Swing Hacks

Show Audio Information While Playing Sound #77

Chapter 10, Audio

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397

HACK

Hacking the Hack

Florian’s message to javasound-interest says it is best if “everybody does

the calculation of the ‘level’ on his own[, based] on the buffers received by

the TDL [(

TargetDataLine

, usually used by capture devices)] or written to

the SDL [(

SourceDataLine

)], respectively.”

Setting aside the argument of duplication of effort, note that the buffers he

speaks of are available in the hack code; it’s what the

PCMFilePlayer reads

from the file and writes to the

Line (specifically, a SourceDataLine, as

Florian’s message notes). So, in theory at least, this can be done. But it’s not

going to be pretty.

First, create a new

DataLineInfoGUI2 class that is identical to the one from

earlier in this hack, except that instead of using a

PCMFilePlayer, it uses a

PCMFilePlayerLeveler, a class that will be defined next.

This new class is pretty much the same as the old

PCMFilePlayer, except that

on each time through the while loop, as it reads the buffer and writes it to

the line, it will call a method to scan through the buffer and determine a

level for this group of samples. So, after reading the bytes from the input

stream but before writing them to the line, add:

// calculate level

calculateLevel (buffer, readPoint, leftover);

As Florian argues in his message, the idea of a level is up for interpretation,

but there is a general sense ...