[theora-dev] Updated VP3 Document
Timothy B. Terriberry
tterribe at vt.edu
Fri Oct 10 00:20:29 PDT 2003
> Feel free to look it over and point out any glaring mistakes. I can't wait
> to see how much sense it makes to me in the morning. But I completely
> revised the DC prediction section so that it is almost entirely separated
> from any specific implementation details (earlier weakness).
Didn't read too deeply yet, but a few comments on the Theora differences
1) We plan to fix the frame orientation to conform to that used with VP3
before the beta (most likely in an alpha3). We want to preserve the
ability to transcode from VP3 losslessly, and there's no real reason to
keep two different orientations around.
2) Theora stores the prefix-free codes directly, in the form of a full
binary tree (this is a change from alpha 1, where the histograms used to
generate the prefix-free codes were stored).
4) Theora removes some of the unused bits in the VP3 frame header. There
are still 3 0 bits in keyframe headers (keyframe type, which is always
0, and 2 unused bits), but the others are gone.
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