[mythtv-users] Current state-of-the-art for h264 cutlist processing?
John Pilkington
J.Pilk at tesco.net
Tue Mar 20 17:36:25 UTC 2018
On 01/02/18 13:10, John Pilkington wrote:
> Hi: I rarely record DVB-T2 HD h264 recordings in which I want to make
> internal cuts, but it would be good to be able to do make them in a way
> that doesn't introduce glitches in playback.
>
> I find that Mythfrontend does a good job in playing uncut recordings
> with cutlists, but uPnP then plays all the ads and skipping is painful.
>
> My MythDVBcut script chops at videokeyframes; there may be glitches at
> cuts but there's no long-term loss of quality or a/v sync. I've found
> other scripts that work similarly and are more elegantly coded. Frontend
> and uPnP glitches may differ in style and severity.
>
> I've tried going via mkvmerge but at present see a/v sync drift and
> haven't found an mkv/audio format that my tv plays acceptably via uPnP
>
> So, before I waste yet more time, has anyone found (or developed) a
> toolchain that is available and does this job properly?
>
> Thanks,
>
I posted that a few weeks ago. There hasn't been much comeback, perhaps
because multi-terabyte disks have become affordable, or perhaps through
disillusionment, but I do now have a script that works reasonably well
with UK DVB-T2 HD h264 recordings and might be useful elsewhere. I have
appended it to the MythDVBcut entry in the MythTV wiki; I've called it
MythTScut.
It uses mythffmpeg, with mapping to give one video and one audio stream.
That could probably be changed, but I haven't tested any more. I find
that it needs two runs, the first with no cutlist, to discard
unrecognised streams and get the cuts in (about) the right position. At
present the most successful commands seem to be:
============
with no cutlist
mythTScut.sh /path/to/infile.ts R 1
mv infile.ts.old ... to somewhere else, say infile_orig.ts
establish editpoints showing wanted keyframes using the frontend editor
mythTScut.sh /path/to/infile.ts R 1
============
The output may be either a Recording (R), replacing the renamed original
file and clearing its cutlist and bookmarks, or a Video (V) which leaves
these unchanged. The third parameter (1,2) is intended to define the way
in which the input streams are synched, but I find that 2 is still
rather unpredictable or prone to failure. I have tried several ffmpeg
options without getting anything that seemed better. YMMV
ffmpeg complains during both passes, which are primarily
disk-speed-limited. It still usually works.
Like my earlier scripts, this is intended for use from the desktop,
giving feedback and creating a logfile that includes the position of the
cutpoints in the output, and stream details from ffprobe. The first
page needs editing to define working directories and database access,
and intermediate files are not all erased on exit.
I'm posting it as work-in-progress with no guarantees and no implied
support, in the hope that it may be useful.
> John P
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