TODO

Improvements :
- Code : continue profiling (why do python and Xorg take so much CPU while profiling shows that most of the time is pent being idle ?)
- Code : comments in the code
- Code/Maths : constant-Q-transform for efficient and precise logarithmic spectrogram
- Code/Maths : **or** adaptive frequency resolution in the fft spectrum and spectrogram
- Code : replace QwtColorMap with QLinearGradient to remove a dependancy on Qwt
- Code/Graphics : use the nicer histogram from octave spectrum fot the fft spectrum

Features :
- Code : overlapping fft windows for smoother spectrograms
- Code/GUI : new widget for long run level measurements

Bugfixes :
- code : unwanted delay between input and display
	Seems related to pulseaudio:
		http://forum.skype.com/index.php?s=7609fb1fac9ee65573e0ceb92562c481&showtopic=237601&st=0&p=1059071&#entry1059071
		https://bugzilla.redhat.com/show_bug.cgi?id=444388
- code : when there is no input, audio data goes to 0., and log spectrum goes to -Inf,
 which seems to slow down computations enormously.
- code : the device info from portaudio reports a low input latency (max 46 ms), but after opening the stream, it is reported to be 139 ms. Why ?
