How to calculate and reduce the Gst-uridecode and Gst-nvstreammux plugin time?

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For live sources, you must know the FPS of these sources. DeepStream SDK FAQ - Intelligent Video Analytics / DeepStream SDK - NVIDIA Developer Forums

And please remember to set “live-source” property to 1 for nvstreammux.
For “new nvstreammux”, please refer to Gst-nvstreammux New — DeepStream 6.3 Release documentation

If it is RTSP sources, please try to set “latency” property of rtspsrc to a smaller value to reduce the network latency. rtspsrc (gstreamer.freedesktop.org)