[MPlayer-users] Re: variable bitrate, fixed quality

Nikolaus Rath Nikolaus at rath.org
Wed Jul 9 23:28:03 CEST 2003

Jonathan Rogers <jonner at teegra.net> wrote:
>>>They're explained in the mplayer man page.
>> Yes. But an explanation like
>>                  vqcomp=<value>
>>                      quantizer compression,  depends  upon  vrc_eq  (pass 1/2)
>>                      (default: 0.5)
>> isn't really helpful if you aren't an MPEG developer.
>> Your explanation below is indeed very good. I think that this type of
>> explanation should be in the manpage.
> It is explained mathematically in the entry for vrc_eq. The default
> function is "tex^qComp", which means that if vqcomp is 0, the
> ratecontrol function always returns 1, meaning constant bitrate. If
> vqcomp is 1, bitrate varies directly with texture complexity, meaning
> constant quality. Understaning of algebra is necessary, but it is
> probably necessary anyway to understand something inherently
> mathematical like video encoding.

Of course, this makes sense. But unfortunately the manpage doesn't say
what the rate control function actually is and what it can return. So
even if you understand the function you won't have the slightest idea
in which way this modifies the codecs behaviour.

Maybe you can say a bit about the return value of the function? How
does the rate controlling work? 


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