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

Nikolaus Rath Nikolaus at rath.org
Thu Jul 10 15:16:49 CEST 2003

Jonathan Rogers <jonner at teegra.net> wrote:
> Nikolaus Rath wrote:
>> 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.
> The default function actually is "tex^qComp" according to the
> manpage. Read it, you'll like it.

I've read it, really.

>> Maybe you can say a bit about the return value of the function? How
>> does the rate controlling work?
> I don't know the all the details, but the manpage does say that if the
> function has a value of 1, bitrate will be constant and if it has a
> value of "tex" (texture complexity) there will be constant
> quality. Clearly, the closer qComp (or vqcomp) is to 1, the more
> constant the quality will be, since n^1=n.

Yes, that's clear. But what kind of value is "tex" Is it in a certain
range (0 - 1)? What happens if I set vrq_eq=0.5? What the manpage
actually says is that a return value of 1 means constant bitrate and
some other value ("tex") means constant quality. Nothing more. You
can't really customize the function with these informations. What is
the allowed range (and scale) of return values and how do they
influence encoding? What scale and in what range are the mentioned


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