@database AHI:User/Help/ahi.guide

@Master ahiusr.texinfo

@Width 72


This is the AmigaGuide®  file AHI:User/Help/ahi.guide, produced by Makeinfo-1.67 from 
the input file ahiusr.texinfo.

   This file documents AHI version 4.16, a hardware independent audio
subsystem for Amiga.

   Copyright (C) 1994-1997 Martin Blom. This publication may not be
modified in any way, including translation, without prior consent, in
writing, by the author.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   THIS PUBLICATION IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS PUBLICATION, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.


     $Id: ahiusr.texinfo,v 4.12 1997/11/02 02:01:48 lcs Exp lcs $
     $Log: ahiusr.texinfo,v $
     Revision 4.12  1997/11/02 02:01:48  lcs
     Added Concierto (again!).
     
     Revision 4.11  1997/10/21 01:33:40  lcs
     The version number is now the AHI release version, not the documents version.
     
     Revision 4.10  1997/09/30 13:11:09  lcs
     Added reasons why "Fast" or "Hifi" modes should be used.
     
     Revision 4.9  1997/09/28 04:31:56  lcs
     Added notes about Maestor Pro and Melody MPEG. Added Thorsten Hansen
     to the contributors section. And some other minor things.
     
     Revision 4.8  1997/09/18 00:51:00  lcs
     Added Maestro Pro stuff.
     
     Revision 4.7  1997/08/10 15:38:57  lcs
     Minor changes. added AHI macro!
     
     Revision 4.6  1997/08/03 22:48:26  lcs
     Added Concierto to list of supported sound cards.
     Added Christian Buchner to the Acknowledgments section.
     Changed Teemu Suikki's email address.
     
     Revision 4.5  1997/07/27 19:04:10  lcs
     Added description of the AHIpaulaSwapChannels env. variable.
     
     Revision 4.4  1997/07/15 00:50:40  lcs
     This is the second bugfix release of AHI 4.
     
     Revision 4.3  1997/05/04 15:52:58  lcs
     Initial revision.


@Node Main "AHI:User/Help/ahi.guide"
@Next "Overview"

AHI User's Guide, version 4.16
******************************

   Copyright (C) 1994-1997 Martin Blom

   The latest release of AHI can always be found at
@{b}http://www.lysator.liu.se/~lcs/ahi.html@{ub}.


 @{" Overview                  " Link "Overview"}  Brief introduction
 @{" Distribution              " Link "Distribution"}  What you are allowed to do and not
 @{" Donations                 " Link "Donations"}  How to show your gratitude

 @{" System description        " Link "System description"}  The components of AHI

 @{" The Author                " Link "The Author"}  Who designed it?
 @{" Acknowledgments           " Link "Acknowledgments"}  Thanks, guys!

 @{" Concept Index             " Link "Concept Index"}  Concept Index


@EndNode

@Node "Overview" "ahi.guide/Overview"
@Next "Distribution"
@Prev "Main"
@Toc "Main"

Overview
********

   The @{i}Amiga@{ui} has always had excellent sound capabilities.  In 1986, they
were awesome.  Today, well.... Perhaps not awesome, but still very
good.  The OS interface, @{b}audio.device@{ub} has however never been as good as
it could have been.  It is tied hard to the underlying hardware, and
doesn't work very well for music.  This has led to a situation where
most audio programs only use @{b}audio.device@{ub} to allocate the audio
resource, and then poke around in the hardware registers--making it
next to impossible to replace the @{i}Paula@{ui} chip (1).

   There have been attempts to write an @{b}audio.device@{ub} clone that uses a
sound card instead of Paula, but so far nobody has succeeded.  It is
definitely possible, but the question is if it is worth the trouble--too
many of the programs bang the hardware.

   Entering AHI (2).  AHI is a new audio subsystem, designed to be
flexible, hardware independent, expandable and future safe.  It is
designed with real-time applications in mind.  It is designed to play
@{i}modules@{ui} (3) and sound effects as efficient as possible, taking
advantage of modern DSP-based sound cards.

   Yet AHI allows applications that don't need full control over the
audio hardware to share the resource, so that many different programs
can play and record sound at the same time, without conflicts.

   As a user you will hopefully not see much of AHI, other than the
audio mode requesters.  They works almost exactly like screen mode
requesters.

   AHI was never supposed to be @{i}the@{ui} standard for hardware independent
audio.  It was meant as a temporary solution until @{i}Amiga Technologies@{ui}
delivered an official standard.  However, the situation looks worse and
worse for every day that passes by, and this may be all you will ever
get.

   ---------- Footnotes ----------

   (1)  Paula is one of the custom chips, and she is responsible for
the sound (and more).  Unfortunately, this chip has not been updated
since the very first Amiga was released.

   (2)  The name AHI was chosen because the functions in the system had
to have a prefix, and the author couldn't come up with anything better
than @{i}Audio Hardware Interface@{ui}, something that he has regretted ever
since.  The suggested pronunciation is "atchii", as in "God bless!".

   (3)  Originally designed in 1986 by Karsten Obarski, modules have
become a de facto standard for game and demo music.  The original format
has been improved many times, and many new music formats have--more or
less--been derived from it, including the popular @{i}S3M@{ui} and @{i}XM@{ui} formats.


@EndNode

@Node "Distribution" "ahi.guide/Distribution"
@Next "Donations"
@Prev "Overview"
@Toc "Main"

Distribution
************

   Copyright (C) 1994-1997 Martin Blom

   AHI is available as @{i}freeware@{ui}.  That is, it may be freely distributed
in unmodified form with no changes what so ever, but you may not charge
more than a nominal fee covering distribution costs.  However,
donations are welcome (see @{"Donations" Link "Donations"}).

