How to save ffmpeg output.mp4 to file

Question

I have a very basic question. I combined an .wav and .mp4 file to output.mp4 using ffmpeg in python:

   !ffmpeg -i /content/input.mp4 -i audio.wav -c:v copy -c:a copy output.mp4

Now how do I save the output.mp4 to an .mp4 file on my computer? Thank you very much in advance

Answer 1

For executing ffmpeg withing Python, you may use subprocess :

import subprocess as sp
sp.run('ffmpeg -y -i /content/input.mp4 -i audio.wav -c:v copy -c:a copy output.mp4')

Test the conversion in ffmpeg command line (in console) before using Python and verify there are no errors.

In most cases you can't keep the audio codec (using -c:a copy ) with .wav file as input, and store result into .mp4 video file.

I am getting the following error message:

[mp4 @ 000001d150ea6780] Could not find tag for codec pcm_s16le in stream #1, codec not currently supported in container Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument

In case of an error, use: -c:a aac .

Using -c:a copy works when the codec of the wav file is ac3 for example (but it's a rare case).

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Testing the solution by generating synthetic audio and video input files:

import subprocess as sp

sp.run('ffmpeg -y -f lavfi -i testsrc=size=192x108:rate=30 -vcodec libx264 -pix_fmt yuv420p -t 5 input1.mp4')
sp.run('ffmpeg -y -f lavfi -i sine=frequency=400 -acodec ac3 -ar 22050 -t 5 audio1.wav')
sp.run('ffmpeg -y -i input1.mp4 -i audio1.wav -c:v copy -c:a copy output1.mp4')

The above code is working because I selected ac3 codec for audio1.wav .