[XviD-devel] current rate control algorithm

[Zhang Fan]

Thanks a lot! :-)

-----Original Message-----
From: xvid-devel-bounces at xvid.org [mailto:xvid-devel-bounces at xvid.org] On Behalf Of Michael Militzer
Sent: 2005年5月23日 19:07
To: xvid-devel at xvid.org
Subject: Re: [XviD-devel] current rate control algorithm

Hi,

the XviD rate-control algorithm is a rather simple, self-developed approach.
For both the one- and two-pass rate-control algorithm, a constant picture
quality is the most important goal. Therefore, only the frame quantizer
parameters are modulated to reach a given target bit-rate and no macro-block
level rate-control is employed in order to achieve a consistent picture 
quality within one frame. Also, the frame quantizer distribution is kept as
smooth as possible in both the one- and two-pass algorithm in order to avoid
fluctuations in perceived quality. Therefore, also the one-pass algorithm
is a VBR/ABR approach and designed for storage and not for e.g. real-time,
low-delay video streaming.

Since rather large rate-control errors can occur by design (and are then
compensated over a longer period) due to the smooth quantizer distribution 
and the aim for constant picture quality, the employed rate-model is also
rather simple. XviD assumes that the coded texture bits for a frame behave
inversely proportional to the frame quantizer and that there's a rather
high correlation of the R(q) curves between temporally adjacent frames. This
is not perfectly true but is very simple and works reasonable well for VBR 
rate-control.

bye,
Michael


Quoting ÕÅ ·« <zhangf1979 at hotmail.com>:

> Hi, all
>     What is the rate control algorithm employed in the current XVID codec?
> Is there any related paper or other documents?
>     Thanks!
> 
> -Fan
> 
> 
> _______________________________________________
> XviD-devel mailing list
> XviD-devel at xvid.org
> http://list.xvid.org/mailman/listinfo/xvid-devel
> 




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