ChannelMixer class needs to override pure virtual function in base class.

[alw1746]

Hardware: ESP32-S3-Supermini
Software: ESP32S3 Module, Audio Tools 1.2.0, Arduino 2.3.6

Following test sketch failed to compile.

Sketch

/*
Stereo-to-mono converter.
*/
#include "AudioTools.h"
AudioInfo info(44100,2,16);
SineWaveGenerator<int16_t> sineWave;                
GeneratedSoundStream<int16_t> sound(sineWave); // Stream generated from sine wave
CsvOutput<int16_t> out(Serial); 
ChannelMixer mixer;
ConverterStream<int16_t> monoStream(out, mixer);    //apply mixer and send to out
StreamCopy copier(monoStream, sound);      //send sound to converter

void setup(void) {  
  Serial.begin(115200);
  AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);
  sineWave.begin(info, N_B4);
  sound.begin();
  out.begin(info);
}

void loop() {
  copier.copy();
  delay(200);
}

Error messages

error: cannot declare variable 'mixer' to be of abstract type 'audio_tools::ChannelMixer'
because the following virtual functions are pure within 'audio_tools::ChannelMixer':
'virtual size_t audio_tools::BaseConverter::convert(uint8_t*, size_t)'

Cause

The abstract class BaseConverter has a pure virtual function convert() which must be overridden in derived classes.
 virtual size_t convert(uint8_t *src, size_t size) = 0;

Workaround

I've modified ChannelMixer class using ChannelAvg as example.

template <typename T = int16_t>
class ChannelMixer : public BaseConverter {
 public:
  ChannelMixer(int channels = 2) { this->channels = channels; }

  size_t convert(uint8_t *src, size_t size) override {      // ==> override pure virtual function in base class
    return convert(src, src, size);
  }
  size_t convert(uint8_t *target, uint8_t *src, size_t size) {
    T *srcT = (T *)src;
    T *targetT = (T *)target;
    int samples = size / sizeof(T);
    assert(samples % channels == 0);
    for (int j = 0; j < samples; j += channels) {
      float sum = 0;
      for (int ch = 0; ch < channels; ch++) {
        sum += srcT[j + ch];
      }
      T avg = sum / channels;
      for (int ch = 0; ch < channels; ch++) {
        targetT[j + ch] = avg;
      }
    }
    return size;
  }

 protected:
  int channels = 2;
};

[alw1746]

Moved to Issues.