1. CS1316: Representing Structure and Behavior
Manipulating Sound
CS1316: Representing Structure and Behavior

2. Story Programming Sampled Sounds in Java Manipulating an array
Manipulating sounds in-place
Returning a new sound
Manipulating an array
Inserting a sound
Deleting a sound segment

3. Loading and playing sounds
Welcome to DrJava.
> Sound s = new Sound(“C:/cs1316/MediaSources/thisisatest.wav")
> s.increaseVolume(2.0);
> s.play();

4. increaseVolume method
/**
* Increase the volume of a sound
**/
public void increaseVolume(double factor){
SoundSample [] samples = this.getSamples();
SoundSample current = null;
for (int i=0; i < samples.length; i++) {
current = samples[i];
current.setValue((int) (factor * current.getValue())); }

5. increaseVolume: How it works
SoundSample is the name of the class for samples.
There’s something named Sample already in Java, so it would get confusing.
getSamples(), getValue(), and setValue() work just the same as in CS1315 Python.
They (respectively) return an array of all the samples, get the value of a given sample object, and set the value of a given sample object.

6. Methods that return sounds
> Sound s = new Sound("D:/cs1316/MediaSources/thisisatest.wav")
> s.play()
> s.reverse()
Sound number of samples: 64513
Why do you think we’re seeing this?

7. Reverse returns a Sound!
/**
* Method to reverse a sound.
**/
public Sound reverse() {
Sound target = new Sound(getLength());
int sampleValue;
for (int srcIndex=0,trgIndex=getLength()-1;
srcIndex < getLength();
srcIndex++,trgIndex--)
sampleValue = this.getSampleValueAt(srcIndex);
target.setSampleValueAt(trgIndex,sampleValue); };
return target; }

8. Methods that cascade nicely in Sound
public Sound reverse()
public Sound append(Sound appendSound)
public Sound mix(Sound mixIn, double ratio)
public Sound scale(double factor)

9. Little sounds in MediaSources
-h: Half second
-q: Quarter second
-1 or -2: 1 or 2 seconds
-tenth: 1/10 second
-twentieth: 1/20 second

10. Making collages public class MySoundCollage {
public static void main(String [] args){
Sound snap = new Sound(FileChooser.getMediaPath("snap-tenth.wav"));
Sound drum = new Sound(FileChooser.getMediaPath("drumroll-1.wav"));
Sound clink = new Sound(FileChooser.getMediaPath("clink-tenth.wav"));
Sound clap = new Sound(FileChooser.getMediaPath("clap-q.wav"));
Sound drumRev = drum.reverse().scale(0.5);
Sound soundA = snap.append(clink).append(clink).append(clap).append(drumRev);
Sound soundB = clink.append(clap).append(clap).append(drum).append(snap).append(snap);
Sound collage = soundA.append(soundB).append(soundB).append(soundA).append(soundA).append(soundB);
collage.play(); }
Making collages

11. How do we insert and delete sound?
Welcome to DrJava.
> Sound test = new Sound("D:/cs1316/MediaSources/thisisatest.wav");
> test.getLength()
64513
> Sound clink = new Sound("D:/cs1316/MediaSources/clink-tenth.wav");
> clink.getLength()
2184
> test.insertAfter(clink,40000)
> test.play()

12. Handling the error cases
> Sound test2 = new Sound("D:/cs1316/MediaSources/thisisatest.wav");
> test.insertAfter(test2,40000)
> test.play()

13. First, making room … 0 1 2 3 this.getLength() start 0 1 2 3 start
this.getLength()
start 12 94
-152
-27 11
inSound.getLength()
start
start+inSound.getLength() 12 94 …

14. Second, copying in … 0 1 2 3 start start+inSound.getLength()
start
start+inSound.getLength() 12 94 …
inSound.getLength()

