[mythtv-users] Alternatives to lossless transcode
mark
perkins1724 at hotmail.com
Thu Nov 14 04:05:25 UTC 2013
On 14/11/13 07:38, Karl Dietz wrote:
> Your version of mythtranscode (looking at the logfile from the 6th) has
> known bugs in the handling of audio (avf and fifo mode) and video
> (lossless mpeg2 mode) timestamps that got fixed a bit less then 2 days
> ago in fixes/0.27 so it may be worth to update to the latest nighly and
> retest with the recording in question (if you still have it around)
> See
> http://code.mythtv.org/cgit/mythtv/log/mythtv/programs/mythtranscode?h=fixes/0.27
Thanks Karl - I see John Finlay's pts patch has been pushed to both
fixes/0.27 and fixes/0.26 so the manual patch is now no longer required.
> The delay information from mediainfo appears to be the delta of the
> first audio audio timestamp and the first video timestamp. (found that
> out by searching their bug tracker, documentation is hard to find) As
> audio and video frames have different durations depending on how you
> cut away excess frames at the beginning you'll get different delays.
>
> Regards,
> Karl
Thanks for the detail. It was probably too much wishful thinking on my
part that I might have found an easy way to accurately compare audio /
video sync, but it was a nice thought.
I updated ffmpeg (and mythtranscode) and re-ran Paul's --fifodir script
and as predicted by Paul there was no change in the audio delay figure.
I also re-ran the updated mythtranscode --mpeg2 with post-processing by
handbrake and it was completely shot as per before with massive (1sec)
audio / video out of sync and a log full of errors. So not sure what it
is about the file but it does not work with --mpeg2 mythtranscode but
will work fine with --fifodir mythtranscode.
I've gone back and re-looked at a few segments to try and see if there
is audio out of sync (using --fifodir) - to be honest if there is it is
very very slight. The ProjectX cut file audio probably leads the video
by as much as the --fifodir audio lags the video, it is very very
slight. Probably less of a difference than what is introduced by the
transmission path and electronic processing circuits of the various
connected sound system devices.
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