[mythtv-users] Joining MP4s

[John Pilkington]

On 01/02/2023 05:05, James wrote:
> 
> 
>> On 1 Feb 2023, at 1:16 am, John Pilkington <johnpilk222 at gmail.com> wrote:
>>
>> SeeOn 31/01/2023 15:10, James wrote:
>>> I recorded a movie that I want to save. Due to the whims of the Australian Open my 20 min post record failed by 2 minutes. Playing Amazon Prime in a VM I screen captured the last 2 min of the movie..
>>> I now have my movie-2min with commercials cut stored as a 'Movie' It plays perfectly.
>>> I have the last 2 minues as a clip. It too plays perfectly.
>>> Each is 720x576 16:9 24.99 Hz. Both are h264 in a mp4 container. The OTA recordings are interlaced.
>>> How on earth can I append the end.mp4?
>>> I tried shotcut which re-rendered giving perfect video but lip sync of 500ms variable, with the end clip in sync
>>> I tried mythffmpeg which muddled everything ie repeated sections general chaos
>>> mythffmpeg -f concat -safe 0 -i /store/TScut_work/file -c copy /store/Movies/Myth-V/Thur\ Vow.mp4
>>> Any experts with handbrake et al
>>> Of interest *some* OTA 720 and 1080 videos maintain lip sync, some do not. I've not looked why I occasionally shotcut a snip to put the MOV atom at the front of the file for downloads.
>>> EG http://tigger.ws/downloads/qna.mp4
>>> James
>>
>> I wasn't sure about concatenating progressive and interlaced segments, but since they are transmitted as equivalent here (ie in the UK) it ought to be ok.  I would suggest demuxing both segments with '-fflags +genpts' and perhaps '-avoid_negative_ts make_zero', and then concatenating with the fflag/genpts options added to what you used above.  This 'issue' has similar examples:
>>
>>   https://github.com/MythTV/mythtv/issues/600#issuecomment-1172873672
>>
>> I doubt that you will get an undetectable smooth join but it might be acceptable.  I'm having to use this technique now with mpeg2 SD recordings from the ITV/Ch4/Ch5 mux, as well as with h264, since they changed encoders around the New Year.
> 
> Clearly a phD's worth of learning to be made
> 
> $ mkvmerge -o result.mp4 TheVow.mp4 end.mp4 (with or without +)
> 
> results in ONLY the end.mp4 and bad (more than 1000ms) lip sync.
> 
> So I bite bullet and scan and have
> The Vow.mp4
> The Vow Ending.mp4
> 
> both of which play perfectly with mythfrontend and with vlc
> 
> I'm happy, but if anyone wants to (see I'm not lying) play then say so and I will post them. My www is Bluehost in the US and they have BIG taps!
> James

A playlist!

John