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SteveBagley

Listed below are comments made by SteveBagley between Wednesday, 24th September 2008 and Friday, 18th September 2009.

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Picture Quality on BBC HD: a response 09:00am on 18 Sep 2009 "Trouble is a lot of complaints are necessarily down to the encoders."

Of course I mean, not necessarily down to the encoder above...

Steve
Picture Quality on BBC HD: a response 08:49am on 18 Sep 2009 "but with less picture redundancy due to the bandwidth cut. By the time this signal reaches viewers, who will have data loss (surely it's impossible to avoid with broadcast transmission?), the decoder has to do the best job it can with what it's received."

The DVB-S transmission standard includes error correction, so reception is either perfect, or it'll break up into blocks. The Signal Quality meter on the box usual shows how hard the error corrector is having to work.

" In this case though, they really need to listen to the complaints instead of nodding along pretending to listen."

Trouble is a lot of complaints are necessarily down to the encoders. There have been some for example about the picture going soft when things move. This is a function of the way TV works and happens in SD, HD and at 4K. I saw a 4K (well, 2.8K in reality) JVC prototype on monday at IBC directly feeding a 4K LCD filming a model trainset. The image was staggering on the things that don't move, but the train itself was a blurred mess. There's a BBC research paper that shows that to keep HD resolution on moving objects requires 300p at least for HD.

Steve

Steven
Picture Quality on BBC HD: a response 08:18am on 18 Sep 2009 The real test of BBC HD's encoders will be tonight, when Strictly Come Dancing is shown. Firstly, the images should be very clean entering the compressors coming straight out of TC1 never having touched a compressor. Secondly, the material -- very fast motion and sparkly dresses -- is an absolute killer for any compression system.

It'll be interesting to see how it looks, but based on material seen so far I suspect it'll pass with flying colours and better than previous years encoders.

Steven
BBC HD: Picture Quality and Dolby Research 09:31am on 18 Aug 2009 ""Can anyone record Eurosport and BBC HD athletics and compare the same picture? (Does Sky HD allow twin recording?) I don't have Sky otherwise I would try to do it. It seems odd to say both pictures are the same quality when Eurosport has twice the bitrate to work with."

Remember BBC HD is 1440x1080 and Eurosport is 1920x1080 -- that means there's 75% of the data going into the BBC compressor and so less bits coming out :)Mind you it will also mean the BBC's arefacts are about 33% wider. MY own comparisons between Eurosport and BBC HD point to most of the problems being upstream of either of them. One wonders if it is coincidence that an episode of House from Sky one take up 4% of my Sky+ box and an episode of Rivers takes up 3% :)

Which leads me to a question to Andy Quested, have you considered running BBC HD at 1920x1080 rather than 1440x1080 but low-pass filtering it to remove the extra detail? (i.e. above 720cycles per picture width) I don't think it'd affect the bitrate needed (there'd be no extra entropy to encode) but it might reduce the visible size of the artefacts somewhat.

Steven
BBC HD: Picture Quality and Dolby Research 10:25pm on 16 Aug 2009 The BBC are planning for 1080p50*. Stop panicing :) They've also been doing a lot of research into how to handle it (the first time I saw 1080p50 was at the BBC R&D display at IBC in 2007), including developing hardware to let them use it in existing HD infrastructure and new codecs that would allow it to be transmitted to the home.

But this doesn't mean that Sky or the BBC are going to be broadcasting it anytime soon though. The biggest problem is consumer-level silicon to decode it -- it doesn't exist yet and when it does it is likely to be expensive.

Steven

* See http://www.bbcstudiosandpostproduction.com/about/archive/080826_hdtc4.html
BBC HD: Picture Quality and Dolby Research 9:03pm on 14 Aug 2009 "- Those three programmes (Proms, GW and Tom Jones) that you keep citing are undemanding programmes for HD transmission - would you agree? "

Actually Gardener's World is likely to be one of the most challenging programmes for any codec to compress, it's basically full of high-detail random motion in just about every shot and interlaced, which is just about deadly for any codec and this one is holding up rather well. (I know of someone who uses a shot of a field of wheat to demonstrate encoders going wrong at training sessions). It's a shame in many ways that 'Strictly Come Dancing' isn't on at the moment, since that would be a very good stress test on the codec. The pictures should be uncompressed from the studio so free from artefacts but all those sparkly dresses and fast motion should be enough to test any codec to destruction.

Comparing bitrates really is meaningless unless you know all the other variables involved. So comparing ITVHD or Sky Sports's bitrate to the BBC's is meaningless (in terms of picture quality) unless you know all the variables involved are. For instance, Sky Sports HD is encoded at 1920x1080, while BBC HD is encoded at 1440x1080 (a sensible decision as up until recently 90% of HD sources, on any channel, are likely to originate as 1440x1080) this means that for same level of compression, Sky Sports is going to need more bits than BBC HD. And its not as if the the previous BBC HD encoders were perfect. They really struggled with credit crawls against black at 16.5Mbps (quite often you'd get tiny splats of magenta or green squares for a single frame where it forget to encode part of the image), for instance.

Having spent the last hour and a half watching BBC HD, I'd say 99% of the picture quality issues I could see where happening higher up the programme chain than the final encoder (e.g. the detail enhancement on Britannia was set to high during the shoot).

Steven
BBC HD: DOGs Update 10:21am on 21 Oct 2008 Excellent News...

Although may I make a suggestion? Part of the problem I have with the DOG is not so much the translucency level as the position at the top of the screen. Shows tend to be framed so that the eye is drawn to the top of the screen and so the DOG sticks out like a sore thumb since it is constantly in your eyeline.

Is it possible that you could follow the US model and move the DOG to the bottom-right? Here it would still perform the same channel branding solution, but would be a lot less distracting in the bottom-right, and wouldn't have to be moved when there was sport on!

Steven
(PS. PVR worked, both Heroes and Silent Witness great!)
BBC HD: What Works Best? 7:17pm on 24 Sep 2008 Indeed, we have the interesting situation that Silent Witness episode 1 on WEds, followed by Heroes episode 2. With Heroes episode 1 on Sunday...

For people like me who want to watch both Heroes and Silent Witness, all in HD, it presents a bit of a scheduling nightmare. The only option seems to be to watch Heroes on BBC2 in SD (ugh -- I try and avoid SD channels as much as possible these days, my TV is almost permanently tuned to BBC HD), turn over for episode 2 in HD, and then watch ep 1 in HD on Sunday. Silent Witness has an HD repeat on Saturday. It's ok for me now, as I've recently sold my soul to Murdoch so can use SkyHD to reorder the shows into a sensible order, all in HD, while trying to avoid any discussion at work of either. However, for those who are using Freesat (and have no PVR option) the situation is less than ideal.

Surely the best option would have been to simulcast Heroes with the BBC2 transmissions, and delay Silent Witness to 2145. (Although, I can see that the viewer demographics for the two shows would suggest the current schedule -- Silent Witness being likely to skew to an older audience who want an earlier bedtime :))

Steven,

Confused of Nottingham

PS. Keep up the good work, as I said before BBC HD is the channel that gets the vast majority of my viewing these days and while it has the current mix of shows I can't see that changing.

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