[libav-tools] AC3 frame sync error

Philip Jägenstedt philip at foolip.org
Thu Oct 6 23:15:14 CEST 2011


I'm attempting to use ffmpeg to encode archive-quality MPEG-2 for
http://www.archive.org/details/jagenstedtska-slaktforeningen-visingso-1991-filmvisning
and similar home videos.

I've encoded using -target pal-dvd -b 8500k -aspect 4:3 -flags
+ilme+ildct and the output MPEG-2 can be found at the above URL.

When playing this or any similarly encoded file with MPlayer, I get
these two messages:

[ac3 @ 0x7f502a64b5e0]frame CRC mismatch
[ac3 @ 0x7f502a64b5e0]frame sync error

The frame sync error is also repeated on every seek. I've tried git
versions of libav going back to v0.6, but it appears this is not a
recent regression.

Is this cause for concern? Is it the encoder or decoder that is buggy?
Comparing the output of MPlayer's -dumpaudio of the original and
encoded audio tracks the lengths are slightly different, with the
encoded version being about 0.04 seconds delayed, but I'm not sure if
that's related in any way.

I want to do this right once, so any help is appreciated. Perhaps AC3
is not even the best option for the purpose?

-- 
Philip Jägenstedt


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