How to stop ffmpeg remotely?

Question

I'm running ffmpeg on another machine for screen capture. I'd like to be able to stop it recording remotely. FFMPEG requires that q is pressed to stop encoding as it has to do some finalization to finish the file cleanly. I know I could kill it with kill/killall however this can lead to corrupt videos.

Press [q] to stop encoding

I can't find anything on google specifically for this, but some there is suggestion that echoing into /proc//fd/0 will work.

I've tried this but it does not stop ffmpeg. The q is however shown in the terminal in which ffmpeg is running.

echo -n q > /proc/16837/fd/0

So how can I send a character to another existing process in such a way it is as if it were typed locally? Or is there another way of remotely stopping ffmpeg cleanly.

Solution 1

Newer versions of ffmpeg don't use 'q' anymore, at least on Ubuntu Oneiric, instead they say to press Ctrl+C to stop them. So with a newer version you can simply use 'killall -INT' to send them SIGINT instead of SIGTERM, and they should exit cleanly.

Solution 2

Here's a neat trick I discovered when I was faced with this problem: Make an empty file (it doesn't have to be a named pipe or anything), then write 'q' to it when it's time to stop recording.

1. $ touch stop
2. $ <./stop ffmpeg -i ... output.ext >/dev/null 2>>Capture.log &
3. $ wait for stopping time
4. $ echo 'q' > stop

FFmpeg stops as though it got 'q' from the terminal STDIN.

Solution 3

Elaborating on the answer from sashoalm, i have tested both scenarios, and here are the results:

My experiments shows that doing

killall --user $USER  --ignore-case  --signal INT  ffmpeg

Produces the following on the console where ffmpeg was running

Exiting normally, received signal 2.

---

While doing

killall --user $USER --ignore-case --signal SIGTERM  ffmpeg

Produces

Exiting normally, received signal 15.

So it looks that ffmpeg is fine with both signals.

System: Debian GNU/Linux 9 (stretch), 2020-02-28

Comments

[sashoalm]

Newer versions of ffmpeg don't use 'q' anymore, at least on Ubuntu Oneiric, instead they say to press Ctrl+C to stop them. So with a newer version you can simply use 'killall -INT' to send them SIGINT instead of SIGTERM, and they should exit cleanly.

[Multimedia Mike]

@satuon: That version of Ubuntu is likely using avconv (part of the forked Libav project). That utility has removed 'q' as an option; main FFmpeg still has it.