ffmpeg - Re-streaming RTSP with higher FPS

Question

I have RTSP stream with very low and non-constant FPS (varying between 0.2 ... 0.5). It is generated using -skip_frame flag to reduce network and CPU usage as much as possible:

ffmpeg -skip_frame nointra -i <rtsp-source> -vsync 2 -f rtsp <low-fps-destination>

As a consequence, it takes a very long time (1 ... 3 minutes) to connect to that stream and see first meaningful image. I want this stream to work with generic players without any tweaks, so my decision was to re-stream it with higher FPS (10, to be exact):

ffmpeg -i <low-fps-source> -vf "fps=fps=10,setpts=N/(10*TB)" -f rtsp <normal-fps-destination>

Not entirely sure how that command is working, but it somehow did the trick and reduced connection time to about 5 seconds. However, I suspect that it's outputting frames in bursts, which is not ideal. For example, if original low-fps stream contains 2 frames which are 3 seconds apart, my re-stream command (probably) does the following:

• When the first input frame comes, output a bunch of frames as fast as possible
• Don't output anything for an entire 3 seconds
• When the second frame comes, output 3 * 10 = 30 frames as fast as possible
• Sleep again until new input frame shows up...

Is there a way to make my re-stream command output frames evenly (with a constant FPS)? Or maybe there's another way to reduce RTSP connection (buffering?) time?

question from:https://stackoverflow.com/questions/66054174/re-streaming-rtsp-with-higher-fps

Answer 1

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