[FFmpeg-devel] [PATCH] FFV1 2pass initial range coder states

Jason Garrett-Glaser darkshikari
Tue Oct 26 04:32:10 CEST 2010

On Mon, Oct 25, 2010 at 7:19 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> Hi
> patch below uses 2 pass to find approximatly good initial states (not global
> optimal, that can be done too and i might try)
> foreman with very small gops like 1 gop == 1 frame gains about 11% in terms
> of compression.
> I will apply this (+ any cleanups/bugfixes i stumble accross) soon

Er... why does this help?  It writes EVERY SINGLE CONTEXT as an
initial state, which should have an equivalent cost to adapting from
the 50/50 state over the course of the video.

Or does this help because at the start of each gop, the contexts are
reset, forcing us to re-adapt each time?  Couldn't the same kind of
benefit be had via some other method, like decoding the first frame of
the video to infer the contexts used for other gops?

And for that matter, could the initial states be compressed, or lower
precision, or interpolated from fewer values?

Dark Shikari

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