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The Scourge Of SCART

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Andy Quested Andy Quested | 10:44 UK time, Tuesday, 14 October 2008

I thought it was time to give you a quick update on some of the technical issues that have come up around BBC High Definition over the last couple of months and what has been happening since the Olympics.

We have taken some time to look at a lot of the issues bought up by you and a few of the things I wanted to investigate myself.

Audio

The big issue of 5.1 / 2.0 switching. Thanks to everyone commenting on this blog and elsewhere to give feedback while we were trying switching options. It's now working, but not as well as we would like - for example, we still have more work to do before we can move between stereo and surround programmes without having to put silence between them.

When things are changed, then no matter how well you plan there's always something that tries to catch you out. While we where upgrading some of the Dolby equipment, we came across an "interesting" problem - fortunately, it didn't go to air!

Some of you may know that we use Dolby E to move surround sound and metadata through the playout area (and if you read my post about the Eurovision Song Contest, you will know how important the metadata are!).

Dolby E is a frame-based data stream - in other words, it comes in packets timed to the video signal. If any packet is corrupt or mistimed, the whole frame is invalid. Some devices can deal with this, but others don't recognise the corrupted package for what it is and think it's a chunk of PCM audio. A Dolby E packet contains a lot of data and if any device treats it as digital audio, it comes out as a very loud "splat". Fortunately for your ears, it's only around 40ms long - this is, however, somewhat unfortunate for your speakers!

The work to get surround and stereo to work together is still going on and I will update whenever we have more to report.

Picture quality

Danielle talked about some of the quality issues you reported on Friday Night With Jonathan Ross in her What Works Best? post. We have looked at the whole studio, post-production and transmission chain to see what was causing the problems.

There were a couple of processes that made some of the cameras quite noisy: these have now been addressed and last Friday's show (October 3rd) looked a lot better, but we are still trying to find ways to improve the quality across all programmes.

Picture quality issues bring me to another story. I'm sure you are getting used these stories from my previous posting about the thoughts of my daughter - who, by the way, is now officially a stroppy teenager!

Actually, this is about a trip to pick her up from one of her school friends' and getting invited in for a coffee while I waited. "You work for the BBC" was the opening from the other dad - "do you have anything to do with this high definition stuff?". My answer was a bit muted, thinking, "what's next?"! He then said he didn't see what all the hype was about: the pictures were a bit better but nothing to get excited about.

I asked the usual questions about type of TV and how he received HD. As expected, it was a new 50" plasma - quite a nice one actually, and a Sky HD box with the full subscription package. "Come and have a look" - so, shoes off, coffee mug in hand, we go through.

He turned the telly on and, after wincing from the volume of one of the music channels left on by his daughter, we went to the BBC HD channel, which looks - to put it politely - "crap".

scart_computerjoe430.jpg
Image by Joe Anderson on Flickr under a Creative Commons licence

At this point I had to put down the coffee mug and admit to my job title. The diagnosis took about five seconds - so, trying to look very professional, I reached round the back of the TV and pulled out the SCART lead. After the usual bumps and flashes, the pictures re-established themselves looking like the high definition I would expect.

There was a short "Ah!" and we went back to coffee and chat about the length of time two teenage girls can spend on a phone after they've only just been at school with each other!

This was not the first instant repair I've done and I doubt it will be the last. One of the things I'm always doing is taking TVs out of "Vivid" or "Dynamic" or some other mode that makes the screen hot enough to do toast on. Others changes include setting the contrast and brightness levels to something resembling normal and most important, turning the sharpness down to zero and finally setting all the picture enhancing modes to "off". That usually results in reasonable pictures on any telly and tends to make HD look like HD!

I'm not sure what to do about the SCART lead. It seems to be the biggest single quality filter in the chain, especially as the default setting for the SCART output on many set-top boxes is PAL. My recommendation is not to have them at all, but there are still a lot of devices out there that seem to need them.

