[opus] Getting audio artifacts from Opus PLC

[Honeyager, Kevin S.]

I'm running Opus (both encoder and decoder) on a Cortex-M7 (using floating point), and am getting an audible artifact each time I call the decoder with a NULL for the input data pointer.   Normal encoding/decoding sounds fine, but when I run a test where I pass in a NULL on every 20th frame, I can hear what sounds like a quieting of the background noise and an impure tone (each time at a different frequency).  I am running with 40ms frames in CBR mode with 16KHz input sample rate and decoded output rate. Signal is set to VOICE and complexity is 10.

Is there anything else I need to do besides pass in a NULL as the input data?  And if I do this consecutive times, what should be the result (audio-wise),  e.g. will it attenuate the output signal each time until the signal goes away?

I don't get this effect when I use opusenc and opusdec utilities, although I can't set all of the encoder controls that I do in my code.  FYI, I am running v1.1.2 of opus (which for some reason is much slower than v1.1.1beta).
Kevin
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