15. insertAfter method /**
* insert the input Sound after the nth sample (input integer).
* Modifies the given sound
insound Sound to insert
start index where to start inserting the new sound
**/
public void insertAfter(Sound inSound, int start){
SoundSample current=null;
// Find how long insound is
int amtToCopy = inSound.getLength();
int endOfThis = this.getLength()-1;
if (start + amtToCopy > endOfThis)
{// If too long, copy only as much as will fit
amtToCopy = endOfThis-start-1;}
else {
// If short enough, need to clear out room.
// Copy from endOfThis-amtToCopy;, moving backwards
// (toward front of list) to start,
// moving UP (toward back) to endOfThis
// KEY INSIGHT: How much gets lost off the end of the
// array? Same size as what we're inserting -- amtToCopy
for (int source=endOfThis-amtToCopy; source >= start ; source--) {
// current is the TARGET -- where we're copying to
current = this.getSample(source+amtToCopy);
current.setValue(this.getSampleValueAt(source)); }
// NOW, copy in inSound up to amtToCopy
for (int target=start,source=0;
source < amtToCopy;
target++, source++) {
current = this.getSample(target);
current.setValue(inSound.getSampleValueAt(source));
insertAfter method

16. Setting up the variables
SoundSample current=null;
// Find how long insound is
int amtToCopy = inSound.getLength();
int endOfThis = this.getLength()-1;

17. Checking for room if (start + amtToCopy > endOfThis)
{// If too long, copy only as much as will fit
amtToCopy = endOfThis-start-1;}
else {
// If short enough, need to clear out room.

18. Now, copy down else { // If short enough, need to clear out room.
// Copy from endOfThis-amtToCopy;, moving backwards
// (toward front of list) to start,
// moving UP (toward back) to endOfThis
// KEY INSIGHT: How much gets lost off the end of the
// array? Same size as what we're inserting -- amtToCopy
for (int source=endOfThis-amtToCopy; source >= start ; source--) {
// current is the TARGET -- where we're copying to
current = this.getSample(source+amtToCopy);
current.setValue(this.getSampleValueAt(source)); }

19. Finally, copy in the new sound
//** Second, copy in inSound up to amtToCopy
for (int target=start,source=0;
source < amtToCopy;
target++, source++) {
current = this.getSample(target);
current.setValue(
inSound.getSampleValueAt(source)); }

20. How do we delete?
> Sound test = new Sound("D:/cs1316/MediaSources/thisisatest.wav");
> test.getLength()
64513
> test.delete(2000,30000)
> test.play() // We hear “This test”

21. First, copy from end to getLength, back to start
this.getLength()
This distance is start-end

22. Then, clear out the end 00000000… This distance is start-end.
this.getLength() …
This distance is start-end.
And we’ll go from the length, backwards.

23. Deleting method /** * Delete from start to end in this sound
start where to start deletion
end where to stop deletion
**/
public void delete(int start, int end){
int value = 0;
// Basically, we simply copy from "end" to getLength back to start
for (int source=end, target=start;
source < this.getLength();
source++, target++)
{value = this.getSampleValueAt(source);
this.setSampleValueAt(target,value);}
// Then clear out the rest. Gap is end-start length
int gap = end-start;
for (int i=1; i <= gap ; i++) {
this.setSampleValueAt(this.getLength()-i,0);} }
Deleting method

24. First, copy up—over the start to end gap
// Basically, we simply copy from "end" to getLength back to start
for (int source=end, target=start;
source < this.getLength();
source++, target++)
{value = this.getSampleValueAt(source);
this.setSampleValueAt(target,value);}

25. Then, clear out the gap at the end
// Then clear out the rest. Gap is end-start length
int gap = end-start;
for (int i=1; i <= gap ; i++) {
this.setSampleValueAt(
this.getLength()-i, 0);}

26. Arrays: Strengths and weaknesses
Easy to understand
Very efficient
“Static”—it’s always the same length (shape?)
Weaknesses:
Any change in the middle is hard to do
Expensive in complexity and processing