This list can be empty, if ChannelCount or PrecisionHW are not accepted by the driver. Even if the function returns a specific sampling frequency, the driver may still reject the configuration just before the playback or recording is about to start. This depends upon the quality of the driver implementation. The function tests only for 4 typical sampling frequencies: 44.1kHz, 48kHz, 96kHz, 192kHz. 

You can test for additional frequencies by setting SamplingFrequency (SamplingFrequencyHW) property and call IsFormatSupported function. If the function returns true, the sampling frequency can be used by the hardware. 

A good apprach is to first set PrecisionHW to asp16 (the most generic format) and then test for all supported frequencies. Once the frequencies are known, test for supported precisions.

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