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Creating multiple outputs

Introduction

The following example command lines, that are usually written in one line, have been split into multiple lines, using the new-line delimiter character \ for more clarity. So, if the example shows something like this:

ffmpeg -i input \
	-acodec … \
	-vcodec … \
	output1

that means the actual command line, typed in the shell, would be:

ffmpeg -i input -acodec … -vcodec … output1

but either iteration will work in a sane shell.

Different parallel outputs

ffmpeg supports multiple outputs created out of the same input(s). The usual way to accomplish this is:

ffmpeg -i input1 -i input2 \
	-acodec … -vcodec … output1 \
	-acodec … -vcodec … output2 \
	-acodec … -vcodec … output3

This way ffmpeg can create several different outputs out of the same input(s).

For example, to encode your video in HD, VGA and QVGA resolution, at the same time, you would use something like this:

ffmpeg -i input\
	-s 1280x720 -acodec … -vcodec … output1 \
	-s 640x480 -acodec … -vcodec … output2 \
	-s 320x240 -acodec … -vcodec … output3

Duplicate outputs

But, what if you want to have duplicate outputs of your encoding? For example, when you are streaming a live audio/video and want to save a duplicate of that stream into the file at the same time. You don't want to encode twice, that wastes cpu.

Tee pseudo-muxer

The tee pseudo-muxer was added to ffmpeg on 2013-02-03, and allows you to duplicate the output to multiple files with a single instance of ffmpeg.

ffmpeg -i input.file -c:v libx264 -c:a mp2 \
-f tee -map 0:v -map 0:a "output.mkv|[f=mpegts]udp://10.0.1.255:1234/"

The above outputs an MKV file, and a UDP stream. Streams are separated by the | symbol. Options can be applied to an individual output: [f=mpegts] is equivalent to -f mpegts in a normal ffmpeg command-line. Multiple options can be separated with a :, which means that any : have to be escaped (so use \:).

Piped processes

Older versions of ffmpeg can also do this, using 2 piped processes, where the first process is used to encode the stream(s) and second process is used to duplicate that to several outputs.

ffmpeg -i input1 -i input2 -acodec … -vcodec … -f mpegts - | \
	ffmpeg -f mpegts -i - \
		-c copy output1 \
		-c copy output2 \
		-c copy output3 \

Note: If you are using older ffmpeg and -c copy is not recognized, then you can replace it with -acodec copy -vcodec copy.

ffmpeg -f v4l2 -i /dev/video0 -vcodec libx264 -f mpegts - | \
	ffmpeg -f mpegts -i - \
		-c copy -f mpegts udp://1.2.3.4:5678 \
		-c copy -f mpegts local.ts

Multiple encodings for same input

You can use one filtering instance for multiple outputs. This can be accomplished via the -map option. In this example the scaling is performed only once then encoded to two outputs:

ffmpeg -i input -an -filter_complex "[0]scale=1000:1000,split=2[a][b]" \
-map "[a]" output1.mp4 -map "[b]" output2.avi 
Last modified 8 months ago Last modified on 04/10/14 19:11:36

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