Over the next few weeks, we are looking at some new cameras and field recorders: we will keep looking at picture quality issues as they come up and talking to Dolby about a better way to mix 5.1 and 2.0 programmes - please keep letting me know how it sounds at home. I have a Sony AV system, but I need feedback from as many systems as possible.

Also, if you know anyone with a SCART lead connected to their HD set-top box, either pull it out or make sure that the SCART switching menu option is set to "OFF"!

Andy Quested is Principal Technologist, BBC Future Media & Technology.

Comments

  • Comment number 1.

    The amount of people that either watch by SCART and wonder why the picture is bad are probably the same people who put the batteries in the wrong way around and then complain the remote doesn't work!

    Any update on the DOG/BUG and whether it will be making a dissappearance?

  • Comment number 2.

    Thanks for the very interesting article, but can I ask what is happening about the BBC HD lip-sync problem that has re-appeared over the last few weeks?

    Sometimes this is varying within programmes: for instance, during Strictly Come Dancing, the sound may be almost OK on the main parts, but way out when they cut to the rehearsal scenes.

    I understand that Humax were recently told by the BBC that the problem lay with their Foxsat receivers, but the fact that many of the complainants about this on Digital Spy and other forums are using other receivers, suggest that it is a transmission issue.


  • Comment number 3.

    How I agree with you about vivid mode. When I got my Sony KDL-46X2000 it was set in this mode and it was horrible. I switched off all the enhancements and used a Digital Video Essentionals DVD to set things up. There is a Blu-ray version available but I have not got it yet. Sky tranmits a Testcard which is very useful but it does not have a colour pluge.

    I think the public do need to be educated about setup. Prehaps you could make a program about setting up like the sky program.

  • Comment number 4.


    Jason97. Hope you should also find last weeks sync error has gone now. After the last equipment upgrade a 2 frame audio delay was introduced that was not properly compensated for in the video chain. This has been corrected. Andy

  • Comment number 5.

    Andy, you are undoubtedly the best blogger on the BBC!

    Can I suggest the BBC seriously consider making a concerted effort to educate people on "Getting the Best out of HD". I am thinking of a decent FAQ on the website, and perhaps most importantly, small video segments on the channel itself - perhaps between programmes and\or during the demo.

    Things such as turning visual enhancements off are seemingly counter-intuitive, and I shudder the think of the number of people, even tech-savvy people, who have under-performing HD setups as a result.

    The number of times I have heard the words "HD is over-hyped" leave me worried that this fine technology will die a death due to poor education and marketing.

  • Comment number 6.

    I was actually told by the Sky installer who upgraded me to HD all about the SCART lead issue. He said he was constantly removing them after getting calls from people complaining the picture looked rubbish. He was a proper Sky installer (in a Simpsons van). The subcontractor guys are a bit of a mixed bunch. Some are excellent, others are just whacking in kit and couldn't give two hoots of whether it's installed properly.

    Glad to see other issues are being resolved though. I love reading this blog, it's technical and suitably geeky for people like me!

  • Comment number 7.

    Hmm... not to sure what to think about the suggestion to remove Scart from the SKY HD boxes.

    For those of us with decent video processing (but not the one particular brand whose product can reconstruct the orignal interlaced signal from a badly de-interlaced progressive signal) its the only way to get 576i out the SKY HD box.

  • Comment number 8.

    Dear Thezapgun. I'm sure you're right, a good SD RGB signal is virtually unbeatable if you have the display to do it justice. As long as you remember to go back to the HDMI for the HD channels - many don't

    Andy

  • Comment number 9.

    Thank you for your blog andy!

    The same thing happens with virgin media wrt SCART. Many people get the box after their tvs or their tvs after the boxes. Some people then immediately plug scart in as that is what they are used to and you have to do this to put it in HDMI (unless you manual reboot) to change the menus. People then either assume it is now working in HDMI or get in a fluster as they know it isn't working in HDMI but can't get it to handshake by following the strange proceedure virgin have. I think it's a really big problem.

