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

[David King]

On 02/01/2018 08:10 AM, 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?

I don't know if what I have is an exact match for what you are trying to
do.  All my recordings come from cable for one thing, not DVB.  But,
anyway, through experimentation I've developed a workflow that produces
cleanly cut videos from MythTV recordings and cutlists.  The key missing
link for me was discovering the "--cleancut" option on the mythtranscode
command.  This lets cuts made on non-keyframes survive the transcoding
process.

My workflow is:

Edit the recording in MythTV, fine tuning the cutlist,
Start mythtranscode feeding the recording into audio and video fifos
with --honorcutlist and --cleancut options,
Start ffmpeg simultaneously, reading from the fifos and outputing a
lossless h264 MKV,
Use Handbrake to transcode the lossless MKV down into standard mp4 format.

I have a Python script that does this plus more.  It's got stuff in it
that's specific to my needs and it isn't generalized for use by others. 
But it might provide you with some hints on command options to try.  I
run it standalone on my desktop PC where I only have mythfrontend
installed.  It talks to the backend over the network and uses NFS to
store the resulting video file on the backend. 
https://pastebin.com/P5P21zJ9

-- 
David King
dave at daveking.com