[alsa-devel] Variable Delay through ALSA driver

[Brandon Yates]

I have an application using the ALSA API that writes to playback device
and simultaneously reads from capture device.  My processing loop is :

1)Read from microphone (blocking)
2)Process Data
3)Write to speaker

I am measuring the delay from the time I play a series of frames to the
speaker until I detect the echo of this coming back in through the
microphone.  This delay seems to be changing every time I initialize the
devices with ALSA. I have measured in the range of 60-160ms delay.  I
know things like period size effect delay, but using the exact same
software and hardware configuration I would expect this to be constant
across runs.  What are some parameters that can help me make the delay
deterministic?

Thanks,
Brandon