GetSamplingRateId
rates |= GetSamplingRateId(frequencies[i]);
rates |= GetSamplingRateId(frequencies[i]);
uint32 GetSamplingRateId(uint32 rate);
format->rate = fAlternates[fActiveAlternate]->GetSamplingRateId(0);
if (format->rate == alternate->GetSamplingRateId(0)