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I'm trying to make a single ffmpeg command that will take multiple inputs, seek specific times within them, then output to a single file.

For example, I have inputA.avi and inputB.avi and each is 1 hour long. I want a single output file that takes inputA.avi from 00:00:00 to 00:20:00 for the beginning and inputB.avi from 00:00:00 to 00:10:00 for the end. The end result should be a 30 minute video file that has the first 20 minutes of inputA then the first 10 minutes of inputB.

I currently can do the following three commands to get the job done:

ffmpeg -ss 00:00:00 -t 00:20:00 -i inputA.avi [rest of command] inputA-trim.avi
ffmpeg -ss 00:00:00 -t 00:10:00 -i inputB.avi [rest of command] inputB-trim.avi
ffmpeg -f concat -i inputList.txt [rest of command] final.mp4

where inputList.txt contains only

file inputA-trim.avi
file inputB-trim.avi

This works, but has unnecessary steps and creates intermediary files. I also have to create a batch file and txt file to get everything to run in succession. I'd like to be able to create a single ffmpeg command that can take multiple inputs with individual -ss and -t commands, then put them in a single output.

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#1 Using concat filter i.e. without textfile

ffmpeg -ss 0 -t 20:00 -i inputA.avi -ss 0 -t 10:00 -i inputB.avi -filter_complex "[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1" out.mp4

--OR--

#2 Using concat demuxer i.e. with textfile

file inputA-trim.avi
inpoint 0
outpoint 20:00
file inputB-trim.avi
inpoint 0
outpoint 10:00

and then your final command

ffmpeg -f concat -i inputList.txt [rest of command] final.mp4

See https://trac.ffmpeg.org/wiki/Concatenate for details.

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  • I have tested the second option listed, with the input txt file. I had to add -safe 0 to avoid an "unsafe filename" error. The final command I used was ffmpeg -f concat -safe 0 -i inputList.txt -vf "scale=1280:720,setsar=1" -crf 30 -an -movflags +faststart final.mp4. I'll test the first option some other time. Thanks.
    – user3643
    Commented Oct 27, 2018 at 23:05
  • I guess I had to use -safe 0 because I had absolute full paths in my input txt file.
    – user3643
    Commented Oct 27, 2018 at 23:17
  • I've been using the first option for some time now. Just noticed I mentioned I would test it, but never reported back.
    – user3643
    Commented Jul 29, 2019 at 21:38
  • Does the concat filter re-encode?
    – Hashim Aziz
    Commented Apr 11, 2021 at 22:07
  • 3
    The concat filter will require a re-encode. All frame filters will lead to a re-encode.
    – Gyan
    Commented Apr 12, 2021 at 4:05

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