Playing MP3 File

File.cd(__DIR__)
Logger.configure(level: :error)

Mix.install([
  {:membrane_core, "~> 1.0"},
  {:membrane_file_plugin, "~> 0.16.0"},
  {:membrane_mp3_mad_plugin, "~> 0.18.2"},
  {:membrane_ffmpeg_swresample_plugin, "~> 0.19.1"},
  {:membrane_aac_fdk_plugin, "~> 0.18.5"},
  {:membrane_kino_plugin, github: "membraneframework-labs/membrane_kino_plugin", tag: "v0.3.1"}
])

Description

This is example of loading MP3 audio from the file, transcoding it to the AAC codec, and playing it via Membrane.Kino.Player.

Pipeline definition

Defines simple linear pipeline of the given structure:

1. Load MP3 file from the file.
2. Transcode MP3 to AAC (it is required by Kino.Player):
   1. Decode MP3 format to RawAudio,
   2. Change sample_format from s24le to s16le (it is required by FDK.Encoder),
   3. Encode it to AAC format.
3. Fill in audio stream to the player via :audio input pad.

import Membrane.ChildrenSpec,
  only: [{:child, 2}, {:child, 3}, {:via_in, 2}]

alias Membrane.{
  File,
  MP3,
  FFmpeg,
  RawAudio,
  AAC,
  Kino
}

audio_path = "./assets/sample.mp3"
kino = Membrane.Kino.Player.new(audio: true)

spec =
  child(:file_source, %File.Source{location: audio_path})
  |> child(:decoder_mp3, MP3.MAD.Decoder)
  |> child(:converter, %FFmpeg.SWResample.Converter{
    input_stream_format: %RawAudio{channels: 2, sample_format: :s24le, sample_rate: 48_000},
    output_stream_format: %RawAudio{channels: 2, sample_format: :s16le, sample_rate: 44_100}
  })
  |> child(:encoder_aac, AAC.FDK.Encoder)
  |> via_in(:audio)
  |> child(:player, %Kino.Player.Sink{kino: kino})

:ok

Player

Run pipeline:

alias Membrane.RCPipeline, as: RC

pipeline = RC.start!()
RC.exec_actions(pipeline, spec: spec)

kino