How to Join Multiple Audio Clips Into One using FFmpeg

13 November 2022 | 2 min read
Casper Kloppenburg


FFmpeg is a free and open-source video editing tool capable of trimming, cropping, concatenating, muxing, and transcoding almost any type of media file you throw at it.

It's also a very robust solution for implementing video automation, as we use it extensively in our own video editing API. For this tutorial we'll use FFmpeg 5.1.2, but any recent version will do.

Joining two audio clips

Use the following command to join two clips into one file:

$ ffmpeg -i audio1.mp3 -i audio2.mp3 -filter_complex "[0:a][1:a]concat=n=2:v=0:a=1" output.mp3

The tracks are joined using the concat filter. When we specify v=0:a=1, we are telling the concat filter that there are no video streams to merge, only audio streams.

Joining more than two audio clips

As with the example above, adding inputs to the concat filter will allow you to concatenate more than two audio files. Here is an example of adding an additional input file:

$ ffmpeg -i audio1.mp3 -i audio2.mp3 -i audio3.mp3 -filter_complex "[0:a][1:a][2:a]concat=n=3:v=0:a=1" output.mp3

Crossfade between clips

Crossfading allows us to fade out one clip while fading in another. We can do this with the acrossfade filter:

$ ffmpeg -i audio1.mp3 -i audio2.mp3 -filter_complex "acrossfade=d=5:c1=tri:c2=tri" output.mp3
  • d=5 specifies the duration of the crossfade.
  • c1=tri:c2=tri specifies the fade transition slope for the first and second input. Tri is an acronym for triangular slope. All available curves can be found on this page.

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