Example:
ffmpeg -s 1280x720 -f rawvideo -i /dev/zero -ar 48000 -ac 2 -f s16le -i \
/dev/zero -c copy -f nut pipe:1 | ffmpeg -y -i pipe:0 -c copy -f nut /dev/null
I see no reason why anyone would do this. Also, there are very few reasons to pipe from ffmpeg to ffmpeg when you can most likely just use one ffmpeg process to do whatever you want.
What the options do:
-s 1280x720 -f rawvideo – Options to describe the input since /dev/zero is not a typical input format and therefore these additional options are required.
-i /dev/zero – The video input. It is being used in this example to generate a video stream out of "nothing". This was used in the example because the question asker refused to provide any information about the inputs being used.
-ar 48000 -ac 2 -f s16le – Options to describe the input since /dev/zero is not a typical audio format.
-i /dev/zero – The audio input. It is being used in this example to generate an audio stream out of "nothing".
-c copy – Stream copy, or re-mux, the inputs to the output. No re-encoding is being performed so the process is lossless. It is unknown if stream copying is acceptable to the question asker or not. Maybe re-encoding is desired instead?
-f nut – You need to tell ffmpeg what format to use for the pipe. Nut is a container format. See ffmpeg -formats for a complete list. Another flexible format is -f matroska, but it is impossible to suggest an appropriate or specific output container format to use without more info from the question asker.
pipe:1 – Use the pipe protocol to output to stdout. Alternatively, the number can be omitted (just pipe
and by default the stdout file descriptor will be used for writing and stdin will be used for reading.
