[FFmpeg-user] -crf ignored

[Paul Gardiner]

On 01/06/2011 16:56, Etienne Buira wrote:
> 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).

Thanks. First I thought that wouldn't help because I tried -preset 
medium and it was producing a far lower bit rate than I was getting
before, but strangely, adding -crf after the -preset arg works
and the crf value is honoured.


And thanks to David for suggestions too.

Cheers,
	Paul.