Sampling Rate Problem - AEC

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Hello All

I need to ensure the waveapi use 8K sampling rate for wavein and
waveout without any sample rate conversion. In the hardware, apparently
there is an option that can force this, even if this is not the case by
default.

I am using Wave apis on an Pocket PC platform.
If I use the wavein and waveout interfaces at 8K sampling rate, there
is drift in the samples which is bad for AEC.

I can think of two possibilities causing this problem
a) The default audio driver behavior uses two clocks. Generally
playback uses audio hardware clock, record uses a derivation CPU master
clock in the master mode settings (default) of the Audio hardware. CPU
master clock is used in both directions for Slave Mode setting, but
there seems to be no mechanism to access it from user level.

b) Sampling rate conversion (from 44.1K to 8K) in the playback path
causing drift. The Windows mixer may be using a sample rate conversion
which is causing the drift.

My questions:
a) Is there a simple solution to force both paths to use same clock and
sampling rate, since the option does exist at hardware level.
b) Can Windows Mobile DDK help in modifying the behavior for the
specific target?

Your input will be deeply appreciated, since I am grappling with this
problem for quite some time

thanks
Venu

.

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