Tasks as input an unparsed stream and provides on each pad an unparsed, transcoded stream with the desired properties.

Input might be MPEG-TS or FLV but other streaming containers might work as well. If the input stream contains more than 1 video and 1 audio stream, which one will be picked is undefined behaviour.

Process lifecycle

Each bin runs FFmpeg once. When the bin observes that process exiting, it sends its parent one notification:

{:transcoder_exited, %{reason: reason, input_eos_received?: boolean}}

reason is :normal for exit zero, {:status, code} for a nonzero exit, or {:signal, signal, core_dump?} for termination by signal. Infrastructure failures may carry another reason, such as :port_closed.

input_eos_received? records whether the FFmpeg filter had handled input EOS when it observed the exit. It is an observation, not a success classification. An exit can be abnormal even after input EOS; decoder warnings can also occur before a successful exit.

Process exit does not mean that the media outputs or downstream sinks have finished. The bin preserves output EOS for normal and abnormal FFmpeg exits, after its readers have drained. The notification and individual output EOS travel through different processes; callers must tolerate either arrival order and use downstream completion to coordinate draining.

The bin never restarts FFmpeg. Its parent owns recovery, drain deadlines, and any replacement run. Internal element/reader failures still use ordinary OTP failure propagation. The notification is not guaranteed during bin teardown or a bin crash; callers must also supervise or monitor their media graph.

Bin options

Passed via struct Membrane.FFmpeg.Transcoder.t/0

• wait_random_access_indicator

  boolean()

  Default value: true
  If enabled, emits packets only after the random access indicator is found in the MPEG-TS PES stream, otherwise packets are emitted immediately. When enabled, it means that the first video packet that comes out is going to be a keyframe unit.

Pads

:input

Accepted formats:

Membrane.RemoteStream

:scte

Accepted formats:

Membrane.RemoteStream

Membrane.AAC

Membrane.H264

Pad options:

• pid

  pos_integer()

  Default value: nil
  PID of the SCTE stream. When nil it grabs the first stream.

:text

Accepted formats:

Membrane.Text

Pad options:

• source

  {:dvb_teletext, 100..899}

  Required
  Defines the source of the captions. Currently supported:
  • Teletext: {:dvb_teletext, page_number}

:video

Accepted formats:

Membrane.RemoteStream

Membrane.AAC

Membrane.H264

Pad options:

• copy

  boolean()

  Default value: false
  If enabled, the stream will not be re-encoded

• resolution

  {integer(), integer()}

  Default value: {-2, 720}
  Resolution of the given output.

• bitrate

  pos_integer()

  Default value: 3300000
  Maximum bitrate

• profile

  atom()

  Default value: :high
  H264 Profile

• crf

  pos_integer()

  Default value: 26

• preset

  atom()

  Default value: :high

• tune

  atom()

  Default value: :zerolatency

• fps

  pos_integer()

  Default value: 30

• gop_size

  pos_integer()

  Default value: 60

• b_frames

  pos_integer()

  Default value: 3

• level

  String.t()

  Default value: "3.1"

:audio

Accepted formats:

Membrane.RemoteStream

Membrane.AAC

Membrane.H264

Pad options:

• copy

  boolean()

  Default value: false
  If enabled, the stream will not be re-encoded

• codec

  :aac | :opus

  Default value: :aac
  Audio codec to use for encoding. Ignored when copy is true.

• bitrate

  pos_integer()

  Default value: 128000
  Maximum bitrate

• sample_rate

  pos_integer()

  Default value: 48000

• channels

  pos_integer()

  Default value: 2