FFMPEG - How to demux LIVE multi-program transport stream?

Question

Assume that I have a fifo of bytes that is essentially coming from a capture card. Basically, this is NOT A FILE ON DISK.

The data in this fifo is a multi-program MPEG-TS. There are three programs, each containing a video stream and one or more audio streams.

When I run FFmpeg by piping in the fifo, it displays the programs and the streams inside of it. However, sometimes Program 1 contains streams 0.1 and 0.3 and other times it may contain 0.4 and 0.2. Even though these are the same PIDs from the MPEG-TS, FFmpeg tends to give them a random numbering.

My question: Is there a way to select the appropriate streams - I'm fine with selecting by PID - using FFmpeg? (I'm using CLI, btw)

Keep in mind that the map option in FFmpeg will not work because the stream numbers are "randomized" each time I run the ffmpeg command.

Answer 1

Say you are capturing using v4l2 from /dev/video0, then you can map using the program id like this:

ffmpeg -i /dev/video0 -acodec copy -vcodec copy -map 0:p:keep_pid -map -0:p:first_remove_pid -map -0:p:second_remove_pid output.m2ts

Checkout: http://ffmpeg.org/ffmpeg.html#Stream-specifiers-1 and http://ffmpeg.org/ffmpeg.html#Advanced-options