[MPlayer-users] Quality suffering with lavc

[Nico]

Hi,

I've been struggling with libavcodec for a lot of time; now it's time to 
ask the opinion of an expert, possibly Michael's.

Note: the problem I have persists even when using mpeg4 as codec.
I use the following script to encode to mpeg1 and I usually run it with 
bitrate 1150 (quite generous) and with pp=lb.


#!/bin/bash

INFILE=$1
BITRATE=$2
OUTFILE=$3
EXTRA=$4
SUBS=$5

shift 5

mencoder -nosound -ovc lavc -lavcopts 
vpass=1:vcodec=mpeg1video:vhq=1:vbitrate=$BITRATE:keyint=16:vrc_maxrate=
9500:vqblur=0.0:vlelim=-4:vcelim=-9:dark_mask=0.0:naq:vqcomp=0.7:vqmax=7:mbqmax=12:vqdiff=2:cmp=0:subcmp=0:mbc
mp=0:trell -of mpeg -sws 2 -vop $EXTRA $INFILE -ofps 25  -o $OUTFILE

mencoder -nosound -ovc lavc -lavcopts 
vpass=2:vcodec=mpeg1video:vhq=1:vbitrate=$BITRATE:keyint=16:vrc_maxrate=
9500:vqblur=0.0:vlelim=-4:vcelim=-9:dark_mask=0.0:naq:vqcomp=0.7:vqmax=7:mbqmax=12:vqdiff=2:cmp=0:subcmp=0:mbc
mp=0:trell -of mpeg -sws 2 -vop $EXTRA $INFILE -ofps 25  -o $OUTFILE.2

(Same effect when using different *cmp and vlelim=-2:vcelim=-5)

The result is usually impressive, but dark scenese are always very ugly, 
because dark/black area are always greyish and full of blocks.
I uploaded this file to mphq to show the problem:
ftp://ftp.mplayerhq.hu/MPlayer/incoming/BlockyBlack/harry.mpg

The problem shows particularly well at the beginning: when the wind 
blows behind the owl.

How can I remove (or at least reduce) this effect?

Another strange effect that I noticed is that when NOT resizing 
(whatever the dimensions) the quality is always much higher then when 
shrinking (with -sws 2), although theoretically the bpp rises.



Thanks,
            Nico