How can I pipe output of ffmpeg to ffplay?

Question

How can I pipe the output of ffmpeg to ffplay?

At the moment I use a workaround in bash :

mkfifo spam
(ffplay spam 2> /dev/null &) ; capture /dev/stdout | ffmpeg -i - spam

Answer 1

I do not know if it is ffmpeg that cannot output its data to stdout, or ffplay that cannot take its input from stdin.

If it is ffmpeg that cannot output its data to stdout:

capture /dev/stdout | ffmpeg -i - >(ffplay 2> /dev/null)

(You migth need to add a - argument to ffplay so it takes its input from stdin.)

If it is ffplay that cannot take its input from stdin:

ffplay <(capture /dev/stdout | ffmpeg -i -) 2> /dev/null

For more informations about the <(command) and >(command) construct, see the Process Substitution section of the bash manual.

Answer 2

ffmpeg supports piping operations. See that section of the documentation here.

I don't know how ffplay works, but to pipe the output of ffmpeg to standard output, you can add the pipe command to the end of the ffmpeg command. Example:

ffmpeg -i input.flv pipe:1 | ffplay -i -