OnAudioDataCallback.cs

public unsafe void OnAudioDataCallback(IntPtr _, char id1, char id2, short* pcmFrames, int frameCount, int frameRateHz, int channels, int isSilence) {
    // ignore silent samples
    if (isSilence == 1) return;
    if (channels != 2) {
        Debug.LogWarning("unexpected number of channels " + channels);
        return;
    }
    
    sampleBytes = new byte[frameCount * 2 * channels]; // each channel has a frame of 2 bytes
    /*
        Starting from pcmFrames pointer, iterate over the array in memory
        expecting vivox frames to be in format LRLRLR...
        which results in byte array: LLRRLLRRLLRR...
    */
    for (int i = 0; i < frameCount * channels; i++) {
        // expand the frame into two bytes
        short frame = pcmFrames[i];
        BitHelpers.ToBytes(frame, out sampleBytes[i * 2], out sampleBytes[i * 2 + 1]);
    }
    
    udpClient.SendAsync(sampleBytes);
}