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Calculate FPS rate of an RTSP stream

This simple python script calculates the framerate of a RTSP stream based on the PTS field of it's frames.

Some camera manufacturers (Hikvision for example) state that their cameras produce output at 30fps. In reality, the FPS of a RTSP stream can be slightly different (30.039 or 29.97 fps for example). This can produce stuttering when live streaming.

Sometimes, the PTS rate might not be monotonically increasing between frames, causing even more stuttering. Knowing the actual framerate can help with fixing the stream (explained at the bottom of this file).

Usage for h264 streams:

python3 run.py 'rtspsrc location=rtspt://user:[email protected]:5540/Streaming/Channels/101 ! \
rtph264depay ! identity name=adjust ! fakesink'

Usage for h265 streams:

python3 run.py 'rtspsrc location=rtspt://user:[email protected]:5540/Streaming/Channels/101 ! \
rtph265depay ! identity name=adjust ! fakesink'

Output:

frames =  2299  pts per frame =  33290094.903001305  fps =  30.039
frames =  2399  pts per frame =  33289677.256356817  fps =  30.0393
frames =  2499  pts per frame =  33289843.523809522  fps =  30.0392
frames =  2599  pts per frame =  33290053.84570989  fps =  30.039
frames =  2699  pts per frame =  33290112.12930715  fps =  30.0389
frames =  2799  pts per frame =  33290178.42300822  fps =  30.0389

The script outputs the FPS every 100 frames. The FPS is calculated based on the timestamp different of the first and the last frame received. The first 300 frames are ignored, because the PTS can be unstable when connecting for the first time.

Keep this script running, until the fps value stops jumping up and down. Stop with Ctrl-C.

What to do with this number?

So let's say you know that your FPS is 30.039. You can now have gstreamer fix the framerate with videorate by providing 30039/1000 (30.039) as a framerate. So even if PTS is not monotonically increasing in some frames the original RTSP stream (which causes stutering), you can still get a stable feed:

gst-launch-1.0 rtspsrc location=rtspt://user:[email protected]:5540/Streaming/Channels/101 ! \
rtph264depay ! h264parse ! avdec_h264 ! \
videorate ! video/x-raw,framerate=30039/1000 ! \
watchdog timeout=10000 ! autovideosink