   If you use this software in a commercial or shareware software
product, please consider giving the author (see @{"The Author" Link "The Author"})--and
preferably each one of the contributors (see @{"Contributors" Link "Contributors"}) too--an
original or registered version of your work.  Should you want to
distribute the AHI software with your own product, there is really
nothing to consider, is it?

   If you wish to distribute this software with a hardware product,
contact the author (see @{"The Author" Link "The Author"}).  Distribution of AHI with hardware
products is @{i}not@{ui} free.

   THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


@EndNode

@Node "Donations" "ahi.guide/Donations"
@Next "System description"
@Prev "Distribution"
@Toc "Main"

Donations
*********

   -AHI is available for personal use without any charges.  I strongly
believe in free software, and I use free high-quality software tools
daily.  But I live, like all of us, in a real world.  As a student, my
income doesn't even suffice for the rent, and much less food, course
literature and entertainments.  Therefore I ask, if you like this
software, please consider showing your gratitude by making a small
donation (see @{"The Author" Link "The Author"} for my address).

   @{i}Martin@{ui}


@EndNode

@Node "System description" "ahi.guide/System description"
@Next "The Author"
@Prev "Donations"
@Toc "Main"

System description
******************


 @{" AddAudioModes             " Link "AddAudioModes"}  Database maintenance
 @{" AHI                       " Link "AHI"}  Preferences program
 @{" AHI-Handler               " Link "AHI-Handler"}  DOS-device

 @{" System Files              " Link "System Files"}  The files in @{b}DEVS:@{ub}


@EndNode

@Node "AddAudioModes" "ahi.guide/AddAudioModes"
@Next "AHI"
@Prev "System description"
@Toc "System description"

AddAudioModes
=============

Format
     [FILES <file|pattern>] [QUIET] [REFRESH] [REMOVE] [DBLSCAN]

Template
     FILES/M,QUIET/S,REFRESH/S,REMOVE/S,DBLSCAN/S

Purpose
     To build and remove a list of audio modes that AHI can understand.

Path
     C:ADDAUDIOMODES

Specification
     @{b}AddAudioModes@{ub} is used to build and remove a list of audio modes
     that AHI can understand.  The definitions of the audio modes are
     stored in @{b}DEVS:Audiomodes@{ub} (see @{"The Mode Descriptors" Link "The Mode Descriptors"}).  Normally
     you don't have to run this program, since @{b}ahi.device@{ub} automatically
     reads all mode descriptors when it is used for the first time.  It
     can, however, be useful in installation scripts.

     The @{b}FILES@{ub} option specifies with descriptor(s) to be added to the
     current mode list.

     The @{b}QUIET@{ub} option, if specified, will suppress error and output
     messages.

     The @{b}REFRESH@{ub} option, if specified, will scan @{b}DEVS:Audiomodes@{ub} and
     add all descriptors found there to the current mode list.

     The @{b}REMOVE@{ub} option, if specified, will flush the current audio mode
     list from memory.

     The @{b}DBLSCAN@{ub} option does not have anything to do with the audio mode
     list.  If specified, it will open and then immediately close a
     native, double-scan screen.  On some systems using a graphic card,
     this will enable >28 kHz sample frequencies with the native audio.
     You need an appropriate monitor driver in @{b}DEVS:Monitors@{ub} to make
     it work.


@EndNode

@Node "AHI" "ahi.guide/AHI"
@Next "AHI-Handler"
@Prev "AddAudioModes"
@Toc "System description"

AHI
===

Format
     [FROM <filename>] [EDIT] [USE] [SAVE] [PUBSCREEN <public screen
     name>

Template
     FROM,EDIT/S,USE/S,SAVE/S,PUBSCREEN/K

Purpose
     To specify default audio options

Path
     SYS:Prefs/AHI

Specification
     @{b}AHI@{ub} without any arguments or with the @{b}EDIT@{ub} argument opens the AHI
     preferences editor.  The @{b}FROM@{ub} argument lets you specify a file to
     open.  This must be a file that was previously saved with the
     @{b}Save As...@{ub} menu item of the AHI preferences editor.  For
     example, if you have saved a special configuration of the AHI
     preferences editor to a file in the @{b}Presets@{ub} drawer, you can use the
     @{b}FROM@{ub} argument to open that file.  If the @{b}USE@{ub} switch is also
     given, the editor will not be opened, but the settings in the @{b}FROM@{ub}
     file will be used.  If the @{b}SAVE@{ub} switch is given, the editor will
     not open, but the settings in the @{b}FROM@{ub} file will be saved.  The
     @{b}PUBSCREEN@{ub} option allows you to specify a public screen on
     which the program will open its window.

     Example:

          AHI Prefs/Presets/AHI.Delfina USE

     loads and uses the specifications saved in the @{b}AHI.Delfina@{ub} file.
     If the system is rebooted, the last saved specifications will be
     loaded.

   Note that the preferences program requires either @{b}bgui.library@{ub}
version 41 (1) or @{i}MUI@{ui} version 3.8 (2)


 @{" Menus                     " Link "Menus"}  
 @{" Pages                     " Link "Pages"} 

   ---------- Footnotes ----------

   (1)  @{i}BGUI@{ui} is Copyright © 1996-1997 Ian J.  Einman

   (2)  @{i}MUI@{ui} is Copyright © 1992-1997 Stefan Stuntz


@EndNode

@Node "Menus" "ahi.guide/Menus"
@Next "Pages"
@Prev "AHI"
@Toc "AHI"

Menus
-----


 @{" Project Menu              " Link "Project Menu"}  
 @{" Edit Menu                 " Link "Edit Menu"}  
 @{" Settings Menu             " Link "Settings Menu"}  
 @{" Help Menu                 " Link "Help Menu"} 


@EndNode

@Node "Project Menu" "ahi.guide/Project Menu"
@Next "Edit Menu"
@Prev "Menus"
@Toc "Menus"

@{b}Project@{ub} Menu
............

