[jokosher-devel] Volume fades UI

["Jono Bacon" <jonobacon gmail com>]

Hi all,

This is mainly for the benefit of Lazlo and Aq about the volume fades
UI and how it should work. This is based off some initial discussion
and the design that has been in my head for a little while.

Right now, if you make a selection, the red markers can be used to
make a volume change, as the slider is dragged it should change the
volume level. Now, when the volume fade has been made, you can see a
red line plotted on the wave form that shows the volume curve. What we
need to do is add a 'control point' at the point where you set the
volume. This control point will just be a small dot. This way, once
you have made the selection and implemented the fade, you can move the
control point up and down to adjust the volume afterwards.

So, as a use case:

 Jono is editing the music he just recorded with his guitar. He wants
to make one particular section a little quieter. He first shift-clicks
and makes a select. Them, he drags the red volume markers down to mark
where the volume should be, and he sees the waveform update and some
control points appear where the red markers set the volume. He
unselects the selection by clicking elsewhere and sees the red line.
When he plays it back, it is a little too quiet, so he clicks on the
little control points and moves them higher to make the volume a bit
louder.

See what I mean?

So, how do we implement this? Well, in terms of the audio, we need to
create a GnlOperation and put a volume element in it. Then, we use a
GstController to set the timestamps where the volume should change.
For a sample of a GnlOperation at work, grab
http://jonobacon.org/files/gnloper2.py and its
http://jonobacon.org/files/buggui.glade glade file. That shows two
GnlOperations for the same audio track in which each applies an
effect.

Laszlo - are you still OK to look at this? If you are having Internet
problems still, do you want someone else to look at it?

 Jono