[MEncoder-users] a/v sync issues transcoding UK DVB-T

jon bird news at onastick.clara.co.uk
Sun Mar 8 20:31:11 CET 2009


I've been using mencoder to record then transcode UK DVB-T transmissions
and more often than not the finished article has slight (roughly half
second) a/v sync issues.

Here's what I doing to record the stream:

mencoder -ovc copy -oac copy -of mpeg -endpos -o somefile.avi

The resultant AVI looks okay and plays without sync issues on VLC
(Windows) & Winamp (ffdshow).

I then transcode it to either compressed x264 format using:

mencoder -ovc lavc -lavcopts vcodec=libx264:vbitrate=200 -x264encopts
subq=5:8x8dct:frameref=2:bframes=3:b_pyramid:weight_b -vf scale=368:288
-oac mp3lame -lameopts abr:br=56 -srate 22050 -sws 2 -o test.avi

or in some instances to DVD:

mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd:tsaf -vf
scale=720:576,harddup -lavcopts
=15:vstrict=0:acodec=mp2:abitrate=192:aspect=16/9 -ofps 25   -o
test.avi infile.avi

Either way the result is often the same - slight a/v sync issues.

I also tried similar transcoding direct with ffmpeg and this also
exhibits a similar problem which makes me think its something in the
source (recorded) format which is causing the issue however that doesn't
add up fully because it plays just fine. It's also interesting that some
recordings will transcode fine but it's very rare.

Here's the version:

MEncoder dev-SVN-r28162-3.3 (C) 2000-2008 MPlayer Team
CPU: AMD Athlon(tm) XP 1800+ (Family: 6, Model: 8, Stepping: 1)
CPUflags: Type: 6 MMX: 1 MMX2: 1 3DNow: 1 3DNow2: 1 SSE: 1 SSE2: 0
Compiled for x86 CPU with extensions: MMX MMX2 3DNow 3DNowEx SSE



== jon bird - software engineer
== <reply to address _may_ be invalid, real mail below>
== <reduce rsi, stop using the shift key>
== posted as: news 'at' onastick 'dot' clara.co.uk

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