[opendtv] Re: 5th gen receivers
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 23 Jan 2005 19:17:05 -0500
Manfredi, Albert E wrote:
> Can't you do that already with MPEG-2? For
> example, isn't that exactly what happens when
> MPEG-2 is used in a fixed bit rate mode? You
> get variable quality.
I think you get variable quality but only by decreasing the precision of
each frequency component of a block, not by decreasing the resolution
and total number of blocks sent. For instance, if you send 720p in
MPEG2 at only 5-6 megabits it will likely look worse than if you instead
scaled it down to 480 lines (or less) and scaled it back up for display.
It seems there is sort of a sweet spot resolution for each source and
bit rate. So it is probably better to vary both the quantization and
resolution IMHO.
- Tom
> Tom Barry wrote:
>
>
>>Thus I'd predict we eventually will have
>>compressed video that has a MAX resolution
>>but not a fixed one and we can then just
>>rate shape everything from a single source
>>to multiple targets such as sub-channels
>>and cell phones. Each step along the way
>>might discard a bit more as needed. But
>>the master archives would be pre-encoded at
>>highest quality
>
>
> Can't you do that already with MPEG-2? For
> example, isn't that exactly what happens when
> MPEG-2 is used in a fixed bit rate mode? You
> get variable quality.
>
> Bert
>
>
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