Class: ALSA::PCM::Stream

Inherits:
Object
  • Object
show all
Defined in:
lib/alsa/pcm/stream.rb

Direct Known Subclasses

Capture, Playback

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#buffer_time_size ⇒ Object

Returns the value of attribute buffer_time_size.



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# File 'lib/alsa/pcm/stream.rb', line 5

def buffer_time_size
  @buffer_time_size
end

#handle ⇒ Object

Returns the value of attribute handle.



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# File 'lib/alsa/pcm/stream.rb', line 4

def handle
  @handle
end

Class Method Details

.open(device = "default", hardware_attributes = {}, &block) ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 7

def self.open(device = "default", hardware_attributes = {}, &block)
  new.open(device, hardware_attributes, &block)
end

Instance Method Details

#available_frame_count ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 123

def available_frame_count
  check_handle!

  ALSA::try_to "wait the interface is ready" do
    ALSA::PCM::Native::wait(self.handle, buffer_time_size)
  end
  available_frame_count = ALSA::try_to "read available space" do
    ALSA::PCM::Native::avail_update(self.handle)
  end

  [available_frame_count, buffer_frame_count].min
end

#buffer_frame_count ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 50

def buffer_frame_count
  @buffer_frame_count ||= hw_params.sample_rate * buffer_time_size / 1000
end

#change_hardware_parameters ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 54

def change_hardware_parameters
  hw_params = ALSA::PCM::HwParameters.new(self).default_for_device

  begin
    yield hw_params
    hw_params.update_attributes :buffer_time => hw_params.buffer_time_max

    ALSA::try_to "set hw parameters" do
      ALSA::PCM::Native::hw_params self.handle, hw_params.handle
    end
  ensure
    hw_params.free
  end
end

#change_software_parameters ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 89

def change_software_parameters
  sw_params = software_parameters

  begin
    yield sw_params

    ALSA::try_to "set sw parameters" do
      ALSA::PCM::Native::sw_params self.handle, sw_params.handle
    end
  ensure
    sw_params.free
  end
end

#check_handle! ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 112

def check_handle!
  raise "Stream isn't opened" unless opened?
end

#close ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 116

def close
  ALSA::try_to "close audio device" do
    ALSA::PCM::Native::close self.handle
    self.handle = nil
  end
end

#hardware_parameters ⇒ Object Also known as: hw_params 



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# File 'lib/alsa/pcm/stream.rb', line 69

def hardware_parameters
  ALSA::PCM::HwParameters.new(self).current_for_device
end

#hardware_parameters=(attributes = {}) ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 74

def hardware_parameters=(attributes= {})
  attributes = { 
    :access => :rw_interleaved, 
    :channels => 2, 
    :sample_format => :s16_le, 
    :sample_rate => 44100,
    # :buffer_time => buffer_time_size * 1000,
    # :period_time => buffer_time_size * 1000 / 4
  }.update(attributes)

  change_hardware_parameters do |hw_params|
    hw_params.update_attributes(attributes)
  end
end

#open(device = "default", hardware_attributes = {}, &block) ⇒ Object 



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# File 'lib/alsa/pcm/stream.rb', line 11

def open(device = "default", hardware_attributes = {}, &block)
  options = {}

  if Hash === device
    options = device
    device = (options[:device] or "default")
  end

  self.buffer_time_size = options[:buffer_time_size] if options[:buffer_time_size]

  handle_pointer = FFI::MemoryPointer.new :pointer
  ALSA::try_to "open audio device #{device}" do
    ALSA::PCM::Native::open handle_pointer, device, native_constant, ALSA::PCM::Native::BLOCK
  end
  self.handle = handle_pointer.read_pointer

  self.hardware_parameters = hardware_attributes

  change_software_parameters do |sw_params|
    sw_params.available_minimum = buffer_frame_count / 4
  end

  ALSA::PCM::Native.prepare(handle)

  if block_given?
    begin
      yield self 
    ensure
      self.close
    end
  else
    self
  end
end

#opened? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/alsa/pcm/stream.rb', line 108

def opened?
  not self.handle.nil?
end

#software_parameters ⇒ Object Also known as: sw_params 



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# File 'lib/alsa/pcm/stream.rb', line 103

def software_parameters
  ALSA::PCM::SwParameters.new(self).current_for_device
end