Ffmpeg Piping output to pifm

Question

I am trying to convert mp3 audio files on the fly with ffmpeg since pifm(a program to transmit over the FM band) only takes a specific file. I was told I could use:

ffmpeg -i input.mp3 -f s16le -ar 22.05k -ac 1 - | sudo ./pifm - 

But ffmpeg returns an error saying that I must select at least one output source. How can I fix this to recognize that it is supposed to pipe it to the pifm program?

Answer 1

The documentation said your syntax should be;

ffmpeg -i input.mp3 -f s16le -ar 22.05k -ac 1 pipe:1 | sudo ./pifm -

- is common and pipe:1 is not, but that's what it supports.