please? When I play a DVD also connected to my TV via HDMI and connect my TV to my amp I get great stereo sound. Thanks in advance for any help
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The article on the the new HD test card has confirmed a fear I have had for some time ie. that new LCD and plasma screens are still affected by the burn-in that used to cause the 'premature death' of many CRT screens (especially during the early days of video games).
The original cause of my concern was the station IDs that are often superimposed on the picture on current transmissions and the confirmation that burn-in is a potential issue on new TVs raises two questions. Can these logos (and any other relatively static items such as subtitles) cause burn-in on flat screen TVs? and, if so, is there any way to stop them from being displayed in order to avoid the problem?
Thanks
Dave
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Dear vascop
Unfortunately I can't help you much with the V+ box as it's one I have never used. We send the HD signal directly to a Virgin Media input point in Television Centre as uncompressed HD SDI. If your system is working using the same TV input and cable from the DVD then check the audio output options on the V+ set up menu. I will ask a few of my colleagues who have V+ boxes when I get back to London next week.
Dear davefelton - there is a difference between true burn in and a residual image. Burn is either permanent or need special care to remove (or at least try to remove!). A residual image will fade fairly quickly with normal use. I have seen residual images after leaving the radio banner up for a while but have not seen it from the current test card or our HD Dog or HD subtitles.
Andy
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Thanks for your reply to my burn-in questions Andy. Just to clarify then, am I correct in thinking that the following comment and warning in your article only relate to CRT displays?
"The second reason is to help protect screens from burn in. The full level test card will burn a screen in quite a short period so please heed this warning:
DO NOT leave the test card on screen for more than 2 minutes if your screen is less than three months old or more than 5 minutes on older screens. Make sure you go back to the promo for several minutes before using the test card again."
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Dear davefelton
To flat screens primarily but anyone with a CRT should be careful but you have t remember the full level testcard is on many broadcast CRTs for many hours with no ill effects
Andy
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A Christmas Present from the HD Channel!
The Queens DOG!
I thought broadcasting The Queen's speech WITH a DOG was a disgrace. The idea the BBC should wish to place commercial branding on The Queen's broadcast is extremely disrespectful to Her Majesty and patronising to viewers.
Come-on BBC Ditch The DOG!
BTW Sky Anytime had a perfect HD version of The Queen's speech without any branding.
Well Done Sky!
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Andy Quested I have to ask if you watched the new episode of The Green Green grass and Hustle?? If so what was your honest view on the picture Quality??
Im just interested to know if you thought both these shows looked stunning as you claim many shows to be. In my view both were awful and and showed lots of noise and especially with Hustle there were lots of Artefacts, which clearly shows that the channels encoders and Bandwith are not up to the job. The dark scenes in Hustle were that bad I turned off. Please can you and Danielle and the powers that be get together with the people responsible and get the bandwith back up to 19/20 mpbs or get rid of the channel and use the bandwith spare on the SD channels.
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wednesday83,
I have just watched a recorded Hustle. To me the picture quality was fine. I certainly did not see "lots of artifacts" and saw no obvious problem with dark scenes.
Now, I deleted the the program and only saw your post afterwards so I can't replay to look out specifically for these problems, however if they were as bad as you suggest I am sure I would have noticed.
I will however critically look at next weeks episode.
At the moment though I simply cannot agree with your assessment of BBChd picture quality.
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Wednesday83,
Looking back at one of your previous comments:-
"Did you watch the olympics??? The swimming sessions looked awful yet on Eurosport HD looked very decent."
This is one area where I do actually agree.
I did not have eurosport to compare but I did see what I consider to be typical compression artifacts.
This was especially noticeable when the bbc replayed previously recorded swimming events. The recording definitely dgraded the picture with motion artifacts.
However you cannot necessarily blame the final transmission bitrate for this, it could have been down to the link from china or any other step in the transmission chain.
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Wednesday83,
I recorded the repeat of hustle and have just had a good look at it. Unfortunately I cannot say that I understand your criticisms of the picture quality.
No obvious motion related compression artifacts were visible and the "dark scenes" were to my mind perfectly acceptable, although did display a small amount of noise which I would attribute to camera noise (I am sure Andy could comment here).
Nothing which would make me scream the transmission bitrate isn't high enough or that the mpeg encoders are not up to the job.
I am sure that Andy could turn on some noise reduction settings in the encoders but this usually has detrimental effects in other areas of picture quality such as fine detail.
Any comments Andy?
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Tagmclaren, in regards to your comments about your comments about the swimming for the olympics, I assume Eurosport HD had the same feed??? Why then was the Quality on so better on Eurosport. The artifacts on show were simply in my view encoder inssues and bitrate.
And why did the quality of the channel decrease dramatically as soon as the bandwith was lowered to 16mbps?? Jools Holland a fine example.
Are we really to believe that on the day bandwith was reduced the bbc decided to use different cameras and production methods??
The majority of problems simply are encoder / bitrate related as few other channels have such problem.
BBC could proove / disproove this by increasing the bandwith to 20 mbps for a day or so and let us see the results. I bet there would be a deffinate increase in the quality.
I will end on a posotive note. I thought the studio shots on "Your Country needs you" were far better than any other studio attempts at HD by the beeb. Although not quite as good as Sky 1 studio shows, it was far better than past attempts. Its just a shame the out of studio shots were not HD. Come on beeb, if you are going to produce an HD show then make the entire show HD.
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Hi
Regarding the swimming, although I obviously cant answer this question for definite (although Andy could), I see NO reason to assume that the BBCs feed from China to England was the same as Eurosport.
With all the interactive feeds they may have had a restriction on bandwidth back to the UK and may have had to make comprimises.
This is pure speculation though.
I am not saying that the BBC HD output is perfect, it is not, however to simply blame the final transmission bitrate as the cause of all ills in a complex transmission chain is a simplistic conclusion.
My main curiosity is actually why you are seeing such imperfections in the picture when I am not. I am critical of picture quality, have a 42" calibrated plasma, viewed at 11ft distance. It resolves the highest frequency grating on the testcard and I am currently watching Duffy on the preview loop and it looks, frankly bloody fantastic!
If we could get to the bottom of why we are seeing differences then perhaps we could all learn something :-)
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Since changing from a 37" HD ready LCD to a 42" 1080p Plasma in November, BBC HD has really improved. Sky channels look as good as ever.
Does BBC HD look better on a plasma?
I note both tagmclaren and Andy Quested have plasmas.
What do you have wednesday83, LCD or Plasma?
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OH NO!
The LCD V Plasma debate!
They both have pros and cons, but I personally far prefer plasma. I find the cons of LCD far more objectionable than the cons of plasma.
I don't think you can say any particular channel will look better / worse on any particular display type.
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Dear wednesday83
Thank you for your recent comments. I have now watched (off air) more Hustle, Green Green Grass and several other series under "normal" viewing conditions and have only one comment.
The overall quality of the programmes was extremely good. However there were I agree, a couple of scenes during last weeks Hustle that had obviously been pushed due to low light on location making the pictures noisy.
