Examples of using ChannelAvg and ChannelMixer class

[alw1746]

ChannelAvg class average pairs of channels in a datastream. If you provide a stereo signal, the output is an averaged mono channel. The channel-converter-avg example generates a mono plot from a stereo signal with 493Hz(N_B4) on L and 987Hz(N_B5) on R.

Without the averager conversion, the plot looks like:

ChannelMixer class mixes all input channels in a datastream. If you provide a stereo signal, the output is a mono signal on both channels. Note the difference: ChannelMixer mixes all channels and outputs the mono signal to all channels.
L (channel_1 + channel_2)/2
R (channel_1 + channel_2)/2

ChannelAvg averages pairs of channels eg. a 4-channel input stream will end up with 2 output channels:
L (channel_1 + channel_2)/2
R (channel_3 - channel_4)/2.
A stereo channel averaging will end up with 1 mono output channel.

ChannelMixer Sketch

/**
 * @file channel-converter-mixer.ino
 * @brief Test mix stereo channel into 2 mono channels.
 * @author Alex Wong
 * @copyright GPLv3
 **/
 
#include "AudioTools.h"

AudioInfo                     info1(44100, 1, 16);
AudioInfo                     info2(44100, 2, 16);
SineWaveGenerator<int16_t>    sineWave1(32000);             // subclass of SoundGenerator with max amplitude of 32000
SineWaveGenerator<int16_t>    sineWave2(32000);             // subclass of SoundGenerator with max amplitude of 32000
GeneratedSoundStream<int16_t> sound1(sineWave1);            // stream generated from sine wave1
GeneratedSoundStream<int16_t> sound2(sineWave2);            // stream generated from sine wave2
InputMerge<int16_t>           imerge;                       // merge two inputs to stereo
ChannelMixer                  mixer;                        // channel mixer
ConverterStream<int16_t>      mixed_stream(imerge, mixer);  // pipe the sound to the mixer
CsvOutput<int16_t>            serial_out(Serial);           // serial output
StreamCopy                    copier(serial_out, mixed_stream); // stream the mixed output to serial port

// Arduino Setup
void setup(void) {

  // Open Serial 
  Serial.begin(115200);
  delay(2000);

  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);

  // Setup sine waves
  sineWave1.begin(info1, N_B4);       //493kHz
  sineWave2.begin(info1, N_B5);       //987kHz(+1 octave)

  // Merge input to stereo
  imerge.add(sound1, 1);
  imerge.add(sound2, 1);
  imerge.begin(info2);                //create stereo signal with L(N_B4) and R(N_B5)

  // Define CSV Output
  serial_out.begin(info2);            //mixer outputs B4+B5/2(mono) to both L/R

}  

// Arduino loop - copy sound to out with conversion
void loop() {
    copier.copy();
}