I’m currently working on a recording system for the Microphone using FMOD. For my single channel microphone this works well, but a tester with a stereo microphone is getting very choppy audio recording.
At the moment my code to setup the recording looks something like this:
var sys = RuntimeManager.CoreSystem;
sys.getRecordDriverInfo(mic, out _, 0, out _, out var rate, out _, out var channels, out _);
// Create a sound with a one second buffer
CREATESOUNDEXINFO exinfo = default;
exinfo.cbsize = Marshal.SizeOf(typeof(CREATESOUNDEXINFO));
exinfo.numchannels = channels;
exinfo.format = SOUND_FORMAT.PCMFLOAT;
exinfo.defaultfrequency = rate;
exinfo.length = (uint)(deviceSampleRate * sizeof(float));
sys.createSound("recording", MODE.LOOP_NORMAL | MODE.OPENUSER, ref exinfo, out _sound);
I only actually need a mono recording, is it possible to tell FMOD to downmix into a single channel for me? For example by replacing exinfo.numchannels = channels; with exinfo.numchannels = 1?
Alternatively, if that’s not possible does my implementation for mixing down to one channel look reasonable?
private ArraySegment<float> DownmixChannels(ArraySegment<float> data)
{
if (_deviceChannels == 1)
return data;
var arr = data.Array;
var channels = _deviceChannels; // This is the same `channels` value from the previous code example
var factor = 1f / channels;
var monoSamples = data.Count / channels;
for (var i = 0; i < monoSamples; i++)
{
// Add together all the channels
var sum = 0f;
for (var j = 0; j < _deviceChannels; j++)
sum += arr[i * channels + j];
// Divide by channel count and save into proper place in buffer
arr[i] = factor * sum;
}
return new ArraySegment<float>(arr, 0, monoSamples);
}