   The @{b}Project@{ub} menu options let you save the editor settings to a
specific file and open previously saved files.

@{b}Open...@{ub}
     Loads the information from a specified preset file.

@{b}Save As...@{ub}
     Specify the preset file in which to save the currently displayed
     settings.  The requester provides a default file name in the
     @{b}Presets@{ub} drawer.  If you want to change it, type in the full
     path to a different file and select @{b}OK@{ub}.

@{b}About...@{ub}
     Shows the credits.

@{b}Quit@{ub}
     Exits the editor without performing any changes (the same as the
     @{b}Cancel@{ub} gadget).


@EndNode

@Node "Edit Menu" "ahi.guide/Edit Menu"
@Next "Settings Menu"
@Prev "Project Menu"
@Toc "Menus"

@{b}Edit@{ub} Menu
.........

   The @{b}Edit@{ub} menu options allow you to restore previously used settings
or the default settings.  The options are:

@{b}Reset to Default@{ub}
     Returns the editor settings to the default settings.

@{b}Last Saved@{ub}
     Returns the editor settings to the last settings you saved.

@{b}Restore@{ub}
     Returns the editor to the settings displayed when the editor first
     opened.


@EndNode

@Node "Settings Menu" "ahi.guide/Settings Menu"
@Next "Help Menu"
@Prev "Edit Menu"
@Toc "Menus"

@{b}Settings@{ub} Menu
.............

   The @{b}Settings@{ub} menu contains the @{b}Create Icons?@{ub} item that allows you to
save project icons representing your editor settings in the same drawer
as your files.  For example, if you save the specifications to the
@{b}SYS:Prefs/Presets/AHI.pre@{ub} file, the icon for the file appears in the
@{b}Presets@{ub} window.  Double-click on the icon to activate the file's
settings.


@EndNode

@Node "Help Menu" "ahi.guide/Help Menu"
@Prev "Settings Menu"
@Toc "Menus"

@{b}Help@{ub} Menu
.........

   The @{b}Help@{ub} menu's items let you view the on-line "AHI User's Guide"
using AmigaGuide.

@{b}Help...@{ub}
     Brings up the chapter about the preferences program (this chapter).

@{b}AHI User's Guide...@{ub}
     Brings up the first page of "AHI User's Guide".

@{b}Concept Index...@{ub}
     Brings up the index of "AHI User's Guide".


@EndNode

@Node "Pages" "ahi.guide/Pages"
@Prev "Menus"
@Toc "AHI"

Pages
-----

   The preferences program's GUI is divided in two pages:


 @{" Mode settings             " Link "Mode settings"}  
 @{" Advanced settings         " Link "Advanced settings"} 


@EndNode

@Node "Mode settings" "ahi.guide/Mode settings"
@Next "Advanced settings"
@Prev "Pages"
@Toc "Pages"

@{b}Mode settings@{ub} Page
..................

   On this page you select which audio mode to use.  You can select
audio mode for both low-level programs (@{b}Music unit@{ub}) and other programs
(@{b}Unit n@{ub}) that don't require low-level audio access such as the
AUDIO:  device (see @{"AHI-Handler" Link "AHI-Handler"}), sample players etc.  You can also
select the sample mixing (and recording) frequency to use and how many
channels you wish use (1).  Furthermore, you can set three hardware
properties of your sound hardware, namely the @{i}output volume@{ui},
@{i}monitor volume@{ui} and @{i}input gain@{ui}.  Finally, you can select which input
and output connectors you wish to use.

   The @{b}Music unit@{ub} is the defaults for low-level programs.  Such
programs often have an audio mode requester that lets you chose an audio
mode.  If you chose @{b}Default audio mode@{ub} from this requester, these
settings will be used.  Note that the number of channels is not
selectable here, it's up to the application program to decide how many
channels to use.

   ---------- Footnotes ----------

   (1)  The more channels you select, the more sounds can you play at
the same time.  However, due to the nature of sound mixing, the volume
will decrease as well.  If you try to play more sounds at the same time
than there are channels, the least important sounds will be muted until
the other sounds have finished playing.


@EndNode

@Node "Advanced settings" "ahi.guide/Advanced settings"
@Prev "Mode settings"
@Toc "Pages"

@{b}Advanced settings@{ub} Page
......................

   This page contains some options that should not be used if you don't
understand them.

@{b}Debug level@{ub}
     Sets the debug level for AHI.  If not @{b}None@{ub}, AHI will print debug
     information to the serial port.

@{b}Echo@{ub}
     On slow processors (like anything below a MC68040) echo can take
     so much CPU power that it becomes unusable, and can therefore be
     disabled.  As an alternative, echo can be done @{b}Fast@{ub}, which means
     that the parameters will be twisted in order to gain speed.  The
     result may not be what the composer or programmer wanted, but at
     least it's echo.

@{b}Surround in "Fast" modes@{ub}
     In modes that use multiplication tables (the so-called "fast"
     modes) all surround sounds have to be mixing without using tables.
     In order to make mixing as fast as possible, surround sounds can
     be forced to ordinary ones by disabling them.

@{b}Master volume@{ub}
     Normally, the "Master volume" feature of AHI can make the output
     heavily distorted if set too high.  Turning "clipping" on can
     reduce the distortion, but will--in the current
     implementation--use 128 kB of extra memory.  Note that the
     so-called "HiFi" modes are not affected by this switch (see
     @{"The Mode Descriptors" Link "The Mode Descriptors"}).