As we all know bit rate is not the tool for dealing with noisy signals and I have said before we are looking at ways to deal with noise without either softening the image or degrading images that don't need any treatment.
We are working on several setups that we hope will reduce the effect of noise.
Other than that though, I cannot agree that the picture quality was in any way awful. The programmes are well shot and other than the scenes I mentioned the lighting and colour are very good too.
TVs are very good amplifiers of noise if they are not set up well and the first thing I always check is the sharpness settings to make sure they are off or zero.
Andy
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Andy,
I did watch the first episode of Hustle and I agree with Wednesday's comments. I noticed in particular on people's face's there seemed to be artefacts and movement.
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Dear digitalscoobiedoo
Happy New Year and thanks for your post. As I said though, other than the noise on some scenes in last weeks episode of Hustle, the quality of the images has been very good. I would need to know more about your viewing conditions before commenting more
Andy
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Andy,
I've noticed a couple of times this week, that once again you're transmitting stereo but telling amps it's 5.1.
Three Men in a Boat and Hustle both did it!!
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Yes, I noticed that on Hustle last night too.
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@ 34 - TagMcLaren,
Yes I know it is technically Dolby Digital. I wasn't clear, my fault.
The problem is the majoity of content (EVEN MAJOR FILMS) are transmitted in stereo alone. eg. Pirates of the Caribbean on ITV 1 HD (albeit this particular example not directly under BBC control).
The few films (counts fingers on 1 hand) that are transmitted in "Dolby Digital", as I understand it, actually use Dolby Stereo encoding in a Dolby Digital Wrapper (commonly used on analogue - thats how out of date it is), this is decoded by a receiver as stereo plus general stereo rear effects (the receiver will use Pro Logic mode to decode).
When the BBC says Freesat is Dolby Digital most people expect Dolby 5.1 not least of which because all movies for about the last 10 years have had this encoding as a minimum standard.
The quality difference between DD 5.1 and Dolby Stereo is marked because only DD 5.1 has discrete channels and can thus make accurate sound placements within a room through accurate channel control.
Most people I talk to expect Freesat to have DD 5.1 on everything except common chat programmes not suited to surround where they expect stereo and this is what they have been led to believe will be the case by the advertised Dolby Digital branding.
What in actual fact we're left with overall is a service thats nearly all plain stereo with just the odd movie transmitted in Dolby Stereo, and with only the previews and the Doctor Who Concert transmitted in Dolby Digital 5.1 so far to my knowledge.
Whereas I can't put accurate percentages on the breakdown of the sound transmissions on the major channels on Freesat, I wouldn't be surprised if they worked out something like:
Stereo - 98%
Dolby Stereo (stereo + rear effects) - 1.5%
Dolby Digital 5.1 - 0.5%
I doubt thats hardly acceptable to most and a real downgrade on analogue where at nearly 100% of films were according to my understanding and receivers decoding display, shown in Dolby Stereo.
I thought Freesat was going to take us forwards to Dolby Digital 5.1 content but it seems we're actually sliding backwards on the sound front.
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Andy Quested could you please answer a question that has been puzzling me.
You say the Quality issues the channel has were down to production and you say maybe settings on our TVS and so forth maybe another reason for what some of us believe is poor quality.
Why then as soon as the channel lowered the bitrate did the quality of shows such as Jools Holland suddenly drop? On the day you lowered the bandwith did the production of such shows change??
And also do you believe that the lowered bitrate to 16mbps had no effect at all on quality?
Is it too much to ask for to have the bitrate increased as a trial just to show how much the quality would increase.
Just be interested to hear your views, thanks.
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"Yes I know it is technically Dolby Digital. I wasn't clear, my fault.
The problem is the majoity of content (EVEN MAJOR FILMS) are transmitted in stereo alone. eg. Pirates of the Caribbean on ITV 1 HD (albeit this particular example not directly under BBC control)."
Pirates of the Caribbean was actually on BBC HD and it was if I recall in DD5.1.
"What in actual fact we're left with overall is a service thats nearly all plain stereo with just the odd movie transmitted in Dolby Stereo, and with only the previews and the Doctor Who Concert transmitted in Dolby Digital 5.1 so far to my knowledge."
There's actually quite a few programmes in DD5.1 on BBC HD, but none on ITV HD.
Examples include, Strictly Come Dancing, Survivors, Torchwood, Tess of the D'Urbevilles, Jools Holland, Wild China and The Proms.
There are many more I can't recall, but I'm sure Andy will confirm there have been others.
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Dear derek500
We are making as many programmes as we can in surround but no as many as we would like. I hope we will get more as the year progresses but there are many sound experts in the industry who are at a loss to see what surround offers that well produced stereo does not! I am not going to agree or disagree with them as I do not know enough about sound acquisition and reproduction - I certainly know what I like (and what I don't). I see no reason for to aim to deliver all live "events" - sport, pageant, entrainment in surround as quickly as we can.
We do transmit feature films in surround when we have them but contrary to some opinions not all movies have real 5.1 surround. You may be interested to know not all programmes are stereo, they may have stereo music and a few stereo effects but actually for most of the programme L=R
Dear wednesday83
Thank you for your comment, I did not actually say "the Quality issues the channel has were down to production" I said "I agree, a couple of scenes during last weeks Hustle that had obviously been pushed due to low light on location making the pictures noisy."
Again we are looking at ways to deal with the noise. Again I point out increasing the bit rate is not the tool for dealing with noisy signals.
Andy
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Dear derek500
5.1/2.0 switching is back to normal now.
Andy
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Dear Andy Quested, When the BBC HD channel started shows such as Jools Holland looked stunning. As soon as the bitrate was lowered shows such as Jools Holland started looking poor.
I have 2 questions for you and please answer honestly.
1) Do you believe that the lowered bitrate had no effect at all on quality?
2) At around the time the bitrate was lowered, did the BBC change production methods on shows like Jools Holland?
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@wednesday83 "At around the time the bitrate was lowered, did the BBC change production methods on shows like Jools Holland?"
Before the studio at TVC was upgraded to HD, I believe JH was produced in the studio, but as an OB, with the production being co-ordinated in OB trucks outside.
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@ Derek 500
So on exactly the same day the bit rate was lowered the BBC changed to an OB and this is why the quality went down on Jools Holland??
If this is the case then why are the "a little later" clips also looking poorer. Im talking about clips from early series when it looked stunning and using bandwith of around 19/20 mbps. This shows the bitrate decrease was to blame for Jools Holland.
Anyone who says bandwith reduction had no effect at all on quality are surely wrong.
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Dear wednesday83 and derek500
Thank you for your comments.
I must point you away from the debate about bit rate and ask you to consider compression toolsets especially how compression handles noise.
The encoder update introduced a lot of better image handling techniques and the next update (when it's ready) will bring a what can only be described as another generation of encoding tools.
Andy
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Dear Andy Quested, thanks for you comments.
I must point you back to the bitrate.
