Module: FormatParser::ISOBaseMediaFileFormat::Utils

Included in:
MOVParser, MP4Parser
Defined in:
lib/parsers/iso_base_media_file_format/utils.rb

Constant Summary collapse

IDENTITY_MATRIX = 
Matrix.identity(3)

Instance Method Summary collapse

Instance Method Details

#dimensions(box_tree) ⇒ Object 



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# File 'lib/parsers/iso_base_media_file_format/utils.rb', line 11

def dimensions(box_tree)
  moov_box = box_tree.find { |box| box.type == 'moov' }
  return unless moov_box
  movie_matrix = moov_box.first_child('mvhd')&.dig(:fields, :matrix) || IDENTITY_MATRIX
  extreme_coordinates = video_trak_boxes(box_tree).each_with_object({}) do |trak_box, extreme_coordinates|
    tkhd_box = trak_box.first_child('tkhd')
    next unless tkhd_box
    x = tkhd_box.fields[:width]
    y = tkhd_box.fields[:height]
    next unless x && y
    track_matrix = tkhd_box.fields[:matrix] || IDENTITY_MATRIX
    [[0, 0], [0, y], [x, 0], [x, y]].each do |coordinates|
      x, y = (Matrix[[*coordinates, 1]] * track_matrix * movie_matrix).to_a[0][0..1]
      extreme_coordinates[:min_x] = x if !extreme_coordinates[:min_x] || x < extreme_coordinates[:min_x]
      extreme_coordinates[:max_x] = x if !extreme_coordinates[:max_x] || x > extreme_coordinates[:max_x]
      extreme_coordinates[:min_y] = y if !extreme_coordinates[:min_y] || y < extreme_coordinates[:min_y]
      extreme_coordinates[:max_y] = y if !extreme_coordinates[:max_y] || y > extreme_coordinates[:max_y]
    end
  end
  unless extreme_coordinates.empty?
    [
      extreme_coordinates[:max_x] - extreme_coordinates[:min_x],
      extreme_coordinates[:max_y] - extreme_coordinates[:min_y]
    ]
  end
end

#duration(box_tree) ⇒ Object 



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# File 'lib/parsers/iso_base_media_file_format/utils.rb', line 38

def duration(box_tree)
  mvhd_box = box_tree.find { |box| box.type == 'moov' }&.first_child('mvhd')
  return unless mvhd_box
  duration = mvhd_box.fields[:duration]
  timescale = mvhd_box.fields[:timescale]&.to_f
  duration / timescale if duration && timescale
end

#frame_rate(box_tree) ⇒ Object 



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# File 'lib/parsers/iso_base_media_file_format/utils.rb', line 46

def frame_rate(box_tree)
  video_trak_boxes(box_tree).each do |trak_box|
    mdhd_box = trak_box.first_descendent_by_path(%w[mdia mdhd])
    stts_box = trak_box.first_descendent_by_path(%w[mdia minf stbl stts])

    next unless mdhd_box && stts_box

    timescale = mdhd_box.fields[:timescale]&.to_f
    sample_delta = stts_box.dig(:fields, :entries, 0, :sample_delta)

    next unless timescale && sample_delta

    return (timescale / sample_delta).truncate(2)
  end
  nil
  # TODO: Properly account for and represent variable frame-rates.
end

#video_codecs(box_tree) ⇒ Object 



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# File 'lib/parsers/iso_base_media_file_format/utils.rb', line 64

def video_codecs(box_tree)
  video_trak_boxes(box_tree).flat_map do |trak_box|
    trak_box.all_descendents_by_path(%w[mdia minf stbl stsd]).flat_map { |stsd_box| stsd_box.children.map(&:type) }
  end.compact.uniq
end