[mythtv-users] Problems with transcoded HD playback

Paul V. Gratz pgratz at gratz1.com
Fri Jun 20 17:55:25 UTC 2008

Hi all,

Recently I've noticed two occasions where I've transcoded a recording
from my HDHomerun and the resultant file has very choppy playback.  I
have my backend setup to transcode all HD recordings because only one
of my frontend's has the horsepower to play the HD streams as they
are.  Typically this seems to work but twice now I've noticed that the
resultant file's playback is very choppy.  In both cases I did not
view the pre-transcoded file so I can't say if it had the same problem
or if the transcoding caused it.  The choppiness is also very odd,
when I first start the show, the video seems to be slowed down and out
of sync relative the audio.  Then after ~10-15 seconds the audio gets
very choppy.  If I stop, fast-forward, or rewind the audio choppiness
goes away for about 15 seconds before starting up again.  If I try a
different recording it works fine so it must be something about that
particular recording.

I am recording OTA HD but I don't think this is a transmission quality
issue, this station is very strong and the picture looks perfect.  I
also don't think this is a frontend horsepower issue because I have
experienced it on my P4 3.2GHz front end (that non-transcoded HD plays
fine on).   Here are some stats:

Gentoo Linux (updated recently)
mythtv v0.21_p17100
Linux v2.6.16-gentoo-r7

I'll try updating to a more recent fixes patch this weekend, does
anyone know of an other possible cause?

Paul Gratz
Electrical and Computer Engineering
The University of Texas at Austin

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