[mythtv] Broken AV sync after mythtranscode

Geoffrey Hausheer mythtv0368 at phracturedblue.com
Thu Dec 22 11:48:35 EST 2005


On 12/22/05, Adam Egger wrote:
> The same problem here, I'm using today's svn (system: debian sid,
> dvb-t, Germany, kernel 2.6.14). It looks like it's starting to get
> asynchronous after there were some bad frames in the stream. I'll send
> you the two logs (the -v all log and the whole mplayer log for this
> file) soon.

> Used command:
> mythtranscode -l -c 9 -s 2005-12-18T14:28:00 -o test.mpg
> --showprogress -v all > log.txt
> By the way, --showprogress doesn't work for mpeg2fix
I'm looking at your logs, but see only one bug (caused by mythtranscode):
in mplayer:
A:1599.9 V:1599.9 A-V:  0.002 ct:  0.171 39992/39992 10%  3%  0.7% 15
0 0%
A:1599.9 V:10593.6 A-V:-8993.666 ct:  0.167 39993/39993 10%  3%  0.7%
15 0 0%
A:1600.0 V:1600.0 A-V:  0.002 ct:  0.167 39994/39994 10%  3%  0.7% 15 0

In mythtranscode:
2005-12-22 13:28:25.423 VID: I #:0 nb: 2 pts: 00:26:39.706 dts: 00:26:39.666
2005-12-22 13:28:25.423 Id:0 00:26:39.706 V:181 MP2: 173
2005-12-22 13:28:25.423 VID: I #:2 nb: 2 pts: 16:11:55.271 dts: 00:26:39.706
2005-12-22 13:28:25.423 Id:0 16:11:55.271 V:180 MP2: 173
2005-12-22 13:28:25.424 AUD #1: pts: 00:26:39.108
The 'Id' which has a PTS of 16:11:55 is bad, and would likely have
caused an issue if it wasn't at the very end of the stream.  I'll look
into fixing it.

I see some other stuff, which isn't good though:
2005-12-22 13:27:39.398 Id:1 00:13:18.348 V:139 MP2: 98
2005-12-22 13:27:39.398 Found invalid audio PTS (off by 00:00:00.504)
at 15:58:33.424
2005-12-22 13:27:39.398 AUD #1: pts: 00:13:17.940
2005-12-22 13:27:39.398 Id:1 00:13:17.940 V:139 MP2: 97
A backwards moving PTS (from 13:18.348 to 13:17.940) will result in
A/V desync.  This isn't a transcoder issue, and I don't really know
any way to solve it.  If your stream is this broken, there isn't much
the transcdoer can do.  I don't see why the transcoder would make it
any worse than it already was though.  I don't see anything in the
mplayer logs telling me about an A/V desync either except for this:
A: 798.3 V: 798.3 A-V: -0.005 ct:  0.553 19952/19952 10%  2%  0.7% 6 0
43%
A: 797.9 V: 798.3 A-V: -0.426 ct:  0.549 19953/19953 10%  2%  0.7% 6 0
45%
which corresponds to the above backwards moving PTS.  It is about 0.5
sec off, and mplayer corrects for it within 2 seconds.  So I guess I
need a more explicit explanation of what you are seeing, and ideally,
a clip around the area of interest that shows it in action.

.Geoff


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