Title: Separate or merge audio and video using ffmpeg

	Title: Separate or merge audio and video using ffmpeg
	Author: Solène
	Date: 20 December 2019
	Tags: ffmpeg
	Description:

	# Extract audio and video (separation)

	If for some reasons you want to separate the audio and the video from a
	file
	you can use those commands:

	ffmpeg -i input_file.flv -vn -acodec copy audio.aac

	ffmpeg -i input_file.flv -an -vcodec copy video.mp4

	Short explanation:

	- `-vn` means `-video null` and so you discard video
	- `-an` means `-audio null` and so you discard audio
	- `codec copy` means the output is using original format from the file.
	If the
	audio is mp3 then the output file will be a mp3 whatever the
	extension you
	choose.

	Instead of using codec copy you can choose a different codec for the
	extracted
	file, but copy is a good choice, it performs really fast because you
	don't need
	to re-encode it and is loss-less.

	I use this to rework the audio with audacity.


	# Merge audio and video into a single file (merge)

	After you reworked tracks (audio and/or video) of your file, you can
	combine
	them into a single file.

	ffmpeg -i input_audio.aac -i input_video.mp4 -acodec copy -vcodec
	copy -f flv merged_video.flv