topical media & game development

topical media & game development

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#graphic-player-10-cube-com-adobe-flash-samples-SoundPitchShift.ax

#graphic-player-10-cube-com-adobe-flash-samples-SoundPitchShift.ax [swf] [flash] flex


  package com.adobe.flash.samples
  {
          import flash.media.*;
          import flash.events.Event;
          import flash.events.EventDispatcher;
          import flash.events.SampleDataEvent;
          import flash.utils.ByteArray;

Used in the Adobe Dynamic Sound quick start example applications. The class includes a play() function, which plays a sound and adjusts its pitch (frequency) by a factor of 1.0 to 2.0.


  
          public class @ax-graphic-player-10-cube-com-adobe-flash-samples-SoundPitchShift extends EventDispatcher
          {
                  private var srcSound:Sound;                                // The source sound.
                  private var soundChannel:SoundChannel;        // Used to stop the sound.
                  private var bytes:ByteArray;                        // Used to store the audio sample bytes used by the output Sound object.
                  public var pitchShiftFactor:Number;                // The factor (from 1.0 to 2.0) to shift the sound pitch.
                  public var position:Number                                // The position in the byte array from which to extract

The constructor function.


  
                  public function @ax-graphic-player-10-cube-com-adobe-flash-samples-SoundPitchShift()
                  {
                  }

Plays audio based on a source Sound object (srcSound) with the pitch adjusted by a specified factor (pitchShiftFactor). The sampleData event handler for the output Sound object (morphedSound) generates audio sample data used by the Sound object. By setting the position to 0, the code will extract audio data from the beginning of the sound on each call to the play() method.


  
                  public function play(srcSound:Sound, pitchShiftFactor:Number):void
                  {
                          this.srcSound = srcSound;
                          this.pitchShiftFactor = pitchShiftFactor;
                          position = 0;
                          
                          var morphedSound:Sound = new Sound();
                          //morphedSound.addEventListener(SampleDataEvent.SAMPLE_DATA, sampleDataHandler);
                          soundChannel = morphedSound.play();
                          soundChannel.addEventListener(Event.SOUND_COMPLETE, soundCompleteHandler);
                  }

Stops the sound, and notifies the host application that the sound is done playing.


  
                  public function stop():void
                  {
                          soundChannel.stop();
                          dispatchEvent(new Event(Event.SOUND_COMPLETE));
                  }

Notifies the host application that the sound is done playing.


  
                  private function soundCompleteHandler(event:Event):void
                  {
                          dispatchEvent(event);
                  }

Provides sample data to the output Sound object. The Sound object dispatches a sampleData event when it needs sample data. This event handler function provides that data. The method calls the shiftBytes() method to shift the pitch of the audio data.


  
                  private function sampleDataHandler(event:SampleDataEvent):void
                  {
                          var bytes:ByteArray = new ByteArray();
                          position += srcSound.extract(bytes, 4096, position);
                          event.data.writeBytes(shiftBytes(bytes));
                  }

This method takes a byte array (the bytes parameter) containing sound data. It returns a modified byte array, with sound samples (each representing two floating point values) removed to adjust to the pitch shift factor (the value of the pitchShiftFactor property). The method uses two numbers, skipCount and skipRate, to determine how frequently to remove sound samples from the byte array. The skipRate number is based on the pitch shift factor (the pitchShiftFactor property). If the factor is 2.0, skipRate is set to 2.0, and every second sound sample is removed. If the factor is 1.5 (3/2), skipRate is set to 3.0, and every third sound sample is removed. If the factor is 1.333 (4/3), skipRate is set to 4.0, and every fourth sound sample is removed. Removing samples causes the pitch (frequency) of the sound to shift higher.


  
                  private function shiftBytes(bytes:ByteArray):ByteArray
                  {
                          var skipCount:Number = 0;
                          var skipRate:Number = 1 + (1 / (pitchShiftFactor - 1));
                          var returnBytes:ByteArray = new ByteArray();
                          bytes.position = 0;
                          while(bytes.bytesAvailable > 0)
                          {
                                  skipCount++;
                                  if (skipCount <= skipRate)
                                  {
                                          returnBytes.writeFloat(bytes.readFloat());
                                          returnBytes.writeFloat(bytes.readFloat());
                                  }
                                  else
                                  {
                                          bytes.position += 8;
                                          skipCount = skipCount - skipRate;
                                  }
                          }
                          return returnBytes;
                  }
          }
  }

[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

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