I know ffmpeg supports piping. I am trying to achieve what was described in this answer quoted below
If you are willing to accept a solution that does not truly stream the resulting frames, but does still adhere to your specification (read FLV from URL resource, output MP4 to stdout), you can always try to first encode the FLV to a temporary file and then output that to stdout.
Would I be able to achive this with ffmpeg via piping with something like this?
ffmpeg -i "%s" -c:v libx264 -c:a copy -f mp4 temp.mp4 | -