AHI
Hardware independent audio for Amiga
AHI User's Guide for AHI release 5.4
Document version 5.2 (2003-01-19)
Martin 'Leviticus' Blom
Table of Contents
AHI User's Guide
For AHI release 5.4. Document version 5.2 (2003-01-19).
Copyright (C) 1994-2003 Martin Blom
The latest release of AHI can always be found at
http://www.lysator.liu.se/~lcs/ahi.html.
The Amiga has always had excellent sound capabilities. In 1986, they
were awesome. Today, well@enddots{} Perhaps not awesome, but still very
good. The OS interface, audio.device
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 audio.device
to allocate the audio resource,
and then poke around in the hardware registers--making it next to
impossible to replace the Paula chip (1).
There have been attempts to write an audio.device
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 modules
(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 the standard for hardware
independent audio. It was meant as a temporary solution until Amiga
Technologies 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.
Copyright (C) 1994-2003 Martin Blom
AHI is available under a dual license. The device itself is under
the "GNU Library General Public License" (see section GNU LIBRARY GENERAL PUBLIC LICENSE), while the
utility programs and the AUDIO:
device is covered by the "GNU
General Public License" (see section GNU GENERAL PUBLIC LICENSE).
If you use this software in a commercial or shareware product, please
consider giving the author (see section The Author)---and preferably each one
of the contributors too (see AHI User's Guide)---an original or
registered copy or sample of your work. Should you want to distribute the
AHI software with your own product, there is really nothing to
consider, right?
- 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
-
AddAudioModes
is used to build and remove a list of audio modes that
AHI can understand. The definitions of the audio modes are stored in
`DEVS:Audiomodes' (see section The Mode Descriptors). Normally you don't
have to run this program, since ahi.device
automatically reads all
mode descriptors when it is used for the first time. It can, however, be
useful in installation scripts.
The `FILES' option specifies with descriptor(s) to be added to the
current mode list.
The `QUIET' option, if specified, will suppress error and output
messages.
The `REFRESH' option, if specified, will scan `DEVS:Audiomodes'
and add all descriptors found there to the current mode list.
The `REMOVE' option, if specified, will flush the current audio mode
list from memory.
The `DBLSCAN' 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 `DEVS:Monitors' to make it work.
- 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
-
AHI
without any arguments or with the `EDIT' argument opens the
AHI preferences editor. The `FROM' argument lets you specify a
file to open. This must be a file that was previously saved with the
`Save As...' 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 `Presets' drawer, you can use the
`FROM' argument to open that file. If the `USE' switch is also
given, the editor will not be opened, but the settings in the `FROM'
file will be used. If the `SAVE' switch is given, the editor will not
open, but the settings in the `FROM' file will be saved. The
`PUBSCREEN' 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 `AHI.Delfina' file. If
the system is rebooted, the last saved specifications will be loaded.
Note that the preferences program requires either bgui.library
version 41 (4) or
MUI version 3.8 (5)
The `Project' menu options let you save the editor settings to a
specific file and open previously saved files.
- `Open...'
-
Loads the information from a specified preset file.
- `Save As...'
-
Specify the preset file in which to save the currently displayed settings.
The requester provides a default file name in the `Presets' drawer.
If you want to change it, type in the full path to a different file and
select `OK'.
- `About...'
-
Shows the credits.
- `Quit'
-
Exits the editor without performing any changes (the same as the
`Cancel' gadget).
The `Edit' menu options allow you to restore previously used settings
or the default settings. The options are:
- `Reset to Default'
-
Returns the editor settings to the default settings.
- `Last Saved'
-
Returns the editor settings to the last settings you saved.
- `Restore'
-
Returns the editor to the settings displayed when the editor first opened.
The `Settings' menu contains the `Create Icons?' 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
`SYS:Prefs/Presets/AHI.pre' file, the icon for the file appears in the
`Presets' window. Double-click on the icon to activate the file's
settings.
The `Help' menu's items let you view the on-line "AHI User's
Guide" using AmigaGuide.
- `Help...'
-
Brings up the chapter about the preferences program (this chapter).
