Class: Wavesync::AcidChunk

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

Constant Summary collapse

RIFF_HEADER_SIZE =

‘RIFF’ (4) + size (4) + ‘WAVE’ (4)

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CHUNK_ID_SIZE = 
4
CHUNK_SIZE_FIELD_SIZE = 
4
ACID_CHUNK_ID = 
'acid'
ACID_CHUNK_DATA_SIZE = 
24
ACID_TYPE_FLAGS_SIZE = 
4
ACID_ROOT_NOTE_SIZE = 
2
ACID_UNKNOWN1_SIZE = 
2
ACID_UNKNOWN2_SIZE = 
4
ACID_NUM_BEATS_SIZE = 
4
ACID_METER_DENOM_SIZE = 
2
ACID_METER_NUMER_SIZE = 
2
ACID_TEMPO_SIZE = 
4
ACID_TEMPO_OFFSET = 
ACID_TYPE_FLAGS_SIZE +
ACID_ROOT_NOTE_SIZE +
ACID_UNKNOWN1_SIZE +
ACID_UNKNOWN2_SIZE +
ACID_NUM_BEATS_SIZE +
ACID_METER_DENOM_SIZE +
ACID_METER_NUMER_SIZE
UINT32_LITTLE_ENDIAN = 
'V'
FLOAT32_LITTLE_ENDIAN = 
'e'

Class Method Summary collapse

Class Method Details

.create_acid_chunk(output, bpm) ⇒ Object 



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# File 'lib/wavesync/acid_chunk.rb', line 97

def self.create_acid_chunk(output, bpm)
  # Write ACID chunk ID
  output.write(ACID_CHUNK_ID)

  # Write chunk size (24 bytes)
  output.write([ACID_CHUNK_DATA_SIZE].pack(UINT32_LITTLE_ENDIAN))

  # Type flags (4 bytes) - 0x01 for one-shot
  output.write([0x01].pack(UINT32_LITTLE_ENDIAN))

  # Root note (2 bytes) - 0x003C (middle C / 60)
  output.write([0x003C].pack('v'))

  # Unknown1 (2 bytes)
  output.write([0x0000].pack('v'))

  # Unknown2 (4 bytes)
  output.write([0x00000000].pack(UINT32_LITTLE_ENDIAN))

  # Number of beats (4 bytes) - 0 for non-loop
  output.write([0x00000000].pack(UINT32_LITTLE_ENDIAN))

  # Meter denominator (2 bytes) - 4 for 4/4 time
  output.write([0x0004].pack('v'))

  # Meter numerator (2 bytes) - 4 for 4/4 time
  output.write([0x0004].pack('v'))

  output.write([bpm].pack(FLOAT32_LITTLE_ENDIAN))
end

.read_bpm(filepath) ⇒ Object 



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# File 'lib/wavesync/acid_chunk.rb', line 30

def self.read_bpm(filepath)
  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 = file.read(CHUNK_SIZE_FIELD_SIZE).unpack1(UINT32_LITTLE_ENDIAN)
      if chunk_id == ACID_CHUNK_ID
        file.seek(ACID_TEMPO_OFFSET, IO::SEEK_CUR)
        return file.read(ACID_TEMPO_SIZE).unpack1(FLOAT32_LITTLE_ENDIAN)
      else
        padding = chunk_size.odd? ? 1 : 0
        file.seek(chunk_size + padding, IO::SEEK_CUR)
      end
    end
  end
  nil
end

.update_riff_size(filepath) ⇒ Object 



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# File 'lib/wavesync/acid_chunk.rb', line 128

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_LITTLE_ENDIAN))
  end
end

.write_bpm(source_filepath, output_filepath, new_bpm) ⇒ Object 



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# File 'lib/wavesync/acid_chunk.rb', line 50

def self.write_bpm(source_filepath, output_filepath, new_bpm)
  bpm_bytes = [new_bpm.to_f].pack(FLOAT32_LITTLE_ENDIAN)
  acid_chunk_found = false

  File.open(source_filepath, 'rb') do |input|
    File.open(output_filepath, 'wb') do |output|
      riff_header = input.read(RIFF_HEADER_SIZE)
      output.write(riff_header)

      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)
        chunk_size = chunk_size_bytes.unpack1(UINT32_LITTLE_ENDIAN)

        output.write(chunk_id)
        output.write(chunk_size_bytes)

        if chunk_id == ACID_CHUNK_ID
          acid_chunk_found = true

          output.write(input.read(ACID_TEMPO_OFFSET))

          input.read(ACID_TEMPO_SIZE)

          output.write(bpm_bytes)

          remaining = chunk_size - ACID_TEMPO_OFFSET - ACID_TEMPO_SIZE
          output.write(input.read(remaining)) if remaining.positive?

          output.write(input.read(1)) if chunk_size.odd?
        else
          padding = chunk_size.odd? ? 1 : 0
          output.write(input.read(chunk_size + padding))
        end
      end

      create_acid_chunk(output, new_bpm.to_f) unless acid_chunk_found
    end
  end

  return if acid_chunk_found

  update_riff_size(output_filepath)
end