To me it seems equally likely because of 8vsb multipath that you will need 1/4 rate FEC instead of 1/2 rate. And that more or less delivers only half the usable payload, pretty much eliminating even mobile AVC video if you started with only 1 mbps out of an ATSC stream.
- Tom Manfredi, Albert E wrote:
Bob Miller wrote:So if all you take away from the main program is 1 Mb/s how much of that is overhead and how much is for WHAT type of video, MPEG2 or MPEG4? How many bits for this MPEG2 or MPEG4 low quality program? If its MPEG4 you will need a new receiver right?The answer to the first question is in Table 6.1 of A/153. If you take away 0.917 Mb/s of the main channel, you can provide a 1/2 rate (over 2/3 rate) robust stream of 312 Kb/s capacity. So that gives you the extra convolutional code and the extra training sequences. Take away 1.8 Mb/s capacity, and you have 629 Kb/s of robust capacity, at 1/2 rate. And so on. This (or these) robust stream(s) would all be H.264 compression. You would need a new receiver no matter what, if you wanted to be capable of receiving the M/H streams. So sure, you would need a new receiver. Initially, an added STB could take care of this, more or less manually. But eventually, CE manufacturers could also build this in more intelligently. Users of HD radio, for example, know that when the signal of the main digital subchannel falls below a certain threshold, HD radios seamlessly switch back to the analog FM signal. Only for the main digital subchannel, though. The other subchannels are allowed to go silent for a bit of time, and they the radio reverts to the analog signal. This same behavior could be programmed into sets with built-in M/H capability without any huge problems. If there's only one robust M/H stream offered, then only the main subchannel will failover to the M/H stream. If more M/H subchannels are offered, other streams would also be allowed to fail over. Bert----------------------------------------------------------------------You can UNSUBSCRIBE from the OpenDTV list in two ways:- Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.
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