    The engineer that set up mine plugged in scart and hdmi and claimed it was in HD and then did a runner.

    It's always nice to hear about new equipment the beeb has and work going on to resolve problems with live events.

  • Comment number 10.

    This is a little goldmine of info - found courtesy of digitalspy.co.uk.
    I have been an HDTV viewer since about week 5 of Sky's service (due to box shortages) and was there when BBC tests with NICAM were starting.
    At present I am waiting some tree work so that I can get back to Sky - and suffer with Virgin cable and theie one HD channel - BBC HD!
    I believe they do some transcoding to MPEG2 because the picture is "softer" than I remember from satellite. The service also suffers from consant sound "farts" and blocking in small parts of the screen (HDMI connection). I have the sound going via optical - just something I have to live with until the trees are reduced....

  • Comment number 11.

    My Sony Plasma TV is pre-HDMI interface days. When Freesat first started I got a great picture HD picture using "Component" leads. Unfortunately the BBC decided to nobble early adopters of HD televisions by getting Humax to disable the Component interface. I returned my Humax box and now watch Freeview instead. I hate being penalised for being an early adopter of what was then a new technology (Plasma TV).

  • Comment number 12.

    Andy,

    Thanks for the blog: most welcome.

    Do you have any news of the HD DOG review the head of BBC HD said she was instigating to understand why it is needed?

    What is your Professional Engineering opinion of the current HD bit-rate used. Is this enough or should the higher rate used during the trials be used (I guess this will have a cost, bit might value for money?).

    I support the suggestion of providing a how to get the best out of your HD system video to be transmitted for us to record and used (a BBC HD test card would be welcome. I have used the Sky one.

  • Comment number 13.

    _paddy_ and Bill-Taylor

    I am hoping for an update/blog post from Danielle sometime next week.

    Nick Reynolds (editor, BBC Internet blog)

  • Comment number 14.

    Yet another entertaining and informative post from Andy. It's fascinating getting this level of detail from the BBC.

    The SCART experience echoes a similar tale of mine from a few years ago. Some friends had a large 4:3 set with Sky and they were complaining they were 'missing the sides' of Eastenders and were going to have to invest in a widescreen which they could ill afford to do with a newborn.

    2 minutes later setting the Sky box to 'letterbox' and they were happy as larry.

    Oh, and a Denon 1909 user who's amp is switching flawlessly betweeb 2.0 and 5.1 with no pops or crackles. V+, connected by HDMI.

  • Comment number 15.

    Good blog!

    With regard to the lip-sync issue, it's much better than a couple of weeks ago, but I would have to say it's still not absolutely perfect. I still perceive an ever-so-slight delay in the audio (maybe one frame's worth?) - noticed it on Silent Witness last night. It's certainly watchable now though, just a little annoying. Before, it was so bad that it was unwatchable.

  • Comment number 16.

    Dear abzerotolerance

    Thanks for the comment. We have now measured the AV sync error of the live programme chain to 1-2ms. This was checked via a test signal injected into the Strictly Come Dancing studio (last Thursday) passing through the chain to the transmission encoder.

    Programmes like Silent Witness are delivered on tape and go through a quality check before loading onto the playout server. These programmes have an AV sync tolerance of +/- 10ms (1/4 of a frame) as do many of the components in the chain. As you can imagine two or three units in a chain sitting at the same end of the allowed tolerance would cause a visible sync error. We continuously check the chain to make sure all devices are well within the manufactures tolerance to minimise this possibility.

    When the channel first started many of the video units were working "flat out" and often introduced a variable video delay and programmes would drift in and out of sync usually with audio ahead. Now processing power is much greater and any delay is more constant and predictable so I hope as we fix problems - they stay fixed!

    Andy

  • Comment number 17.

