AHI User's Guide

For AHI release 6.0. Document version 5.9.2.8 (2005-09-22).

Copyright (C) 1994-2005 Martin Blom

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

1. Overview		Brief introduction
2. Distribution		What you are allowed to do and not

3. System description

The components of AHI

4. The Author		Who designed it?
5. Acknowledgments		Thanks, guys!

GNU GENERAL PUBLIC LICENSE		The main license
GNU LIBRARY GENERAL PUBLIC LICENSE		The ahi.device license

Concept Index

1. Overview

The Amiga has always had excellent sound capabilities. In 1986, they were awesome. Today, well.... 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.

2. Distribution

Copyright (C) 1994-2005 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 4. 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?

3. System description

3.1 AddAudioModes		Database maintenance and more
3.2 AHI		Preferences program
3.3 AHI-Handler		DOS-device

3.4 System Files

The files in `DEVS:'

3.1 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

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 3.4.2 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.

In addition to rebuilding the audio mode database, it has the side effect that the audio drivers are loaded into memory. This causes the audio hardware to be initialized and, perhaps, AC97 mixers to be set up to the default, which is good if, for example, your CD is connected to your soundcard.

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.

3.2 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

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)

3.2.1 Menus
3.2.2 Pages

3.2.1 Menus

3.2.1.1 `Project' Menu
3.2.1.2 `Edit' Menu
3.2.1.3 `Settings' Menu
3.2.1.4 `Help' Menu

3.2.1.1 `Project' Menu

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).

3.2.1.2 `Edit' Menu

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.

3.2.1.3 `Settings' Menu

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.

3.2.1.4 `Help' Menu

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".

3.2.2 Pages

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

3.2.2.1 `Mode settings' Page
3.2.2.2 `Advanced settings' Page

3.2.2.1 `Mode settings' Page

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 3.3 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.

Normally, you configure one unit per sound card. Since most people only have one sound card, all units but unit 0 are often unused.

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.

3.2.2.2 `Advanced settings' Page

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 3.4.2 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!

`Default anti-click time'

Starting with AHI V6, the software mixer can delay the sounds an application wants to play until the currently playing sound goes through a zero-crossing, in order to avoid nasty clicks. Normally, it's the applications job to specify the maximum time the sounds may be delayed, but not all applications provide this information. By setting this slider to the desired value, all applications not specifying their own limit will will default to this value instead.

`Volume scaling'

When more than one application is using AHI at the same time, care has to be taken so no audible distortion is created. In AHI V4 and before, this implied that the volume was lowered in such a way that there were never any distortion. Since "clipping" (see above) was optional, this was the only sensible thing to do. In AHI V6, clipping is always used and the distortion created is often not audible. Because of this, all sounds are now played at full volume.

However, should you wish so, it's possible to manually select that strategy to use. The available options are `Safe' (as in AHI V4), `Safe, Dynamic' (volume is dynamically adjusted based on how many sounds are curreltly being played), `Full volume' (the new default) and finally `-3 dB' and `-6 dB', which plays all sounds at -3 or -6 dB.

3.3 AHI-Handler

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 writing 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.

3.4 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:

• AmigaXL
• Aura (sampling only)
• Clarity (sampling only)
• Concierto
• Delfina
• DraCo Motion
• ESS Solo-1
• ForteMedia FM801
• Maestro Pro
• Melody
• Paula (the built-in audio)
• Prelude
• Repulse
• SoundBlaster 128
• SoundBlaster Live!
• Sunrize
• Terratec 128i PCI
• Terratec 512i digital
• Toccata
• VIA AC97
• Wavetools

3.4.1 The Drivers
3.4.2 The Mode Descriptors

3.4.1 The Drivers

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. This file can be created by using Christian Buchner's CyberSound calibration tool, which is available from http://www.lysator.liu.se/~lcs/files/ahi/extras/CyberSound.lha, among other places.

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 so-called `Paula:DMA 8 bit stereo' mode uses Paula's built-in DMA engine to play the sounds; no software mixing at all is performed. Because of this, only four channels are available and no stereo panning is available (just like all other plain "stereo" modes). In addition, the only mixing frequency available is Paula's master clock.

