[MEncoder-users] Compression too great, bitrate too low on detelecined deinterlaced mpeg2video

[Laine Lee]

On 12/24/08 10:15 AM, "Reimar Döffinger"
<Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:

> On Wed, Dec 24, 2008 at 09:13:05AM -0600, Laine Lee wrote:
>> I don't care about how long the encoding process takes, and I
>> don't care much about limiting output file size.
> 
> If bitrate is not critical you should never specify bitrate. Use e.g.
> vqscale=2 instead.
> Also my guess is that *cmp=2 is the wrong option if you care more about
> a sharp picture than about avoiding blocking artifacts.

Thanks for the reply. I shouldn't have said that my output pictures aren't
pixilated, because they are. What I maybe should have said is that I don't
see blocking artifacts. So my problem seems to be that reducing the size of
the pictures is sacrificing too much of their quality. I tried removing all
of the bitrate options for lavc
(vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=8000) as well as removing
cmp=2, and adding vqscale=2, and the quality remained about the same, but
the bitrate went down. I even tried using vqscale=1 and specifying a muxrate
of 36000 in mpegopts to prevent the buffer errors. That improved things a
little, but not a lot.

My problem is not the motion, because that is is nearly perfect (the pullup
is working quite well), but that I want my pictures to look better. I don't
mind paying for that improvement with a higher bitrate and file size.
Currently the output bitrate is between 4000 and 5000 and I think 6000 or
higher should be acceptable. I read one list contribution that mentioned the
possibility of introducing noise to increase bitrate, but that wouldn't
enhance picture quality, wouldn't it?

I played with more options and here's my command line now, which offers some
improvement, but not enough. One basic thing that I'm doing is to eliminate
lavc options vrc_buf_size and vrc_maxrate. I'm not sure whether that is
acceptable for a DVD output target or not. Thanks.

mencoder -oac copy -ovc lavc -lavcopts
vcodec=mpeg2video:vbitrate=9200:trell:mbd=2:precmp=2:subcmp=3:cbp:mv0:vqmin=
1:lmin=1:dc=10:keyint=15:vstrict=0:aspect=16/9:vpass=1:turbo -vf
framestep=2,filmdint=fast=0,softskip,hqdn3d=4:3:6,scale=720:480,harddup
-noskip -of mpeg -mpegopts format=dvd:tsaf:muxrate=36000 -fps 60000/1001
-ofps 24000/1001 -o /dev/null infile.mpg && mencoder -oac copy -ovc lavc
-lavcopts 
vcodec=mpeg2video:vbitrate=9200:trell:mbd=2:precmp=2:subcmp=3:cbp:mv0:vqmin=
1:lmin=1:dc=10:keyint=15:vstrict=0:aspect=16/9:vpass=2 -vf
framestep=2,filmdint=fast=0,softskip,hqdn3d=4:3:6,scale=720:480,harddup
-noskip -of mpeg -mpegopts format=dvd:tsaf:muxrate=36000 -fps 60000/1001
-ofps 24000/1001 -o outfile.mpg infile.mpg

-- 
Laine Lee