    A good blog Andy but you really could save yourself alot of time and effort. The reduction in birate over the last 132 months is unacceptable and is the main cause of the shocking picture quality on BBC HD.

    Jools Holland 12 months ago looked amazing. You guys lower the bandwith and what happens - yes the picture looks awful and not much better than SD.

    May i suggest the BBC does what is required and ups the birate to what it was. ITS SIMPLE. The BBC was without doubt the best looking HD channel 12 mths ago. Now its run by a bunch of people who dont seem to give a damn about its viewers.

    maybe you could proove me wrong and up the birate to what it was, but you guys at the beeb wont as it costs money.

    Anyone with a brain cell can work out most of the problems with quality are down to the major birate drop. its pathetic all the excuses we hear.

  • Comment number 18.

    A good blog Andy but you really could save yourself alot of time and effort. The reduction in birate over the last 12 months is unacceptable and is the main cause of the shocking picture quality on BBC HD.

    Jools Holland 12 months ago looked amazing. You guys lower the bandwith and what happens - yes the picture looks awful and not much better than SD.

    May i suggest the BBC does what is required and ups the birate to what it was. ITS SIMPLE. The BBC was without doubt the best looking HD channel 12 mths ago. Now its run by a bunch of people who dont seem to give a damn about its viewers (in my view).

  • Comment number 19.

    My concern at this blog is that it's coming from the angle that picture quality is all down to poor LCD tvs and people who don't know how to set up their HD tvs. Now I agree in part, that a lot of people don't know how to set up their tv.

    But what happens when you've got a decent new Panasonic plasma TV hooked up to BBC HD on Freesat? The answer - a lot of the time dreadful HD pictures

    This was last Friday night's picture quality on BBC HD 17/10/08:
    - Not Going Out - Extremely poor picture
    - Little Britain - Bad picture again
    - That Mitchell and Webb Look - was this even in HD at times?
    - Johnathon Ross - best of the bunch, but still poor

    The worst I saw over the weekend though was "the Verve" at Glastonbury on BBC HD. Lights, movement, smoke - what do you get? - a screen full of artefacts and a dreadful picture on a first rate plasma screen.

    Also take, the 30 second advert for the waterfall from Planet Earth - the last bit that has artefacts in it too from poor bitrate.

    It isn't just people's set ups in my view, its what's being transmitted in the first place, a very poor HD encoding.

  • Comment number 20.

    I have to agree with the people who have posted about the decreasing picture quality on BBC HD. I have noticed a steady decrease since I first started watching in September of last year.

    I have a 37in Panasonic PX70 plasma screen connected to my Sky HD box via HDMI (no troublesome Scart leads). My picture settings are not the rubbishy defaults such as dynamic.

    I know the picture quality problem is not my plasma's fault, because I get excellent results from Blu-ray and HD DVD playback.

    I also know it's not a problem with the Sky box because I get excellent picture quality when watching HD broadcasts on channels such as Sky One HD, Discovery HD and National Geographic HD.

    I am not an expert about bitrates but there is a perception that the ones used on BBC HD have been reduced over the past year and that this is, at least in part, the cause of the lower picture quality.

    If this is incorrect then I will bow to your superior knowledge - but I'd pose a further question:

    What on earth has the BBC changed since last year and when do they intend to retrace their steps and undo this dreadful mistake so that we can see their fine programme content in all its glory?

  • Comment number 21.

    I have to chime in and say compared to the other services on Sky HD the BBC's is bordering on appalling. I expected more from the BBC to be honest. Surely a simple increase in the bitrate would solve these issues in quality?

  • Comment number 22.

    Andy, a good blog and it is really interesting to hear the work you are doing behind the scenes, I will look forward to future updates.

    I agree with many posters that the PQ has lost its edge on certain broadcasts (unfortunately some of the posters are becoming a bit fanatical about it and it dilutes their very valid points).

