GNUitar
			Guitar processor software

(C) 2000-2005 Max V.Rudensky <fonin@gnuitar.com>

1. What is GNUitar ?

GNUitar is a real-time sound effects software that allows
you to use your computer as a guitar processor. It has GTK+ based
interface. It can be compiled on any flavor of UNIX that have
GTK+ 1.2, Glib, pthreads and OSS sound driver. It also works on Windows.
Program is inspired by 2 works:
    o Ele 0.1 by Morris Slutsky
      http://www-personal.umich.edu/~mslutsky/elepage/index.html
    o Guitar FX Processor by Marin Vlah
      http://fly.srk.fer.hr/~mvlah/fx_processor.html

GNUitar is free software and is distributed under GNU GPL license.

2. Download

http://www.gnuitar.com/downloads.php
http://freshmeat.net/projects/gnuitar
http://sourceforge.net/projects/gnuitar

3. Requirements

You will need
    o GTK+ version 1.2.6 or better; we also support now GTK+ 2.x branch.
    o GLIB 1.2 or better
    o POSIX threads on UNIX
    o full-duplex sound card
    o To compile: GCC on UNIX, Microsoft Visual C++ 6.0 on Windows

4. Performance

GNUitar is a CPU-consuming program. Pentium/166 is sufficient
to run GNUitar, Pentium II/300 is recommended, and on Pentium II/450
it will work just fine.
Real performance is very depend on your CPU/sound card/sound driver/OS
combination. The best performance can be achieved on Linux,
because of its great real-time features and advanced OSS sound drivers.

When running the program, make sure you close all unnecessary applications,
to give more resources to it. Avoid anything that can cause disk I/O
or CPU usage.

GNUitar runs with increased priority; this may cause hang-ups
and delayed system response on low-end machines. Therefore you
should care to save all important data in other applications,
before you launch GNUitar.

4.1 UNIX notes

GNUitar executable file should be setuid root to process sound with
real-time priority; otherwise you'll hear glitches and delays while
switching between windows. It switches to real user id as soon as
it set real-time priority to effect-processing thread, and before
any GTK initializations are being performed, so it shouldn't break
security on your system.
GNUitar has a latency of about 4-8ms on Linux/Pentium II/450/AWE64 ISA !

4.2. Windows notes

Windows have complex problems with latency when processing audio in real time,
mostly because of its non-uniform drivers architecture.
GNUitar latency on Windows is much higher than on Linux. The real latency
is very depend on sound board driver.

GNUitar for Windows has two playback methods:
 o Playback via MME
 o Playback via DirectSound

The first method uses the standard MME API (functions waveOut*()).
The second method requires DirectX to be installed and uses DirectSound
for playback. The method can be switched from the sampling parameters dialog,
by checking/unchecking the "Playback via DirectSound" checkbox.

DirectSound playback shows the best results that are almost close to
Linux performance. The MME playback exists for compatibility purposes,
and for another reason. If a driver is not optimized for DirectSound,
Windows will automatically emulate DirectSound output using the MME devices.
If a WDM driver is used (see below), DirectSound support is not implemented
by the driver developer but by the operating system. MME playback support exists
specially for this case, when the output via DirectSound is emulated by OS.

4.3. Windows Sound Drivers Overview

There are few kinds of sound drivers for Windows: old VXD (Win95/98),
NT4-kernel style, and modern WDM drivers that were introduced in Windows 98/SE.
Currently GNUitar uses common MME API (MME=MultiMedia Extension) that is
compatible with all kinds of drivers; however AFAIK WDM drivers provide
much lower latency. Therefore, avoid VXD drivers; use modern WDM drivers
instead, if possible.

The difference in latency between two kinds of drivers is really noticeable:
I had 100ms up to ~400ms on Pentium III/850/ISA AWE64/VXD/MME playback,
and ~60ms on Pentium MMX/166/Yamaha OPL3/WDM/MME playback laptop.
Try to re-launch GNUitar few times, if the initial latency is bad.

The kind of bus (PCI/ISA) of the sound card does not affect
the latency very much, the deal is with OS and its architecture.
So do not through away your old ISA Sound Blaster and replace it with
modern sound card, first try it on Linux !

4.4. How To Control Latency
The latency can be controlled with a high degree from the GNUitar interface.
There is a settings dialog that can be called from the
``Options->Sampling Parameters'' menu (or by ``Ctrl-P'').
There is an option called "Fragment Size". The greater is the fragment size,
the greater is the latency, BUT... You might want to increase fragment size
on low-end computers, to decrease the system load and number of buffer overruns
(drops). The buffer overrun is the immediate result of the bad performance.
Buffer overruns have a hearable effect of a scratches, sometimes
periodic (ten overruns per second produce a 10 Hz tone).

General notes on how to achieve the best performance:
 o The lower is the sampling rate, the better is the latency. Drawback is
   the sound quality.
 o The lower is the fragment size, the better is the latency. Drawback is the
   higher system load.
 o The hearable periodic scratches (DirectSound output) can be fixed
   by decreasing the overrun threshold (sampling params dialog).
 o Increase the fragment size and decrease the sampling rate on
   low-end CPU, to gain the best latency/overruns/load ratio.
 o On Windows, prefer WDM drivers, if possible. Try both MME and
   DirectSound playback; choose which is the best.
 o Prefer Linux over Windows. Properly tuned Linux kernel has 10-100 times
   better latency on the same hardware.
 o Make gnuitar executable setuid root on UNIX, to allow it run with
   increased priority.

5. Installation

See INSTALL file for common installation notes.

