Converting the Number of Input and Output Channels

We can use the ChannelFormatConverterStream class to convert the number of input and output channels: we just need to wrap the final input or output class in the constructor. This class is supporting both: the conversion on the input and on the output side. Here are examples for the different scenarios:

Increasing Output Channels

#include "AudioTools.h"

uint16_t sample_rate=44100;
uint8_t from_channels = 1;                                           
uint8_t to_channels = 2;                                            
SineWaveGenerator<int16_t> sine_wave(32000);                         // subclass of SoundGenerator with max amplitude of 32000
GeneratedSoundStream<int16_t> in_stream(sine_wave);                  // Stream generated from sine wave
CsvStream<int16_t> out(Serial, to_channels);                         // Output to Serial
ChannelFormatConverterStream<int16_t> conv(out);
StreamCopy copier(conv, in_stream);                                  // copies sound to out

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  sine_wave.begin(from_channels, sample_rate, N_B4);
  conv.begin(from_channels, to_channels);
  in_stream.begin();

  out.begin();
}

void loop(){
    copier.copy();
}

Decreasing Output Channels

#include "AudioTools.h"

uint16_t sample_rate=44100;
uint8_t from_channels = 2;                                           
uint8_t to_channels = 1;                                             
SineWaveGenerator<int16_t> sine_wave(32000);                         // subclass of SoundGenerator with max amplitude of 32000
GeneratedSoundStream<int16_t> in_stream(sine_wave);                  // Stream generated from sine wave
CsvStream<int16_t> out(Serial, to_channels);                         // Output to Serial
ChannelFormatConverterStream<int16_t> conv(out);
StreamCopy copier(conv, in_stream);                                  // copies sound to out

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  sine_wave.begin(from_channels, sample_rate, N_B4);
  conv.begin(from_channels, to_channels);
  in_stream.begin();

  out.begin();
}

void loop(){
    copier.copy();
}

Increasing Input Channels

#include "AudioTools.h"

uint16_t sample_rate=44100;
uint8_t from_channels = 1;                                           // The stream will have 2 channels 
uint8_t to_channels = 2;                                             // The stream will have 2 channels 
SineWaveGenerator<int16_t> sine_wave(32000);                         // subclass of SoundGenerator with max amplitude of 32000
GeneratedSoundStream<int16_t> in_stream(sine_wave);                  // Stream generated from sine wave
CsvStream<int16_t> out(Serial, to_channels);                         // Output to Serial
ChannelFormatConverterStream<int16_t> conv(in_stream);
StreamCopy copier(out, conv);                                       // copies converted sound to out

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  sine_wave.begin(from_channels, sample_rate, N_B4);
  conv.begin(from_channels, to_channels);
  in_stream.begin();

  out.begin();
}

void loop(){
    copier.copy();
}

Decreasing Input Channels

#include "AudioTools.h"

uint16_t sample_rate=44100;
uint8_t from_channels = 2;                                           // The stream will have 2 channels 
uint8_t to_channels = 1;                                             // The stream will have 2 channels 
SineWaveGenerator<int16_t> sine_wave(32000);                         // subclass of SoundGenerator with max amplitude of 32000
GeneratedSoundStream<int16_t> in_stream(sine_wave);                  // Stream generated from sine wave
CsvStream<int16_t> out(Serial, to_channels);                         // Output to Serial
ChannelFormatConverterStream<int16_t> conv(in_stream);
StreamCopy copier(out, conv);                                       // copies converted sound to out

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  sine_wave.begin(from_channels, sample_rate, N_B4);
  conv.begin(from_channels, to_channels);
  in_stream.begin();

  out.begin();
}

void loop(){
    copier.copy();
}

Similar Logic - Converters

We can also reduce the number of channels by using a ChannelReducer Converters:

#include "AudioTools.h"
#include "AudioLibs/PortAudioStream.h"

uint16_t sample_rate=44100;
uint8_t channels = 2;                                             // The stream will have 2 channels 
SineWaveGenerator<int16_t> sine_wave(32000);                                           // subclass of SoundGenerator with max amplitude of 32000
GeneratedSoundStream<int16_t> in_stream(sine_wave);                   // Stream generated from sine wave
PortAudioStream out;                                              // Output to Desktop
StreamCopy copier(out, in_stream);                                // copies sound to out
ChannelReducer<int16_t> reducer(channels,1);

void setup(){
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Info);  

  sine_wave.begin(channels, sample_rate, N_B4);
  in_stream.begin();
  
  auto cfg1 = out.defaultConfig();
  cfg1.sample_rate = sample_rate;
  cfg1.channels = channels;
  cfg1.bits_per_sample = 16;
  out.begin(cfg1);
}

void loop(){
    copier.copy(reducer);
}