Class: WaveFile::Reader

Inherits:
Object
  • Object
show all
Defined in:
lib/wavefile/reader.rb

Overview

Public: Provides the ability to read sample data out of a wave file, as well as query a wave file about its metadata (e.g. number of channels, sample rate, etc).

When constructing a Reader a block can be given. All data should be read inside this block, and when the block exits the Reader will automatically be closed.

Reader.new("my_file.wav") do |reader|
  # Read sample data here
end

Alternately, if a block isn’t given you should make sure to call close when finished reading.

reader = Reader.new("my_file.wav")
# Read sample data here
reader.close

Instance Method Summary collapse

Constructor Details

#initialize(io_or_file_name, format = nil) ⇒ Reader

Public: Constructs a Reader object that is ready to start reading the specified file’s sample data.

io_or_file_name - The name of the wave file to read from,

or an open IO object to read from.

format - The format that read sample data should be returned in

(default: the wave file's internal format).

Returns a Reader object that is ready to start reading the specified file’s sample data.

Raises Errno::ENOENT if the specified file can’t be found.

Raises InvalidFormatError if the specified file isn’t a valid wave file.



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# File 'lib/wavefile/reader.rb', line 34

def initialize(io_or_file_name, format=nil)
  if io_or_file_name.is_a?(String)
    @io = File.open(io_or_file_name, "rb")
    @io_source = :file_name
  else
    @io = io_or_file_name
    @io_source = :io
  end

  @closed = false

  riff_reader = ChunkReaders::RiffReader.new(@io, format)
  @data_chunk_reader = riff_reader.data_chunk_reader
  @sample_chunk = riff_reader.sample_chunk

  if block_given?
    begin
      yield(self)
    ensure
      close
    end
  end
end

Instance Method Details

#close ⇒ Object

Public: Closes the Reader. If the Reader is already closed, does nothing. After a Reader is closed, no more sample data can be read from it. Note: If the Reader is constructed from an open IO instance (as opposed to a file name), the IO instance will not be closed. You’ll have to manually close it yourself. This is intentional, because Reader can’t know what you may/may not want to do with the IO instance in the future.

Returns nothing.



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# File 'lib/wavefile/reader.rb', line 153

def close
  return if @closed

  if @io_source == :file_name
    @io.close
  end

  @closed = true
end

#closed? ⇒ Boolean

Public: Returns true if the Reader is closed, and false if it is open and available for reading.



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# File 'lib/wavefile/reader.rb', line 141

def closed?
  @closed
end

#current_sample_frame ⇒ Object

Public: Returns the index of the sample frame which is “cued up” for reading. I.e., the index of the next sample frame that will be read. A sample frame contains a single sample for each channel. So if there are 1,000 sample frames in a stereo file, this means there are 1,000 left-channel samples and 1,000 right-channel samples.



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# File 'lib/wavefile/reader.rb', line 196

def current_sample_frame
  @data_chunk_reader.current_sample_frame
end

#each_buffer(sample_frame_count = 4096) ⇒ Object

Public: Starting from the current reading position, reads sample frames into successive Buffers of the specified size, until there are no more sample frames to be read. When the final sample frame has been read the Reader is automatically closed. Each Buffer is passed to the given block.

If the Reader is constructed from an open IO, the IO is NOT closed after all sample data is read. However, the Reader will be closed and any attempt to continue to read from it will result in an error.

Note that sample_frame_count indicates the number of sample frames to read, not number of samples. A sample frame include one sample for each channel. For example, if sample_frame_count is 1024, then for a stereo file 1024 samples will be read from the left channel, and 1024 samples will be read from the right channel.

sample_frame_count - The number of sample frames to read into each Buffer from each channel. The number

of sample frames read into the final Buffer could be less than this size, if there
are not enough remaining.

