message: AudioSummer: do not use disabled channels
diff: @@ -7,17 +7,25 @@ void AudioSummer4_F32::update(void) {
  int channel = 0;
  while (channel < 4) {
  out = receiveWritable_f32(channel);
  - if (out) break;
  + if (out && flag_useChan[channel]) {
  + //yes, this is an audio block and use it
  + break;
  + } else {
  + //this may or may not be an audio block, but don't use it
  + if (!out) AudioStream_F32::release(out);
  + }
  channel++;
  }
  if (!out) return; //there was no data available. so exit.
  - //add in the remaining channels, as available
  + //add in the remaining channels, as available and if enabled
  channel++;
  while (channel < 4) {
  in = receiveReadOnly_f32(channel);
  if (in) {
  + if (flag_useChan[channel]) {
  arm_add_f32(out->data, in->data, out->data, in->length);
  + }
  AudioStream_F32::release(in);
  } else {
  //do nothing, this vector is empty
  