- `AHI User's Guide...'
-
Brings up the first page of "AHI User's Guide".
- `Concept Index...'
-
Brings up the index of "AHI User's Guide".
The preferences program's GUI is divided in two pages:
On this page you select which audio mode to use. You can select audio
mode for both low-level programs (`Music unit') and other
programs (`Unit n') that don't require low-level audio access
such as the AUDIO:
device (see section AHI-Handler), sample players
etc. You can also select the sample mixing (and recording) frequency
to use and how many channels you wish use (6).
Furthermore, you can set three hardware properties of your sound
hardware, namely the output volume, monitor volume and
input gain. Finally, you can select which input and output
connectors you wish to use.
The `Music unit' 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 `Default audio mode' 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.
This page contains some options that should not be used if you don't
understand them.
- `Debug level'
-
Sets the debug level for AHI. If not `None', AHI will print
debug information to the serial port.
- `Echo'
-
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 `Fast', 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.
- `Surround in "Fast" modes'
-
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.
- `Master volume'
-
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 section The Mode Descriptors).
- `CPU usage limit'
-
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!
The AHI-Handler
is an I/O mechanism that is used to play and record
sounds. The AHI-Handler
is normally mounted as AUDIO:
at
startup time, or later by double-clicking on its icon or by giving the
following command in a Shell window: mount AUDIO: RET.
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 (`/') 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
`BITS' can be one of 8, 16 or 32. `CHANNELS' can be either 1 for
mono or 2 for stereo. The `FREQUENCY' is in Hertz, `TYPE' is one
of `SIGNED', `AIFF' or `AIFC'. `VOLUME' ranges from 0
(silence) to 100 (full volume), and `POSITION' ranges from -100
(far left) via 0 (center) to 100 (far right). The `PRIORITY' can be
from -128 to 127 (unstoppable). `LENGTH' is how many bytes you
wish to read or write, and `SECONDS' is the same, but in seconds
instead of bytes. The `BUFFER' size is specified in bytes. Note that
two buffers are always used, which means that the memory usage will be two
times BUFFER. `UNIT' selects which ahi.device
unit to use.
The default options for reading are `BITS=8' `CHANNELS=1'
`FREQUENCY=8000' `TYPE=SIGNED' `LENGTH=very-very-much'
`BUFFER=32768' `UNIT=0'.
The default options for reading are `BITS=8' `CHANNELS=1'
`FREQUENCY=8000' `TYPE=<none>' `VOLUME=100'
`POSITION=0' `PRIORITY=0' `LENGTH=very-very-much'
`BUFFER=32768 UNIT=0'.
If `TYPE' is not specified, the default behaviour is to identify the
data stream as IFF-AIFF or IFF-AIFC. If so, the default values
of `BITS', `CHANNELS', `FREQUENCY' and `LENGTH' 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
`SIGNED'.
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 `Louise.AIFF'.
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 `sample.AIFC' as
uncompressed IFF-AIFC, 16 bit stereo at 44.1 kHz.
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:
-
Aura (sampling only)
-
Clarity (sampling only)
-
Concierto
-
Delfina DSP and Delfina Lite
-
DraCo Motion
-
Maestro Pro
-
Melody MPEG
-
Paula (the built-in audio)
-
Prelude
-
Toccata
-
Wavetools
The hardware drivers themself are located in the `DEVS:AHI' drawer,
and are named as `<name>.audio'. They are actually libraries, in
spite of being located under the `DEVS:' 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.
concierto.audio
-
Requires
concierto.library
.
delfina.audio
-
Requires
delfina.library
version 4 or greater (7).
maestropro.audio
-
Requires
maestix.library
version 40.10 or greater (8). For
more information about this driver as well as the most recent version of
maestix.library
, please visit the author's WWW page (9).
melody.audio
-
Requires
melodympeg.device
version 1.40 or greater (10).
paula.audio
-
On startup, the file `ENV:CyberSound/SoundDrivers/14Bit_Calibration'
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 `AHIpaulaFilterFreq' 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 `AHIpaulaSampleLimit' 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 `0', the frequency will always be limited to 28
kHz and if set to `1', 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.