Examples

# sample_frame_count not given, so default buffer size
Reader.new("my_file.wav").each_buffer do |buffer|
  puts "#{buffer.samples.length} sample frames read"
end

# Specific sample_frame_count given for each buffer
Reader.new("my_file.wav").each_buffer(1024) do |buffer|
  puts "#{buffer.samples.length} sample frames read"
end

# Reading each buffer from an externally created IO
file = File.open("my_file.wav", "rb")
Reader.new(file).each_buffer do |buffer|
  puts "#{buffer.samples.length} sample frames read"
end
# Although Reader is closed, file still needs to be manually closed
file.close

reader = Reader.new("my_file.wav")
reader.read(100)
# Reading using `each_buffer` will start at the 101st sample frame:
reader.each_buffer do |buffer|
  puts "#{buffer.samples.length} sample frames read"
end
# At this point, the Reader is now closed (even without
# a call to `close()`)

Returns nothing. Has side effect of closing the Reader.



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# File 'lib/wavefile/reader.rb', line 106

def each_buffer(sample_frame_count=4096)
  begin
    while true do
      yield(read(sample_frame_count))
    end
  rescue EOFError
    close
  end
end

#format ⇒ Object

Public: Returns an object describing how sample data is being read from the Wave file. I.e., number of channels, bits per sample, sample format, etc. If #readable_format? is true, then this will be a Format object. The format the samples are read out as might be different from how the samples are actually stored in the file. Therefore, #format might not match #native_format. If #readable_format? is false, then this will return the same value as #native_format.



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# File 'lib/wavefile/reader.rb', line 188

def format
  @data_chunk_reader.format
end

#native_format ⇒ Object

Public: Returns an object describing the sample format of the Wave file being read. This returns the data contained in the “fmt ” chunk of the Wave file. It will not necessarily match the format that the samples are read out as (for that, see #format).



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# File 'lib/wavefile/reader.rb', line 171

def native_format
  @data_chunk_reader.raw_native_format
end

#read(sample_frame_count) ⇒ Object

Public: Reads the specified number of sample frames from the wave file into a Buffer. Note that the Buffer will have at most sample_frame_count sample frames, but could have less if the file doesn’t have enough remaining.

sample_frame_count - The number of sample frames to read. Note that each sample frame includes a sample for

each channel.

Returns a Buffer containing sample_frame_count sample frames.

Raises UnsupportedFormatError if file is in a format that can’t be read by this gem.

Raises ReaderClosedError if the Reader has been closed.

Raises EOFError if no samples could be read due to reaching the end of the file.



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# File 'lib/wavefile/reader.rb', line 131

def read(sample_frame_count)
  if @closed
    raise ReaderClosedError
  end

  @data_chunk_reader.read(sample_frame_count)
end

#readable_format? ⇒ Boolean

Public: Returns true if this is a valid Wave file and contains sample data that is in a format that this class can read, and returns false if this is a valid Wave file but does not contain a sample format that this gem knows how to read.



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# File 'lib/wavefile/reader.rb', line 178

def readable_format?
  @data_chunk_reader.readable_format
end

#sampler_info ⇒ Object

Public: Returns a SamplerInfo object if the file contains “smpl” chunk, or nil if it doesn’t. If present, this will contain information about how the file can be use by a sampler, such as corresponding MIDI note, or loop points.



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# File 'lib/wavefile/reader.rb', line 210

def sampler_info
  @sample_chunk
end

#total_duration ⇒ Object

Public: Returns a Duration instance which indicates the playback time of the file.



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# File 'lib/wavefile/reader.rb', line 164

def total_duration
  Duration.new(total_sample_frames, @data_chunk_reader.format.sample_rate)
end

#total_sample_frames ⇒ Object

Public: Returns the total number of sample frames in the file. A sample frame contains a single sample for each channel. So if there are 1,000 sample frames in a stereo file, this means there are 1,000 left-channel samples and 1,000 right-channel samples.



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# File 'lib/wavefile/reader.rb', line 203

def total_sample_frames
  @data_chunk_reader.total_sample_frames
end