@type config() :: %{
  :codec => codec(),
  :input_stream_structure => input_stream_structure(),
  :input_alignment => input_alignment(),
  optional(:output_stream_structure) => stream_structure() | nil,
  optional(:repeat_parameter_sets) => boolean(),
  optional(:initial_parameter_sets) => [binary()],
  optional(:generate_best_effort_timestamps) =>
    generate_best_effort_timestamps()
}

Configuration of the parsing engine:

• :codec - the codec of the parsed stream, either :h264 or :h265.
• :input_stream_structure - see input_stream_structure/0.
• :input_alignment - see input_alignment/0.
• :output_stream_structure - the stream structure the output access units are intended for. Determines how the parameter sets are handled: for the structures carrying them out-of-band (:avc1, :hvc1) they are stripped from the access units and carried solely by the DCRs of the :parameter_sets events. Defaults to the input stream structure.
• :repeat_parameter_sets - if true, all the active parameter sets are attached to each keyframe access unit. Takes no effect for the :avc1 and :hvc1 output stream structures, where the parameter sets travel out-of-band. Defaults to false.
• :initial_parameter_sets - raw (unprefixed) payloads of parameter sets absent from the stream, scheduled to be parsed before the first pushed payload. Defaults to [].
• :generate_best_effort_timestamps - see generate_best_effort_timestamps/0. Defaults to false.

@type event() ::
  {:access_unit, Membrane.H26x.AccessUnit.t()}
  | {:parameter_sets,
     %{
       output_raw_stream_structure: raw_stream_structure(),
       active: [Membrane.H26x.NALu.t()]
     }}

An item of the engine's output.

Access units (see Membrane.H26x.AccessUnit.t/0) are interleaved with parameter set change notifications: whenever the set of active parameter sets changes, a :parameter_sets event is emitted right before the access unit that introduced the change. The event carries all the parameter sets active at that point of the stream (the most recent set per parameter set type and id) and the raw output stream structure (see raw_stream_structure/0) - for the length-prefixed output stream structures its Decoder Configuration Record is generated out of the active parameter sets.

@type generate_best_effort_timestamps() ::
  false
  | %{
      :framerate => {frames :: pos_integer(), seconds :: pos_integer()},
      optional(:add_dts_offset) => boolean()
    }

If set to a map, timestamps are generated based on the provided constant framerate (available only for the :bytestream input alignment). :add_dts_offset shifts DTS values so that they don't exceed PTS values, defaults to true.

@type input_alignment() :: :bytestream | :nalu | :au

Alignment of the payloads fed to the engine - an arbitrary stream of bytes (:bytestream), a single NAL unit per payload (:nalu) or a whole access unit per payload (:au).

@type input_stream_structure() ::
  stream_structure()
  | {codec_tag :: :avc1 | :avc3 | :hvc1 | :hev1, dcr :: binary()}

The structure of the input stream.

For the length-prefixed structures (:avc1, :avc3, :hvc1, :hev1), instead of the NALu length size, a Decoder Configuration Record binary (e.g. coming from an MP4 container) may be provided - the NALu length size is then read from it and the parameter sets it carries are scheduled to be parsed before the first pushed payload.

@type raw_stream_structure() ::
  :annexb | {codec_tag :: :avc1 | :avc3 | :hvc1 | :hev1, dcr :: binary() | nil}

Structure of the H26x stream in the raw form transferred out-of-band: either :annexb, or a codec tag along with a Decoder Configuration Record binary carrying the stream's parameter sets (nil if no SPS has been seen yet, so no DCR can be generated).

@type stream_structure() ::
  :annexb
  | {codec_tag :: :avc1 | :avc3 | :hvc1 | :hev1,
     nalu_length_size :: pos_integer()}

Structure of the H26x stream - either Annex B, where the NALus are separated by a start code (0x(00)000001), or length-prefixed (as described in ISO/IEC 14496-15), where each NALu is prefixed with its length.