[mythtv-users] hd-pvr and mytharchive: cutting commercials before re-encoding?
J.Pilk at tesco.net
Sat Jan 8 17:25:48 UTC 2011
On 08/01/11 16:38, Will Dormann wrote:
> Hi all,
> I've been playing around with mytharchive on my new mythtv system. I've
> already gathered that one of the current weaknesses with the ion
> platform is that mythcommflag and mytharchive (ffmpeg) won't leverage
> vdpau for decoding hd-pvr content. In testing mytharchive, I tried a
> 10-second long cutlist from a recording so that I don't have to wait a
> day for each test!
> The problem I am running into is that the commercial cutting appears to
> happen *after* the transcoding from mpeg4 into mpeg2. This appears to
> be the case regardless of whether the mytharchive option to use
> mythtranscode or projectx is selected.
> Wouldn't it make sense to cut commercials *before* re-encoding the
> video? This would be a nice performance gain for us low-power backend
> folks, but I would think that it would also "clean up" video streams
> before encoding. The test I ran last night stopped with the following
> ffmpeg errors in mythburn.log: "error, non monotone timestamps" and
> immediately following: "av_interleaved_write_frame(): Operation not
> permitted". I assume that this is some sort of glitch in the
> recording, which happens to play back just fine.
> I'm not sure about using mythtranscode with mpeg4 source, but from what
> I've read, ProjectX handles h.264 ts files just fine.
I don't have any h264 recordings, but I would guess that mytharchive
cuts after h264 > mpeg2 so that it can use the existing mpeg2 transcode
with cutlist. The ProjectX documentation that I've seen only refers to
use with mpeg2, but a grep through the code does suggest that it could
work. You might look at http://www.mythtv.org/wiki/Mythcutprojectx to
see if it could be used or modified for that.
Notice that at present, with mpeg2 recordings and 0.24, the polarity of
the cut within Mytharchive is probably inverted. See ticket #9389.
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