6. Interface and Controls

There are 3 areas in the main window. The right area is a list of all
available effects. The central area contains effects that are currently used.
There are few buttons right to it should be used to add/remove effects
and change its order. Each effect has separate top-level control window with
appropriate sliders.  Each effect-control box is shown in the window manager
task bar.

The left area contains available effect layouts, or presets, and button
to add the one. Layout is a "snapshot" of your effects and its'
settings, you can load/save using "File" menu.

Big "Switch" button is used to switch layouts. In this manner,
you can change current sound by one mouse/keyboard click.

Big "START/STOP" button is used to start/stop playback.
You may want to press it few times if you experience buffer overruns
or broken sound output.

You can write track of what you play to a file. Just click
check-box "Write track" at the bottom of program window, enter
filename and play. Don't forget that continuous track write
can fill out your hard drive.
The track file format is raw data, word length, signed
(the sampling rate and mono/stereo are controlled from the sampling parameters
dialog). You can convert it with SoX program like this

    sox -w -s -c 1 -r 44100 track.raw track.wav,

and then to MP3:

    bladeenc track.wav

Sox is available at http://home.sprynet.com/~cbagwell/sox.html,
and Bladeenc is at http://home8.swipnet.se/~w-82625.

Windows users can write track directly to .wav file
(currently it is not available on UNIX).

Autowah

speed    - speed of wah-wah'ing
freq.low - low frequency (the cycle starts from this freq.)
freq.hi  - high frequence (the cycle stops at this freq.)
mix      - mix clean sound with processed sound

7. Effects

The controls and description of the effects are described below.

7.1. Reverberator

Reverberator produces echoed "space" sound. Controls:

delay  - delay time
wet    - "wet" (processed) sound volume
dry    - "dry" (clean) sound volume
regen  - number of repeats

7.2. Delay

Another kind of reverberation.

decay  - this controls how the repeated sound is fading out
time   - this is the delay time
repeat - number of repeats

7.3. Distortion

distort    - power of effect
level      - volume, for the case if you need to mute it quickly
saturation - high-frequency "sand" in the sound
lowpass    - low-band filter that can be used to change the sound feel

7.4. Vibrato

Vibrato sounds like when you turn the master volume on and off very quickly
(few times per second).

speed     - the speed of modulation
amplitude - the depth of modulation

7.5. Chorus

depth     - the depth of modulation
speed     - the speed of modulation
wet       - "wet" (processed) sound volume
dry       - "dry" (clean) sound volume
regen     - hard to explain

7.6. Echo

Another reverberation effect, not like the others.
While other reverb effects are just kinds of sound patterns repeating,
echo attempts to achieve a large hall echo.

decay     - this controls how the repeated sound is fading out
count     - number of repeats
size      - controls delay time

7.7. Distortion 2

Another cool distortion. Emulates Ibanez TS9 pedal.

drive      - power of effect
lowpass    - low-band filter that can be used to change the sound feel.

7.8. Noise Gate

Simple noise reduction effect. Should be used BEFORE distortion.
IMPORTANT NOTES:
- Should be used BEFORE the distortion.
- If you want to achieve a note slight attack (fade in),
  you must increase the Hold time as much as possible.
  Otherwise with the low Attack time and low signal you
  the effect will be constantly false triggered, therefore
  breaking the fadein effect.

Controls are:
threshold    - minimal volume of the sound required to pass signal
               to the output.
hold         - if the signal is below threshold during this time,
               it will be muted. Should be as low as possible.
	       Simply - it is an effect triggering time.
release time - if the signal is below threshold, the playback
               is not muted immediately but fades out this time instead
attack       - if the signal is above the threshold, it will fade in
               this time. Ususally should be 0, but having it
	       non-zero will produce interesting effect just like the
	       violin sound.
hysteresis   - the threshold required to turn off the playback when
               it is already asound (the regular threshold affects
	       only the growing signal, while hysteresis
	       affects fading signal). Should not be larger than
	       the threshold.

8. Bugs

 o Windows version is not very stable yet. There could be problems
   with memory leaks and with sound initialisation/closing.

Send bug reports to fonin@gnuitar.com

9. About Free Software Development

You should always keep in mind, that development of free software
doesn't work in the same way as commercial development. Every
successful free software project has an active userbase behind it. This
means that your comments, ideas and bug reports are extremely
important. If something doesn't work, or some feature is missing,
please mail me about it. Thank you in advance! You can send GNUitar
related mails to me at mailto:fonin@gnuitar.com.

10. Legal Issues

GNUitar is a free software and is distributed under the terms of
GNU GPL license.
You are free to copy and share the program with other people,
you are not limited with the number of computers where you can use it.
You can redistribute the program and the works based on it
under the terms of GPL license. You have complete sources and detailed compile
instructions to build the program yourself, as well as binaries.
You have full freedom with using and sharing the program,
according to the GNU software concept.

11. Related Links

http://www.gnuitar.com/downloads.php and
http://sourceforge.net/projects/gnuitar and
http://freshmeat.net/projects/gnuitar - GNUitar project pages
http://linux-sound.org - excellent categorized list of Unix sound software
http://home.sprynet.com/~cbagwell/sox.html - SoX playback/record/processing
  software
http://home8.swipnet.se/~w-82625 - BladeEnc, free MP3 encoder

12. Authors

Max Rudensky <fonin@gnuitar.com>
	     <fonin@yahoo.com>
	     http://www.omnistaronline.com/~fonin
Eugen Bogdan aka Dexterus <dexterus@hackernetwork.com>