[MEncoder-users] B-frames and GOP with MPEG-2 for DVD

[Nico Sabbi]

Nicolas Hesler wrote:

>BUT, I've got another problem (that it appears I've had all along with 
>mencoder encodes), which I've only just discovered and that is that I 
>have pulsating (grain/artifacts) frames at what I'm guessing is every 
>keyint.   It's not noticeable on every video I've encoded but some 
>become unwatchable. I've tried encoding with b frames and closed gop, 
>but to no avail.   I've tried simplifying my command line to make 
>testing for manageable but had no luck with
>
>( mencoder -oac lavc -ovc lavc -of mpeg -mpegopts 
>format=mpeg2:muxrate=10080:tsaf:telecine
>-vf scale=720:480,harddup -srate 48000 -af lavcresample=48000:0:2
>-lavcopts 
>vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=7000:vbitrate=6000:keyint=12:
>trell:mbd=2:vpass=1:acodec=ac3:abitrate=224:aspect=16/9:vstrict=0 -ofps 
>24000/1001 -o $output $input)
>
>Any ideas on how to resolve the pulsating???
>
>current command line:
>
>mencoder -oac lavc -ovc lavc -of mpeg -mpegopts 
>format=mpeg2:muxrate=10080:tsaf:telecine
>-vf scale=720:480,harddup -srate 48000 -af lavcresample=48000:0:2
>-lavcopts 
>vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=7000:vbitrate=6000:keyint=12:
>trell:mbd=2:precmp=2:subcmp=2:cmp=2:dia=-10:predia=-10:cbp:mv0:vqmin=1:lmin=1:dc=10:
>vpass=1:acodec=ac3:abitrate=224:aspect=16/9:vstrict=0 -ofps 24000/1001 
>-o $output $input
>  
>

vstrict should be set to 1 and dc=10 looks very suspicious to me when 
targeting dvd.
Someone suggested some variation on vi_qfactor and vi_qoffset to reduce 
the pulsating effect,
but unfortunately I don't remember the values he adviced.
Another parameter I always use is sc_threshold=-1500 to increase lavc's 
sensitivity
to scene changes