title: Library for waveform plotting
body: <p>I am looking for a library to plot the waveform and/or the spectrum of a real time recording. <br>I'm using C/C++ and Qt 4.8.1 under Windows XP.</p>
  
  <p>Audio sources come from 8 different microphones (may be more in the future), so I would like a fast-enough rendering to plot 8 waveform without too much delay. I'm using Portaudio to acquire the data. <br>
  The tracks need not to be recorded, but I need to do some computation on them in real time. I know this may slow down things, so eventually I'd be happy also with a spectrum plot (...less expensive to draw?).</p>
  
  <p>I tried to compile and run Qt's <code>Spectrum Analyzer</code> demo, but I found it pretty slow (around 1 sec of delay). I don't know if it's assumed to be that slow or I am missing something...</p>
  
  <p>Searching the web I came across <a href="http://mathgl.sourceforge.net/" rel="nofollow">MathGL</a> but I'm not sure if it's well-suited for this purpose, maybe it's better to go for something more specific.</p>
  
  <p>I would like to be as portable as possible but I definitely prefer ease of use rather than portability.</p>
  
  <p>Any suggestions?</p>