[jokosher-devel] New Levels: Decibel Range

[Laszlo Pandy <laszlok2 gmail com>]

The new levels and waveforms are pretty much complete in Jokosher SVN. 
Today I committed a patch to fix a problem we were having with the old 
display routine in which some levels would be too big to fit in the 77px 
high rows we use.

The change takes away the old sample scaling that we have been using 
since we first displayed waveforms and replaces it with real decibel 
values. That means the height in pixels on the screen actually 
corresponds to the RMS dB value of the audio at that time.

The first thing you will notice is that most files will be at least half 
green, whereas before you might just have a small waveform near the 
bottom. Because decibels are logarithmic you have to be really quiet to 
get close to the bottom and really loud to get near the top. I have put 
in a variable which sets an 80dB range between the 0th pixel to the 77th 
pixel. This number was an arbitrary choice but it seems to work well 
with my audio files. When I blow air into my microphone it just touches 
the top of the drawing area, which is the proper behaviour because at 
this point the microphone is clipping.

I would like to know what everyone else's experience is, and if anyone 
has some comments on this. Take your microphone and try the loudest and 
quietest sounds. Do the same with the music on your computer. You will 
have to update SVN, but for simply loading clips you do not need the 
newest version of Gstreamer. If you can send a small screenshot of just 
the waveform along as well, that would be great.

Laszlo