Bin handling one RTP session, that may consist of multiple incoming and outgoing RTP streams.

Incoming streams

Incoming RTP streams can be connected via :rtp_input pads. As each pad can provide multiple RTP streams, they are distinguished basing on SSRC. Once a new stream is received, bin sends new_stream_notification_t/0 notification, meaning the parent should link Pad.ref(:output, ssrc) pad to consuming components. The stream is then depayloaded and forwarded via said pad.

Outgoing streams

To create an RTP stream, the source stream needs to be connected via Pad.ref(:input, ssrc) pad and the sink - via Pad.ref(:rtp_output, ssrc). At least one of :encoding or :payload_type options of :rtp_output pad must be provided too.

Payloaders and depayloaders

Payloaders are Membrane elements that transform stream so that it can be put into RTP packets, while depayloaders work the other way round. Different codecs require different payloaders and depayloaders. Thus, to send or receive given codec via this bin, proper payloader/depayloader is needed. Payloaders and depayloaders can be found in membrane_rtp_X_plugin packages, where X stands for codec name. It's enough when such plugin is added to dependencies.

RTCP

RTCP packets for inbound stream can be provided either in-band or via a separate rtp_input pad instance. Corresponding receiver report packets will be sent back through rtcp_output with the same id as rtp_input for the RTP stream. RTCP for outbound stream is not yet supported.

Bin options

Passed via struct Membrane.RTP.SessionBin.t/0

• fmt_mapping

  %{RTP.payload_type_t() => {RTP.encoding_name_t(), RTP.clock_rate_t()}}

  Default value: %{}
  Mapping of the custom payload types ( > 95)

• custom_payloaders

  %{RTP.encoding_name_t() => module()}

  Default value: %{}
  Mapping from encoding names to custom payloader modules

• custom_depayloaders

  %{RTP.encoding_name_t() => module()}

  Default value: %{}
  Mapping from encoding names to custom depayloader modules

• rtcp_interval

  Time.t()

  Default value: 5 |> Membrane.Time.seconds()
  Interval between sending subseqent RTCP receiver reports.

• receiver_ssrc_generator

  (local_ssrcs :: [pos_integer], remote_ssrcs :: [pos_integer] -> ssrc :: pos_integer)

  Default value: &Membrane.RTP.SessionBin.generate_receiver_ssrc/2
  Function generating receiver SSRCs. Default one generates random SSRC that is not in local_ssrcs nor remote_ssrcs.

• secure?

  boolean

  Default value: false
  Specifies whether to use SRTP. Requires adding srtp dependency to work.

• srtp_policies

  [ExLibSRTP.Policy.t()]

  Default value: []
  List of SRTP policies to use for decrypting packets. Used only when secure? is set to true. See ExLibSRTP.Policy.t/0 for details.

• receiver_srtp_policies

  [ExLibSRTP.Policy.t()] | nil

  Default value: nil
  List of SRTP policies to use for encrypting receiver reports and other receiver RTCP packets. Used only when secure? is set to true. Defaults to the value of srtp_policies. See ExLibSRTP.Policy.t/0 for details.

Pads

:rtp_input

:input

:rtcp_output

:rtp_output

Options:

• payload_type

  RTP.payload_type_t() | nil

  Default value: nil
  Payload type of output stream. If not provided, determined from :encoding.

• encoding

  RTP.encoding_name_t() | nil

  Default value: nil
  Encoding name of output stream. If not provided, determined from :payload_type.

• clock_rate

  integer() | nil

  Default value: nil
  Clock rate to use. If not provided, determined from :payload_type.

:output

Options:

• encoding

  RTP.encoding_name_t() | nil

  Default value: nil
  Encoding name determining depayloader which will be used to produce output stream from RTP stream.

• clock_rate

  integer() | nil

  Default value: nil
  Clock rate to use. If not provided, determined from fmt_mapping or defaults registered by proper plugins i.e. Membrane.RTP.X.Plugin where X is the name of codec corresponding to encoding.

• extensions

  [extension_t()]

  Default value: []
  List of extensions. Currently :vad is only supported.

  • :vad will turn on Voice Activity Detection mechanism firing appropriate notifications when needed. Should be set only for audio tracks. For more information refer to Membrane.RTP.VAD module documentation. Extensions are applied in the same order as passed to the pad options.