# Membrane Audio Mix Plugin
[](https://hex.pm/packages/membrane_audio_mix_plugin)
[](https://hexdocs.pm/membrane_audio_mix_plugin/)
[](https://circleci.com/gh/membraneframework/membrane_audio_mix_plugin)
Plugin providing elements for mixing and interleaving raw audio frames.
It is a part of [Membrane Multimedia Framework](https://membraneframework.org).
## Installation
Add the following line to your `deps` in `mix.exs`. Run `mix deps.get`.
```elixir
{:membrane_audio_mix_plugin, "~> 0.12.0"}
```
## Description
Both elements operate only on raw audio (PCM), so some parser may be needed to precede them in a pipeline.
The elements expect to receive the same audio stream format on each input pad. It can be additionally enforced by setting an element option (`:stream_format`)
Input pads can have offset - it tells how much silence should be added before first sample
from that pad. Offset has to be positive.
All inputs have to be added before starting the pipeline and should not be changed
during mixer's or interleaver's work.
Mixing and interleaving is tested only for integer audio formats.
### Mixer
The Mixer adds samples from all pads. It has two strategies to deal with the overflow:
scaling down waves and clipping.
### Interleaver
This element joins several mono audio streams (with one channel) into one stream with interleaved channels.
If audio streams have different durations, all shorter streams are appended with silence to match the longest stream.
Each channel must be named by providing an input pad name and the channel layout using those names must be provided (see [usage example](#audiointerleaver)).
## Usage Example
### AudioMixer
```elixir
defmodule Mixing.Pipeline do
use Membrane.Pipeline
@impl true
def handle_init(_ctx, _options) do
structure = [
child({:file_src, 1}, %Membrane.File.Source{location: "/tmp/input_1.raw"})
|> get_child(:mixer),
child({:file_src, 2}, %Membrane.File.Source{location: "/tmp/input_2.raw"})
|> via_in(:input, options: [offset: Membrane.Time.milliseconds(5000)])
|> get_child(:mixer),
child(:mixer, %Membrane.AudioMixer{
stream_format: %Membrane.RawAudio{
channels: 1,
sample_rate: 16_000,
sample_format: :s16le
}
})
|> child(:converter, %Membrane.FFmpeg.SWResample.Converter{
input_stream_format: %Membrane.RawAudio{channels: 1, sample_rate: 16_000, sample_format: :s16le},
output_stream_format: %Membrane.RawAudio{channels: 2, sample_rate: 48_000, sample_format: :s16le}
})
|> child(:player, Membrane.PortAudio.Sink)
]
{[spec: structure], %{}}
end
end
```
### AudioInterleaver
```elixir
defmodule Interleave.Pipeline do
use Membrane.Pipeline
alias Membrane.File.{Sink, Source}
@impl true
def handle_init(_ctx, {path_to_wav_1, path_to_wav_2}) do
structure = [
child({:file, 1}, %Source{location: path_to_wav_1})
|> child({:parser, 1}, Membrane.WAV.Parser)
|> get_child(:interleaver),
child({:file, 2}, %Source{location: path_to_wav_2})
|> child({:parser, 2}, Membrane.WAV.Parser)
|> get_child(:interleaver),
child(:interleaver, %Membrane.AudioInterleaver{
input_stream_format: %Membrane.RawAudio{
channels: 1,
sample_rate: 16_000,
sample_format: :s16le
},
order: [:left, :right]
})
|> child(:file_sink, %Sink{location: "output.raw"})
]
{[spec: structure], %{}}
end
end
```
## Copyright and License
Copyright 2021, [Software Mansion](https://swmansion.com/?utm_source=git&utm_medium=readme&utm_campaign=membrane)
[](https://swmansion.com/?utm_source=git&utm_medium=readme&utm_campaign=membrane)
Licensed under the [Apache License, Version 2.0](LICENSE)
