   oscilloscope
  i have absolutely no where to begin. I want to make one of those kool visualizations, like in iTunes or WMP, as a standalone app using C++ and OpenGL. my problem is that i have no idea where to find either an api for this, or at least how to access the sound card to attain the information necessary for this. Is that even how real time PC-based oscilloscopes work?   
  Oscilloscopes in things like iTunes or Winamp are implemented by analyzing the waveforms of audio. Because digital audio is a constant stream of signal information, you need to evaluate it in windows using a fourier transform, in the Frequency Domain. Most fourier work is done using FTTs, or Fast-Fourier transforms. The idea is to take a sliding window of digital audio, convert it to the frequency domain and do some analysis.In terms of getting the audio, you can test it with any kind of audio, but for real-time analysis you could use direct sound and capture from the sound card's input. I would guess you would want to take the frequency data and use it to inform a series of points and draw them with direct3d or the like.You can find information and source here: http://www.musicdsp.org/Specifically http://www.musicdsp.org/search.action.php with FFT;  well you got my plan exactly, and ill check out the websites. ty!   