added average_rate
added average_rate

mcpv/PyAV,danielballan/PyAV,xxr3376/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,markreidvfx/PyAV,mikeboers/PyAV,danielballan/PyAV,markreidvfx/PyAV,PyAV-Org/PyAV,markreidvfx/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,mikeboers/PyAV,mcpv/PyAV,danielballan/PyAV,xxr3376/PyAV,mcpv/PyAV,xxr3376/PyAV,PyAV-Org/PyAV