[FFmpeg-devel] [PATCH] libx264: support for BUILD >= 63
Wed Sep 17 20:04:32 CEST 2008
On Wed, Sep 17, 2008 at 06:20:38PM +0100, Robert Swain wrote:
> 2008/9/17 Michael Niedermayer <michaelni at gmx.at>:
> > 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?
> Can do. Shall I make a presets dir and put them in there? Or ffpresets
> or something like that?
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Thouse who are best at talking, realize last or never when they are wrong.
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