Bob Miller wrote: > Your logic seems to say, if I understand it, that is by > switching to MPEG-4 and doing HD only they will sacrifice > 3 or 4 SD MPEG-2 program channels per HD program channel. Yes, that is what the BBC wrote. > Following that logic though you could do 2 HD program > channels with MPEG-4 and have either 3 SD or 1 SD program > with MPEG-2 also. In a 23.42 Mb/s channel (64-QAM, 2/3 FEC, 1.16 GI), the BBC would be able to pack anywhere from 6 to 8 SDTV streams, since these SD streams are average 3 to 4 Mb/s. Instead of 6 to 8 SD streams, in that same 8 MHz channel they could transmit 2 HDTV streams. They did not give an actual range of bit rates for HDTV, only stated that 19.5 was the maximum. The important point that everyone prefers to ignore, but only using words and never numbers, is that this is not substantially different from MPEG-2. I'm sure the HD would be subjectively better with H.264, but we are NOT talking about a big difference, *from what they report*. If we assume that "3 to 4 SD streams" can translate to 9 Mb/s for HDTV H.264 as a very bare minimum, then in the 23.42 Mb/s you could potentially transmit two HD streams and have 5.42 Mb/s left over for SDTV. Again, not substantially different from MPEG-2, where you can also use an average of ~9 Mb/s for a 24p HD stream, as a minimum. > But if you went completely to MPEG-4, then you could have > the 2 HD program channels and 6 or 2 SD program channels > also They didn't say what SD bit rates were possible with H.264. But from the Sky comment, you might say that 5.42 left over b/s (from two bare minimum HD streams) could either be used for 2 SD streams with MPEG-2, or 3 SD streams with H.264. But these would be low quality SD, less than 3 Mb/s for MPEG-2. This is everything at the bare minimum. If the HD streams were sports, for instance, or one of them was, you wouldn't have this option. 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.