Class: MIDI::Tempo

Inherits:
MetaEvent show all
Defined in:
lib/midilib/event.rb

Constant Summary collapse

MICROSECS_PER_MINUTE = 
1_000_000 * 60

Instance Attribute Summary

Attributes inherited from MetaEvent

#data, #meta_type

Attributes inherited from Event

#delta_time, #print_channel_numbers_from_one, #print_decimal_numbers, #print_note_names, #status, #time_from_start

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from MetaEvent

bytes_as_str, #data_as_str, str_as_bytes

Methods inherited from Event

#<=>, #channel_to_s, #number_to_s, #quantize_to

Constructor Details

#initialize(msecs_per_qnote, delta_time = 0) ⇒ Tempo

Returns a new instance of Tempo.



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# File 'lib/midilib/event.rb', line 518

def initialize(msecs_per_qnote, delta_time = 0)
  super(META_SET_TEMPO, msecs_per_qnote, delta_time)
end

Class Method Details

.bpm_to_mpq(bpm) ⇒ Object

Translates beats per minute to microseconds per quarter note (beat).



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# File 'lib/midilib/event.rb', line 509

def self.bpm_to_mpq(bpm)
  MICROSECS_PER_MINUTE / bpm
end

.mpq_to_bpm(mpq) ⇒ Object

Translates microseconds per quarter note (beat) to beats per minute.



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# File 'lib/midilib/event.rb', line 514

def self.mpq_to_bpm(mpq)
  MICROSECS_PER_MINUTE.to_f / mpq.to_f
end

Instance Method Details

#data_as_bytes ⇒ Object 



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# File 'lib/midilib/event.rb', line 530

def data_as_bytes
  data = []
  data << @status
  data << @meta_type
  data << 3
  data << ((@data >> 16) & 0xff)
  data << ((@data >> 8) & 0xff)
  data << (@data & 0xff)
end

#tempo ⇒ Object 



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# File 'lib/midilib/event.rb', line 522

def tempo
  @data
end

#tempo=(val) ⇒ Object 



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# File 'lib/midilib/event.rb', line 526

def tempo=(val)
  @data = val
end

#to_s ⇒ Object 



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# File 'lib/midilib/event.rb', line 540

def to_s
  "tempo #{@data} msecs per qnote (#{Tempo.mpq_to_bpm(@data)} bpm)"
end