Class: WaveFile::Duration

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

Overview

Calculates playback time given the number of sample frames and the sample rate. For example, you can use this to calculate how long a given Wave file is.

The hours, minutes, seconds, and milliseconds fields return values like you would see on a stopwatch, and not the total amount of time in that unit. For example, a stopwatch running for exactly 2 hours would show something like “2:00:00.000”. Accordingly, if the given sample frame count and sample rate add up to exactly 2 hours, then hours will be 2, and minutes, seconds, and milliseconds will all be 0.

This class is immutable - once a new Duration is constructed, it can’t be modified.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(sample_frame_count, sample_rate) ⇒ Duration

Constructs a new immutable Duration.

sample_frame_count - The number of sample frames, i.e. the number

samples in each channel.

sample_rate - The number of samples per second, such as 44100

Examples:

duration = Duration.new(400_000_000, 44100)
duration.hours         # => 2
duration.minutes       # => 31
duration.seconds       # => 10
duration.milliseconds  # => 294

Note that the hours, minutes, seconds, and milliseconds fields do not return the total of the respective unit in the entire duration. For example, if a duration is exactly 2 hours, then minutes will be 0, not 120.



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# File 'lib/wavefile/duration.rb', line 30

def initialize(sample_frame_count, sample_rate)
  @sample_frame_count = sample_frame_count
  @sample_rate = sample_rate

  sample_frames_per_millisecond = sample_rate / 1000.0
  sample_frames_per_second = sample_rate
  sample_frames_per_minute = sample_frames_per_second * 60
  sample_frames_per_hour = sample_frames_per_minute * 60
  @hours, @minutes, @seconds, @milliseconds = 0, 0, 0, 0

  if(sample_frame_count >= sample_frames_per_hour)
    @hours = sample_frame_count / sample_frames_per_hour
    sample_frame_count -= sample_frames_per_hour * @hours
  end

  if(sample_frame_count >= sample_frames_per_minute)
    @minutes = sample_frame_count / sample_frames_per_minute
    sample_frame_count -= sample_frames_per_minute * @minutes
  end

  if(sample_frame_count >= sample_frames_per_second)
    @seconds = sample_frame_count / sample_frames_per_second
    sample_frame_count -= sample_frames_per_second * @seconds
  end

  @milliseconds = (sample_frame_count / sample_frames_per_millisecond).floor
end

Instance Attribute Details

#hours ⇒ Object (readonly)

Returns the value of attribute hours.



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# File 'lib/wavefile/duration.rb', line 60

def hours
  @hours
end

#milliseconds ⇒ Object (readonly)

Returns the value of attribute milliseconds.



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# File 'lib/wavefile/duration.rb', line 63

def milliseconds
  @milliseconds
end

#minutes ⇒ Object (readonly)

Returns the value of attribute minutes.



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# File 'lib/wavefile/duration.rb', line 61

def minutes
  @minutes
end

#sample_frame_count ⇒ Object (readonly)

Returns the value of attribute sample_frame_count.



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# File 'lib/wavefile/duration.rb', line 58

def sample_frame_count
  @sample_frame_count
end

#sample_rate ⇒ Object (readonly)

Returns the value of attribute sample_rate.



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# File 'lib/wavefile/duration.rb', line 59

def sample_rate
  @sample_rate
end

#seconds ⇒ Object (readonly)

Returns the value of attribute seconds.



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# File 'lib/wavefile/duration.rb', line 62

def seconds
  @seconds
end