[FFmpeg-user] Why isn't "-q:v <value>" mapped to "-x264opts?crf=<value>"?

[Lou]

On Sat, 16 Mar 2013 16:12:45 +0100
Nicolas George <nicolas.george at normalesup.org> wrote:

> Le sextidi 26 ventôse, an CCXXI, Carl Eugen Hoyos a écrit :
> > I don't think this makes the request to map q to crf invalid though.
> 
> True, but it should map to -qp, not -crf.

I don't think this is a good idea: a message informing the user that,
"-q:v is ignored with this encoder (libx264) and the default of -crf 23
will be applied" would probably be better. I'm not sure how often it
will be read, but it will be easy to point out to users requesting help
on the subject.

For general x264 use, -qp should not be used over -crf, and -crf is
probably what the users want even if they don't know it. Having them
use -qp when they are most likely equating it to -crf, or whatever
arbitrary "constant quality" concept they imagine, will end in
unexpected results and more time spent by us explaining the situation.