Google Summer of Code: Visualization-support in Phonon

Martin Sandsmark sandsmark at
Mon Jun 1 20:06:48 BST 2009

On Mon, Jun 01, 2009 at 08:19:15PM +0200, Ricard Marxer Piñón wrote:
> I like this idea.  If the ring buffer will be in the AudioDataOutput
> it would be nice to be able set the frameSize and the hopSize? Then it
> would be very useful also for audio analysis, because this would allow
> to avoid to create another ringbuffer.  And even for some
> visualizations it's also really nice to control this.
> Probably if you will be already writing a ringbuffer it should'nt be
> too hard to also implement these parameters.

Yes, that came up during the discussion with “tball” on IRC too, I just
forgot to write it down ;-)

But yeah, should be quite doable.

> You can use an external library to implement FFT or FHT, for instance
> there are several:
> fftw: (GPL)
> FFT Ooura: (a very
> permissive license)
> FFTReal: (LGPL)
> I really like fftw and have used it in some of my projects, but the
> license could be a problem for Phonon, don't know.

These are probably superior to whatever I can come up with, but something
simple but effective enough for simple audio visualization should be doable
without an external library, I think.

> If you need any help with the signal processing part, I might be able
> to give a hand, I have some code at github, where I use Eigen to do
> audio analysis processing:
> it might be of your interest.

Thanks! I don't have much experience with signal analysis, so I will probably
take you up on that ;-)

Martin Sandsmark 
GSoC Student
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