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 necessary 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 3.1 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.

`AHItoccataPlayBufferSize' specifies the number of bytes transferred to the card when playing and defaults to `512'. It must between 512 and 16384 and also a multiple of 512. If you encounter problems with serial port hardware, you might want to set this variable to a higher value than the default.

`AHItoccataRecordBufferSize' specifies the number of bytes transferred from the card when recording and defaults to `16384'. It must between 512 and 16384 and also a multiple of 512. If you think the latency when recording is too high, 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.

3.4.2 The Mode Descriptors

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 3.2.2.2 `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 3.2.2.2 `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.

`HiFi 7.1'

"HiFi 7.1" modes can be used by movie players or audio editors.

4. The Author

The author can be reached at the following addresses:

Electronic mail

martin@blom.org

Standard mail

Martin Blom
Luftvärnsgatan 42
SE-587 34 Linköping
Sweden

World-Wide Web

http://martin.blom.org

4.1 The Man
4.2 The Myth
4.3 The Concept

4.1 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 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.

4.2 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 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.

4.3 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 (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?

5. Acknowledgments

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.

5.1 Special thanks
5.2 Contributors
5.3 Donors
5.4 Honourable mention

If you feel your name ought to be present here, please accept my apologies and don't hesitate to contact me as soon as possible.

5.1 Special thanks

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.

bbrv and Genesi

For the Pegasos and that cool OS.

Przemyslaw Gruchala

For finding all those bugs.

Ben Hermans and Hyperion Entertainment

For hiring me to write a SBLive! driver.

Steve Krueger and SAS Institute, Inc.

For the SAS/C 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: Alex Plotnicov, Andrija Antonijevic, Bernardo Innocenti, Dósa Márton, Eivind Olsen, Frederico Borges, Ljubomir Jankoviá, Marcin Orîowski, Martin Sprenger, Michael Malyshev, Michel Vissers, Ondrej Zima, Pauli Porkka, Petteri Kallio, Piergiorgio Ghezzo, Roger Hågensen, Rúben Alvim, Samuel Aguilera, Sini¹a Loliæ, Stéphane Barbaray, Sönke Tesch, Thomas Petersen, Vit Sindlar, Vörös Viktor, me, myself and I....

5.2 Contributors

The following people have contributed to the AHI project with code or drivers:

Stéphane Barbaray

The MUI version of the preferences program.

Olaf Barthel

The Concierto driver.

Chris Brenner

A (never finished?) Sunrize driver.

Valenta Ferenc

The VSS driver.

Ben Fuller

A never finished Sunrize driver. May he rest in peace.

Simon N Goodwin

A good attempt on the Silicon Studio driver. :-)

Przemyslaw Gruchala

A C-Media and a Yet To Be Named driver. :-)

Thorsten Hansen

The Melody MPEG and Amithlon drivers.

Richard Körber

The Maestro Pro driver.

Frank Mariak

The GREX and Pegasos drivers.

Bernd `Bernie' Meyer

The--sniff!---never to be released Umilator driver.

Gunther Nikl

Patches!

Kenneth Nilsen

A (never finished?) Sunrize driver. And here I was, thinking the "Amiga" curse was the worst curse of them all ....

Johan Nyblom

The latest Wavetools driver.

Pauli Porkka

The first version of the Toccata driver.

Markus Pöllmann

The AmigaXL driver.

Bernd Roesch

The UAE driver.

Harry Sintonen

The very first source code patch!

Sigbjørn Skjæret

A 'C' version of paula.audio.

Stefan Sommerfeld

The RePulse driver.

Rüdiger Sopp

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

Pawel Stypula

The Mediator drivers.

Teemu Suikki

The Delfina driver and the first PPC port.

Benjamin Vernoux

An FM801 driver.

Davy Wentzler

The AmigaOS 4.x port and many drivers.

Thomas Wenzel

The Prelude driver.

Frank Wille

The (no longer used) ELF loader.

