[opus] Opus and sender and receiver sample rate drift.

George de Vries George.deVries at oa.com.au
Sun Sep 21 19:29:30 PDT 2014

Hi All.

I have an application where the sample rate of the sender and receiver can vary by a small margin and the latency needs to be maintained within bounds and can't drift significantly and the system has to be able to cope with clock mismatches up to 0.5%.  For example, the sender may have a clock rate of 48.1kHz and the receiver may have a clock rate of 47.9kHz.
Unfortunately the clock rate of the receiver cannot be adjusted as this is a multichannel device with a common clock and potentially senders from different geographic locations can be sending to different channel on this device at the same time.

I am using the OPUS codec in mono celt mode with a data rate of 32,000 bits per second.

What is the best practice for dropping a frame?  Will there be significant audio artefacts if a frame is just dropped,  that is opus_decode (n-1) and then opus_decode (n+1)?

What is the best practice for adding a frame to the jitter buffer?  Will there be significant audio artefacts if a packet is added by calling opus_decode with a null input playload, that is opus_decode(n), opus_decode(null) and followed by opus_decode(n+1)?


George de Vries
Senior Software Engineer

Open Access
Ph:  +61(0)2 9978 7105

For every complex problem, there is a solution that is simple, neat, and wrong
H.L Mencken.

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