[Ffmpeg-devel] [PATCH] flacenc - rice param search

[Michael Niedermayer]

Hi

On Tue, Jun 27, 2006 at 10:38:21PM -0400, Justin Ruggles wrote:
> Michael Niedermayer wrote:
> > Hi
> > 
> > On Tue, Jun 27, 2006 at 02:27:06AM -0400, Justin Ruggles wrote:
> > 
> >>Hello,
> >>
> >>Here is another update for the FLAC encoder.  I only added a few things,
> >>but it's still a pretty large patch.
> >>
> >>1) search for optimal rice parameters and partition order. i also
> >>modified the stereo method estimation to use this to calculate estimated
> >>bit count instead of using just the pure sums.
> >>
> >>2) search for the best fixed prediction order
> >>
> >>3) constant subframe mode (good for encoding silence)
> >>
> >>Note that the regression test for the decoded wav file also changed.
> >>This is due to FFmpeg's FLAC decoder truncating the file, which it did
> >>before anyway...just at a different cutoff point.  The generated FLAC
> >>files are still 100% lossless.
> >>
> >>With this update, FFmpeg's FLAC encoder has speed and compression
> >>somewhere between "flac -1" and "flac -2".  On my machine, it's about
> >>15% faster than "flac -2", and about 10% slower than "flac -1".  The
> >>encoding parameters are identical to "flac -2" (fixed predictors, 1152
> >>blocksize, partition order 0 to 3).
> > 
> > 
> > applied
> > 
> > [...]
> > 
> 
> Great! Thanks. :)
> 
> Now I have a question. I want to eventually add capability for the user
> to specify the compression level. Would it be okay to use "-aq", which
> uses avctx->global_quality, for this purpose?  I know it isn't really
> "audio quality" since it's lossless, but it is compression quality, and
> this seems like the simplest solution to me.

no, quality is a distortion vs. bitrate thing not speed vs compressionrate

you can either add a option for every indvidually switchable thing or a
single "compression level", later would certainly be usefull for using 
external libs in ffmpeg too

also note that nothing prevents us from adding lossy support to flac, after
all the syntax just stores compressed samples, they dont have to be identical
to the source ...

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
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