[Empeg-general] Re: Question about the EQ visualizations...

[Prolux Real Time Visuals]

The logarithmic ffts are logarithmic in two dimensions whereas the original Spectrometer visuals are logarithmic in only one dimesion.

Decibels is a logarithmic scale of loudness and both types of fft display their results in decibels, therefore both use a logarithmic vertical scale.

The Spectrometer visuals employ a pretty much linear frequency scale horizontally.  This is fairly easy.

The logarithmic fft visuals use a cunning algorithm developed by myself, John Graley, and John Ripley.  It uses an a recursive undersampling technique to produce 10 or so input samples and generates some 15 individual transforms from this.  The results are then combined to produce the final logarithmic fft.  We are extremely excited by the algorithm as we have never seen a high resolution logarithmic fft anywhere, not even in Winamp.  With conventional linear transform techniques one would need to generate a 16,000 point fft in order to get the same resolution (this would consume vast amounts of CPU).  The trick we have developed gives us the same results at a fraction of the cost.  The Rio Central employs these ffts and displays up to 480 point log ffts.

Toby