Please note that this 31 kHz screen mode is not neccessary the screen mode
you're seeing on your monitor. If you're using a graphic card, you must
force the Amiga video signal to 31 kHz. CyberGraphX users might want to
try this command (see section AddAudioModes for more information):
AddAudioModes DBLSCAN
Picasso 96 users just need to set the `Picasso96/AmigaVideo' variable
to `31kHz':
SetEnv Picasso96/AmigaVideo 31kHz
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. paula.audio
uses the correct order (right, left, left,
right) but many other programs don't. The `AHIpaulaSwapChannels'
variable was added to let the user decide if the correct or incorrect
behaviour should be used. In not present or set to `0', the correct
behaviour is used. If set to `1', the left and right channels will be
swapped.
By setting the `AHIpaulaFakeMixFreq' variable to `1', you can make
paula.audio
not report the actual mixing frequency used, but rather
exactly the frequency that the program asked for. The default, `0',
will report the nearest possible mixing frequency that the Paula sound chip
can use.
Why would anyone want this, you may ask. Well, by setting the variable
to `1', you will make paula.audio
behave exactly like
filesave.audio
, which can be important if you are making music that
you will later render and put on a CD, for example. Be warned, however, that
setting this variable to `1' can make the sound produced sound a little
false (but not when rendered, of course)!
Finally, the variable `AHIpaulaBufferLength' controls the minimum
playback buffer size to use. Because of the limited Chip RAM
bandwidth, a MC68060 CPU might run into trouble when using the
default minimum buffer size (0). By setting this variable to `1024',
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.
toccata.audio
-
Requires
toccata.library
version 12 or greater (11).
This driver also reads the environment variables `AHItoccataNoTask'
and `AHItoccataIrqSize'. If `AHItoccataNoTask' is set to
`1', all mixing will be done in a Software Interrupt 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:
`AHItoccataIrqSize' specifies the number of bytes transferred to the
card each interrupt and defaults to `512'. It must be one of
`32', `64', `128', `256' or `512'. 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.
wavetools.audio
-
Requires
dad_audio.device
.
The files in `DEVS:AudioModes' 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:
- `Mono'
-
Mono output, all sounds will be centered, and no surround sound is
possible.
- `Stereo'
-
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.
- `Stereo++'
-
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.
- `Fast mono'
-
- `Fast stereo'
-
- `Fast stereo++'
-
"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 section `Advanced settings' Page) 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!
- `HiFi mono'
-
- `HiFi stereo'
-
- `HiFi stereo++'
-
"HiFi" modes use much better mixing algorithms than the other modes,
using 32 bits internally and linear interpolation. They are also
much slower than the other modes. "HiFi" modes turn on master
volume with clipping automatically (see section `Advanced settings' Page).
"HiFi" modes are useful when you're playing music---MIDI songs or
modules, for example--and want the best possible quality AHI
has to offer.
The author can be reached at the following addresses:
- Electronic mail
-
martin@blom.org
- Standard mail
-
Martin Blom
Alsättersgatan 15A:24
SE-584 35 Linköping
SWEDEN
- World-Wide Web
-
http://martin.blom.org
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 it entered his life.
At once, there were fights among the brothers. They all wanted to use
it. Martin started to avoid playing with kids that didn't share his
passion for it. The school work suffered. Other interests
suffered. It 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 Computer Science and Engineering at Linköping
Institute of Technology, 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.
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 has to do.
Martin used to say
-
If you can't write applications, write games.
-
If you can't write games, write demos.
-
If you can't write demos, write utilities.
-
If you can't write utilities, write BBS intros and doors.
-
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.
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 (12). 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?
There are quite a few people that have helped with the development of
AHI. Where would be a better place to thank them than in the
acknowledgments chapter? You tell me.
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
Wavetools card. I'm sure AHI would not have been accepted as
quick as it was without this driver.
- Christian Buchner
-
For the calibrated 14 bit routines for Paula.
- MacroSystem Computer GmbH
-
For lending me a Toccata card.
