[mythtv-users] Current state-of-the-art for h264 cutlist processing?

Anthony Giggins seven at seven.dorksville.net
Wed Mar 21 21:56:49 UTC 2018


On 21 March 2018 at 03:36, John Pilkington <J.Pilk at tesco.net> wrote:

> 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
>
> Thanks John,

I'll give it a whirl, typically I just been avoiding recording h264
channels where possible.

Cheers,

Anthony
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