[hpsdr] Call for Comments OzyII

[Alex, VE3NEA]

FFT alone does not result in any compression since it has exactly the same 
number of values as the original data. Compression is achieved by discarding 
the spectral components whose amplitude is below a certain threshold. This 
approach works great for audio but cannot be used with I/Q data because in 
the SDR applications weak signals is exactly what we are after.

73 Alex VE3NEA



> L. Van Warren wrote:
> One could FFT the signal BEFORE transmission, transmit the FFT 
> coefficients
> as numbers and then do the reconstruction on the receive side.
>  Isn't this (mutatis mutandis) what MP3 compression does ? Actually, MP3 
> use a cosine transform,
> not an FFT, but conceptually there are not many differences. When you send 
> a musical MP3 file,
> what you send are the coefficients of the cosine transform, which are then 
> used during playback to
> reconstruct the analog version of your favorite musical performance.
>
> 73  Alberto  I2PHD 


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