This element performs audio mixing.

Audio format can be set as an element option or received through stream_format from input pads. All received stream_format have to be identical and match ones in element option (if that option is different from nil).

Input pads can have offset - it tells how much silence should be added before first sample from that pad. Offset has to be positive.

Mixer mixes only raw audio (PCM), so some parser may be needed to precede it in pipeline.

Element options

Passed via struct Membrane.AudioMixer.t/0

• stream_format

  RawAudio.t()

  Default value: nil
  The value defines a raw audio format of pads connected to the element. It should be the same for all the pads.

• frames_per_buffer

  pos_integer()

  Default value: 2048
  Assumed number of raw audio frames in each buffer. Used when converting demand from buffers into bytes.

• prevent_clipping

  boolean()

  Default value: true
  Defines how the mixer should act in the case when an overflow happens.

  • If true, the wave will be scaled down, so a peak will become the maximal value of the sample in the format. See Membrane.AudioMixer.ClipPreventingAdder.
  • If false, overflow will be clipped to the maximal value of the sample in the format. See Membrane.AudioMixer.Adder.

• native_mixer

  boolean()

  Default value: false
  The value determines if mixer should use NIFs for mixing audio. Only clip preventing version of native mixer is available. See Membrane.AudioMixer.NativeAdder.

• synchronize_buffers?

  boolean()

  Default value: false
  The value determines if mixer should synchronize buffers based on pts values.

  • If true, mixer will synchronize buffers based on its pts values. If buffer pts value is lower then the current mixing time (last_ts_sent) it will be dropped.
  • If false, mixer will take all incoming buffers no matter what pts they have and put it in the queue.

Pads

:input

Accepted formats:

%RawAudio{sample_format: sample_format}
when sample_format in [:s8, :s16le, :s16be, :s24le, :s24be, :s32le, :s32be]

RemoteStream

Pad options:

• offset

  Time.non_neg()

  Default value: 0
  Offset of the input audio at the pad.

:output

Accepted formats:

RawAudio