How to run Riva ASR Realtime from rtsp source?

I have a rtsp video source, i want to run riva asr realtime, but input-file in examples/riva_streaming_asr_client.py is wav file with LINEAR_PCM encoding. I tried using the ffmpeg library to download and simultaneously run python files, but it was delayed by about 10-15 seconds. Help me run Realtime!