FFmpeg: Transfer Audio to MP4 in One Command

Use the following command to transfer an audio track from one MP4 file to another without re-encoding:

ffmpeg -i 1080.mp4 -i 360.mp4 -map 0:v:0 -map 1:a:0 -c copy 1080_sound.mp4

Table of Contents

• Main Command
• Command Component Breakdown
• Alternative Options
• Handling Multiple Audio Tracks
• Checking the Result
• Conclusion

Main Command

To transfer the audio track from the 360.mp4 file to the 1080.mp4 file without re-encoding, use:

ffmpeg -i 1080.mp4 -i 360.mp4 -map 0:v:0 -map 1:a:0 -c copy 1080_sound.mp4

This command combines the video from the first file with the audio from the second file, preserving both streams without re-encoding.

Command Component Breakdown

Let’s break down each component of the command:

• -i 1080.mp4 - first input file (video without sound)
• -i 360.mp4 - second input file (video with sound)
• -map 0:v:0 - take the video stream (v) with index 0 from the first file (0)
• -map 1:a:0 - take the audio stream (a) with index 0 from the second file (1)
• -c copy - copy both streams without re-encoding
• 1080_sound.mp4 - output file

Important: The -map key allows you to precisely specify which streams from which files to use in the output file.

Alternative Options

More Concise Notation

You can use a more concise form of the command:

ffmpeg -i 1080.mp4 -i 360.mp4 -map 0:v -map 1:a -c copy 1080_sound.mp4

In this case, FFmpeg will automatically select the first video stream and the first audio stream from the specified files.

Explicit Codec Specification

For greater clarity, you can specify codecs separately:

ffmpeg -i 1080.mp4 -i 360.mp4 -map 0:v:0 -map 1:a:0 -c:v copy -c:a copy 1080_sound.mp4

This is equivalent to -c copy but more explicitly shows that both video and audio are copied without changes.

Handling Multiple Audio Tracks

If the 360.mp4 file contains multiple audio tracks, you can select the desired one using its index:

# Second audio track (index 1) from the second file
ffmpeg -i 1080.mp4 -i 360.mp4 -map 0:v:0 -map 1:a:1 -c copy 1080_sound.mp4

To view the available streams in the files, use:

ffmpeg -i 360.mp4

This will show all streams with their indices.

Checking the Result

After running the command, you can check the result:

ffprobe 1080_sound.mp4

This command will show the structure of the output file, including the presence of video and audio streams.

You can also check the audio quality using:

ffmpeg -i 1080_sound.mp4 -f null -

If the command executes without errors, it means the file has a correct structure.

Conclusion

Using a single FFmpeg command to transfer an audio track between files has several advantages:

1. Efficiency - no need to create intermediate files
2. Speed - the process is faster as there’s no re-encoding step
3. Quality - audio is preserved in its original quality without loss
4. Convenience - just one command instead of two

The main command for your task:

ffmpeg -i 1080.mp4 -i 360.mp4 -map 0:v:0 -map 1:a:0 -c copy 1080_sound.mp4

Sources

1. r/ffmpeg on Reddit: Adding Audio Track from one mp4 to another mp4
2. Super User: How to use ffmpeg to rip audio from mp4 and add it to another
3. Stack Overflow: FFMPEG mux video and audio (from another video) - mapping issue
4. JSON2Video: FFmpeg - How to extract audio from video
5. Mapping multiple input files - python-ffmpeg