[MPlayer-dev-eng] Audio Visualization Plugin

[Anders Johansson]

Hi Gustavo,

The current audio plugin layer will soon be replaced by a new more
generic one. Attached to this mail is the current work in progress. 
Warning the attached files "mplayer.c" and "Makefile" brakes mplayer a
little bit so take appropriate precautions before you use them.

As for where to start:

If you want to do something that works for real (which imho you
should) then you could use Welch periodogram method to do the
spectral estimation. This will give you a good spectral estimates
where the level of each frequency bin represents the actual energy
level in that frequency band. 

To do the required FFT you could use the fftw package (very fast).

If you have access to Matlab (and understands matlab code) you could
have a look at the source code for the psd() function to get the
implementation started (search for psd.m in the matlab installation
directory to find it). I guess you can find something similar in
Octave. I can also recommend the following two books on the subject:

"Digital spectral analysis with application", S.Lawrence Marple, Jr
"Statistical Digital Signal Processing and Modeling", Monson H. Hayes

I have some sample code for using fftw if you want it (can't send it
public so contact me outside list).

To check your results try dumping the estimates to file and read them
with gnuplot or matlab.

I will be happy to help you with the audio part of the work.

Good luck,
//Anders


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