[mythtv-users] seeking/editing in mythfrontend
leo.butler81 at googlemail.com
Sat Mar 27 12:04:59 UTC 2021
John Pilkington <johnpilk222 at gmail.com> writes:
> On 27/03/2021 08:26, Stephen Worthington wrote:
>> On Fri, 26 Mar 2021 20:50:26 -0500, you wrote:
>>> I transcode my recordings to an x264-encoded video stream in a matroska
>>> container. I use ffprobe to update the recordedseek table after
>>> transcoding. I have been doing this for a couple years.
>>> In both v0.28 and v0.29 (from the mythbuntu ppa), I was able to seek and
>>> edit these mkv files without difficulty. In v0.31/fixes from the same
>>> ppa, seeking and editing is broken for these transcoded files--it
>>> appears that any movement in the video is only by a keyframe. Playback
>>> is fine.
>>> Seeking and playback in fine in vlc and ffplay, fwiw.
>>> This seems like a regression to pre v0.28 behaviour.
>>> Has anyone seen similar behaviour? Suggestions on how to workaround the
>>> problems? Ideas about what caused the regression?
>> Have you tried using the mythcommflag --rebuild option to rebuild
>> seek table using the official method?
> TTBOMK the MythTV seektable isn't used for playback of files in
> matroska format.
A seektable is certainly needed for editing and seeking in
mythfrontend, although not for playback.
> If you somehow create one it may upset things. ISTR that
> 'recordings' and 'videos' get different treatment.
To clarify: I transcode to mkv and replace the original recording with
And to repeat, with this method, seeking and editing with the transcoded
recordings worked flawlessly until my recent 'upgrade' to
v0.31/fixes. That upgrade was caused by the changes at SD and the
resulting need to get a current grabber.
> I 'transcode' to mythffmpeg -f mpegts format, which is myth-native
> and plays well for me in the frontend or via UPnP or Firestick 4k.
> But all my video cutting, mostly from mpeg2 recordings, is
> keyframe-based; I find that acceptable. I still get the best results
> by using ProjectX to demux and sync-adjust before remuxing, but can't
> do that for h264.
99.9% of my editing is of mpeg2 recordings, yes. You can find the ffmpeg
command (template) on line 405 here:
The code automatically rounds cutpoints to keyframes (in the right
direction on each end of a cut).
I don't have any issues with playback quality, just seeking and editing
(the transcoding is so good, that I need to use the 'playback data'
information to verify that I am watching a transcoded file, not the
original). A year or so ago, I did change from the concat demuxer to the
concat filter, and that seemed to fix any problems I had seen with video
and audio streams going out of sync.
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