Many thanks!

5.3 Donors

The following people has donated money to the project. It has ment a lot to me, and please forgive me for not being able to finish a working WarpUp or PowerUp PPC version of AHI. I hope the MorphOS and upcoming AmigaOS 4 versions made up for that.

Agneta Nord, Alan Surrette, Anders Drejer, Andreas Johansson, Ben Hermans, Bernardo Innocenti, Björn Hagström, Christopher Lakatos, Davy Wentzler, Fabio Barzagli, Fredrik Westermarck, Fredrik Zetterlund, Gregory Donner, Göran Karlsson Ismo Houvinen, Johan Lind, John Haubrich, John Hertell, John Hindle, John Rörland, Jonas Hulten, Jonny C. Kitchens, Jorma Valli, Linus Silvander, Magnus Bouvin, Malcolm Harnden, Marijan Franovic, Matteo Consolati Matthew K. Massa, Mematex AB, Mike Masquith, Niko Tomatsidis, Ola Karlsson, Pasi Langerroos, Per Jonsson, Robert Korzeniewski, Robert Nilsson, Staffan Bengtsson, Stefan Nilsson, Steve Hodson, Steven Maes, The Magic Lantern Thomas & Stefan Lorenz, Ulf Tidstrand, Vincent Morenas, Winfried Krüger and Zafer KANTAR.

5.4 Honourable mention

The road from AHI version 4 to version 6 has been a long one. Maybe not when counted in actual work hours, but definitely when counted in calendar time.

It began with a failed attempt to port the device to the PowerPC processor, at which time AHI became a "shareware" product in order to finance a Cyberstorm/PPC CPU card (see section 5.3 Donors). When I realized I couldn't deliver, AHI instead became Free Software, which it still and will probably always be.

The first release of the source code under the "GPL" was made on April 1st, 1999, as part of the "Divine Records" joke (see http://martin.blom.org/ds/ and http://martin.blom.org/dr/(13)).

Some people actually took their time to fill in the source code registration form. You know who you are. Thank you! I'm sure I'll figure out what to do will all addresses real soon now.

But here comes the best part: Benoit Deschenes (Quebec, Canada), Thomas Houlberg (Sdr. Bjert, Denmark) and Patrice Machin (Paris, France) actually ordered my CD. Unfortunately, I only made a limited amount of those CDs (17 plus one pre-production CD, if I remember correctly) and have been out of stock ever since. To compensate for this unusually long delivery delay, I've decided to try to produce three extra copies and send them to you for free. Benoit, Thomas and Patrice, if you read this and have moved since 1999, please let me know of your new address as soon as possible!

GNU GENERAL PUBLIC LICENSE

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.

Preamble

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 Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

1. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

   Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

2. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

   You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

3. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
   1. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

   2. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.

   3. If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

   These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

   Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

   In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

4. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
   1. Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

   2. Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

   3. Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

   The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

   If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

5. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

6. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

7. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

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   It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

   This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

9. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

10. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

11. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.
    NO WARRANTY

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13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found.

one line to give the program's name and an idea of what it does. Copyright (C) 19yy name of author This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

Gnomovision version 69, Copyright (C) 19yy name of author Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. This is free software, and you are welcome to redistribute it under certain conditions; type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w' and `show c'; they could even be mouse-clicks or menu items--whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names:

Yoyodyne, Inc., hereby disclaims all copyright interest in the program `Gnomovision' (which makes passes at compilers) written by James Hacker. signature of Ty Coon, 1 April 1989 Ty Coon, President of Vice

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.

GNU LIBRARY GENERAL PUBLIC LICENSE

Copyright (C) 1991 Free Software Foundation, Inc. 675 Mass Ave, Cambridge, MA 02139, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. [This is the first released version of the library GPL. It is numbered 2 because it goes with version 2 of the ordinary GPL.]

Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public Licenses are intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users.

This license, the Library General Public License, applies to some specially designated Free Software Foundation software, and to any other libraries whose authors decide to use it. You can use it for your libraries, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the library, or if you modify it.

