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

Teemu Likonen tlikonen at iki.fi
Sat Mar 16 12:37:06 CET 2013

Nicolas George [2013-03-16 11:09:42 +0100] wrote:

> Le sextidi 26 ventôse, an CCXXI, Teemu Likonen a écrit :
>> It seems that with most codecs we can use "-q <value>" option to
>> define constant quality encoding.
> That is a common misconception. -q means constant quantizer, not
> constant quality; most codec do not have a constant quality encoding,
> constant quantizer is one of the best approximation but not the same.

OK. Thanks. The ffmpeg(1) manual page speaks about quality, though:

    -q[:stream_specifier] q (output,per-stream)
    -qscale[:stream_specifier] q (output,per-stream)
        Use fixed quality scale (VBR). The meaning of q is codec-dependent.

A user might expect that such codec-dependent option would be mapped to
the most obvious codec option, even though it might be slightly
different technical concept in different codecs.
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