With audio files A and B:

A : |--- Some content ---|--- Extra content --- |

B : |--- Some content ---|

Assume the end of B is where the start of the extra content in A.

I want to append that extra content at the end of B.

Can I achieve this with some command line programs, such as ffmpeg?

  • Do you know the duration of B? Do the files have the same format/codec properties?
    – Gyan
    Mar 18, 2019 at 5:40
  • I think I could get the duration of B with some methods. A and B may or maybe in different codecs.
    – kit
    Mar 18, 2019 at 6:28

2 Answers 2


Assuming the duration of B is X (in seconds), you would use

ffmpeg -i A -i B -filter_complex "[0]volume=0:enable='lt(t,X)'[a];[a][1]amix=duration=first:dropout_transition=0,volume=2" out
ffmpeg -f concat -i playlist.txt $OTHER_OPTIONS

In playlist.txt, write this:

file 'B'
file 'A'
inpoint <start_of_extra_content>

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