[x264-devel] [PATCH] Relaxed parameter checking at encoder/encoder.c

[Jason Garrett-Glaser]

2010/12/11 Marco Aurélio Graciotto Silva <magsilva at gmail.com>:
> Dear x264 developers,
>
> Lately, I'm trying to compress some movies using MPEG-4 AVC
> Predictive Profile (aka lossless compression). I wasn't using
> x264 directly, but FFmpeg. Then I strumbled across an issue
> regarding some parameters that FFmpeg defined by itself and
> which, when using x264 in lossless mode, results in an error:
> 'broken ffmpeg default settings detected'. Further information
> and instructions to reproduce this are described at
> http://permalink.gmane.org/gmane.comp.video.ffmpeg.user/29323
>
> I traced the issue to encoder/encoder.c, more precisely at
> line 471, in a block of code that, as its comment says, "Detect
> default ffmpeg settings and terminate with an error."
>
> From the FFmpeg side, I can workaround this by setting
> some parameters (such as qmin, qmax, etc), even though
> such parameters will be overriden by x264 (because of the
> lossless mode).
>
> However, a better solution would be to, in the code that x264 tries
> to detect FFmpeg defaults, ignore some parameters that will be
> overwritten anyway in lossless mode. I created a patch
> x264-lossless-ffmpeg_parameter_check.patch and it worked
> just fine here. Is it okay?
>
>
> Regards,
>
> Marco Aurélio

As I already told you on the ffmpeg thread, this is not a bug; this is
entirely intentional behavior.  x264 uses the broken defaults of
ffmpeg to detect when a user has not set a -vpre.  Relaxing these to
allow users to remove parts of the ffmpeg preset is entirely
contradictory to the purpose of said code.

Patch, again, rejected.

Jason