FFMPEG mux video and audio (from another video) - mapping issue

Question

I would like to place the audio from a video to another video without an audio (in one command):

ffmpeg.exe -i video1_noAudio.mov -i video2_wAudio.mov -vcodec copy -acodec copy video1_audioFromVideo2.mov

I guess "-map" is the correct way to do it but I got confused with it.

Can you suggest how to resolve it?

Answer 1

Overview of inputs

input_0.mp4 has the desired video stream and input_1.mp4 has the desired audio stream:

In ffmpeg the streams look like this:

$ ffmpeg -i input_0.mp4 -i input_1.mp4

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input_0.mp4':
  Duration: 00:01:48.50, start: 0.000000, bitrate: 4144 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 4014 kb/s, SAR 115:87 DAR 1840:783, 23.98 fps, 23.98 tbr, 16k tbn, 47.95 tbc (default)
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 124 kb/s (default)

Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'input_1.mp4':
  Duration: 00:00:30.05, start: 0.000000, bitrate: 1754 kb/s
    Stream #1:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 720x480 [SAR 8:9 DAR 4:3], 1687 kb/s, 59.94 fps, 59.94 tbr, 60k tbn, 119.88 tbc (default)
    Stream #1:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 55 kb/s (default)

ID numbers

ffmpeg refers to input files and streams with index numbers. The format is input_file_id:input_stream_id. Since ffmpeg starts counting from 0, stream 1:1 refers to the audio from input_1.mp4.

Stream specifiers

This can be enhanced with stream specifiers. For example, you can tell ffmpeg that you want the first video stream from the first input (0:v:0), and the first audio stream from the second input (1:a:0). I prefer this method because it's more efficient. Also, it is less prone to accidental mapping because 1:1 can refer to any type of stream, while 2:v:3 only refers to the fourth video stream of the third input file.

Examples

The -map option instructs ffmpeg what streams you want. To copy the video from input_0.mp4 and audio from input_1.mp4:

$ ffmpeg -i input_0.mp4 -i input_1.mp4 -c copy -map 0:0 -map 1:1 -shortest out.mp4

This next example will do the same thing:

$ ffmpeg -i input_0.mp4 -i input_1.mp4 -c copy -map 0:v:0 -map 1:a:0 -shortest out.mp4

• -map 0:v:0 can be translated as: from the first input (0), select video stream type (v), first video stream (0)

• -map 1:a:0 can be translated as: from the second input (1), select audio stream type (a), first audio stream (0)

Additional Notes

• With -c copy the streams will be stream copied, not re-encoded, so there will be no quality loss. If you want to re-encode, see FFmpeg Wiki: H.264 Encoding Guide.

• The -shortest option will cause the output duration to match the duration of the shortest input stream.

• See the -map option documentation for more info.

Answer 2

The accepted answer is an excellent explanation of ffmpeg's flexible stream selection using the -map option.

However, the documentation linked above also describes a simpler syntax to do what the questioner asks, without -map:

ffmpeg -an -i video1_noAudio.mov -vn -i video2_wAudio.mov -c:a copy -c:v copy video1_audioFromVideo2.mov

Here -an means discard any audio from the first input file, -vn discards any video from the audio recording. ffmpeg then combines them in the obvious way to produce a single output file.

(-c:a and -c:v are just alternatives for -acodec and -vcodec in the question, which can be used to copy for speed, or re-encode a stream if needed. -c copy matches all streams, so is a shorter equivalent for both options.)

Extra options to consider

Without any further options, if the two streams are of different length, they are included in their entirety. If the audio stream is shorter than the video, the player should continue silently. If the video is shorter it should display the final frame or black.

If you want to stop with the shortest stream, add -shortest, or to stop at another point, use -to and a position argument. If an audio track is incidental music, you can also repeat it one or more times with -stream_loop. For example:

ffmpeg -an -i video1_noAudio.mov -vn -stream_loop 1 -i video2_wAudio.mov -to 8:02 -c copy video1_audioFromVideo2.mov

Re-encoding options can also be added in place of copy if a particular format of finished file is required.

Answer 3

I have a new command for merging audio to video

ffmpeg -i video.mp4 -i audio.mp4 -map 0.0 -map 1.0 -acodec copy -qscale 4 -vcodec mpeg4 outvideo.mp4

-qscale is option set quality to video of ffmpeg

-acodec copy is option copy default quality of audio to output video

-vcodec mpeg4 is option copy default quality of video to output video