add 2D led spectrum analyser - (remix)

[un1versal]

Best reviewed with ?w=1 un1versal@82c6602?w=1

See http://forum.kodi.tv/showthread.php?tid=204991&pid=2011733#pid2011733

Can be seen in action at https://www.shadertoy.com/view/Mlj3WV#

I tried to match it as closely to the request in forums http://forum.kodi.tv/showthread.php?tid=204991&pid=1799716#pid1799716

This is as close as I could get hacking around with this, maybe @topfs2 or somone can give me a few pointers and see if I can indeed get it to exact match (i.e the trailing grey peak indicators) which would make this extra nice.

It works a treat in Kodi (My wife and other women in family all agreed)

Some screenshots for an idea.

[kib]

There is something wonky going on with your commits there. Check the diff :)

Otherwise: nice addition !

[topfs2]

The wonkyness is fixed now right? It looks nice afaict now? Just making sure before I merge :)

[topfs2]

Oh and regarding the trailing peak trails I don't think you can accomplish it with the data we upload, we would need to upload peak history as a separate texture. I guess we could do that but ideally I'd like to follow the shadertoy API as much as possible, but perhaps we could open up a dialog with them and perhaps they'd be interested in adding it to theirs too. I know they have 2x512 texture for audio, and we could have peak history in one row. But I think some shaders utilize the linear fading of that row so would need some changes.

[un1versal]

Well Ive no idea what wonkiness it was or whatever it was meant by that commnet, god bless vague comments.

Its rebased and pushed ready for merge.

regarding the peak history, its not important, it would be nice all in one shader but Ive no idea how to achieve that currently even if shadertoy api supported it.