We want to record stereo audio signals by AudioRecord as the below. If we set sample rate to 44,100, are both stereo channels recorded at 44,100Hz or 22,050Hz?
According to our implementation, it seems that half sampling frequency is applied to each channel
AudioRecord audioInputStream = new AudioRecord(Media.Recorder.CAMCORDER,
sampleRate, AudioFormat.CHANNEL_IN_STEREO, AudioFormat.ENCODING_PCM_16BIT,
samplesPerBuffer * bytesPerSample)
The sample rate is constant no matter what the number of channels. So 1 channel at 44.1k you get 44100 total samples per second and with 2 channels you would get 88200 total samples per second.
I don't really know about the API you are using but I can point to one possible area that arises from terminology. The is the difference between a sample and a frame. Usually you consider a sample to be a single value a frame to contain a single sample for each channel. So if you encounter any API that looks something like this: process(double* samples, int numChannels, int numFrames) just beware that the actual number of samples in the buffer is numChannels*numFrames. And misinterpreting something like that could definitely lead to consuming half as many samples as you expect. Also some APIs will confusingly use the term numSamples when they should have used numFrames, etc...
