Class: WaveFile::ChunkReaders::SampleChunkReader

Inherits:
BaseChunkReader show all
Defined in:
lib/wavefile/chunk_readers/sample_chunk_reader.rb

Overview

Internal

Instance Method Summary collapse

Methods inherited from BaseChunkReader

#raise_error, #read_entire_chunk_body

Constructor Details

#initialize(io, chunk_size) ⇒ SampleChunkReader

:nodoc:



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# File 'lib/wavefile/chunk_readers/sample_chunk_reader.rb', line 5

def initialize(io, chunk_size)
  @io = io
  @chunk_size = chunk_size
end

Instance Method Details

#read ⇒ Object 



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# File 'lib/wavefile/chunk_readers/sample_chunk_reader.rb', line 10

def read
  if @chunk_size < CORE_BYTE_COUNT
    raise_error InvalidFormatError, "The sample chunk is incomplete; it contains fewer than the required number of fields."
  end

  raw_bytes = read_entire_chunk_body(CHUNK_IDS[:sample])

  fields = {}
  fields[:manufacturer_id],
  fields[:product_id],
  fields[:sample_nanoseconds],
  fields[:midi_note],
  fields[:fine_tuning_cents],
  fields[:smpte_format],
  smpte_offset_frames,
  smpte_offset_seconds,
  smpte_offset_minutes,
  smpte_offset_hours,
  loop_count,
  sampler_data_size = raw_bytes.slice!(0...CORE_BYTE_COUNT).unpack("VVVVVVCCCcVV")
  fields[:fine_tuning_cents] = (fields[:fine_tuning_cents] / 4_294_967_296.0) * 100
  fields[:smpte_offset] = SMPTETimecode.new(hours: smpte_offset_hours,
                                            minutes: smpte_offset_minutes,
                                            seconds: smpte_offset_seconds,
                                            frames: smpte_offset_frames)

  fields[:loops] = []
  loop_count.times do
    if raw_bytes.length < LOOP_BYTE_COUNT
      raise_error InvalidFormatError, "`smpl` chunk loop count is #{loop_count}, but it does not contain that many loops"
    end

    loop_fields = {}
    loop_fields[:id],
    loop_fields[:type],
    loop_fields[:start_sample_frame],
    loop_fields[:end_sample_frame],
    loop_fields[:fraction],
    loop_fields[:play_count] = raw_bytes.slice!(0...LOOP_BYTE_COUNT).unpack("VVVVVV")
    loop_fields[:type] = loop_fields[:type]
    loop_fields[:fraction] /= 4_294_967_296.0

    fields[:loops] << SamplerLoop.new(**loop_fields)
  end

  if sampler_data_size > 0
    if raw_bytes.length < sampler_data_size
      raise_error InvalidFormatError, "`smpl` chunk \"sampler specific data\" field is smaller than expected."
    end

    fields[:sampler_specific_data] = raw_bytes.slice!(0...sampler_data_size)
  else
    fields[:sampler_specific_data] = ""
  end

  SamplerInfo.new(**fields)
end