@{b}CPU usage limit@{ub}
     Some hardware drivers (but not all) can be told not to use more
     that a given percentage of the available CPU time in order to
     prevent lockups.  If your mouse pointer freezes when playing
     music, reduce the limit slightly.  If on the other hand the sound
     becomes cut and distorted, you can try to increase the limit--but
     remember that you risk locking up the computer!


@EndNode

@Node "AHI-Handler" "ahi.guide/AHI-Handler"
@Next "System Files"
@Prev "AHI"
@Toc "System description"

AHI-Handler
===========

   The @{b}AHI-Handler@{ub} is an I/O mechanism that is used to play and record
sounds.  The @{b}AHI-Handler@{ub} is normally mounted as @{b}AUDIO:@{ub} at startup time,
or later by double-clicking on its icon or by giving the following
command in a Shell window:  @{b}mount AUDIO:  <RET>@{ub}.

   The DOSDriver entry is:

     Handler         = L:AHI-Handler
     Stacksize       = 4096
     Priority        = 5
     GlobVec         = -1

   When the device is mounted, you can read from the device to record
and write to it to play.  Options can be given like this:

     "AUDIO:PRIORITY=1 VOLUME=50"

   All slashes (@{b}/@{ub}) in the name will be translated to spaces.  Thus, if
you use slashes instead of spaces, you don't have to use quotes around
the name:

     AUDIO:PRIORITY/1/VOLUME/50

   The full template for reading is:

     B=BITS/K/N,C=CHANNELS/K/N,F=FREQUENCY/K/N,T=TYPE/K,L=LENGTH/K/N,
     S=SECONDS/K/N,BUF=BUFFER/K/N,UNIT/K/N

   The full template for writing is:

     B=BITS/K/N,C=CHANNELS/K/N,F=FREQUENCY/K/N,T=TYPE/K,V=VOLUME/K/N,
     P=POSITION/K/N,PRI=PRIORITY/K/N,L=LENGTH/K/N,S=SECONDS/K/N,
     BUF=BUFFER/K/N,UNIT/K/N

   @{b}BITS@{ub} can be one of 8, 16 or 32.  @{b}CHANNELS@{ub} can be either 1 for mono
or 2 for stereo.  The @{b}FREQUENCY@{ub} is in Hertz, @{b}TYPE@{ub} is one of @{b}SIGNED@{ub},
@{b}AIFF@{ub} or @{b}AIFC@{ub}.  @{b}VOLUME@{ub} ranges from 0 (silence) to 100 (full
volume), and @{b}POSITION@{ub} ranges from -100 (far left) via 0 (center) to 100
(far right).  The @{b}PRIORITY@{ub} can be from -128 to 127 (unstoppable).
@{b}LENGTH@{ub} is how many bytes you wish to read or write, and @{b}SECONDS@{ub} is
the same, but in seconds instead of bytes.  The @{b}BUFFER@{ub} size is
specified in bytes.  Note that two buffers are always used, which means
that the memory usage will be two times BUFFER.  @{b}UNIT@{ub} selects which
@{b}ahi.device@{ub} unit to use.

   The default options for reading are @{b}BITS=8@{ub} @{b}CHANNELS=1@{ub} @{b}FREQUENCY=8000@{ub}
@{b}TYPE=SIGNED@{ub} @{b}LENGTH=very-very-much@{ub} @{b}BUFFER=32768@{ub} @{b}UNIT=0@{ub}.

   The default options for reading are @{b}BITS=8@{ub} @{b}CHANNELS=1@{ub} @{b}FREQUENCY=8000@{ub}
@{b}TYPE=<none>@{ub} @{b}VOLUME=100@{ub} @{b}POSITION=0@{ub} @{b}PRIORITY=0@{ub} @{b}LENGTH=very-very-much@{ub}
@{b}BUFFER=32768 UNIT=0@{ub}.

   If @{b}TYPE@{ub} is not specified, the default behaviour is to identify the
data stream as @{i}IFF-AIFF@{ui} or @{i}IFF-AIFC@{ui}.  If so, the default values of
@{b}BITS@{ub}, @{b}CHANNELS@{ub}, @{b}FREQUENCY@{ub} and @{b}LENGTH@{ub} will taken from the file.
You can still override them if you wish.  If the stream could not be
identified, the data format is assumed to be @{b}SIGNED@{ub}.

   Both when reading and writing the sample rate will be converted on
the fly to what the underlying hardware is configured to.  Normally
this is not a big problem when writing, but the quality when reading
leaves quite a lot to wish for, since no low-pass filters are used.

   Example 1:

     copy Louise.AIFF AUDIO:

   plays the file @{b}Louise.AIFF@{ub}.

   Example 2:

     copy AUDIO:SECONDS/10/TYPE/AIFC/B/16/F/44100/C/2 sample.AIFC

   records 10 seconds of audio and stores it in the file @{b}sample.AIFC@{ub} as
uncompressed @{i}IFF-AIFC@{ui}, 16 bit stereo at 44.1 kHz.


