[FFmpeg-devel] request for feedback on video codec idea
Paul B Mahol
onemda at gmail.com
Wed Oct 14 21:04:34 CEST 2015
Dana 14. 10. 2015. 20:42 osoba "Hendrik Leppkes" <h.leppkes at gmail.com>
> On Wed, Oct 14, 2015 at 8:08 PM, Roger Pack <rogerdpack2 at gmail.com> wrote:
> > Lacking a better place to debate this, I would like to ask some
> > questions on a video codec idea...
> > The goal is basically to create a very fast lossless screen capture
> > codec (i.e. in the input there will be lots of repeated "colors" of
> > neighboring pixels, not a lot of dynamic content between frames).
> > I have become aware of some "fast" compression tools like LZO, LZ4,
> > density, etc. It seems like they all basically compress "the first
> > 64KB then the next 64KB" or something like that .
> > My idea is to basically put pixels of the same position, from multiple
> > frames, "together" in a stream, then apply normal (fast) compression
> > algorithms to the stream. The hope being that if the pixels are the
> > "same" between frames (presumed to be so because of not much dynamic
> > content), the compression will be able to detect the similarity and
> > compress it well.
> > For instance, given 3 frames of video ("one after another" from the
> > incoming video stream), "combine them" into one stream like:
> > pixel 1 frame 1, pixel 1 frame 2, pixel 1 frame 3, pixel 2 frame 2,
> > pixel 2 frame 2, pixel 2 frame 3 ...
> > then basically apply LZ4 or density algorithm to those bytes.
> > The theory being that if there is a lot of repeated content between
> > frames, it will compress well.
> > The basic need/desire for this was that huffyuv, though super fast at
> > encoding (it basically zips the frame), seems to create *huge* files,
> > I assume because "each frame is an I-frame" so it has to re encode
> > everything each frame. And also the egotistical desire to create the
> > "fastest video codec in existence" in case the same were useful in
> > other situations (i.e. use very little cpu--even huffyuv uses quite a
> > bit of cpu) :)
> > Any feedback on the concept?
> > Also does anything similar to this already exist? (though should I
> > create my new codec, it would be open source of course, which is
> > already different than many [probably efficient] screen capture codecs
> > out there).
> > Thanks.
> > -roger-
> I can't really comment on the merits of this compression scheme, but
> note that you might have trouble with the ffmpeg API when handling
> such a codec, since every single data packet would result in X output
> frames (3 in your example) - this is not a scheme that avcodec can
> really represent well.
> On top of that, containers might have troubles timestamping this properly.
Well each packet would have several frames, I assume encode2 can handle it.
> - Hendrik
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