The question is do you genuinely believe that the bit rate reduction had no effect on picture quality at all.
You dont seem to want to talk about this.
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Dear wednesday83
Thank you for your post but I do feel now I have fully addressed your comments.
The views of myself and many others is that the overall picture quality of the HD Channel is now very good. Currently the primary cause of poor picture quality seems to be noise (as I mentioned in reply to your comment about Hustle). We are working on ways to reduce the impact noisy pictures have on the transmission encoders.
Andy
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Dear Andy Quested. yes the overall quality of the channel is ok but not stunning.
The fact you wont answer the question about the bit rate reduction says it all.
I know you wont want to answer this, but do you believe the quality of picture is as good now as it was when it was a test channel?
Please answer. I know you are working for the bbc but you are allowed to have a view.
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Dear wednesday83
Using the Wimbledon coverage as a base line measure we absolutely know the quality of the channel is better now than it was a the start of the trial. I have said this before in previous posts.
Andy
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By the way Andy, did you remember to ask your colleagues about stereo from the Virgin Media V+ box?
On another topic with regard to picture quality. I think that ITV's SD pictures are often of better quality than the BBC SD & HD pictures. I went to a lot of trouble using specially purchased DVDs to adjust my TV picture. I mention this so that you don't think my observations are due to a badly adjusted set.
I have noticed that pictures of people outside look much better than in the studio these days. This didn't used to be the case.
Watching programs like "your country needs you" and other studio based programmes I have noticed that peoples faces on BBC appear washed out/flat/yellow - all detail lost, whereas on ITV you can see natural skin tones and details.
Also a lot of the lighting in BBC studios seems calculated to put an overall colour tinge to the picture as well.
In summary I think that the studio lighting and makeup leaves a lot to be desired.
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Dear vascop
Thanks for the comments. I did speak to a colleague at Virgin and they said they would look into the issues. We pass the HD signal directly to a Virgin "inject" point in Television Centre and they take over from there.
I have watched a many hours of our studio output and some of what you suggest is style issue also the LED screen in "your country needs you" doesn't lend itself to any form of compression. I have mentioned this to the studio engineers.
As for the DVD comparison - I never make them! DVDs are compressed using multi-pass techniques with skilled "compressionists" checking every scene. We do all that in 4 seconds and the same compression has to work for Sport, Drama, Studio, OB, Documentary etc. etc. It's not going to be perfect for evert situation but we get the best we can for the majority and work to improve the remainder - but this takes time.
Andy
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Andy,
As requested....
Sound on my larkrise recording seemed out (sound late).
Particularly noticeable on the road building scenes when hitting slabs with the pick axe.
My recording of the sync test card made some weeks ago is consistently fine, so I believe the foxsat is playing back within a good tolerence.
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I have to second tagmclaren's comment re lipsync on Lark Rise, and my recording was on Sky+. This receiver has been consistently good since the latest software update, but Lark Rise was way out. Super pictures, super sound, just not together!
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Dear Andy Quested, Are you watching the Obama Inauguration on BBC HD??
If so have you compared the quality to that which sky are offering on SkyArts HD??
Ive compared both feeds and Sky Arts HD wins hands down.
The Sky coverage is far crisper with more detail whilst the BBC coverage lacks detail and has many artefacts on show. This was most noticable on crowd waving flags shots. This shows that the BBC HD channel is struggling with the bandwith and encoders currently in use.
Its time to get the bandwith upped now and get in new encoders similar to the ones used by sky hd.
Oh and before you blame the poor picture quality for the Obama show on production, it was exactly the same feed shown by SKY.
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FWIW I agree with Wednesday83. It's not that BBC HD isn't very good most of the time. Andyquested and others seem to take critcism personally and that we are insulting them and the channel. I'd very much like the BBC to resolve the issue so we can get onto talking about future programming and direction instead. We are comparing to other channels. The problem is your codecs are poor and outdated. The Sky Codecs get a better picture out of a lower bitrate, most of the time. Sky codecs work well down to about 9Mbs where things start to rapidly fall to bits. Sometimes BBC HD looks better than some of the other HD channels (not often), but then you have to consider whether the huge extra bitrate on BBC HD merits the slightly better picture. I've said it before, the BBC should be getting 3 HD channels off that transponder on satellite. One day you'll need to.
The point is an extremely pressing one as Ofcom recently made it clear that on freeview (different system) they'd like four HD channels running on about 8.4Mbs. Under such a scheme BBC HD would be eaten alive as things currently stand. It'd be woeful picture quality.
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The pictures were the same but was the feed?
The BBC may have got the EBU feed
http://www.ebu.ch/en/union/news/2009/tcm_6-64219.php
They may have got it from elsewhere.
Where did Sky get their feed?
No idea.
Who did the standards conversion from 60 to 50Hz?
The point is we know nothing about how the pictures were sourced or processed or vision mixed before they were broadcast in the UK.
Blaming the final transmission bitrate and encoders for the very average quality of HD parts of the BBC broadcast is simply jumping to conclusions, especially when BBChd shows lots of programs with complex motion with no problems such as noise and compression artifacts.
However I do agree that the BBC could have tried harder on this one. Could they really not source an HD prod unit for this job?
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(Copied from the Obama's inauguration on BBC HD blog)
Dear wednesday83
It was a shame you didn't enjoy the HD programme as many others did. I am now at a complete loss to even try and understand your comments.
I have the Sky Arts and BBC HD coverage of the inauguration on my pvr and have watched them at less than 1m on a 50" screen. Other than a few minor difference (we do use encoders from different manufacturers) the HD images are identical.
I will not comment on the SD pictures as the local bureaux coverage from Sky and the BBC was SD only.
I am afraid to suggest your posts about the BBC's coverage cannot really be regarded as fair criticism any more.
We value the comments from there blogs and I regularly post on Digital Spy under my own name where I get a fair amount of flack back but I respect the criticisms and technical comment expressed there.
I do not think I can say any more to you on the subject of bit rate.
Andy
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Dear tagmclaran and DavidJRob.
We have been instigating the AV sync issue (I spotted MI High was out) and have traced it to some maintenance done on Thursday. When we went on air the system was stuck in 5.1 mode with a frame of delay missing in the audio chain. The switching was corrected on Friday but we missed the vision delay.
This has been reset and we are talking to the playout area about future engineering and maintenance procedures to make sure ALL the check are done before system goes back into service.
Apologies
Andy
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I was not the only person though Andy to think skys coverage was far better than BBC. Ive looked at posts on Av forums and sev
I know you deffend the bit rate and encoders to death but please try and look at some programmes from over 12 months ago and tell me the reduction in bandwith has had no bearing on quality what so ever.
If you genuinely think there was no difference in quality from the bbc and Sky arts coverage then maybe I should invest in the same TV as mine obviosuly cannott get the same picture as yours on bbc hd.
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Dear wednesday83
Thank you for your last comment. In the interest of improved picture I will (and always do) take my pvr to our R&D centre to measure and compare!!
