Recover audio signal to analyse them with JMF

Question

Hello,
I'm a french student in informatics in Paris.
(Sorry for my poor english...)
We're developping an audio player in JAVA for our end study project with a friend. This player will contain a graphics plugin to "show" music in real time (like the graphics plugin of winamp or media player).
We are using the Java Media Frameworks API to develope this player. We succeed to read a song, but we don't manage to get audio signal to analyse them. In fact, we want to get audio spectrum in real time, so we have to get audio signal with the intention of analyse it with Fourier tools.
Did you got an idea of the way to do this?
Maybe we could re-implements the Player interface of the jmf API, rather than use the Manager.createPlayer method? (actually I also don't really understand how work the Manager.createPlayer() method. And how implements Player interface, when we don't really know what to put in the methods?...).
Thanks a lot for your help.
Thomas

Answer 1

Hi Thomas,
what you want to do is possible with JMF.... but beware that sometimes Java will prove slower than what you expect.... I don't know if this is the correct way to do it, but you can get the samples by creating a class that implements the Effect interface (see sun GainEffect).
In the process(Buffer inputBuffer, Buffer outputBuffer) method you have the inputBuffer that contains the sampled audio (in 2 channels, odd and even bytes or words depending on your 8/16 bit preferences).
You can use this data to compute your FTT animaton... You must then create a 'chain' that will include your processor (again see sun examples, the function assignEffect).
If you want to be very JMF-complant, you should also implement some other interface to return you 'visual' component that display your graphic animation (probably the right method is the getControlComponent in the Control interface).
Ok then...I hope this will prove helpful and to see your effects as soon as possible :-)
Bye
Marco