Reference: http://help.adobe.com/en_US/Director/11.5/UsingScripting/WS05253F9E-DF3D-4797-A0D6-3BF2F4C0BE60.html

A soundObject can be configured to receive data from user and that audio gets played. We can pass audio data using byteArray.

Following are the steps involved in passing audio data using byteArray

1. Configure soundObject to read from byteArray through callback
2. Prepare audio samples either by generating them or reading it from external file
3. Pass the audio samples in byteArray to soundObject inside callback.

The code below configures soundObject to read from the byteArray.

--A sample code to generate a sinewave and passing it to the audio

--engine using byteArray

global gMix, gB8BitPCMSample, gFreq

on startmovie

  -- Set the frequency of the sine wave to be generated (in Hz)

  gFreq = 400.0

  -- Generate and keep the sine wave PCM samples ready

  generateSineWavePCMSamples()

  -- Create a new Mixer

  gMix = new(#mixer)

  -- Set the Mixers format to that of the sound object so that there need not be

  -- any reformat of sound objects samples while mixing

  gMix.sampleRate   = 48000

  gMix.bitDepth     = 8

  gMix.channelCount = 1

  -- #audioInput is the callback function

  -- Set the format of the sound as 48000 Hz, 8 bit, mono

  -- The third parameter specifies the parent script reference. Its optional.

  so = gMix.createsoundobject("byteArraySObj", #audioInput, void, [#samplerate:48000, #channelcount:1, #bitdepth:8])

  -- Play the mixer

  gMix.play()

end

The callback function that was registered will be called as soon as the soundObject is played. The inpByteArray parameter will always be of 0 length. This byteArray needs be fed with audio samples as below. Once the data passed is played the callback is called again. To stop soundObject from calling the callback we have to return false. This will change the state of the soundObject to #stopped.

-- the callback funtion for the sound object

on audioInput inpByteArray

  -- Set the position from where we will write

  inpByteArray.position = 1

  -- Pass b8BitPCMSample.length number of data

  inpByteArray.writeByteArray(gB8BitPCMSample, 1, gB8BitPCMSample.length)

  -- Make sure we are called again

  return true

  -- In case we should not be called again then we need to pass false

  --return false

end

The below code just generates the PCM samples once for a duration of 1 sec. This data is continuously passed to the soundObject from inside the callback function. This code needs to be called again in case the frequency of the sinewave (gFreq) is changed dynamically.

on generateSineWavePCMSamples

  -- Create the byteArray which stores the PCM samples

  gB8BitPCMSample = bytearray()

  -- Create 1 sec buffer. Since the format of the soundObject is

  -- 48kHz, 8 bit, mono, create 48000 samples.

  repeat with i = 1 to 48000

    -- Get the sine value for frequency of gFreq Hz

    -- Sin( 2 * PI * f ) where f varies from 0 to gFreq

    sineValue = sin( 2.0 * 3.141592 * (i-1) * gFreq / 48000.0 )

    -- Convert the sineValue to 8 bit unsigned values

    -- Scale the sineValue to value between 0 and 255 for 8 bit PCM

    -- For simplicity we will map it from 1 to 255

    sample = sineValue * 127 + 128

    -- convert the sample to integer

    byte = integer(sample)

    -- write it into byteArray

    gB8BitPCMSample.writeint8(byte)

  end repeat

end

Once the data is passed to the soundObject it behaves the same way as any other soundObject. One can apply audio filters on the soundObject or Mixer, control the properties of soundObject like playRate or even apply panning on the sound Object or Mixer to get surround sound out of it. The power of this feature is only limited by one’s imagination. :)

Download the sample movie here

Feedback:
If you have any questions or comments concerning this article, please send a message to shrinidhi@gmail.com