One thing we do not do by the way, is use aperture correction to sharpen our images and I always ask our compression experts to check to see if it's been used on our pictures and on picture of others.
I will let you know what they say (but it will take a week or two)
I have a Panasonic 50 PZ700E. It took a lot of research and time to find a display I liked. It may not suite you though as I firmly believe choosing a display is just like choosing speakers (I have Missions). You know what you like and what you don't and a display should enhance what you like while "reducing" what you don't.
As I said before I am always open to fair criticism and comment and (as in post 88) will always say when we get things wrong. I value these posts and although I don't have time to respond to them all, I do try and deal with the key issues.
All I can say again about bit rate is it is not the critical key to better pictures - to overcome some issues you have mentioned with bit rate alone would require bluray's 30+Mbs. The real trick is the compression tools that deal with noise, contrast and motion and we are working on those at the moment.
Andy
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Andy,
Thanks for getting the AV sync issue resolved - I had a problem watching Hunter which I blamed Sky for (major lipsync with sound well behind picture) - I assume this was the cause of it as I've been watching other HD material with no problems.
Is this the place to report other such problems if we see them?
It must be a bit frustrating to set up a blog like this, knowing that most user comments will be complaints (goes with the territory I guess), but thanks for providing the info and updates that you do.
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http://www.avforums.com/forums/hd-tv-programmes/916406-obamas-inauguration-pq-skyhd-v-bbc-hd.html
Most people on this forum going with skys pciture quality over bbc as well.
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Missions...Hmmmmm!
Is there anywhere I can download a good quality BBC test card down to DVD?
I've calibrated the DVD input to a very high standard. I just want to make sure that I have replicated that calibration with the freesat box input.
Thanks.
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Dear delphiplasma
Missions...?????? I like them - 770s studios and they are just short of 25yrs old.
Anyway - I can only suggest you either wait for bluray recorders or use a pc card with a bluray drive
Andy
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I'm still getting sound consistently behind vision on BBC HD
All other channels (including ITV HD) are perfect, but audio on BBC HD is over 30ms behind vision.
This seems to affect everything (eg Hunter, A short stay in Switzerland and As you like it)
I'm using a Humax PVR, into a Panasonic Plasma via HDMI, also sound via optical to an AV amp behaves the same (on the amp I can get an effective -30ms adjustment and it's still out).
Is there something wrong with my setup or are you still having issues at the broadcasting end?
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I was going to say that the delay in audio was probably due to Andy’s speakers being over 25years old, takes a while to come through. No seriously, they are a good British built speaker, which probably knocks the socks off many, overly bright, modern speakers.
I don’t experience any problems with audio/video sync. However, I’m using analogue Component inputs and analogue 2 channel audio. Could it be your set-up?
Watched a film last night, don’t know what it was called? Seemed to have a lot of edge enhancement. I know that when CD first came out, the producers would artificially increase the high frequencies to give the impression of greater audio resolution. Now I hope this isn’t happening with HDTV.
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Andy,
The audio on Hustle tonight appeared to be late?
Also there was lots of noise on Mickey's jacket throughout the show - Particularly a couple of minutes in when he leaves Frank's shop with the 'ruby'.
Any thoughts?
Thx
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Audio on Hustle was miles out (again) - any news on when this might get sorted once and for all?
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Dear BikeNutt and dtmarmot
I have just watched it and e-mails have already been sent. As other programmes were in sync this evening it is either the delivered programme or the replay from the server and I will be checking both tomorrow.
I have it on my PVR and will be waiving my arms around a lot to find out what happened. As this come after last weeks fault that put the whole channel was out I am non too pleased.
Apologies for spoiling the programme - I need to watch it again too as I was trying to find out what had gone on and missed the plot.
Unfortunately I was watching time shifted so it was not possible to track it during transmission.
Will keep you updated and have a closer look at the video noise to see what was going on there as soon as I can
Andy
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Thanks Andy - good to know someone is on the case!
Whilst Hustle was miles out yesterday, everything else seems to be out too (albeit by a much smaller margin)
I'm using an effective -30ms audio 'delay' and audio is still slightly lagging video on everything I've watched recently on BBC HD (A short stay in Switzerland, the Hunter repeat, As you like it).
All other channels are spot on though.
Is this a known fault, or could it be something with my setup?
(I'm using a Humax PVR, sound is out on both HDMI direct to TV - a Panasonic 42PZ80 and via optical to an Onkyo 905 AV amp, on all other channels I need a 30ms delay on the Onkyo to get it in sync, on BBC HD I set it to 0 to get the effective -30ms and it still doesn't look quite right).
Only thing I can think that's strange with my setup is that I did once set a 40ms delay on the Humax, long since set back to 0 in favour of using the Onkyo (partly because the Humax doesn't seem to retain the setting) - if you could confirm that other programmes are definitely in sync I'll try a full reset on my box to see if that clears it.
Thanks
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@dtmarmot "I'm using an effective -30ms audio 'delay' and audio is still slightly lagging video on everything I've watched recently on BBC HD (A short stay in Switzerland, the Hunter repeat, As you like it)"
If your audio is lagging behind the video, why are delaying it at all? Surely the audio delay is for when the audio comes before the video?
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Dear dtmarmot and derek500
I have just had a look at the programme from the tape and the server and it is "almost" spot on. Rowan is going to check again to confirm.
We are also checking the sync of the play out chain - on Monday it was within 5ms. The EBU recommendation for A/V sync is +20 to -40ms for programmes delivered to the broadcast chain. For HD I changed this to +10/-20ms making our target for delivery to home (after decode) +20/-40ms measured via an HDMI connection.
Two things though.
1. Have you confirmed your AV sync with the test signal this week?
2. Have you checked the relative sync of your systems between the TV speakers (via HDMI) and the AV system?
I will keep you updated as we go
Andy
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To derek500:
I'm not delaying the audio - I'm effectively getting a minus 30ms adjustment by taking the sound direct as the TV takes that long to process the picture (sound via HDMI to TV is delayed by the TV to compensate)
To Andy:
I haven't yet been able to try the AV sync test signal (PVR is too full to record the demo loop!) - but plan to this weekend.
I have checked the TV speakers vs AV - it needs a 30ms delay through the AV amp to get them in sync (on all programmes, including the affected BBC HD ones).
Are you saying Hustle was broadcast without any sync issues ?
But you agreed the sound was wrong when you watched it?
If that is true it sounds more like the Humax PVR is faulty (I'm assuming that's what you used to watch it too?) and we're complaining to the wrong person.
Strange though that only BBC HD is affected - and some programmes noticeably worse than others. Is there a difference in the broadcast that could cause this (I'm guessing that a Dolby digital signal would be processed differently by the box - but since other Dolby digital signals haven't been affected to the same extent is there something different about the Hustle sound track?)
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Dear dtmarmot
Thanks for the comments. No I'm not saying the programme was in sync as it certainly wasn't when I watched it at home!
