[Qt-interest] Frequency of Audio Tracks

[Dan Mills]

On Sat, 2010-07-24 at 22:59 +0530, Vijay Kansal wrote:
> Hi,
> I want to develop an audio editor using Qt.
> For this, I need to plot a waveform of the music track which I
> think should be a plot of frequency of sound versus time(please
> correct me if I am wrong).

Normally you need the peak amplitude vs time for a standard audio editor
display (Often switching to actual sample values once you zoom in far
enough). 

The complexity comes from needing this at different resolutions
depending on the zoom level of the display.  

If the audio file is reasonably long then you will really want to create
the peak data out of line and store it either as a levl chunk if the
file is a wav, or as a separate file depending on what is appropriate. 

One final note, do NOT do the screen painting from the same thread as
the one that actually pushes data to the audio hardware (it will work
very badly).


> Currently, I have been using Phonon::AudioOutput class object as an
> audio sink and connected it with my Phonon::MediaObject class
> object to play the audio file.

I have never used either, but have a feeling you may need to go lower
level then that to get what you want. 

Regards, Dan.