[MPlayer-dev-eng] [PATCH] fix for ve_xvid4 fixed quantizer modeproblem

[Ivan Kalvachev]

Commited

I'm sorry for this stupied bug :(

Wish You Best
 Ivan Kalvachev
iive

Michael Neuhauser said:
> Hi, all!
>
> Fixed quantizer mode does not work properly with the XviD 1.0 export
> module libmpcodecs/xvid4.c: With the command
>
>   mencoder in.vob -o out.avi -oac copy -endpos 10 -ovc xvid \
>     -xvidencopts fixed_quant=2:psnr
>
> (i.e. encode 10 secs with xvid at a fixed quantizer of 2 and generate
> psnr stats), the following quantizer histograms can be obtained from the
> psnr_* files:
>
> original mencoder (cvs HEAD of 2004-07-13)
>
>  Q     #
>  1    48 (20.3%) ************
>  2    70 (29.7%) ******************
>  3    86 (36.4%) **********************
>  4    32 (13.6%) ********
>
> cvs-mencoder + attached patch
>
>  2    82 (34.7%) *********************
>  4   154 (65.3%) ****************************************
>
> The latter being correct (q=4 values because of B-frames).
>
> An inspection of libmpcodecs/xvid4.c and
> xvidcore-1.0.1/src/plugins/plugin_single.c:rc_single_before() revealed
> that the fixed quantizer zone parameters base & increment are set to 1/q
> instead of q (for fixed_quant == q) in set_create_struct() (i.e. base
> has to be set to the denominator of q, not the numerator as it is done
> in cvs).
>
> Regards,
> 	Mike
> --
> Dr. Michael Neuhauser                phone: +43 1 789 08 49 - 30
> Firmix Software GmbH                   fax: +43 1 789 08 49 - 55
> Vienna/Austria/Europe                      email: mike at firmix.at
> Embedded Linux Development and Services    http://www.firmix.at/
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