Class: AudioEngine
- Inherits:
-
Object
- Object
- AudioEngine
- Defined in:
- lib/audioengine.rb
Overview
This class actually generates the output audio data that is saved to disk.
To produce audio data, it needs two things: a Song and a Kit. The Song tells it which sounds to trigger and when, while the Kit provides the sample data for each of these sounds.
Example usage, assuming song and kit are already defined:
engine = AudioEngine.new(song, kit)
engine.write_to_file("my_song.wav")
Constant Summary collapse
- SAMPLE_RATE =
44100
- PACK_CODE =
All output sample data is assumed to be 16-bit
"s*"
Instance Attribute Summary collapse
-
#step_sample_length ⇒ Object
readonly
Returns the value of attribute step_sample_length.
Instance Method Summary collapse
-
#initialize(song, kit) ⇒ AudioEngine
constructor
A new instance of AudioEngine.
- #write_to_file(output_file_name) ⇒ Object
Constructor Details
#initialize(song, kit) ⇒ AudioEngine
Returns a new instance of AudioEngine.
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# File 'lib/audioengine.rb', line 16 def initialize(song, kit) @song = song @kit = kit @step_sample_length = AudioUtils.step_sample_length(SAMPLE_RATE, @song.tempo) @composited_pattern_cache = {} end |
Instance Attribute Details
#step_sample_length ⇒ Object (readonly)
Returns the value of attribute step_sample_length.
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# File 'lib/audioengine.rb', line 76 def step_sample_length @step_sample_length end |
Instance Method Details
#write_to_file(output_file_name) ⇒ Object
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# File 'lib/audioengine.rb', line 24 def write_to_file(output_file_name) packed_pattern_cache = {} num_tracks_in_song = @song.total_tracks samples_written = 0 # Open output wave file and preparing it for writing sample data. wave_file = BeatsWaveFile.new(@kit.num_channels, SAMPLE_RATE, @kit.bits_per_sample) file = wave_file.open_for_appending(output_file_name) # Generate each pattern's sample data, or pull it from cache, and append it to the wave file. incoming_overflow = {} @song.flow.each do |pattern_name| key = [pattern_name, incoming_overflow.hash] unless packed_pattern_cache.member?(key) sample_data = generate_pattern_sample_data(@song.patterns[pattern_name], incoming_overflow) if @kit.num_channels == 1 # Don't flatten the sample data Array, since it is already flattened. That would be a waste of time, yo. packed_pattern_cache[key] = {:primary => sample_data[:primary].pack(PACK_CODE), :overflow => sample_data[:overflow], :primary_length => sample_data[:primary].length} else packed_pattern_cache[key] = {:primary => sample_data[:primary].flatten.pack(PACK_CODE), :overflow => sample_data[:overflow], :primary_length => sample_data[:primary].length} end end file.syswrite(packed_pattern_cache[key][:primary]) incoming_overflow = packed_pattern_cache[key][:overflow] samples_written += packed_pattern_cache[key][:primary_length] end # Write any remaining overflow from the final pattern final_overflow_composite = AudioUtils.composite(incoming_overflow.values, @kit.num_channels) final_overflow_composite = AudioUtils.scale(final_overflow_composite, @kit.num_channels, num_tracks_in_song) if @kit.num_channels == 1 file.syswrite(final_overflow_composite.pack(PACK_CODE)) else file.syswrite(final_overflow_composite.flatten.pack(PACK_CODE)) end samples_written += final_overflow_composite.length # Now that we know how many samples have been written, go back and re-write the correct header. file.sysseek(0) wave_file.write_header(file, samples_written) file.close() return wave_file.calculate_duration(SAMPLE_RATE, samples_written) end |