For example, if you distribute copies of the library, whether gratis or for a fee, you must give the recipients all the rights that we gave you. You must make sure that they, too, receive or can get the source code. If you link a program with the library, you must provide complete object files to the recipients so that they can relink them with the library, after making changes to the library and recompiling it. And you must show them these terms so they know their rights.

Our method of protecting your rights has two steps: (1) copyright the library, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the library.

Also, for each distributor's protection, we want to make certain that everyone understands that there is no warranty for this free library. If the library is modified by someone else and passed on, we want its recipients to know that what they have is not the original version, so that any problems introduced by others will not reflect on the original authors' reputations.

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How to Apply These Terms to Your New Libraries

If you develop a new library, and you want it to be of the greatest possible use to the public, we recommend making it free software that everyone can redistribute and change. You can do so by permitting redistribution under these terms (or, alternatively, under the terms of the ordinary General Public License).

To apply these terms, attach the following notices to the library. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found.

one line to give the library's name and an idea of what it does. Copyright (C) year name of author This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Also add information on how to contact you by electronic and paper mail.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the library, if necessary. Here is a sample; alter the names:

Yoyodyne, Inc., hereby disclaims all copyright interest in the library `Frob' (a library for tweaking knobs) written by James Random Hacker. signature of Ty Coon, 1 April 1990 Ty Coon, President of Vice

That's all there is to it!

Concept Index

Jump to:	1   6   A   C   D   E   F   H   I   J   L   M   N   O   P   R   S   T   V   W

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 Audio Hardware Interface, 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 S3M and XM formats.

(4)

BGUI is Copyright © 1996-1997 Ian J. Einman

(5)

MUI is Copyright © 1992-1997 Stefan Stuntz

(6)

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.

(7)

The latest version of the Delfina software can be found at Petsoff Limited Partnership's WWW page: http://www.sci.fi/~petsoff.

(8)

maestix.library is available from AmiNet, for example
ftp://ftp.germany.aminet.org/pub/aminet/util/libs/Maestix.lha.

(9)

Richard Körber's WWW page: http://www.is-koeln.de/einwohner/shred.

(10)

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.

(11)

toccata.library is available from AmiNet, for example
ftp://ftp.germany.aminet.org/pub/aminet/util/libs/toclib12.lha.

(12)

Three Letter Acronym

(13)

Believe it or not, but I still get mail from people who want me to publish their music now and then!

Table of Contents

1. Overview
2. Distribution
3. System description

3.1 AddAudioModes
3.2 AHI

3.2.1 Menus

3.2.1.1 `Project' Menu
3.2.1.2 `Edit' Menu
3.2.1.3 `Settings' Menu
3.2.1.4 `Help' Menu

3.2.2 Pages

3.2.2.1 `Mode settings' Page
3.2.2.2 `Advanced settings' Page

3.3 AHI-Handler
3.4 System Files

3.4.1 The Drivers
3.4.2 The Mode Descriptors

4. The Author

4.1 The Man
4.2 The Myth
4.3 The Concept

5. Acknowledgments

5.1 Special thanks
5.2 Contributors
5.3 Donors
5.4 Honourable mention

GNU GENERAL PUBLIC LICENSE

Preamble
How to Apply These Terms to Your New Programs

GNU LIBRARY GENERAL PUBLIC LICENSE

Preamble
How to Apply These Terms to Your New Libraries

Concept Index

Short Table of Contents

1. Overview
2. Distribution
3. System description
4. The Author
5. Acknowledgments
GNU GENERAL PUBLIC LICENSE
GNU LIBRARY GENERAL PUBLIC LICENSE
Concept Index

About this document

• 1. Section One
• 1.1 Subsection One-One
• ...
• 1.2 Subsection One-Two
• 1.2.1 Subsubsection One-Two-One
• 1.2.2 Subsubsection One-Two-Two
• 1.2.3 Subsubsection One-Two-Three     <== Current Position
• 1.2.4 Subsubsection One-Two-Four
• 1.3 Subsection One-Three
• ...
• 1.4 Subsection One-Four