@EndNode

@Node "System Files" "ahi.guide/System Files"
@Prev "AHI-Handler"
@Toc "System description"

System Files
============

   AHI uses a set of hardware drivers for each sound card.  This means
that it's easy to add support for new sound cards as they appear.  At
the time of writing, the following sound cards are supported:

   @{b}*@{ub} Aura (sampling only)

   @{b}*@{ub} Clarity (sampling only)

   @{b}*@{ub} Concierto

   @{b}*@{ub} Delfina DSP and Delfina Lite

   @{b}*@{ub} DraCo Motion

   @{b}*@{ub} Maestro Pro

   @{b}*@{ub} Melody MPEG

   @{b}*@{ub} Paula (the built-in audio)

   @{b}*@{ub} Prelude

   @{b}*@{ub} Toccata

   @{b}*@{ub} Wavetools


 @{" The Drivers               " Link "The Drivers"}  
 @{" The Mode Descriptors      " Link "The Mode Descriptors"} 


@EndNode

@Node "The Drivers" "ahi.guide/The Drivers"
@Next "The Mode Descriptors"
@Prev "System Files"
@Toc "System Files"

The Drivers
-----------

   The hardware drivers themself are located in the @{b}DEVS:AHI@{ub} drawer,
and are named as @{b}<name>.audio@{ub}.  They are actually libraries, in spite
of being located under the @{b}DEVS:@{ub} assign, and will be flushed out from
memory when not in use and the system needs more RAM.  Many of the
drivers require additional files; see below.  These extra files are not
delivered with AHI.

@{b}concierto.audio@{ub}
     Requires @{b}concierto.library@{ub}.

@{b}delfina.audio@{ub}
     Requires @{b}delfina.library@{ub} version 4 or greater (1).

@{b}maestropro.audio@{ub}
     Requires @{b}maestix.library@{ub} version 40.10 or greater (2).  For more
     information about this driver as well as the most recent version of
     @{b}maestix.library@{ub}, please visit the author's WWW page (3).

@{b}melody.audio@{ub}
     Requires @{b}melodympeg.device@{ub} version 1.40 or greater (4).

@{b}paula.audio@{ub}
     On startup, the file @{b}ENV:CyberSound/SoundDrivers/14Bit_Calibration@{ub}
     is read and used for the 14 bit DAC calibration.

     The 14 bit modes cannot be used for recording, but the 8 bit modes
     supports both generic parallel port samplers as well as both the
     Aura and Clarity samplers.

     The environment variable @{b}AHIpaulaFilterFreq@{ub} is checked every time
     playback starts, and should be set to a frequency in Hertz.  If
     the mixing frequency is higher than this value, the internal
     low-pass filter will be turned off.  If it is lower, the filter
     will be activated.  The default is 0 Hz, which means that the
     filter will always be turned off.  Example:

          SetEnv AHIpaulaFilterFreq 16000
          Copy ENV:AHIpaulaFilterFreq ENVARC:

     The variable @{b}AHIpaulaSampleLimit@{ub} is also checked.  This variable
     controls how the driver should handle mixing frequencies greater
     than 28 kHz, which is the limit of the hardware when using 15 kHz
     screen modes (PAL, NTSC, Euro36).  If the current screen mode is a
     VGA (31 kHz) mode, the driver allows frequencies up to 48 kHz.
     Normally, the driver checks the current screen mode, and decides
     if the higher mixing frequencies should be available or not.  By
     setting this variable, you can control that decision.  If set to
     @{b}0@{ub}, the frequency will always be limited to 28 kHz and if
     set to @{b}1@{ub}, there will never be any limit.  Example:

          SetEnv AHIpaulaSampleLimit 1
          Copy ENV:AHIpaulaSampleLimit ENVARC:

     This will disable any screen mode checking, and will always allow
     up to 48 kHz in the mode requesters.

          Delete ENV:AHIpaulaSampleLimit
          Delete ENVARC:AHIpaulaSampleLimit

     This will turn on the screen mode checking again.

     Because of incorrect hardware documentation, there is great
     confusion about which hardware channels are sent to the left
     speaker, and which are sent to the right.  @{b}paula.audio@{ub} uses the
     correct order (right, left, left, right) but many other programs
     don't.  The @{b}AHIpaulaSwapChannels@{ub} variable was added to let the
     user decide if the correct or incorrect behaviour should be used.
     In not present or set to @{b}0@{ub}, the correct behaviour is used.  If set
     to @{b}1@{ub}, the left and right channels will be swapped.

     Finally, the variable @{b}AHIpaulaBufferLength@{ub} controls the minimum
     playback buffer size to use.  Because of the limited @{i}Chip RAM@{ui}
     bandwidth, a @{i}MC68060@{ui} CPU might run into trouble when using the
     default minumum buffer size (0).  By setting this variable to @{b}1024@{ub},
     for example, you will reduce the number of interrupts caused and
     increase the number of samples transferred each time to at least
     1024 samples.  But take care!  Setting this variable too high will
     cause long periods with multitasking disabled.

@{b}toccata.audio@{ub}
     Requires @{b}toccata.library@{ub} version 12 or greater (5).  This driver
     also reads the environment variables @{b}AHItoccataNoTask@{ub} and
     @{b}AHItoccataIrqSize@{ub}.  If @{b}AHItoccataNoTask@{ub} is set to @{b}1@{ub}, all
     mixing will be done in a @{i}Software Interrupt@{ui} which means the sound
     output will not suffer when multitasking is turned off.  The back
     side is that it requires a faster CPU.  Much faster.  Only use
     this option as a last resort.  Example:

          SetEnv AHItoccataNoTask 1
          Copy ENV:AHItoccataNoTask ENVARC:

     @{b}AHItoccataIrqSize@{ub} specifies the number of bytes transferred to the
     card each interrupt and defaults to @{b}512@{ub}.  It must be one of @{b}32@{ub},
     @{b}64@{ub}, @{b}128@{ub}, @{b}256@{ub} or @{b}512@{ub}.  If you encounter problems with
     serial port hardware, you might want to set this variable to a
     lower value than the default.

     Please note that this driver is used for both the DraCo Motion and
     the Toccata.

@{b}wavetools.audio@{ub}
     Requires @{b}dad_audio.device@{ub}.

   ---------- Footnotes ----------

   (1)  The latest version of the Delfina software can be found at
Petsoff Limited Partnership's WWW page:  @{b}http://www.sci.fi/~petsoff@{ub}.

