View Source Membrane.H264.FFmpeg.Encoder (Membrane H264 FFmpeg plugin v0.31.6)

Membrane element that encodes raw video frames to H264 format.

The element expects each frame to be received in a separate buffer, so the parser (Membrane.Element.RawVideo.Parser) may be required in a pipeline before the encoder (e.g. when input is read from Membrane.File.Source).

Additionally, the encoder has to receive proper stream_format with picture format and dimensions before any encoding takes place.

Please check t/0 for available options.

Element options

Passed via struct Membrane.H264.FFmpeg.Encoder.t/0

  • crf


    Default value: 23
    Constant rate factor that affects the quality of output stream. Value of 0 is lossless compression while 51 (for 8-bit samples) or 63 (10-bit) offers the worst quality. The range is exponential, so increasing the CRF value +6 results in roughly half the bitrate / file size, while -6 leads to roughly twice the bitrate.

  • preset


    Default value: :medium
    Collection of predefined options providing certain encoding. The slower the preset chosen, the higher compression for the same quality can be achieved.

  • profile

    H264.profile() | nil

    Default value: nil
    Sets a limit on the features that the encoder will use to the ones supported in a provided H264 profile. Said features will have to be supported by the decoder in order to decode the resulting video. It may override other, more specific options affecting compression (e.g setting max_b_frames to 2 while profile is set to :baseline will have no effect and no B-frames will be present).

  • tune

    tune() | nil

    Default value: nil
    Optionally tune the encoder settings for a particular type of source or situation. See x264 encoder's man page for more info. Available options are:

    • :film - use for high quality movie content; lowers deblocking
    • :animation - good for cartoons; uses higher deblocking and more reference frames
    • :grain - preserves the grain structure in old, grainy film material
    • :stillimage - good for slideshow-like content
    • :fastdecode - allows faster decoding by disabling certain filters
    • :zerolatency - good for fast encoding and low-latency streaming
  • use_shm?


    Default value: false
    If true, native encoder will use shared memory (via Shmex.t/0) for storing frames

  • max_b_frames

    non_neg_integer() | nil

    Default value: nil
    Maximum number of B-frames between non-B-frames. Set to 0 to encode video without b-frames

  • gop_size

    non_neg_integer() | nil

    Default value: nil
    Number of frames in a group of pictures.

  • sc_threshold


    Default value: 40
    Sets the threshold for scene change detection. This determines how aggressively x264 will try to insert extra I-frames (higher values increase the number of scene changes detected). Set to 0 to disable scene change detection (no extra I-frames will be inserted). See this page for more info.



Accepted formats:

%RawVideo{pixel_format: format, aligned: true} when format in [:I420, :I422]
Flow control::auto


Accepted formats:

%H264{alignment: :au, stream_structure: :annexb}
Flow control::auto




Struct containing options for Membrane.H264.FFmpeg.Encoder


Returns description of options available for this module


@type preset() ::
  | :superfast
  | :veryfast
  | :faster
  | :fast
  | :medium
  | :slow
  | :slower
  | :veryslow
  | :placebo
@type t() :: %Membrane.H264.FFmpeg.Encoder{
  crf: 0..63,
  gop_size: non_neg_integer() | nil,
  max_b_frames: non_neg_integer() | nil,
  preset: preset(),
  profile: Membrane.H264.profile() | nil,
  sc_threshold: non_neg_integer(),
  tune: tune() | nil,
  use_shm?: boolean()

Struct containing options for Membrane.H264.FFmpeg.Encoder

@type tune() :: :film | :animation | :grain | :stillimage | :fastdecode | :zerolatency


@spec options() :: keyword()

Returns description of options available for this module