Class: Wavesync::CueChunk

Inherits:
Object
  • Object
show all
Defined in:
lib/wavesync/cue_chunk.rb

Constant Summary collapse

RIFF_HEADER_SIZE = 
12
CHUNK_ID_SIZE = 
4
CHUNK_SIZE_FIELD_SIZE = 
4
CUE_CHUNK_ID = 
'cue '
LIST_CHUNK_ID = 
'LIST'
ADTL_LIST_TYPE = 
'adtl'
LABL_CHUNK_ID = 
'labl'
DATA_CHUNK_ID = 
'data'
CUE_HEADER_SIZE = 
4
BYTES_PER_CUE_POINT = 
24
UINT32_LE = 
'V'

Class Method Summary collapse

Class Method Details

.read(filepath) ⇒ Object

: (String filepath) -> Array[Integer, sample_offset: Integer, label: String?]



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# File 'lib/wavesync/cue_chunk.rb', line 20

def self.read(filepath)
  cue_points = [] #: Array[{identifier: Integer, sample_offset: Integer, label: String?}]
  labels = {} #: Hash[Integer, String]

  File.open(filepath, 'rb') do |file|
    file.seek(RIFF_HEADER_SIZE)

    until file.eof?
      chunk_id = file.read(CHUNK_ID_SIZE)
      break if chunk_id.nil? || chunk_id.length < CHUNK_ID_SIZE

      chunk_size_bytes = file.read(CHUNK_SIZE_FIELD_SIZE)
      break if chunk_size_bytes.nil?

      chunk_size = chunk_size_bytes.unpack1(UINT32_LE).to_i
      chunk_data_start = file.tell

      if chunk_id == CUE_CHUNK_ID
        num_cues = file.read(4)&.unpack1(UINT32_LE).to_i
        num_cues.times do
          identifier = file.read(4)&.unpack1(UINT32_LE)&.to_i
          file.read(16) # skip position, fcc_chunk, chunk_start, block_start
          sample_offset = file.read(4)&.unpack1(UINT32_LE)&.to_i
          cue_points << { identifier: identifier, sample_offset: sample_offset, label: nil } if identifier && sample_offset
        end
      elsif chunk_id == LIST_CHUNK_ID && chunk_size >= 4
        list_type = file.read(4)
        read_adtl_labels(file, chunk_data_start + chunk_size, labels) if list_type == ADTL_LIST_TYPE
      end

      chunk_padding = chunk_size.odd? ? 1 : 0
      file.seek(chunk_data_start + chunk_size + chunk_padding)
    end
  end

  cue_points.map { |cue_point| { identifier: cue_point[:identifier], sample_offset: cue_point[:sample_offset], label: labels[cue_point[:identifier]] } }
end

.read_adtl_labels(file, list_end, labels) ⇒ Object

: (untyped file, Integer list_end, Hash[Integer, String] labels) -> void



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# File 'lib/wavesync/cue_chunk.rb', line 145

def self.read_adtl_labels(file, list_end, labels)
  while file.tell < list_end - 8
    sub_id = file.read(CHUNK_ID_SIZE)
    break if sub_id.nil? || sub_id.length < CHUNK_ID_SIZE

    sub_size_bytes = file.read(CHUNK_SIZE_FIELD_SIZE)
    break if sub_size_bytes.nil?

    sub_size = sub_size_bytes.unpack1(UINT32_LE).to_i
    sub_data_start = file.tell

    if sub_id == LABL_CHUNK_ID && sub_size >= 4
      identifier = file.read(4)&.unpack1(UINT32_LE)&.to_i
      text_size = sub_size - 4
      text = text_size.positive? ? (file.read(text_size) || '') : ''
      labels[identifier] = text.delete("\x00") if identifier
    end

    sub_padding = sub_size.odd? ? 1 : 0
    file.seek(sub_data_start + sub_size + sub_padding)
  end
end

.update_riff_size(filepath) ⇒ Object

: (String filepath) -> void



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# File 'lib/wavesync/cue_chunk.rb', line 169

def self.update_riff_size(filepath)
  File.open(filepath, 'r+b') do |file|
    file.seek(0, IO::SEEK_END)
    file_size = file.tell
    riff_size = file_size - 8
    file.seek(4)
    file.write([riff_size].pack(UINT32_LE))
  end
end

