Change default audio track in mp4 video

Question

I often download mp4 videos with multiple audio tracks. Is it any way or some tools with explanation to change default audio track ?

Answer 1

Use FFmpeg:

ffmpeg -i input.mp4 -map 0 -c copy -disposition:a:0 0 -disposition:a:1 default output.mp4

Audio tracks (streams) are numbered from 0.

Supposing the input video has 2 audio streams, and the default audio stream is 0, we need to

• remove the “default” disposition from it (by setting it to 0: -disposition:a:0 0) and
• set it to the audio stream 1 (by setting it to “default”: -disposition:a:1 default).

In general, remove the “default” disposition from all audio streams except one, and set it for it.

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Note:

Not all media players honor default audio stream — for example Media Player Classic don't honor it (but you may set the preference by the language of audio streams), while VLC Media Player and FFplay do.

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Proof (note the location of the “(default)” tag):

ffprobe -hide_banner input.mp4

gives (among others)

Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 69 kb/s (default)
Metadata:
  handler_name    : SoundHandler
Stream #0:2(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 74 kb/s
Metadata:
  handler_name    : SoundHandler

while

ffprobe -hide_banner output.mp4

gives

Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 69 kb/s
Metadata:
  handler_name    : SoundHandler
Stream #0:2(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 74 kb/s (default)
Metadata:
  handler_name    : SoundHandler

The numbering here numbers all tracks, so #0:0 (omitted from the FFprobe outputs) is the first (video) track, and #0:1 and #0:2 are audio tracks.

Answer 2

Some media players simply start playing the first audio stream (track). For them you may simply change the order of audio streams.

For example, suppose you have 1 video stream and 3 audio streams in your input file, and you want to move the 3rd audio stream to be the first of audio streams.

Use

ffmpeg -i input.mp4 -map 0:v -map 0:a:2 -map 0:a:0 -map 0:a:1 -c copy output.mp4 

so -map 0:a:2 places the 3rd audio stream (stream numbers begin with 0, so 2 is the 3rd one) in front of all others audio streams (-map 0:a:0 -map 0:a:1).

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Note:

• 0:v means all video streams in the input file 0 (input files are numbered from 0)
• 0:a:2 means: input file 0, audio stream number 2
• 0:a:0 means: input file 0, audio stream number 0
• 0:a:1 means: input file 0, audio stream number 1

Answer 3

I found the following solution in Avidemux. (prveious answers are not always working)

1. Open video in Avidemux
2. In "Audio -> Select track" choose only one track you need
3. In "output format" select "mp4 muxer"
4. Save the file using "File -> Save as"

There is also a disadvantage in this method. It removes all other tracks but it's good enough for some cases.