[MEncoder-users] Status with MEncoder muxrate problem?

[L Lee]

Hi Francois,

I'm always interested in MPEG-2 methods because for me it's still one of the
most versatile solutions for storage and portability of video.

> mencoder -field-dominance 1 -mc 0 -vf hqdn3d=2:1:2,harddup -oac lavc -ovc
> lavc -lavcopts
> abitrate=128:acodec=ac3:autoaspect:ilme:ildct:keyint=15:mbd=2:top=0:trell:vbit
> rate=%BITRATE%:vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vstrict=0%
> PSNR%:vmax_b_frames=2%VB_STRAT%:dia=2:preme=2:predia=2:mbcmp=6:precmp=2:cmp=2:
> subcmp=6:last_pred=2:mv0:mv0_threshold=0
> -of mpeg -mpegopts format=dvd:tsaf %1 -o %OUTPUT% >%OUTPUT%.%PASS%.txt
> This problem seems widely reported on the Internet but I haven't found any
> solutions to it. All versions of MEncoder I've tried so far have the problem
> with slight variations in behaviour.

Do you mind my asking where the values for your variables (%[VALUE]) come
from?

> 
> 1) To your knowledge has this problem been fixed and if so, in what
> release/SVN?

I know of no fixes.

> 
> 2) The problem seems to be with the _muxrate_. After encoding, I split the
> video and audio into elementary streams for DVD authoring, where only the
> video and audio bitrates matter. So personally I don't really care what
> muxrate _MEncoder_ uses. What would be a sensible way of determining what
> muxrate to specify to avoid this problem? Keeping in mind video and audio
> streams need to remain DVD-compliant.
> 

I've gotten so accustomed to the buffer underflow message, I just add
muxrate=36000 to my mpegopts as a reflex. That has always prevented the
message except in cases for which the video was already known to have
problems. It's never caused any harm that I'm aware of.

Thanks for your post. I'm interested in trying some of those lavc options,
although recently I've been relying on "vqscale=1" and a strategy of using
vrc_minrate, vrc_rate, and vrc_maxrate to insure high quality for most of my
conversions. MEncoder issues warnings when I use those options, but I like
what I get. I usually try to keep whatever is the current SVN for my
MEncoder configuration (some might warn me of being a little too haphazard
that way), and I'm not sure how my strategies have been affected by code
changes recently, but I'm please that I'm able to combine those options in
such a way so as to keep high quality at a target bit rate.

Laine