Merge Video and Audio with FFmpeg

FFmpeg is a powerful tool for manipulating multimedia files. Here are some useful commands for merging video and audio files.

Replace Audio in a Video with MP3

To replace the audio in a video file with an MP3 file:

ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -map 0:v:0 -map 1:a:0 -shortest output.mp4

Explanation

• -c:v copy: Copies the video stream without re-encoding (faster, lossless)
• -map 0:v:0: Takes the video stream from the first input file (video.mp4)
• -map 1:a:0: Takes the audio stream from the second input file (audio.mp3)
• -shortest: Makes the output as long as the shortest input file

Mix Audio with Existing Video Audio

To mix the new audio with the existing audio in the video:

ffmpeg -i video.mp4 -i audio.mp3 -filter_complex "[0:a][1:a]amix=inputs=2:duration=shortest" -map 0:v -c:v copy -c:a aac -shortest output.mp4

Explanation

• -filter_complex "[0:a][1:a]amix=inputs=2:duration=shortest": Mixes both audio streams
• -c:a aac: Encodes the mixed audio in AAC format (compatible with most players)
• Other parameters are similar to the previous command

Notes

• Make sure FFmpeg is installed: sudo apt install ffmpeg
• The first input file should be the video, and the second should be the audio
• The output format is determined by the file extension (.mp4, .mkv, etc.)
• For best quality, use lossless formats like .wav for audio if possible