We have checked the master tape and the copy on the server, these appear to be in sync. (By appear, I mean they are close enough to need better measurement than just standing in front of a screen in a control room)
Rowan will measure the tape and server version more accurately then check the play-out chain using the AV sync signal. If we find nothing wrong we will check the repeat tonight to see if it was a "one-off error" or is consistent - further action will depend on what we find out.
More to follow
Andy
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Andy,
My recorded AV sync test pattern is still correct at +60ms (which is normal for my setup watching BBCHD via Virgin Media V+)
Having re-activted the audio delay on my AVR after Hustle, I watched a bit of Survivors and that seemed to be ok.
Thanks for your continued support!
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Dear BikeNutt
We have just measured the sync of tape as audio slightly late wrt video.
We are now checking the stereo path through the play out chain to make sure the correct delay was inserted after the switch from the previous surround junction.
Andy
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As requested here is my BBC HD Sync Test Result
Date: 30/01/09
Time: 11:50 AM
Receiver Setup: Humax Foxsat HD -> HDMI -> Philips 47PFL9632D
Firmware: TV 64.14.18, Foxsat 1.00.15
HDMI: TV has version 1.3a (i.e. it supports the auto lip-sync feature).
Test Method.
A stereo .wav file was recorded with the TV audio occupying the left channel and the amplified photodiode output occupying the right channel. The resulting file was analysed in the time domain using Nero Wave Editor.
Test Results.
Sync Flash Bars.
The top bar was visible. The sound starts 70ms after the top bar is lit.
Measurement Bar.
The photodiode was placed just above the lower calibration marks in the path of the measurement bar. At the zero point the sound commenced 40ms after the measurement bar passed the photodiode. At the sound late 1 frame point the sound commenced at the same time as the measurement bar passed the photodiode.
Comments.
0. The results accord with my perceptions on viewing the BBC HD sync test.
1. The BBC HD channel is the only one on which I notice that the sound is delayed. ITV HD and all SD Freesat channels do not have a noticeable sound delay. I notice no sound delay on Freeview channels (TV internal tuner, no HDMI).
2. This TV has HD natural motion for extreme motion sharpness. In it displays a new frame every 10ms.
3. Both Humax and Philips tell me that the BBC HD sound delay problem is not due to a fault in their products.
Questions.
Why is the sound delay greater when measured against the sync flash bar at the top of the picture? Do the BBC synchronise their sound to start after a complete 2 field 40ms frame has been displayed? If so, given that the BBC HD broadcast is 1048i, would it be better for the BBC HD sound to start after just one 20ms field has been displayed?
Request.
Please would the BBC work with the receiver and TV manufacturers to eliminate the long running BBC HD sound delay problem first reported by me in October.
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For those interested in the Hustle synch issue above Andy Quested just called me to say that there will be an unscheduled transmission of the synch test signal between now and 4.15.
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Dear Viewer00
Thank you for your fascinating post. Can I ask what the .wav file is for? Any process that separates the A/V signal is subject to some form of "tolerance" error.
We use the EBU recommendation of +20/-40ms for AV sync, but instead of applying it to the master tape, we try to keep the whole chain from camera to STB within this tolerance.
Our test signal is calibrated to be 0ms measured on a CRT using the top bar (only visible if the display has no overscan) or 1ms audio early if measured on the second bar. This measurement was made from the master tape and you can find more details in Rowan's blog.
The traveling bars cannot be used to measure sync as interlace and flat screen de-interlacing processes make the result unpredictable and therefore invalid. These parts of the test signal are for "sync by eye" checks and can only be accurate to around 6ms (around 1/4 frame)
If you are measuring AV sync from a screen where audio and video are via the HDMI connection, the only accurate way is to use a microphone against one of the speakers. The AV sync via the HDMI connection is not (usually) adjustable as it is built into the TV and not all STBs have adjustable the sync of the HDMI output.
We have also measured the transport stream AV sync giving us a total play-out error of under 10ms.
The channel was measured again today at under 5ms on a surround signal and very slightly longer on a stereo programme. I will be looking at ways to make these exactly the same as soon as possible.
This seems to have been the cause of the Hustle sync error. We think the audio is slightly over 30ms late on the tape and this was added to a stereo play-out path delay. We have reduced the stereo path delay today to make sure Hustle looks better tonight but I need to keep an eye on other stereo programmes to make sure the audio is not early.
I will send your comments to Humax but i am not aware of any AV sync issues with the current software version.
Andy
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The Hustle repeat was still not right - though it did seem to be a bit better than the original showing (had deleted that so can't do a direct comparison).
One bit of good news though - 'Not going out' looked to be in perfect sync
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dear dtmarmot
We believe the programme is at the very far end of tolerance and I will be talking to the quality control area to see what they think tomorrow
Andy
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PS
This also means it was out of sync on the standard definition channel!
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Dear Andy
Thank you for your reply to my sync test post and for your work in progressing solutions to the BBC HD sound delay problem.
You ask what the .wav file is for.
The .wav file is a 44100Hz sampled 16bit depth two channel recording. The input for one channel is the TV sound, the input for the other channel is the amplified photodiode signal. This .wav file, together with the Nero Wave Editor software takes the place of the dual beam oscilloscope as described in your blog Method 2 “How do you use the signal to check audio/video A/V sync?”.
I did measure AV sync from a screen where audio and video are via the HDMI connection. You say the only accurate way is to use a microphone against one of the speakers. I was using a direct electrical connection from the TV’s headphone socket. I feel this should also result in a valid measurement as I expect the headphone electrical signal to be synchronised with audio sound from the speakers.
The AV sync via the HDMI connection from the Foxsat is adjustable, but the sound can only be further delayed. A reduction in delay (negative delay) is needed to offset the BBC HD sound delay problems.
My understanding is that AV should automatically be in sync when a tuner is connected to a TV via an HDMI connection. No adjustment for sound delay should be needed.
I note you say that travelling bars cannot be used to measure sync as interlace and flat screen de-interlacing processes make the result unpredictable and therefore invalid. However, please note that my "sync by eye" check using the travelling bar does give the same result as the photodiode measurement. (Note: the photodiode measurement can only be accurate to + or - 5ms as the TV’s backlight is 100Hz with a 50% duty cycle.)
Thank you for confirming that the BBC’s test signal is calibrated to be 0ms measured on a CRT using the top bar, or 1ms audio early if measured on the second bar. I realise that my TV is an LCD; not a CRT, but I would still expect the received test signal to be 0ms at the top bar; not the 70ms sound delay I measured.
Over the weekend I did not notice any obvious delayed sound on the BBC HD channel programmes I watched. So I’m hoping to catch the test signal again to see if the results are now different.
In the meantime I ask these further questions as the answers might help unravel what’s going on.
