Originally Posted by andgarden
Could broadcasters do the following: devote 2MB/s to a 480i MPEG-2 feed for those using converter boxes and use the rest of the ATSC bandwidth for h.264? Would two 720p feeds about about 8MB/s look acceptable using h.264?
I'm not sure that would be acceptable to the mainstream consumer would it?
Many have bought HDTVs with built-in ATSC/QAM demodulators and HD MPEG2 decoders - to deliver HDTV onto their HDTV display.
If this kit now only delivers 480i (whether 16:9 or 4:3) SD pictures, and they are required to buy an H264 compatible external set top box to continue to get HDTV from the main station, then surely that would cause uproar?
There is an argument that the subchannels could shift to H264 - reducing the requirement for bitrate - but the economics of this don't stack up. Who would buy an H264 external decoder just to watch a sub-channel?
It's a problem.
The US ATSC OTA system is really only capable of delivering one HDTV signal at an acceptable quality.
If you want to deliver more than one HDTV signal in quality you need to change both modulation and encoding systems to more modern variants - but this would require ANOTHER change-over - and the current one isn't finished yet.
We're having a slightly different debate in the UK.
When we introduced DTV in 1998, around the time the US did, we went for MPEG2 SD 16:9 rather than HD 16:9, and thus we multicast as standard - and new BBC, ITV and Channel Four stations launched (these are channels with reasonable schedules and some carry quite a lot of original production - they aren't infomercials, local news re-runs, weather loops etc.) and they now get not insignificant audiences. We have 6 RF channels dedicated to DTV in each region - carrying around 90 distinct TV, Radio and data services.
However we don't have HD OTA. Yet.
Because we haven't got any HDTV MPEG2 receivers in the market yet - we are able to introduce a new DTV standard for HDTV. We're going H264 and using DVB-T2 - which delivers 36Mbs per UK 8MHz RF channel (cf 18/24Mbs now in the UK and 19.2Mbs in a 6MHz ATSC channel) - and at the moment the plan is to re-locate the services from one of the six SD 18/24Mbs channels to the remaining five and switch the sixth channel to the new HD standard, when analogue is switched off in that region. (In some regions the HD system is going to be broadcast on a temporary 7th RF channel where this is available prior to analogue switch off)
The US is in a more tricky position. By introducing HD in the 90s, it chose an early system, which is now looking dated in tech terms. However it is capable of good results if it runs just as a single HD stream... But broadcasters want to increase their revenue and are compromising picture quality as a result.
On the other hand - the US switching early undoubtedly drove the HD production market - and other countries probably wouldn't be switching NOW if the US hadn't switched 10 years ago...