Swing Hacks

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Chapter 10, Audio

#75 Build an Audio Waveform Display

HACK

What you want is more like this:

1010 1101 (high byte)

+ 0011 0010 (low byte)

---------------------

1010 1101 0011 0010

And in order to get this to work with standard addition, you need to add

two 16-bit bytes with bits shifted and placeholder

0s added where neces-

sary. Then you get something like this:

1010 1101 0000 0000 (high byte)

+ 0000 0000 0011 0010 (low byte)

---------------------

1010 1101 0011 0010

The high byte needs to be bit shifted. Bit shifting, the process of sliding bits

around, is typically a big no-no in Java—as a result, you’ve probably never

seen the bit-shifting operator before (it’s

<< or >> depending on the direction

followed by the number of bits to shift in either direction). However, here it

is necessary to use bit shifting, so you will bit shift the high byte 8 bits to the

left:

high << 8

Now, you need to prepend the leading 0s onto the low byte. You can do this

using the bit

AND operator and using a 16-bit byte consisting of all 0s. It

works like this:

0000 0000 0000 0000 (all 0's bytes)

+ 0011 0010 (low byte)

---------------------

0000 0000 0011 0010

Here is the code for the sample conversion:

private int getSixteenBitSample(int high, int low) {

return (high << 8) + (low & 0x00ff);

}

Creating a Single Waveform Display

Now that you have the audio sample data organized by channels, it’s time to

get to painting. To