Google Summer of Code: Visualization-support in Phonon

Ricard Marxer Piñón email at
Tue Jun 2 12:33:19 BST 2009

On Mon, Jun 1, 2009 at 9:06 PM, Martin Sandsmark <sandsmark at> wrote:
> 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.

Yep, you are right that creating a dependency for this might not be a
good idea, but some of these, such as FFT Ooura is just a simple pair
of .h and .cpp files, which you can include directly in your

>> 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
> :wq
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