Remove unvanted clicks in generated sound in AS3 - actionscript-3

Question

I am having the following problem when generating sound wave in Flash.
This is the generator part :
const SAMPLING_RATE:int = 44100;
const TWO_PI:Number = 2 * Math.PI;
const TWO_PI_OVER_SR:Number = TWO_PI / SAMPLING_RATE;
const SAMPLE_SIZE:int = 8192 / 4;
function generateSine(fq:Number):ByteArray
{
var bytes:ByteArray = new ByteArray();
var sample:Number;
var amp:Number = 1;
for (var i:int=0; i<SAMPLE_SIZE; i++)
{
sample = amp* Math.sin(i * TWO_PI_OVER_SR * fq );
bytes.writeFloat(sample);
}
bytes.position = 0;
return bytes;
}
and this is the playback part:
function playbackSampleHandler(event:SampleDataEvent):void
{
var sample:Number;
for (var i:int = 0; i < SAMPLE_SIZE && soundData.bytesAvailable; i++)
{
sample = soundData.readFloat();
event.data.writeFloat(sample);
event.data.writeFloat(sample);
}
}
function onClickPlay(e:MouseEvent)
{
soundData= new ByteArray();
var sound:ByteArray= new ByteArray();
sound=generateSine(440);
soundData.writeBytes(sound,0,sound.length);
soundData.position = 0;
morphedSound.addEventListener(SampleDataEvent.SAMPLE_DATA, playbackSampleHandler);
soundChannel = morphedSound.play();
}
Quick explanation:
I basically write values for the sine function into the ByteArray and than playback handler reads that array and plays back the sound. I write only one 8192/4 sample buffer.
Problem:
My problem is that when you do this there are annoying clicks on the end of sound, which are the artifacts of sine wave being cut on a value other than 0. So my question is how can I avoid this?
Bonus:
I would also like to know how can I generate for example exactly 100 ms of sine wave when buffers in Flash are so strict i.e. from 2048 to 8192 ?
Links:
If it helps my code is based on this tutorial
http://www.bit-101.com/blog/?p=2669
and my own explorations.

Answer 1

You need to preserve phase of sine wave that occurs at the end of your sample data processing. Otherwise your sine wave is not continued smoothly and you get the clicks you speak of.
var totalSamples:int=0;
function generateSine(fq:Number):ByteArray
{
var bytes:ByteArray = new ByteArray();
var sample:Number;
var amp:Number = 1;
for (var i:int=0; i<SAMPLE_SIZE; i++)
{
sample = amp* Math.sin((i+totalSamples) * TWO_PI_OVER_SR * fq );
// this uses stored phase ^^^
bytes.writeFloat(sample);
}
totalSamples+=SAMPLE_SIZE; // this preserves phase between subsequent samples
bytes.position = 0;
return bytes;
}
Update: I've noticed you are calling generator twice in a row - this is awful. You must never call a function twice if you only need one result of its work.
function onClickPlay(e:MouseEvent)
{
soundData= generateSine(440); // why using writeBytes if we can just use assignment?
soundData.position = 0;
morphedSound.addEventListener(SampleDataEvent.SAMPLE_DATA, playbackSampleHandler);
soundChannel = morphedSound.play();
}
Also, to make the sound end with a full (half-)wave of sound and remove the last click you need, use this technique:
function generateSine(fq:Number,cleanFinish:Boolean=false):ByteArray
{
var bytes:ByteArray = new ByteArray();
var sample:Number;
var amp:Number = 1;
for (var i:int=0; i<SAMPLE_SIZE; i++)
{
sample = amp* Math.sin((i+totalSamples) * TWO_PI_OVER_SR * fq );
// this uses stored phase ^^^
bytes.writeFloat(sample);
if (cleanFinish)
if ((Math.abs(sample)<(SAMPLING_RATE/fq/3))&&(i>SAMPLE_SIZE-SAMPLING_RATE/fq)) break;
// this triggers a drop if we are sampling the last wave already
}
totalSamples+=i; // this preserves phase between subsequent samples
bytes.position = 0;
return bytes;
}
Call this function with an optional Boolean parameter set to true to receive correctly terminated wave.

Answer 2

All SAMPLE_SIZE values of "sample" must be split in three pieces:
The first and the third piece must have 250 values each and the middle one
the rest: SAMPLE_SIZE - 500. Make this as follows:
Generate an array of 250 values between 0 and .996 with step .004 :
I mean: .000, .004, .008, ... , .996, and fill with them an array, say, mod[i]
with i from zero to 249.(mod is for modulation...)
Modify initial loop as below and so will result a fade from 0 to (+/-)amp(first 250 values) then the rest of values up to the last 250 remain (+/-)amp and, finally, the last 250 values have a fade from (+/-)amp to 0. The nasty clicks remain...history! I Hope this help.
function generateSine(fq:Number):ByteArray
{
var bytes:ByteArray = new ByteArray();
var sample:Number;
var amp:Number = 1;
for (var i:int=0; i< 250; i++)
{
sample = amp* Math.sin(i * TWO_PI_OVER_SR * fq ) * mod[i];
bytes.writeFloat(sample);
}
for (var i:int=250; i<SAMPLE_SIZE - 250; i++)
{
sample = amp* Math.sin(i * TWO_PI_OVER_SR * fq );
bytes.writeFloat(sample);
}
for (var i:int=SAMPLE_SIZE - 250; i<SAMPLE_SIZE; i++)
{
sample = amp* Math.sin(i * TWO_PI_OVER_SR * fq ) * (.996 - mod[i]);
bytes.writeFloat(sample);
}
bytes.position = 0;
return bytes;
}