Please can you confirm what is the top bar. Is it a single line in 1 field or 2 lines in 1 frame? If 2 lines, does the sound follow 0ms after the first top bar line is lit? Or, again if 2 lines, is it 0ms after both top bar lines are lit (i.e. 20ms after the 1st line is lit)? [Note: My photodiode picks up light from more than one line. It covers about 3 display lines on my TV]
Also, given the position of the travelling bar in the screen, please can you confirm whether the scale has been positioned to allow for this area of the screen being written later than the top bar (about 15ms later for an interlaced display). Please also confirm whether the travelling bar is moved every field (i.e. every 20ms) so that 100Hz (or 200Hz) TVs can properly render the extra (intermediate) frames they show.
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Interestingly I did also have an SD recording of Hustle from DTT.
You're right - the sync is slightly out on that too, but nowhere near as noticeable as even the repeat off BBC HD
I have to look quite closely to see the sync issue on the SD version - the HD repeat was obviously out, even with a -30ms adjustment.
I'll check last nights showing of Larkrise tonight - be interesting to see if that's ok.
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Following on from your reported corrective action, here is my next BBC HD Sync Test Result.
Date: 02/02/09
Time: 4:50 PM
The Setup and Test Method was the same as the test on 30/01/09 at 11:50 AM.
Test Results.
For all results the sound delay was 20ms less than measured on the sync test broadcast on 30/01/09 at 11:50 AM.
[Note: Due to the 100Hz strobed backlight on my TV, all my measurements have to be in 10ms intervals]
Sync Flash Bars.
The top bar was visible. The sound starts 50ms after the top bar is lit.
The sound starts 40ms after the second bar is lit.
The sound also starts 40ms after the middle bar is lit.
The sync flash bars seem to occupy 2 lines (odd and even fields). A second flash (greater brightness seen by the photodiode) is evident, occurring 20ms later than the first.
Measurement Bar.
At the zero point the sound commenced 20ms after the measurement bar passed the photodiode. At the sound late 1 frame point the sound commenced 20ms before the measurement bar passed the photodiode. My visual perception agrees with the test results (i.e. the sync test shows the sound to be late by half a frame).
Comment.
I did not detect any obvious sound delay in the preview footage immediately before the test.
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Sync on Larkrise was a bit out too. Not unwatchably so, but definitely not quite right.
On the other hand the Darwin programme seemed fine.
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I've put up a screenshot of the Nero Wave Editor window which shows a BBC HD Top Sync Flash Bar measurement I made.
http://myweb.tiscali.co.uk/luculent/Pictures/SyncTest0.PNG
The sound delay is equal to the difference between the "selected" timings shown at the bottom of the window.
This measurement shows that on 30/01/09 at 11:50 AM the sound was 70ms later than the Top Sync Flash Bar with my reception setup [Humax->HDMI->TV].
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Viewer00,
Hi
Interesting tests, you are using a similar methodolgy as I was going to implement using cooledit and bunch of bits from maplin. Unfortunately they are still sat in their jiffy bag waiting for me to get the soldering iron out.
Just a couple of things to bear in mind when performing tests.
The Foxsat HD does not use HDMI 1.3 auto lip sync features as it is HDMI 1.2a. However your TV should automatically insert an appropriate delay to the sound to account for it's video processing.
But far more importantlythe Foxsat has a design tolerence of + / - 20ms for it's audio sync. The reality is a bit different, but we wont go there.
Therefore in worst case scenereo you could have a difference of 40ms between measurements on different days! A whole frame! This is on top of what any tolerence the BBC has (mind you IMHO 5ms is bloody good going, well done Andy).
The Foxsat video/audio sync will change when you tune to a channel,so sometimes tuning away and back to BBCHD will make a difference.
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Dear all
I am sorry to say use of any audio/video editing package or file is not accurate enough due to the tolerance allowance of each process.
Even a dual beam oscilloscope has to be able to fire both traces simultaneously not consecutively (although if the timebase is high enough the delay may be negligible). A scope that can freeze a trace to allow a second trace timing to be compared would work well as it's relatively easy to calibrate.
The method used to make the master tape allowed us to move the AV relationship in 100th frame (0.4ms) increments. This was checked on replay of the tape, from the play-out server and finally in the transport stream. The AV relationship was always measured within one device so no secondary tolerance (e.g. file generation processing etc.) could cause problems.
The methods above are really innovative and could be made to work if they could be calibrated.
The traveling bars are not really useful for accurate measurement as we cannot compensate for the video processing in displays and more importantly when measured on a CRT the bar is 12-15ms later (depending where you measure it) than the top line - both measured on field one .
They are good for anyone to check by eye though and will easily get the system to within 20ms.
Andy
Andy
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Dear Andy
It is not any audio/video editing package I use, it is the Nero Wave Editor. There is no video involved. The photodiode output and the sound are simply recorded and analysed as audio waveforms.
When I conceived the test setup I was concerned about the photodiode response and so ahead of you regarding calibration.
To calibrate my test setup I used a clapperboard. I mounted the photodiode 1mm behind the shutter, and the microphone within 1 cm of the shutter.
Also, to check that there were no time differences occurring in the treatment of the two channels during recording and analysis I swapped over the audio and photodiode inputs.
Both calibration results can be seen here
http://myweb.tiscali.co.uk/luculent/Pictures/SyncCal0.PNG
http://myweb.tiscali.co.uk/luculent/Pictures/SyncCal1.PNG
The calibration results show that as fast as I could shut the clapper, and whichever channel takes whatever signal, the test of the test setup exhibits no detectable timing error.
The rise time on the photodiode trace represents the clapper shutter moving 5mm in 1ms. That’s over 100MPH! At this speed it was impossible to stop shutter bounce, and you can even see the test setup continues to follow this faithfully.
I hope you will take my BBC HD sync test results as an accurate representation of what I experience when watching BBC HD programmes. As I’m using an HDMI connection and have no control with which to reduce sound delays, I’m still hoping that the BBC will work with the receiver and TV manufacturers so that the BBC HD programmes can be watched with sound in sync (at least within your 20ms target).
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Dear Viewer00
Thank you for your explanation. I am afraid I cannot explain why your display and set top box are not delivering the same results as our measurements. My set up at home and the demonstration set ups we use are well within the +10/-20ms (on the test signal) we were aiming for.
We will check again after we have finished the work on the small difference between the stereo and surround paths in the playout area.
Can I just confirm if the photodiode is picking up the top or second flash bar?
Andy
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Dear Andy,
Thank you for your continuing interest in resolving the BBC HD delayed sound issue.
I confirm that the photodiode was picking up the top Sync Flash Bar for the following Sync Flash Bar measurement results.
On 30/01/09 at 11:50 AM the sound starts 70ms after the top bar is lit.
http://myweb.tiscali.co.uk/luculent/Pictures/SyncTest0.PNG
On 02/02/09 at 4:50 PM the sound starts 50ms after the top bar is lit.
Also, when the photodiode was picking up the Measurement Bar as it passes the zero calibration mark, I obtained the following Measurement Bar results.
On 30/01/09 at 11:50 AM the sound starts 40ms after the bar passes the zero mark.
On 02/02/09 at 4:50 PM the sound starts 20ms after the bar passes the zero mark.
