[FFmpeg-user] -crf ignored

[Etienne Buira]

On Wed, Jun 01, 2011 at 03:09:30PM +0100, Paul Gardiner wrote:
> Hi,
> I've been using this command:
> 
> ffmpeg -i <input file> -f mp4 -vcodec libx264 -crf 18.0 -acodec ac3 -ab 
> 160k <output file>
> 
> and it works to some extent, but the report on stdout/stderr says
> that it is using crf=23.0. The results support 23.0 being used,
> plus if I change the value I pass in, it has no effect on the file
> size or quality. Can anyone tell me what I'm doing wrongly? I
> can easily supply more info if that helps.
> 
> Paul.

Hi.

This is because of the weird way libx264 options are handled.

You're best bet is to use presets (-preset, look at x264 --help to see
which exists and what they do).