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

[Michael Niedermayer]

On Tue, Oct 26, 2010 at 04:33:00AM -0700, Jason Garrett-Glaser wrote:
> On Tue, Oct 26, 2010 at 4:26 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> > 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 ...
> 
> But you're not doing the second part (the variable precision)! ;)

applied patch, ill look into variable precission tomorrow

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

If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20101027/376b4819/attachment.pgp>