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Discussion on: Concatenate Videos Together Using ffmpeg!

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gkarumba profile image
gkarumba • Edited

Thank you for your awesome write, quick question is it possible to join a video to another at a specific time? Say for example video1.mp4 is 30s long and video2.mp4 is 10s long, I want to join video2 to video1 at exactly 00:00:20s. So in the final output the first 20s are from video1 then the next 10s from video2 and the final 10s from video1. The final video output should be 40s long

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dak425 profile image
Donald Feury Author

Try something like this and see what you get, this does a re-encode though:

ffmpeg -t 20 -i video1.mp4 -i video2.mp4 -ss 20 -i video1.mp4 -filter_complex \
"[0:v][0:a][1:v][1:a][2:v][2:a]concat=n=3:v=1:a=1[outv][outa]" \
-map "[outv]" -map "[outa]" final.mp4

-t before the first input is indicating we only want 20 seconds of this stream
-ss before the third input indicates to start reading from the stream at twenty seconds in

There might be some overlap when the first section of video 1 end and starts back up again after video 2. With most formats, ffmpeg can't seek exactly to what time you specify, only the closet seek point.

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gkarumba profile image
gkarumba • Edited

thank you, this works perfectly final question how can I introduce a fadeIn and fadeOut to the video being inserted?

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dak425 profile image
Donald Feury Author

Try something like this, might need tweaking.

This will add a fade out to the end of the first section, a fade in to the start of the second section, a fade out at the end of the second section, and finally a fade in to the start of the last section.

This should mimic the effect of an actual scene transition

ffmpeg -t 20 -i video1.mp4 -i video2.mp4 -ss 20 -i video1.mp4 -filter_complex \
"[0:v]fade=t=out:st=19.5:d=0.5[v0];
[1:v]fade=t=in:st=0:d=0.5,fade=t=out:st=9.5:d=0.5[v1];
[2:v]fade=t=in:st=0:d=0.5[v2];
[v0][0:a][v1][1:a][v2][2:a]concat=n=3:v=1:a=1[outv][outa]" \
-map "[outv]" -map "[outa]" final.mp4

You notice that the argument I passed in for the st value of the fade filters for the fade out effects is basically equal to

CLIP_LENGTH - DURATION_OF_FADE_OUT_EFFECT