   (2) @{b}maestix.library@{ub} is available from AmiNet, for example
@{b}ftp://ftp.germany.aminet.org/pub/aminet/util/libs/Maestix.lha@{ub}.

   (3) Richard Körber's WWW page:
@{b}http://www.is-koeln.de/einwohner/shred@{ub}.

   (4) @{b}melodympeg.device@{ub} and the latest version of this driver can be
found at the Kato Development Group's WWW page:
@{b}http://home.pages.de/~kato@{ub}.

   (5) @{b}toccata.library@{ub} is available from AmiNet, for example
@{b}ftp://ftp.germany.aminet.org/pub/aminet/util/libs/toclib12.lha@{ub}.


@EndNode

@Node "The Mode Descriptors" "ahi.guide/The Mode Descriptors"
@Prev "The Drivers"
@Toc "System Files"

The Mode Descriptors
--------------------

   The files in @{b}DEVS:AudioModes@{ub} describes the available audio modes
that you can chose from in the audio mode requester.  All files located
in this drawer will be scanned the first time AHI is used, and added to
the internal mode database.

   The following modes are available for most drivers:

@{b}Mono@{ub}
     Mono output, all sounds will be centered, and no surround sound is
     possible.

@{b}Stereo@{ub}
     Stereo output, but all sounds are either forces to the extreme
     left or extreme right--centered sounds are not possible, for
     example.  This mode will probably use slightly more CPU power than
     the "mono" mode.  Since all sounds are forced to one of the
     extreme positions, stereo sounds will play with either the left or
     the right part muted.

@{b}Stereo++@{ub}
     Stereo output with free positioning of all sounds--an instrument
     can be placed anywhere between the two speakers, for example.
     Unless the program only uses the extremes when positioning a
     sound, this mode will eat more CPU cycles than the "stereo" mode.

@{b}Fast mono@{ub}
@{b}Fast stereo@{ub}
@{b}Fast stereo++@{ub}
     "Fast" modes take some shortcuts in order to reduce the CPU usage.
     For 8 bit samples, multiplication tables will be used, which
     speeds up mixing by magnitudes and still gives the same quality
     with the exception of volume levels--instead of 256 levels only 32
     are available.  The disadvantage of multiplication tables is that
     they require a fair amount of free RAM.  For 16 bit samples, the
     shortcuts are a bit more crude:  the volume of each sound will be
     rounded to a power of 2 before it's played.  This means that a 16
     bit sound will only be played at volume levels of 100%, 50%, 25%,
     12.5% etc.  If surround sounds are played, the normal (not "fast")
     mixing routines will be used.  You can use the preferences program
     (see @{"Advanced settings" Link "Advanced settings"}) to disable surround sounds for "fast"
     modes.

     "Fast" modes are useful if you wish to use as little CPU power as
     possible, but don't mind spending some memory to reach that goal.
     They are also very useful when playing 16 bit audio streams--from
     a sample or MPEG player, for example--since that usually doesn't
     involve volume scaling and frequency recalculation. However, if
     used for playing streams, make sure the mixing frequency is the
     same as the stream frequency!

@{b}HiFi mono@{ub}
@{b}HiFi stereo@{ub}
@{b}HiFi stereo++@{ub}
     "HiFi" modes use much better mixing algorithms than the other
     modes, using 32 bits internally and linear interpolation.  They
     are also @{i}much@{ui} slower than the other modes.  "HiFi" modes turn on
     master volume with clipping automatically (see @{"Advanced settings" Link "Advanced settings"}).

     "HiFi" modes are useful when you're playing music--@{i}MIDI@{ui} songs or
     @{i}modules@{ui}, for example--and want the best possible quality AHI
     has to offer.


@EndNode

@Node "The Author" "ahi.guide/The Author"
@Next "Acknowledgments"
@Prev "System description"
@Toc "Main"

The Author
**********

   The author can be reached at the following addresses:

Electronic mail
     <lcs@lysator.liu.se>

Standard mail
     Martin Blom
     Alsättersgatan 15A:24
     SE-584 35 Linköping
     Sweden

World-Wide Web
     @{b}http://www.lysator.liu.se/~lcs@{ub}


 @{" The Man                   " Link "The Man"}  
 @{" The Myth                  " Link "The Myth"}  
 @{" The Concept               " Link "The Concept"} 


@EndNode

@Node "The Man" "ahi.guide/The Man"
@Next "The Myth"
@Prev "The Author"
@Toc "The Author"

The Man
=======

   Martin Blom was born 1974 in a town in Sweden called Jönköping.
He had a happy childhood, lots of good friends, and a great family.  He
did his homework and went to church every Sunday.

   But then, one cold, dark Christmas Eve in the year of our Lord 1986,
everything went wrong.  This was the day when @{i}it@{ui} entered his life.  At
once, there were fights among the brothers.  They all wanted to use @{i}it@{ui}.
Martin started to avoid playing with kids that didn't share his
passion for @{i}it@{ui}.  The school work suffered.  Other interests suffered.
@{i}It@{ui} was the Commodore 64 home computer, and it would forever change
his life.

   Today, more than ten years after the tragedy, things are worse than
ever.  He is studying @{i}Computer Science and Engineering@{ui} at
@{i}Linköping Institute of Technology@{ui}, surrounded every day by other
computer nerds.

   Martin has spent loads of money on computers over the years:  Amiga
500, Amiga 4000/040, Commodore 128D, Commodore 64 (in order of
appearance), modem, monitors, disks, mice etc.  Interesting enough, no
sound card.  He did, however, build a sound card of his own for the
Commodore 64, and he likes to mention that now and then (you see, this
was one of the few hardware projects that actually worked!).  4
channels, 8 bit samples.  He even wrote a module player for the good
old 64.  And it had quadrascopes.


