[opendtv] Re: Food for thought
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 22 Feb 2007 09:04:12 -0500
At 2:35 PM -0500 2/21/07, Manfredi, Albert E wrote:
I wonder why there's so much resistance to this notion. After all, we
knew all along that one of the biggest improvements allowed by H.264 was
to move the I frames further apart, and we knew all along what that
probably meant for practical implementations. Right? It should not be
such a big surprise that the savings would not be as much as
theoretically possible.
Here we go again with another Bertclusion that is completely unsupportable.
I-frame spacing has little if anything to do with the improvements in h.264.
The major gains in h.264 come from:
1. Replacement of the 8x8 DCT transform with a 4 x 4 integer-based transform;
2. The ability to optimize the transform for different source
frequency content, improving the quality of the quantization results;
3. Significant improvement in the tools for block-based motion
compensation, improving prediction efficiency and accuracy;
4. A deblocking filter to reduce the visibility of excessive quantization.
I have been conservative in my estimates of the improved efficiency
of h.264 versus h.262. Most of the published papers suggest a 2x
improvement. As the quality of h.264 encoders improves, it is likely
that this expectation will be met.
Not only that, but it should be a relief for broadcasters. They can
charge ahead without having to think they are so heavily compromised.
The spin doctors might be disappointed, but those who depend on this
stuff for a living should instead breathe easier. No excuse to sit
still.
Broadcasters who are actually thinking about charging ahead are
looking to h.264 and other evolutionary improvements to support their
business models. Broadcasters who are in retreat and choose to rely
upon alternative distribution platforms have no reason to care.
Regards
Craig
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