[FFmpeg-devel] [PATCH] libx264: support for BUILD >= 63

Michael Niedermayer michaelni
Wed Sep 17 18:40:11 CEST 2008

On Wed, Sep 17, 2008 at 04:40:54PM +0100, Robert Swain wrote:
> 2008/9/17 Daniel G. Taylor <dan at programmer-art.org>:
> > On Wed, 2008-09-17 at 09:44 -0500, Dion Galbreath wrote:
> >> The only worry I have is that when you use the latest x264 the bitrate
> >> might as well not even be there since it's not really used.. it will
> >> give you whatever it feels like. I have since been using  version 803
> >> which works great however these new changes now effectively kill that
> >> from working, and your forced to go back to new builds of x264 which the
> >> bitrate once again becomes a useless property...   any chance that that
> >> part of ffmpeg can be fixed, I'm guessing that at the time v803 was
> >> around ffmpeg was coded to use those properties but since 804 to now
> >> that property had changed? I never looked much into it, it's just hard
> >> to appreciate a fix in ffmpeg that degrades such a major encoding
> >> function as bitrate.....
> >
> > I've noticed that qmax now defaults to around 31, which means you cannot
> > achieve low bitrates that degrade quality beyond q=31. You can fix this
> > by passing -qmax 51, which should allow any bitrate regardless of how
> > bad the quality will be.
> >
> > I've had a quick look through the code to find where the lower qmax
> > value could be set but haven't had any luck. Anybody know anything about
> > this?
> This is an issue of reusing variables for all codecs. Prior to h.264,
> I think all quantiser ranges were 1-31. The qmax variable was
> naturally reused but its default value remains as 31 despite having
> its maximum possible value increased to 51.
> Regardless, there are a number of other poor defaults in FFmpeg that
> make using simple command lines for x264 and obtaining a good quality
> output not possible. However, we do have the possibility of using
> presets in FFmpeg now.
> Presets:
> http://rob.opendot.cl/index.php/2008/07/23/lc-aac-and-sbr-amr-nb-floating-point-presets/
> (Note: rc_eq has been removed from the public x264 API and no longer
> needs to be specified at all. Manually specify -threads 0 for
> automatic choice of the number of threads x264 should use.)

what about putting the x264 preset files in svn?

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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