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

[John Pilkington]

On 02/02/18 15:56, David King wrote:
> 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
> 
Thank you for posting this.  I should have said above that I have found 
cutting at keyframes quite acceptable with almost all my SD recordings 
from digital sources, but I think this must depend on the way the 
content is edited at source - and I'm usually just trying to remove 
commercials rather than striving for a subtle artistic effect.  But I 
will certainly examine your code with interest.  It may take some time.

Thanks again.

John