[opendtv] Re: (S) DTV adaptors available for less than 50 euros in France
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 22 Sep 2005 11:02:53 -0400
At 6:54 PM -0400 9/21/05, Manfredi, Albert E wrote:
>Craig Birkmaier wrote:
>
>> Ultimately, the greatest potential for further
>> gains in compression efficiency will come from
>> improvements in the ability to predict B-frames.
>> The good news is that what we are doing today is
>> still VERY CRUDE - as more MIPs become available
>> it will be possible to further refine the
>> prediction routines.
>
>This seems logical.
>
>In my mind, the even better news, from a standpoint
>of compatibility, is that the improvements made in
>predicting B frames should also apply to MPEG-2.
>After all, the cruder they are today, the more they
>have a potential for improvement.
>
>For systems that won't jump to AVC quite so quickly,
>such as Aussie and US DTT, and digital cable, this
>could breathe some extra life in the existing
>standard.
To a very large extent, this has already been done with MPEG-2. This
year at NAB, Snell And Wilcox offered an MPEG-2 pre-processor based
on their standards convertor technology. There is some room for
application of these techniques, but the gains are probably going to
be a few percent at best. The main reason is that there is no way to
improve prediction accuracy beyond what is possible in an MPEG-2
decoder. Issue like the macroblock size, the impact of the DCT on
small area distortions, and the accuracy of motion vectors limit what
is possible.
For example, H.264 allows for 1/4 pel accuracy for motion vectors
while MPEG-2 is limited to 1/2 pel. The H.264 algorithm allows for 4
x 4 coding blocks, which further isolates the energy in the block
limiting the negative impact on small area distortions that causes so
many problems in MPEG-2; this works hand-in-hand with the more
accurate motion vectors, allowing the decoder prediction to be more
accurate. With MPEG-2 you may know where the pixels are supposed to
be, but if you can't put them there due to the limits on the encoding
tools, you cannot do a better job.
Bottom line, you can only work around these limitations through more
clever encoder designs - in the end, you must live with the limits of
existing decoders. This is one case where periodically replacing
hardware based decoders can make a huge difference.
Regards
Craig
----------------------------------------------------------------------
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.
Other related posts:
