Class: AudioFingerprint::WaveFile

Inherits:
Object
  • Object
show all
Defined in:
lib/audio_fingerprint/wave_file.rb

Constant Summary collapse

CHUNK_ID = 
"RIFF"
FORMAT = 
"WAVE"
FORMAT_CHUNK_ID = 
"fmt "
SUB_CHUNK1_SIZE = 
16
PCM = 
1
DATA_CHUNK_ID = 
"data"
HEADER_SIZE = 
36

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(num_channels, sample_rate, bits_per_sample, sample_data = []) ⇒ WaveFile

Returns a new instance of WaveFile.



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# File 'lib/audio_fingerprint/wave_file.rb', line 16

def initialize(num_channels, sample_rate, bits_per_sample, sample_data = [])
    if num_channels == :mono
        @num_channels = 1
    elsif num_channels == :stereo
        @num_channels = 2
    else
        @num_channels = num_channels
    end
    @sample_rate = sample_rate
    @bits_per_sample = bits_per_sample
    @sample_data = sample_data

    @byte_rate = sample_rate * @num_channels * (bits_per_sample / 8)
    @block_align = @num_channels * (bits_per_sample / 8)
end

Instance Attribute Details

#bits_per_sample ⇒ Object

Returns the value of attribute bits_per_sample.



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# File 'lib/audio_fingerprint/wave_file.rb', line 311

def bits_per_sample
  @bits_per_sample
end

#block_align ⇒ Object (readonly)

Returns the value of attribute block_align.



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# File 'lib/audio_fingerprint/wave_file.rb', line 311

def block_align
  @block_align
end

#byte_rate ⇒ Object (readonly)

Returns the value of attribute byte_rate.



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# File 'lib/audio_fingerprint/wave_file.rb', line 311

def byte_rate
  @byte_rate
end

#num_channels ⇒ Object

Returns the value of attribute num_channels.



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# File 'lib/audio_fingerprint/wave_file.rb', line 311

def num_channels
  @num_channels
end

#sample_rate ⇒ Object

Returns the value of attribute sample_rate.



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# File 'lib/audio_fingerprint/wave_file.rb', line 312

def sample_rate
  @sample_rate
end

Class Method Details

.open(path) ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 32

def self.open(path)
    file = File.open(path, "rb")

    begin
        header = read_header(file)
        errors = validate_header(header)

        if errors == []
            sample_data = read_sample_data(file,
            header[:num_channels],
            header[:bits_per_sample],
            header[:sub_chunk2_size])

            wave_file = self.new(header[:num_channels],
            header[:sample_rate],
            header[:bits_per_sample],
            sample_data)
        else
            error_msg = "#{path} can't be opened, due to the following errors:\n"
            errors.each {|error| error_msg += "  * #{error}\n" }
            raise StandardError, error_msg
        end
    rescue EOFError
        raise StandardError, "An error occured while reading #{path}."
    ensure
        file.close()
    end

    return wave_file
end

Instance Method Details

#duration ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 205

def duration()
    total_samples = sample_data.length
    samples_per_millisecond = @sample_rate / 1000.0
    samples_per_second = @sample_rate
    samples_per_minute = samples_per_second * 60
    samples_per_hour = samples_per_minute * 60
    hours, minutes, seconds, milliseconds = 0, 0, 0, 0

    if(total_samples >= samples_per_hour)
        hours = total_samples / samples_per_hour
        total_samples -= samples_per_hour * hours
    end

    if(total_samples >= samples_per_minute)
        minutes = total_samples / samples_per_minute
        total_samples -= samples_per_minute * minutes
    end

    if(total_samples >= samples_per_second)
        seconds = total_samples / samples_per_second
        total_samples -= samples_per_second * seconds
    end

    milliseconds = (total_samples / samples_per_millisecond).floor

    return  { :hours => hours, :minutes => minutes, :seconds => seconds, :milliseconds => milliseconds }
end

#inspect ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 299

def inspect()
    duration = self.duration()

    result =  "Channels:        #{@num_channels}\n" +
                "Sample rate:     #{@sample_rate}\n" +
                "Bits per sample: #{@bits_per_sample}\n" +
                "Block align:     #{@block_align}\n" +
                "Byte rate:       #{@byte_rate}\n" +
                "Sample count:    #{@sample_data.length}\n" +
                "Duration:        #{duration[:hours]}h:#{duration[:minutes]}m:#{duration[:seconds]}s:#{duration[:milliseconds]}ms\n"
end

