Is it possible to save snapshots from multiple video streams using ffmpeg?

Question

I would like to periodically save a snapshot from a video stream using ffmpeg. This is is possible using the following command:

ffmpeg -i [source] -r 0.2 -f image2 ./image-%04d.jpeg

or the (rough) equivalent in ffmpge-python:

ffmpeg.input(source, **inputArgs)
    .filter("fps", fps=1 / 5, round="up")
    .output("./image-%04d.jpeg")

I would like to do this for N input streams simultaneously. So, I would be saving 1 frame every 5 seconds for each of the input streams. Is this possible using ffmpeg or ffmpeg-python? I can't find any examples with multiple input streams.

Just for some more information: the sources are all rtsp streams and N can be between 10 and 60. I also would like to limit the number of files on disk at any one time (similar to G-streamer's max-files property) but this is less important.

Answer 1

One approach would be to use run_async(). From the docs:

Asynchronously invoke ffmpeg for the supplied node graph.

https://kkroening.github.io/ffmpeg-python/index.html#ffmpeg.run_async

This creates a subprocess which runs FFMPEG concurrently with your Python program. You can then call run_async() multiple times.

Danger note: if you use pipe_stdin, pipe_stdout, or pipe_stderr, be aware that this will cause your FFMPEG processes to freeze if you do not call process.communicate() on each subprocess occasionally to drain their output pipes.