[MEncoder-users] Vertical streaks corruption in FLV transcode output

[Geoffrey Broadwell]

I have been transcoding various videos into FLV in a number of bitrates
using MEncoder.  I've found that a fair number of them exhibit a nasty
corruption in certain frames -- the top section of the frame looks
normal, but below a certain scanline, the entire rest of the frame is
just copies of the same line.  This ends up looking like most of the
frame is composed of vertical streaks of color.  This only happens to
single frames; the frames before and after look fine.

Here's an example of the problem:  I started with the 1080p version of
the Transformers trailer on the Apple site, and transcoded it to FLV
using the following command line (my apologies for the line wrapping):

/usr/local/bin/mencoder -v -quiet -mc 0 -of lavf -lavfopts
i_certify_that_my_video_stream_does_not_use_b_frames -oac mp3lame -ovc
lavc -lavcopts
vcodec=flv:mbd=2:v4mv:mv0:last_pred=3:preme=2:trell:cbp:vbitrate=538:keyint=23 -lameopts q=6 -srate 44100 -ofps 11.976 -vf-add scale=640:256 -o "./transformers-1080p_650.flv" "transformers-1080p.mov" 2>&1

Here's a copy of the transcode:

    http://broadwell.org/images/misc/transformers-1080p_650.flv

The corruption can be seen at frame 427 (35.6 seconds), frame 659 (54.9
seconds), frame 847 (70.6 seconds), etc.

I've tried various versions of MEncoder (the above file was made using
SVN as of Friday), and they all show this corruption, but on *different
frames*.

What's going wrong here?  Am I using some bad combination of encoding
options, or is this a known bug?  If it's a known problem, what's the
workaround?


-'f