- Steve Krueger and SAS Institute, Inc.
-
For the compiler and all the updates.
- Johan Otterström
-
For all the help with the Toccata driver.
- 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,
Sini¹a Loliæ,
Eivind Olsen,
Marcin Orîowski,
Thomas Petersen,
Pauli Porkka,
Vit Sindlar,
Martin Sprenger,
Sönke Tesch,
Vörös Viktor,
Michel Vissers,
Ondrej Zima,
me, myself and I@enddots{}
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 and the first PPC port.
- Thomas Wenzel wenzel@unixserv.rz.fh-hannover.de
-
The Prelude driver.
- Frank Wille frank@phoenix.owl.de
-
The ELF loader.
Many thanks!
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
The licenses for most software are designed to take away your
freedom to share and change it. By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users. This
General Public License applies to most of the Free Software
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14 bit calibration
68060 CPU
Acknowledgments
AddAudioModes, AddAudioModes
Advanced settings
AHI, overview
AHI, preferences program
AHI-Handler
AHIpaulaBufferLength variable
AHIpaulaFakeMixFreq variable
AHIpaulaFilterFreq variable
AHIpaulaSampleLimit variable
AHIpaulaSwapChannels variable
AHItoccataIrqSize variable
AHItoccataNoTask variable
AIFC
AIFF
AmigaVideo
Audio mode database
Audio mode settings
Audio modes, overview
AUDIO:
Aura
Author of AHI
Calibration, 14 bit
Clarity
Clipping, master volume
Concierto
Contributors
Copyright
CPU usage limit
CyberGraphX
CyberSound
DAC calibration
Database, audio modes
Debug level
Delfina DSP
Delfina Lite
Disclaimer
Distortion, while recording
Distribution
DraCo Motion
Drivers
Echo, enable/disable/fast
Fame
Fast Mono (audio mode)
Fast Stereo (audio mode)
Fast Stereo++ (audio mode)
HiFi Mono (audio mode)
HiFi Stereo (audio mode)
HiFi Stereo++ (audio mode)
IFF-AIFC
IFF-AIFF
Interpolation, linear
Jesus Christ
Legal nonsense
License
Linear interpolation
Maestro Pro
Master volume, clipping
MC68060 CPU
Melody MPEG
Mode settings
Modules on a C64
Mono (audio mode)
Multiplication tables
Nerd, definition of
Overview
Paula
Paula, custom chip
Picasso96
Preferences
Preferences, advanced
Preferences, audio mode
Prelude
Recursion
Settings
Settings, advanced
Settings, audio mode
Software license
Sound card drivers
Special thanks
Stereo (audio mode)
Stereo++ (audio mode)
Surround sound, enable/disable
System description
System Files
Tables, multiplication
The Author
The Concept
The Drivers
The Man
The Mode Descriptors
The Myth
Toccata
VGA screen mode
Wavetools
Footnotes
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.
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 Audio Hardware Interface, something that
he has regretted ever since. The suggested pronunciation is "atchii", as
in "God bless!".
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 S3M and XM
formats.
BGUI is Copyright © 1996-1997 Ian J. Einman
MUI is Copyright © 1992-1997 Stefan
Stuntz
The more channels
you select, the more sounds can you play at the same time. However,
due to the nature of sound mixing in version 4, the volume will
decrease as well. This limitation is not present in version 6, where
the volume will be adjusted dynamically. 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.
The latest
version of the Delfina software can be found at Petsoff Limited
Partnership's WWW page: http://www.sci.fi/~petsoff.
maestix.library
is available from AmiNet, for example
ftp://ftp.germany.aminet.org/pub/aminet/util/libs/Maestix.lha.
Richard Körber's WWW page: http://www.is-koeln.de/einwohner/shred.
melodympeg.device
and the latest version of this driver can be found
at the Kato Development Group's WWW page:
http://home.pages.de/~kato.
toccata.library
is available from AmiNet, for example
ftp://ftp.germany.aminet.org/pub/aminet/util/libs/toclib12.lha.
Three
Letter Acronym
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