View Source Membrane.AudioMixer.NativeAdder (Membrane Audio Mix plugin v0.16.0)

Module responsible for mixing audio tracks (all in the same format, with the same number of channels and sample rate). The result is a single track in the format mixed tracks are encoded in. If overflow happens during mixing, a wave will be scaled down to the max sample value. Uses NIFs for mixing.

Description of the algorithm:

  • Start with an empty queue
  • Enqueue merged values while the sign of the values remains the same
  • If the sign of values changes or adder is flushed:
    • If none of the values overflows limits of the format, convert the queued values to binary samples and return them
    • Otherwise, scale down the queued values, so the peak of the wave will become maximal (minimal) allowed value, then convert it to binary samples and return them.