@EndNode

@Node "The Myth" "ahi.guide/The Myth"
@Next "The Concept"
@Prev "The Man"
@Toc "The Author"

The Myth
========

   Some people actually seem to believe that Martin is a good
programmer.  They couldn't be more wrong.  He is lazy, has no patience,
he is a slow thinker and he doesn't like anything he @{i}has@{ui} to do.

   Martin used to say

   @{b}*@{ub}  If you can't write applications, write games.

   @{b}*@{ub}  If you can't write games, write demos.

   @{b}*@{ub}  If you can't write demos, write utilities.

   @{b}*@{ub}  If you can't write utilities, write BBS intros and doors.

   @{b}*@{ub}  If you can't do that either, get a modem and start trading.

   And guess what?  He tried demos.  He tried utilities.  He tried
intros.  He wrote a door for /X.  And he traded warez.


@EndNode

@Node "The Concept" "ahi.guide/The Concept"
@Prev "The Myth"
@Toc "The Author"

The Concept
===========

   What do you do if you don't have the patience to write applications,
if you only write moderate demos, are tired of utilities, hate BBS
doors, are totally fed up with playing games and have decided to get
legal and stop pirating software?  Simple.  Try a new concept!

   Take a deep breath.  Close your eyes.  Think of one thing your
computer lacks.  Think of one of the things that makes your favorite
toy feel outdated.  Think of something that nobody has (successfully)
tried before.  Then write the software, and release it as Freeware.

   In Martins case, that something was hardware independent audio.

   Come on, admit it!  It's brilliant.  It doesn't matter if you are a
good programmer.  It doesn't matter if it takes 3 years to get to a
half-finished product.  It doesn't matter if you give it the most
unimaginative name in the world--you can even use a TLA (1).  Nobody is
going to say your software sucks, because nobody can say he has done
better himself.  Nobody is going to complain if you're slow on
releasing bug fixes and updates, because the software is free.  And
nobody is going to be angry with you if you stop developing the
software--because it sucked in the first place, remember?

   This concept won't make you rich, but are rich people really happier?

   ---------- Footnotes ----------

   (1)  Three Letter Acronym


@EndNode

@Node "Acknowledgments" "ahi.guide/Acknowledgments"
@Next "Concept Index"
@Prev "The Author"
@Toc "Main"

Acknowledgments
***************

   The author wish to give special thanks to the following persons (in
alphabetical order):

Amiga Translators' Organization
     For the catalog translations.

Daniel Arthursson and Johan Nyblom
     For making it possible to write the first driver for a sound card,
     the @{i}Wavetools@{ui} card.  I'm sure AHI would not have been accepted as
     quick as it was without this driver.  Funny that it didn't even
     work....

Christian Buchner
     For the calibrated 14 bit routines for Paula.

SAS Institute, Inc. and Steve Krueger
     For the compiler and all the updates.

Jyrki Petsalo and Teemu Suikki
     For the Delfina driver, and for supporting AHI in the early days.
     And of course, for the sound card!

Pauli Porkka
     For active support and promotion of AHI from the beginning.

All the rest
     Many, many other have helped me, sent suggestions etc.  I owe you
     a lot.

   And of course, the actual catalog translators: Samuel Aguilera,
Andrija Antonijevic Rúben Alvim, Stéphane Barbaray, Frederico Borges,
Piergiorgio Ghezzo, Roger Hågensen, Bernardo Innocenti, Ljubomir
Jankovic, Petteri Kallio, Eivind Olsen, Marcin Orîowski, Thomas
Petersen, Pauli Porkka, Vit Sindlar, Martin Sprenger, Sönke Tesch,
Michel Vissers, Ondrej Zima, me, myself and I....


 @{" Contributors              " Link "Contributors"}  Who has contributed to the AHI project?


@EndNode

@Node "Contributors" "ahi.guide/Contributors"
@Prev "Acknowledgments"
@Toc "Acknowledgments"

Contributors
============

   The following people has contributed to the AHI project with code:

Stéphane Barbaray <opty@club-internet.fr>
     The MUI version of the preferences program.

Olaf Barthel <olsen@sourcery.han.de>
     The Concierto driver.

Thorsten Hansen <hansen_t@informatik.fh-hamburg.de>
     The Melody MPEG driver.

Richard Körber <shred@chessy.aworld.de>
     The Maestro Pro driver.

Johan Nyblom <nyblom@ludd.luth.se>
     The latest Wavetools driver.

Pauli Porkka <pporkka@iki.fi>
     The first version of the Toccata driver.

Rüdiger Sopp
     The first version of the preferences program.  Too bad things
     didn't work out as planned.

Teemu Suikki <tsuikki@lut.fi>
     The Delfina driver.

Thomas Wenzel <wenzel@unixserv.rz.fh-hannover.de>
     The Prelude driver.

   Many thanks!


