@database SFX

(C) Copyright 1993-1996 Stefan Kost
All Rights Reserved

@Remark $VER: Operators.guide (26.11.95)
@Remark AmigaGuide-OnLine-Help for SoundFX

@master /guides/sfx.guide
@index /guides/sfx-index.guide/index

@node main "General information"

General information
-------------------

Most SFX-Operators are built in a similar fashion. I'd therefore like to ex-
plain some things you'll encounter in most Operators.
All parameters you change are saved internally by SFX, so when you want to use
the operator (effect) again you'll get the parameters as you left them. Should
the buffer you were then using be closed, the parameters will be changed by SFX
(write in if you don't like this - English Ed.).
When coding SFX I wanted to make it as variable(flexible) as possible. The
user had to be able to access and edit all the parameters in a way either as
simple or complex as he/she desired. This led to the development of the 'Blend-
shapes'. These are curves (or graphs) that modulate a parameter. A 'Blendshape'
returns you values ranging 0.0 - 1.0. The following variations are implemented :
None	 :	This shape returns in every case a value of 0.0 (if you don`t
		want to modulate something). If you use this enter the value in
		the first field - the second will be ignorated.
Linear   :	Runs values from 0.0 at sample start to 1.0 at the end of
		the sample in the linear way.
SpeedUp  :	Similar to the above but the values run at 'slow' rate and
		'faster' to the end.
SlowDown :	Opposite of 'SpeedUp'
User 0   :	Probably the most fexible way of modulation. If activated, the
		field "Mod" (which isn't ghosted anymore) lets you choose a
		sample buffer, whose sample data gives you the modulating cur-
		ve. Maximum negative amplitude of the sample gives you the
		value 0.0, maximum positive 1.0.
User 1	 :	Pretty much the same as User0 with one difference. Sample data
		of the value 0 (flatline:) gives you values of 0.0 for the mo-
		dulation curve, maximum negative or positive amplitude of the
		sample a 1.0.
User 2   :	This shape gives you the volume envelope of the modulating
		sample (Imagine you stretch a rubberband around the sample).

The two parameter after "Par" let you decide upon the strength of modulation
for curve values of 0.0 and 1.0. The "<->" switch lets you swap the values.
The sample buffer you want to use for the modulation curve can be of different
length than your to-be-modulated sample. How to handle this is described here :
Single	 :	If the sample is shorter the rest is filled with empty space.
Repeat	 :	If the sample is shorter, it is repeated for as many times as
		needed.
Stretch	 :	Sample is stretched/shrunk to fit. (Sound like Jeans to me:)

Examples for the Amplify-Operator :
1.)	You'd like to amplify the volume of the sample by 5%.
	Par.0 :	105 (100%+5%)
	Par.1 :	doesn`t matter
	Mode  :	None
2.)	You want to amplify the sample to 10% at the start and lower to 60% in
	the end AND the volume change should be faster during the process.
	Par.0 :	110 (100%+10%)
	Par.1 :	 60
	Mode  :	SpeedUp
3.)	You'd like to produce a tremolo effect (cyclic change of volume -
	"Helicopter" effect). For this we need to make a slow sine wave with
	@{" Synthesize-Add " link FX-Synthesize-Add } of ONE period.
	Par.0 : 120
	Par.1 :  80
	Modus : User 0
	Choose our sine wave as modulation source and activate
	Blendmode "Repeat".
Examples for the FilterLowPass-Operator :
4.)	You want to give a Bass some nice filter treatment. Get yourself a
	sample that gives you the desired volume curve.
	Start the LowPass-Filter and enter the follwing parameters.
	Par.0 :	20
	Par.1 : 1
	Modus : User 2
	Choose the (Envelope) buffer for modulation source and activate	Blend-
	mode Stretch, should your sample be of different length.

Also I'd like to explain some switches that appear virtually everywhere.
Src	:	That's the source buffer. It contains the wave that's to be
		used by the Operator.
		The cycle-gadget after the name of the source buffer lets you
		choose the type of 'range' that the operator will work with.
		The following types are available :
			All	:	the entire sample is used
			Window	:	only the visible (zoomed) area is used.
			Range	:	only the marked range is used.
		SFX will automatically suggest the mode you'll probably want.
		If for example a Range is marked then 'Range' is set.
Mod	:	Describes a modulation buffer.This contains a waveform, that is
		used to modify a parameter.
Go	:	Start the calculation
Reset	:	Reset the parameters to default values.

Following ARexx-Parametersare global defined too.

ModBuf	:	ID of the modulationbuffer
ModShape:	typ of shape for modulation 0..6
ModMode	:	mode of modulationsource 0->Single/1->Repeat/2->Stretch
The correspondenting ARexx-Params are mentioned in the following descriptions.
@endnode