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

  0..63

  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

  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?

  boolean()

  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

  non_neg_integer()

  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.

Pads

:input

Accepted formats:

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

:output

Accepted formats:

%H264{alignment: :au, stream_structure: :annexb}