    It is good to hear you are working on the issues, whatever they are.

    On a positive note I was very impressed with the transmission of Sunshine, the PQ was really good - proper HD as I would see it - what was even more impressive was the audio mix - it felt like a movie! 10/10 for audio on that one, I look forward to more like it in the future.

  • Comment number 23.

    Why isn't the BBC using the more efficent DVB-S2 system that would increase the bandwidth avaliable for BBC HD.

    Although that means moving 2 SD channels of the transponder it means the BBC can lease the spare space to another HD broadcaster and hold onto it for BBC HD 2 which will no doubt be avaliable by 2010 as the BBC wants all of its content in HD.

  • Comment number 24.

    Sunshine pic quality is superb, this should be a benchmark for all other HD programming. Generally, the 5.1 mix on my Yamaha sound system is really good.

  • Comment number 25.

    Only to comment that I was watching "Little Dorrit" Last week and although my Amp was showing a 5.1 signal, it was clearly only delivering left and right channel content. Centre and surrounds were missing.

    Looks like you've a bit more work to do on this audio problem.

  • Comment number 26.

    Dear FronArran

    What was the date 26/10 or 2/11

    Andy

  • Comment number 27.

    BBC HD Test card:

    Glad you found your black spot (Black level clip). I thought it might have fallen into the Hadron Collider and turned into a black hole.

    Just a couple of questions, which I posed in another forum:

    I was just wondering what frequencies each of the 6 grating segments represent (Do they start at 1 MHz or 3 MHz?)?

    What sorts of level are those black level dots suppose to be? 2% or 4% above black video level? To me it looks more like 10%!

    What are the ‘ire’ levels of the greyscale boxes? Are they 20,40,60,80 and 100?

    Is the test card image a true 1.78:1 aspect ratio? I’ve had to produce a slight overscan of approx 2% due to the SD digital channels showing vertical black bars at the sides of the image. I’ve adjusted the image size so that the white boxes, in the 4 extreme corners, are truly square. This way I assume correct aspect ratio. However, it just seems the circle becomes ever so slightly elliptical towards the top and bottom. Might just be me.

    BTW: If anyone is looking for a SMPTE colour bars try (Astra 2A 28.2E 11260V 27500).

    Keep up the good work!

  • Comment number 28.

    Dear delphiplasma

    My next blog is due out very soon with full details. We have one more test signal for AV sync to go up but we are still testing

    Andy

  • Comment number 29.

    Andy,

    Just wondered whether there needs to be some form of basic tutorial for the general public with regards help on basic settings, brightness, contrast and colour...etc?

    Reason I mention this, is because a friend mentioned he didn't know what all the fuss was about regarding HD. He said the colours were all gaudy, the contrast excessive...etc. The person in question has a high technology job position. I advised him to re-adjust the user controls to correct the image.
    I advised him that the majority of HD set box/TV usually have these OTT settings as default.

    Maybe some form of useful bite size "how to get the most from HD" text images could be squeezed in between the preview trailer loop? E.g. "tip" "Switch of any Dynamic controls"

    You could have around 10 Bite size text clips randomly spread within the trailer loop.

    Regards

  • Comment number 30.

    Dear delphiplasma

    Can you point your friend to the test card and :


    http://www.bbc.co.uk/blogs/bbcinternet/2008/12/a_christmas_present_from_the_h.html


    Andy

  • Comment number 31.

    Hi Andy,

    I've advised my friend, accordingly, how to get the best from HD. However, I was thinking about the rest of the population who have no idea. Little bite size screen images would start to filter into peoples mindS, sublimanally (No, I'm no Derren Brown!). Most domestic HD products have terrible default settings which are OTT, and not a lot of users understand that they can correct the image.

    I still hear a lot of people saying they cannot see what all the fuss is about HD.

  • Comment number 32.

    Thank you.. http://www.gelsesli.com/ sesli sohbet

 

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