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

[Michael Niedermayer]

On Mon, Oct 25, 2010 at 11:01:02PM -0700, Jason Garrett-Glaser wrote:
> On Mon, Oct 25, 2010 at 8:10 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Mon, Oct 25, 2010 at 07:32:10PM -0700, Jason Garrett-Glaser wrote:
> >> 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?
> >
> > i suspect so. Also having slices in ver2 multiplies the initial state issue
> >
> >
> >> 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?
> >
> > That seems harder and i dont think this could reach the same benefit
> >
> >
> >>
> >> And for that matter, could the initial states be compressed,
> >
> > they are, better ideas are welcome
> >
> >
> >> or lower
> >> precision,
> >
> > will try
> >
> >
> >> or interpolated from fewer values?
> >
> > I tried replicating initial values from a smaller context set (no LL/TT based
> > contexts) and this didnt work very well
> >
> > either way storing all the states costs ~120kb this is negligible for a full
> > length movie. So its just short clips that would benefit.
> 
> Compression: golomb codes based on the delta from the previous
> context, or the arithcoding equivalent.

you arent reading the patch you comment about ;)
thats what iam doing already ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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