[mythtv-users] Joining MP4s

James jam at tigger.ws
Wed Feb 1 13:04:09 UTC 2023

> On 1 Feb 2023, at 5:15 pm, John Pilkington <johnpilk222 at gmail.com> wrote:
> 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!

I was totally unaware, but it looks most interesting, thanks

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