Class: TorchCodec::Decoders::AudioDecoder

Inherits:
Object
  • Object
show all
Defined in:
lib/torchcodec/decoders/audio_decoder.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(source, stream_index: nil, sample_rate: nil, num_channels: nil) ⇒ AudioDecoder

Returns a new instance of AudioDecoder.



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# File 'lib/torchcodec/decoders/audio_decoder.rb', line 6

def initialize(
  source,
  stream_index: nil,
  sample_rate: nil,
  num_channels: nil
)
  @decoder = Decoders.create_decoder(source, "approximate")

  container_metadata = Core.get_container_metadata(@decoder)
  @stream_index =
    stream_index.nil? ? container_metadata[:best_audio_stream_index] : stream_index
  if @stream_index.nil?
    raise ArgumentError, "The best audio stream is unknown and there is no specified stream."
  end
  if @stream_index >= container_metadata[:streams].length
    raise ArgumentError, "The stream at index #{@stream_index} is not a valid stream."
  end

  @metadata = container_metadata[:streams][@stream_index]
  if !@metadata.key?(:sample_rate)
    raise ArgumentError, "The stream at index #{@stream_index} is not an audio stream."
  end

  @desired_sample_rate =
    !sample_rate.nil? ? sample_rate : @metadata[:sample_rate]

  Core.add_audio_stream(
    @decoder,
    stream_index,
    sample_rate,
    num_channels
  )
end

Instance Attribute Details

#metadata ⇒ Object (readonly)

Returns the value of attribute metadata.



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# File 'lib/torchcodec/decoders/audio_decoder.rb', line 4

def metadata
  @metadata
end

Instance Method Details

#get_all_samples ⇒ Object 



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# File 'lib/torchcodec/decoders/audio_decoder.rb', line 40

def get_all_samples
  get_samples_played_in_range
end

#get_samples_played_in_range(start_seconds: 0.0, stop_seconds: nil) ⇒ Object 



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# File 'lib/torchcodec/decoders/audio_decoder.rb', line 44

def get_samples_played_in_range(start_seconds: 0.0, stop_seconds: nil)
  if !stop_seconds.nil? && !(start_seconds <= stop_seconds)
    raise ArgumentError, "Invalid start seconds: #{start_seconds}. It must be less than or equal to stop seconds (#{stop_seconds})."
  end
  frames, first_pts = Core.get_frames_by_pts_in_range_audio(
    @decoder,
    start_seconds,
    stop_seconds
  )
  first_pts = first_pts.item

  sample_rate = @desired_sample_rate
  # TODO: metadata's sample_rate should probably not be Optional
  raise if sample_rate.nil?

  if first_pts < start_seconds
    offset_beginning = ((start_seconds - first_pts) * sample_rate).round
    output_pts_seconds = start_seconds
  else
    # In normal cases we'll have first_pts <= start_pts, but in some
    # edge cases it's possible to have first_pts > start_seconds,
    # typically if the stream's first frame's pts isn't exactly 0.
    offset_beginning = 0
    output_pts_seconds = first_pts
  end

  num_samples = frames.shape[1]
  last_pts = first_pts + num_samples / sample_rate
  if !stop_seconds.nil? && stop_seconds < last_pts
    offset_end = num_samples - ((last_pts - stop_seconds) * sample_rate).round
  else
    offset_end = num_samples
  end

  data = frames[0.., offset_beginning...offset_end]
  {
    data: data,
    pts_seconds: output_pts_seconds,
    duration_seconds: data.shape[1] / sample_rate.to_f,
    sample_rate: sample_rate
  }
end