#mono? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/audio_fingerprint/wave_file.rb', line 193

def mono?()
    return num_channels == 1
end

#normalized_sample_data ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 112

def normalized_sample_data()    
    if @bits_per_sample == 8
        min_value = 128.0
        max_value = 127.0
        midpoint = 128
    elsif @bits_per_sample == 16
        min_value = 32768.0
        max_value = 32767.0
        midpoint = 0
    else
        raise StandardError, "Bits per sample is #{@bits_per_samples}, only 8 or 16 are supported"
    end

    if mono?
        normalized_sample_data = @sample_data.map {|sample|
            sample -= midpoint
            if sample < 0
                sample.to_f / min_value
            else
                sample.to_f / max_value
            end
        }
    else
        normalized_sample_data = @sample_data.map {|sample|
            sample.map {|sub_sample|
                sub_sample -= midpoint
                if sub_sample < 0
                    sub_sample.to_f / min_value
                else
                    sub_sample.to_f / max_value
                end
            }
        }
    end

    return normalized_sample_data
end

#reverse ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 201

def reverse()
    sample_data.reverse!()
end

#sample_data ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 108

def sample_data()
    return @sample_data
end

#sample_data=(sample_data) ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 150

def sample_data=(sample_data)
    if sample_data.length > 0 && ((mono? && sample_data[0].class == Float) ||
                                (!mono? && sample_data[0][0].class == Float))
    if @bits_per_sample == 8
        # Samples in 8-bit wave files are stored as a unsigned byte
        # Effective values are 0 to 255, midpoint at 128
        min_value = 128.0
        max_value = 127.0
        midpoint = 128
    elsif @bits_per_sample == 16
        # Samples in 16-bit wave files are stored as a signed little-endian short
        # Effective values are -32768 to 32767, midpoint at 0
        min_value = 32768.0
        max_value = 32767.0
        midpoint = 0
    else
        raise StandardError, "Bits per sample is #{@bits_per_samples}, only 8 or 16 are supported"
    end

    if mono?
        @sample_data = sample_data.map {|sample|
            if(sample < 0.0)
            (sample * min_value).round + midpoint
            else
            (sample * max_value).round + midpoint
            end
        }
    else
        @sample_data = sample_data.map {|sample|
            sample.map {|sub_sample|
                if(sub_sample < 0.0)
                    (sub_sample * min_value).round + midpoint
                else
                    (sub_sample * max_value).round + midpoint
                end
            }
        }
    end
    else
        @sample_data = sample_data
    end
end

#save(path) ⇒ Object 



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# File 'lib/audio_fingerprint/wave_file.rb', line 63

def save(path)
    # All numeric values should be saved in little-endian format

    sample_data_size = @sample_data.length * @num_channels * (@bits_per_sample / 8)

    # Write the header
    file_contents = CHUNK_ID
    file_contents += [HEADER_SIZE + sample_data_size].pack("V")
    file_contents += FORMAT
    file_contents += FORMAT_CHUNK_ID
    file_contents += [SUB_CHUNK1_SIZE].pack("V")
    file_contents += [PCM].pack("v")
    file_contents += [@num_channels].pack("v")
    file_contents += [@sample_rate].pack("V")
    file_contents += [@byte_rate].pack("V")
    file_contents += [@block_align].pack("v")
    file_contents += [@bits_per_sample].pack("v")
    file_contents += DATA_CHUNK_ID
    file_contents += [sample_data_size].pack("V")

    # Write the sample data
    if !mono?
        output_sample_data = []
        @sample_data.each{|sample|
            sample.each{|sub_sample|
                output_sample_data << sub_sample
            }
        }
    else
        output_sample_data = @sample_data
    end

    if @bits_per_sample == 8
        file_contents += output_sample_data.pack("C*")
    elsif @bits_per_sample == 16
        file_contents += output_sample_data.pack("s*")
    else
        raise StandardError, "Bits per sample is #{@bits_per_samples}, only 8 or 16 are supported"
    end

    file = File.open(path, "w")
    file.syswrite(file_contents)
    file.close
end

#stereo? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/audio_fingerprint/wave_file.rb', line 197

def stereo?()
    return num_channels == 2
end