[mythtv-users] Cutting HD-PVR recordings

Christopher Meredith chmeredith at gmail.com
Sat Dec 12 14:31:03 UTC 2009

On Sat, Dec 12, 2009 at 5:52 AM, Marius Schrecker <marius at schrecker.org> wrote:
> Christopher Meredith wrote:
>>I cobbled together a script that does this using avidemux2_cli and
>>which can be run as a user job. You can read more about it here:
>>It usually works pretty well for me, but I have been noticing that I
>>get sync problems on recordings where the HDPVR hiccups during
>>recording. The resulting file starts out in sync then jumps out at the
>>hiccup point. I'm not sure how this can be addressed (if at all).
> Hi again,
>  I was looking at this, and the mythcommflag patch ticket was closed as a wontfix with some comments about there being cleaner ways...
> Is the patch still recommended/required, and will it compile into the 0.22 - fixes version of mythcommflag?

Yes, the patch is still required but it does apply against recent SVN.
As for "cleaner ways," I asked about that very thing a couple months
ago and was told that there really is no other way, and that no one is
working on HD-PVR support for mythtranscode. So for now, this is the
only way.

As for frame accuracy, unfortunately it is a limitation that it cuts
to keyframes only. In fact, sometimes not even then. I've had the most
success setting my cutpoints to one keyframe into the commercial and
one keyframe into the show when it resumes from commercial. Avidemux
seems to cut slightly to the "left" of the actual cutpoint locations.

I've been having increasing problems getting clean transcodes out of
avidemux. The resulting files usually jump out of sync at some point
even though the source files playback fine. I'm wondering if truly
lossless, reliable commercial cutting is actually possible at this
point. I'm looking at recording at the highest bitrate, transcoding to
mpeg2, then reencoding to lower bitrate h264 with mencoder and EDL
(edit decision lists). That will give frame accuracy and I'm hoping
minimal visible quality loss.

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