Boombox.Bin is a Membrane Bin for audio and video streaming. It can be used as a Sink or Source in your Membrane Pipeline.

If you use it as a Membrane Source and link :output pad, you have to specify :input option, e.g.

child(:boombox, %Boombox.Bin{
  input: "path/to/input/file.mp4"
})
|> via_out(:output, options: [kind: :audio])
|> child(:my_audio_sink, My.Audio.Sink)

If you use it as a Membrane Sink and link :input pad, you have to specify :output option, e.g.

child(:my_video_source, My.Video.Source)
|> via_in(:input, options: [kind: :video])
|> child(:boombox, %Boombox.Bin{
  output: "path/to/output/file.mp4"
})

Boombox.Bin cannot have :input and :output pads linked at the same time.

Boombox.Bin cannot have :input and :output options set at the same time.

If you use Boombox.Bin as a source, you can either:

• link output pads in the same spec where you spawn it

• or wait until Boombox.Bin returns a notification {:new_tracks, [:audio | :video]} and then link the pads according to the notification.

Bin options

Passed via struct Boombox.Bin.t/0

• input

  Boombox.input() | nil

  Default value: nil

• output

  Boombox.output() | nil

  Default value: nil

Pads

:input

Accepted formats:

format when Transcoder.Audio.is_audio_format(format) or Transcoder.Video.is_video_format(format)

Pad options:

• kind

  :video | :audio

  Required
  Specifies, if the input pad is for audio or video.

  There might be up to one pad of each kind at the time.

:output

Accepted formats:

format when Transcoder.Audio.is_audio_format(format) or Transcoder.Video.is_video_format(format)

Pad options:

• kind

  :video | :audio

  Required
  Specifies, if the output pad is for audio or video.

  There might be up to one pad of each kind at the time.

• codec

  H264
  | VP8
  | VP9
  | AAC
  | Opus
  | RawVideo
  | RawAudio
  | [H264 | VP8 | VP9 | AAC | Opus | RawVideo | RawAudio]
  | nil

  Default value: nil
  Specifies the codec of the stream flowing through the pad.

  Can be either a single codec or a list of codecs.

  If a list is provided

  • and the stream matches one of the codecs, the matching codec will be used,
  • and the stream doesn't match any of the codecs, it will be transcoded to the first codec in the list.

  If the codec is not specified, it will be resolved to:

  • Membrane.H264 for video,
  • Membrane.AAC for audio, if the input is not WebRTC,
  • Membrane.Opus for audio, if the input is WebRTC.

• transcoding_policy

  :always | :if_needed | :never

  Default value: :if_needed
  Specifies the transcoding policy for the stream flowing through the pad.

  Can be either :always, :if_needed, or :never.

  If set to :always, the media stream will be decoded and/or encoded, even if the format of the stream arriving at the Boombox.Bin endpoint matches the output pad codec. This option is useful when you want to make sure keyframe request events going upstream the output pad are handled in Boombox when the Boombox input itself cannot handle them (i.e. when the input is not WebRTC).

  If set to :if_needed, the media stream will be transcoded only if the format of the stream arriving at the Boombox.Bin endpoint doesn't match the output pad codec. This is the default behavior.

  If set to :never, the input media stream won't be decoded or encoded. Changing alignment, encapsulation, or stream structure is still possible. This option is helpful when you want to ensure that Boombox.Bin will not use too many resources, e.g., CPU or memory.

  If the stream arriving at the Boombox.Bin endpoint doesn't match the output pad codec, an error will be raised.