Please note that for each test transmission (date and time) I moved the photodiode around to the relevant locations against the TV screen and so captured on the .wav file about 20 results for each test (i.e. 20 clicks for each of the three sync flash bars and the one measurement bar). On analysis, for each test, the results (i.e. the measured delay) showed no noticeable variation.
I understand your concern about the validity of the Measurement Bar results, but for myself I can accept that on 02/02/09 at 4:50 PM, the sound delay was just within the -20ms (on the test signal) we are aiming for.
The only explanation I can suggest for the sound starting 50ms after the top bar is lit on the same occasion (Sync Flash Bar measurement results on 02/02/09 at 4:50 PM), it that Philips may do “enhancements” which “compensate” for psychological factors. (i.e. motion and sound are close because the human brain can predict, whereas, because a bright flash takes time to register in the brain, the sound is delayed to allow the brain time first to register the flash).
As for your setup at home, I’m wondering if you are using a separate audio feed from the Foxsat HD (via an amplifier) to your Mission 770s studios. In which case you might be using the Foxsat Lip Sync control to offset both the display delay of your 50 inch plasma, any delay in the Humax Foxsat, and any delays in the BBC’s HD programme or distribution. Whereas if using the HDMI connection, the Humax Lip Sync control cannot offset delayed sound; it can only add to it.
And you may have noticed there’s another “funny” with the Humax Foxsat Lip Sync Control. Whilst the on screen scale jumps in 5ms quanta, the actual delay jumps in ~50ms (guess - not measured) quanta. If your Foxsat behaves this way, then the best you’ll be able to do is +-25ms (i.e. outside the target).
Please do tell us all about your home setup and how you test/measure lip sync.
Future tests I hope to do are:
1. Tuning away from BBC HD and back again during a test transmission to see whether the sync changes.
2. Using the Foxsat Lip Sync Control during a test transmission to measure the actual incremental delay “quanta” against the scale.
Hopefully others (including tagmclaren) will soon be in a position to use your “Method 2” (or adaptations of it) and share their findings.
P.S. For me, the sound in last night’s BBC HD Hustle, whilst occasionally spot on, in some scenes seemed delayed and in others advanced.
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Dear Viewer00
Thanks for the reply. As we are doing some work on the stereo programme chain I will have to repeat some of our measurements anyway just to confirm we haven't done anything "stupid" putting it all back together again.
I have measured my audio via the optical out and HDMI - I have also confirmed they are very close by just turning the volume of both up!!! I get phasing.
Re the target, the EBU +20/-40 is for programmes delivered to us for transmission - the "delivered to armchair" spec is more like +40/-60ms! (or it might be -80ms!!!!) There is even an ITU recommendation that says the tolerance level on sync is as much as +80/-160ms - that must be from watching too many overdubbed programmes!
Hustle looked good last night at home but i had to record it so will not watch properly until the weekend. Your comment around wandering sync does worry me as it's not always repeatable i.e. if we play the programme again it may be OK or the sync issues may be in areas that were sync before.
Andy
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Andy, Viewer00,
I have finally got around to making my photodiode/mic sync tester.
Set up is as follows:-
Photodiode and mini electret mic into mic input on laptop.
Recording and analysing these signals with Adobe Audition @ 48KHz 16bit.
Playing back HD sync test recorded on 18/12/08.
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306743190021870786
Test 1 - Humax Foxsat HDR playing via HDMI into Panasonic TH42PZ80 plasma. Using plasma inbuilt speakers.
Test 2 - Humax Foxsat HDR playing via HDMI into DVDO vp50pro deinterlacer / scaler into Plasma @ 50p. Sound via hdmi into vp50 then via electrical spdif into Tag Mclaren AV amp.
Test 3 - HDR playing into Panasonic basic CRT via composite, using crt built in speaker.
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306743176061430706
Calibration - placed mic and photodiode next to flash on camera. Result within i sample!
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742127092244242
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742149222281170
Test 1 results - top, middle and bottom lines measured identical with 15 ms sound delay.
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742170132081378
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742246058620514
Test 2 rsults - top middle and bottom lines measured identical with 7 ms delay.
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742267065297842
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742319397866834
test 3 results - this one is interesting. Due to overscan I cannot see the top line. Middle line sound is leading video by 45ms and bottom line by 55ms. Both fields visible.
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742428431451106
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742376674245410
http://picasaweb.google.com/u006852/BBCHDSoundSync#5306742406328503522
I can only guess this last result is actually a humax problem???
The first two tests seem sensible results to me.
Also one other observation, after repeating these tests a number of times (tag dvdo setup) I observe a variation of between 6 and 23 ms for the sound delay. This I attribute to the tolerence of the humax HDR playback.
cheers
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Just a note on th above, the dvdo scaler automatically inserts a delay into the sound to account for its video processing. Its menu states this is set at 68 ms.
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Dear tagmclaren
I like what you have done!! I have forwarded your post to R&D and Humax for comment as I don't have much time this week.
The most interesting bit is the CRT test 3. The top line (the one you can't see) is 0ms as measured on the master tape, the second is 1ms and the middle 10ms - so your 10ms difference (+/-1ms) is correct but offset but just over 1 frame. As the third bar is half way down the screen it is 10ms later than the first on a CRT. I assume you used on of the SCART outputs?
We expect the signal we transmit to vary, but our measurements suggest somewhere around +/- 5ms.
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Hi
Having re-measured the difference between middle and bottom lines on the CRT it is actually 9ms, so this does appear to be an accurate and very cost effective measurement method.
The parts only cost literally a few pounds!
I was actually using the phono composit output on the Humax and not from the scart.
I don't know if these would be on seperate DACs or same DAC buffered (or not buffered eek!)
The measurements were confirmed by visual observation of the travelling bar, the sound is indeed a frame early (or video is late, whichever you prefer). I have also plugged the signal into another TV (a 37" plasma) and seen exactly the same result.
So, it does indeed look like a Humax problem.
It would be interesting to see if the RGB and svideo outputs suffer with this problem, but these outputs are prohibited, I believe by the BBC flagging, with HD content.
Any chances of getting this policy changed, or at least more granular in it's application?
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Dear tagmclaren
Sopt on with 9ms then! - we are looking at the CP issue now and hope to have some form of resolution soon.
Andy
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Andy, just re-read your blog and noticed your comments about the frequency gratings:-
"1. 5MHz 2. 10MHz 3. 15MHz 4. 20MHz 5. 25MHz 6. 30MHz
The BBC HD transmission system will pass frequencies 1 - 4. "
So why can see 6. 30MHz?
http://picasaweb.google.com/u006852/BBCHD#5291106363905160082
Or is this a case of the frequency response dropping off rather than not being passed at all?