@EndNode

@Node "Concept Index" "ahi.guide/Concept Index"
@Prev "Acknowledgments"
@Toc "Main"

Concept Index
*************

@Index "Concept Index"



 @{" 14 bit calibration                       " Link "The Drivers"}   The Drivers
 @{" 68060 CPU                                " Link "The Drivers"}   The Drivers
 @{" Acknowledgments                          " Link "Acknowledgments"}   Acknowledgments
 @{" AddAudioModes                            " Link "AddAudioModes"}   AddAudioModes
 @{" Advanced settings                        " Link "Advanced settings"}   Advanced settings
 @{" AHI, overview                            " Link "Overview"}   Overview
 @{" AHI, preferences program                 " Link "AHI"}   AHI
 @{" AHI-Handler                              " Link "AHI-Handler"}   AHI-Handler
 @{" AHIpaulaBufferLength variable            " Link "The Drivers"}   The Drivers
 @{" AHIpaulaFilterFreq variable              " Link "The Drivers"}   The Drivers
 @{" AHIpaulaSampleLimit variable             " Link "The Drivers"}   The Drivers
 @{" AHIpaulaSwapChannels variable            " Link "The Drivers"}   The Drivers
 @{" AHItoccataIrqSize variable               " Link "The Drivers"}   The Drivers
 @{" AHItoccataNoTask variable                " Link "The Drivers"}   The Drivers
 @{" AIFC                                     " Link "AHI-Handler"}   AHI-Handler
 @{" AIFF                                     " Link "AHI-Handler"}   AHI-Handler
 @{" Audio mode database                      " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Audio mode settings                      " Link "Mode settings"}   Mode settings
 @{" Audio modes, overview                    " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" AUDIO:                                   " Link "AHI-Handler"}   AHI-Handler
 @{" Aura                                     " Link "System Files"}   System Files
 @{" Author of AHI                            " Link "The Author"}   The Author
 @{" Calibration, 14 bit                      " Link "The Drivers"}   The Drivers
 @{" Clarity                                  " Link "System Files"}   System Files
 @{" Clipping, master volume                  " Link "Advanced settings"}   Advanced settings
 @{" Concierto                                " Link "System Files"}   System Files
 @{" Contributors                             " Link "Contributors"}   Contributors
 @{" Copyright                                " Link "Distribution"}   Distribution
 @{" CPU usage limit                          " Link "Advanced settings"}   Advanced settings
 @{" CyberSound                               " Link "The Drivers"}   The Drivers
 @{" DAC calibration                          " Link "The Drivers"}   The Drivers
 @{" Database, audio modes                    " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Debug level                              " Link "Advanced settings"}   Advanced settings
 @{" Delfina DSP                              " Link "System Files"}   System Files
 @{" Delfina Lite                             " Link "System Files"}   System Files
 @{" Disclaimer                               " Link "Distribution"}   Distribution
 @{" Distortion, while recording              " Link "AHI-Handler"}   AHI-Handler
 @{" Distribution                             " Link "Distribution"}   Distribution
 @{" Donations                                " Link "Donations"}   Donations
 @{" DraCo Motion                             " Link "System Files"}   System Files
 @{" Drivers                                  " Link "System Files"}   System Files
 @{" Echo, enable/disable/fast                " Link "Advanced settings"}   Advanced settings
 @{" Fame                                     " Link "The Concept"}   The Concept
 @{" Fast Mono (audio mode)                   " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Fast Stereo (audio mode)                 " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Fast Stereo++ (audio mode)               " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" HiFi Mono (audio mode)                   " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" HiFi Stereo (audio mode)                 " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" HiFi Stereo++ (audio mode)               " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" IFF-AIFC                                 " Link "AHI-Handler"}   AHI-Handler
 @{" IFF-AIFF                                 " Link "AHI-Handler"}   AHI-Handler
 @{" Interpolation, linear                    " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Jesus Christ                             " Link "The Man"}   The Man
 @{" Legal nonsense                           " Link "Distribution"}   Distribution
 @{" License                                  " Link "Distribution"}   Distribution
 @{" Linear interpolation                     " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Maestro Pro                              " Link "System Files"}   System Files
 @{" Master volume, clipping                  " Link "Advanced settings"}   Advanced settings
 @{" MC68060 CPU                              " Link "The Drivers"}   The Drivers
 @{" Melody MPEG                              " Link "System Files"}   System Files
 @{" Mode settings                            " Link "Mode settings"}   Mode settings
 @{" Modules on a C64                         " Link "The Man"}   The Man
 @{" Mono (audio mode)                        " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Multiplication tables                    " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Nerd, definition of                      " Link "The Man"}   The Man
 @{" Overview                                 " Link "Overview"}   Overview
 @{" Paula                                    " Link "System Files"}   System Files
 @{" Paula, custom chip                       " Link "Overview"}   Overview
 @{" Preferences                              " Link "AHI"}   AHI
 @{" Preferences, advanced                    " Link "Advanced settings"}   Advanced settings
 @{" Preferences, audio mode                  " Link "Mode settings"}   Mode settings
 @{" Prelude                                  " Link "System Files"}   System Files
 @{" Recursion                                " Link "Concept Index"}   Concept Index
 @{" Settings                                 " Link "AHI"}   AHI
 @{" Settings, advanced                       " Link "Advanced settings"}   Advanced settings
 @{" Settings, audio mode                     " Link "Mode settings"}   Mode settings
 @{" Software license                         " Link "Distribution"}   Distribution
 @{" Sound card drivers                       " Link "System Files"}   System Files
 @{" Starvation                               " Link "Donations"}   Donations
 @{" Stereo (audio mode)                      " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Stereo++ (audio mode)                    " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" Surround sound, enable/disable           " Link "Advanced settings"}   Advanced settings
 @{" System description                       " Link "System description"}   System description
 @{" System Files                             " Link "System Files"}   System Files
 @{" Tables, multiplication                   " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" The Author                               " Link "The Author"}   The Author
 @{" The Concept                              " Link "The Concept"}   The Concept
 @{" The Drivers                              " Link "The Drivers"}   The Drivers
 @{" The Man                                  " Link "The Man"}   The Man
 @{" The Mode Descriptors                     " Link "The Mode Descriptors"}   The Mode Descriptors
 @{" The Myth                                 " Link "The Myth"}   The Myth
 @{" Toccata                                  " Link "System Files"}   System Files
 @{" Wavetools                                " Link "System Files"}   System Files

@EndNode

