[FFmpeg-user] Video in video not from start

[Michael Koch]

Am 05.01.2024 um 10:26 schrieb Cecil Westerhof via ffmpeg-user:
> Ferdi Scholten <ferdi at sttc-nlp.nl> writes:
>
>> I want to play a video in a video from a certain point. I understood I
>>> could do something like:
>>>       ffmpeg              \
>>>         -i input1.mp4     \
>>>         -i input2.mp4     \
>>>         -filter_complex "
>>>           [0:v][1:v] overlay=25:25:
>>>           enable='between(t,8,20)'
>>>         "                 \
>>>         -pix_fmt yuv420p  \
>>>         -c:a copy         \
>>>         output.mp4
>>>
>>> But this starts input2.mp4 from the start of input2.mp4 on the 8
>>> second, for twelve seconds.
>>> Is it possible to let input2.mp4 not start from second 0, but from
>>> second 17?
>>>
>> Try putting -ss 17 between the two inputs.
> I was thinking about that. But that means that if I want to use
> input2.mp4 several times, I should use input2.mp4 several times with
> the correct -ss. Not really a problem, but I had hoped for a more
> efficient way.

You can cut off the beginning of the second stream with the "trim" 
filter, but then you must also use the "atrim" filter for audio. "-ss" 
is easier, but can only make a cut at a keyframe, if I remember right.

Michael