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tagmclaren - see this new post from Andy (with picture)
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Now this may seem obvious, but exactly how wide is the HD Test Card? I ask because on my TV it comes out slightly too wide:
http://i455.photobucket.com/albums/qq277/raveydavey_notts/BBCHDTestCard.jpg
For comparison, here's an SD card I made earlier:
http://i455.photobucket.com/albums/qq277/raveydavey_notts/MyTestCard.jpg
(Ignore the circle, obviously this is a 4:3 card but the limit arrows are still valid at 16:9, they represent 1% 2% and 3% overscan.)
My image is 576x720 overall but the test card itself is 702 pixels wide, this of course is the PAL standard. The extra pixels are there to accommodate the transitions to/from line blanking.
The TV seems to be assuming that this applies to HD as well i.e. if the transmitted width is 1440 pixels then the active picture should be 1440 * 702/720 = 1404.
I realise this is fairly academic in a world where some people watch 4:3 pictures stretched to widescreen, and others watch widescreen cropped the 4:3, but I'm just curious to know what the standard is...
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Dear DavidJRob
You must remember SD is a non-square pixel system and HD is square pixel so there is no direct correlation. The HD image is 1920 x 1080 i.e. 16:9 have a look at
http://www.bbc.co.uk/commissioning/tvbranding/picturesize.shtml
for a bit of light reading!
The test card (+/- a pixel or so) is the correct size and shape. Looking at your screen grab, it looks like a lot more pixels are missing and there is a slight vertical over scan too.
Andy
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Andy, thanks for your quick reply. This has confirmed that my TV is at fault in that it gives excessive width on HD. Fortunately I use a video processor (scaler) ahead of the TV. I have now created a separate setup memory on the scaler for HD only and I have used this to make the necessary compensating adjustments. Job done!
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Dear DavidJRob
Sounds like you had to create a setup to go between non-square SD pixels and square HD pixels. Only the 702-720 mapping to worry you know!!! (NO don't go down that road!)
Andy
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Don't worry Andy, I've been down that road and reached home! I tell the scaler that the image aspect ratio is 16/9 = 1.78 and that the display (TV) aspect ratio is (16/9) * (720/702) = 1.82. This causes the scaler to shrink the width and restore the correct display.
The scaler can memorise settings on a 'per input, per format' basis so the correction only applies to HD, SD is unaffected.
These scalers are not cheap but boy are they useful. I bought it initally to replace the TV's rather ropey deinterlacing and to take out the TV's non-adjustable 3% overscan. Now with this AR issue it's scaler to the rescue again!
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What time is the card shown? Where? Countless sites say how often it is shown and for how long but is it shown on the hour?
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Dear Reasonforit
To get the testcard and sync check signal. Check the off air time of the channel and add 1 hour. Set a manual record for 15 mins. The sync test signal goes out 50 mins later so set another recording starting 25 mins after the end of the previous. So if we are off air at 01:00, set the first recording for 02:00 - 02:15 and the second for 02:40 - 02:55. Each test signal is on for 90 seconds.
Andy
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Can anybody help a novice.
I have bought a Bush Freesat HD box and have the sync problem with BBC HD.
I am using the SPDIF output into my Whalfdale 5.1 amp.
All channels including ITV HD are in sync apart from BBC HD.
I have done the sync test on the BBC channel and it appears to be 2 frames early.
I can't alter the delay time on my amp.Do I have to purchase a new one?
I thougt it would just be plug in and go.
Don't really understand why ITV HD is ok and BBC is not.
Thanks for any help
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Dear maxsuzy
When you measure using the is the audio two frames early? If the audio is early you need to go into the set up menu for audio and adjust the audio delay. You haven't TV you have but most flat screens have a delay of 2 to 3 frames. Adjust the audio delay to 80ms and look at the test signal again.
I haven't managed to get a look at the Bush STB yet so I don't know what the default settings are
Andy
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Dear maxsuzy
When you measure using the is the audio two frames early? If the audio is early you need to go into the set up menu for audio and adjust the audio delay. You haven't said what TV you have but most flat screens have a delay of 2 to 3 frames. Adjust the audio delay to 80ms and look at the test signal again.
I haven't managed to get a look at the Bush STB yet so I don't know what the default settings are
Andy
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Now that's strange - my correction in preview put the post up twice!!
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Dear Andy
Thank you for your reply (in stereo).
The digital box is a BUSH BFSAT01HD.
Sorry the amp is not Whalfdale but GOODMANS HOME THEATRE GHC 56 PRO.
My TV is PHILIPS DV3.
The sync test is fine using the HDMI output and listening to the internal sound on the TV, but 2 frames EARLY going through the GOODMANS useing the SPDIF output, but only on BBC HD, all other channels are fine.
There is no option in the BUSH or GOODMANS to put in a delay.
Am I Bushed?
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Dear maxsuzy
Virtually all flat screens have a video delay due to picture processing. If you listen to the audio via the HDMI lead through the TV speakers, the TV delays the audio to match the video - this seems to be happening correctly from your description. The audio and video leaving your box are in sync and the TV compensates for its own processing delay.
If the audio is sent to another device via the SCART, HDMI or SPDIF output the audio is still in sync BUT your TV delays the video and unless the audio is delayed too it will be out of sync (ahead of the video).
The Humax and Sky HD boxes have a option in the audio set-up menu to add delay to the audio (SPDIF/optical out only on the Sky box). It is a variable delay because different TVs have different processing delays - from 20ms up to 200ms! The delay is adjustable in 20ms (1/2 frame) steps.
I have had a quick look at the Bush web site and found the instruction manual BUT I can't see an explanation of audio delay on the setting page
http://www.bushdigital.co.uk/downloads/Bush%20BFSAT01HD%20IB-Rev1-140308.pdf
Have a look and let me know what you find - if there isn't one I will be calling Bush on Monday!!!!
Andy
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Dear Andy
Thank you for your time.
There is definetly NO options to alter audio delay.
The only audio options are to alter the language between English,Welsh or Gaelic!
Thanks again
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Hi Andy
Did you have any luck with Bush?
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Dear maxsuzy
I have found out an audio delay is in the Freesat specification and have forwarded the details to Freesat. Will chase if I've not had a reply by Friday
Andy
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Dear maxsuzy
Freesat are looking into it
Andy
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Hi Andy
Any news from Freesat.
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Dear maxsuzy
I will try and find out how far they have got
Andy
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youve got to love HD.. when you think back to when we were kids... 4 channels c*appy picture and not alot of choice, but now? WOW!! the only problem we face as we all succome to the HD revolution is that when we get anything less that the "perfect" picture what will we do? lol :)
www.euronetwork.co.uk
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The new promo is on air now. Here are the timings you need if want to record the testcard and A/V sync signal.
1. Check the time the last programme of the day finishes
2. Set a manual record starting 25 mins later for 15 mins for testcard
3. Set another manual record starting 35 mins later (1 hour after the last programme finishes) for 15 mins for the A/V signalmins
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Hi Andy
I gave up on my Bush box and now have have a Humax box.
I now have no problem with sync.
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Thanks for letting me know maxsuzy. Do you still have the Bush? If so I will let you know when there is a firmware fix. Andy
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Hi Andy
No,managed to get my money back.
Thanks
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