.write(source_filepath, output_filepath, cue_points) ⇒ Object

: (String source_filepath, String output_filepath, Array[Integer, sample_offset: Integer, label: String?] cue_points) -> void



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# File 'lib/wavesync/cue_chunk.rb', line 59

def self.write(source_filepath, output_filepath, cue_points)
  File.open(source_filepath, 'rb') do |input|
    File.open(output_filepath, 'wb') do |output|
      output.write(input.read(RIFF_HEADER_SIZE))

      until input.eof?
        chunk_id = input.read(CHUNK_ID_SIZE)
        break if chunk_id.nil? || chunk_id.length < CHUNK_ID_SIZE

        chunk_size_bytes = input.read(CHUNK_SIZE_FIELD_SIZE)
        break if chunk_size_bytes.nil?

        chunk_size = chunk_size_bytes.unpack1(UINT32_LE).to_i
        chunk_padding = chunk_size.odd? ? 1 : 0

        if chunk_id == CUE_CHUNK_ID
          input.read(chunk_size + chunk_padding)
        elsif chunk_id == LIST_CHUNK_ID && chunk_size >= 4
          list_type = input.read(4)
          if list_type == ADTL_LIST_TYPE
            input.read(chunk_size - 4 + chunk_padding)
          else
            output.write(chunk_id)
            output.write(chunk_size_bytes)
            output.write(list_type)
            output.write(input.read(chunk_size - 4 + chunk_padding))
          end
        else
          output.write(chunk_id)
          output.write(chunk_size_bytes)
          output.write(input.read(chunk_size + chunk_padding))
        end
      end

      unless cue_points.empty?
        write_cue_chunk(output, cue_points)
        labeled_cue_points = cue_points.select { |cue_point| cue_point[:label] }
        write_adtl_chunk(output, labeled_cue_points) if labeled_cue_points.any?
      end
    end
  end

  update_riff_size(output_filepath)
end

.write_adtl_chunk(output, cue_points) ⇒ Object

: (untyped output, Array[Integer, sample_offset: Integer, label: String?] cue_points) -> void



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# File 'lib/wavesync/cue_chunk.rb', line 122

def self.write_adtl_chunk(output, cue_points)
  labl_entries = cue_points.map do |cue_point|
    text = "#{cue_point[:label]}\x00"
    data_size = 4 + text.length
    pad = data_size.odd? ? 1 : 0
    { identifier: cue_point[:identifier], text: text, data_size: data_size, pad: pad }
  end #: Array[{identifier: Integer, text: String, data_size: Integer, pad: Integer}]

  adtl_data_size = 4 + labl_entries.sum { |entry| 8 + entry[:data_size] + entry[:pad] }
  output.write(LIST_CHUNK_ID)
  output.write([adtl_data_size].pack(UINT32_LE))
  output.write(ADTL_LIST_TYPE)

  labl_entries.each do |entry|
    output.write(LABL_CHUNK_ID)
    output.write([entry[:data_size]].pack(UINT32_LE))
    output.write([entry[:identifier]].pack(UINT32_LE))
    output.write(entry[:text])
    output.write("\x00") if entry[:pad] == 1
  end
end

.write_cue_chunk(output, cue_points) ⇒ Object

: (untyped output, Array[Integer, sample_offset: Integer, label: String?] cue_points) -> void



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# File 'lib/wavesync/cue_chunk.rb', line 105

def self.write_cue_chunk(output, cue_points)
  chunk_size = CUE_HEADER_SIZE + (cue_points.size * BYTES_PER_CUE_POINT)
  output.write(CUE_CHUNK_ID)
  output.write([chunk_size].pack(UINT32_LE))
  output.write([cue_points.size].pack(UINT32_LE))
  cue_points.each_with_index do |cue_point, index|
    identifier = cue_point[:identifier] || (index + 1)
    output.write([identifier].pack(UINT32_LE))
    output.write([0].pack(UINT32_LE))
    output.write(DATA_CHUNK_ID)
    output.write([0].pack(UINT32_LE))
    output.write([0].pack(UINT32_LE))
    output.write([cue_point[:sample_offset]].pack(UINT32_LE))
  end
end