This archive contains the developer documentation and
example source code for AHI, both for programmer who wish
to use AHI in their own applications and those who want
to write hardware drivers.
Changes since last release
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* Anti-click mixing routines, which makes AHI search for a
zero-crossing before playing a new note
* Playback of 32 bit samples.
* Multi-channel audio. Eight channels are supported.
* Support for four more architectures: MorphOS/PPC, AmigaOS4/PPC,
Amithlon/ix86, AROS/ix86.
* Support for PowerPC accelerator cards (MorphOS and AmigaOS4
only).
* A new driver, device.audio, can be used to make all low-level AHI
applications, which normally open AHI in exclusive mode, behave
as if they used the high-level API which allows several AHI
applications to work simultaneously. (Note that this driver
currently does not work with applications that require less than
20 ms latency.)
* The 68000 processor is no longer supported; a 68020 or better is
required.
For a full log of everything that has been updated, see the
ChangeLog file.
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TITLE
AHI Audio system
VERSION
Release 6.0
AUTHOR
Martin Blom <martin@blom.org>
DESCRIPTION
Retargetable Audio for AmigaOS
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(When refering to this software, the correct term is
'AHI audio system' or just 'AHI', never 'Audio Hardware
Interface'! 'AHI' is pronounced 'atchii', as in 'God bless!'.)
AHI now supports the PowerPC processor. Thanks to the users who
donated money and Syscom & Mematex AB who sponsored the hardware,
I was finally able you buy a Cyberstorm PPC card. The current
version is for MorphOS only, but a WarpUp version will hopefully
follow later.
Version 6.0 supports 68020, 68030, 68040 and 68060 from
the m68k family and 603 and 604 from the PowerPC family.
Staring with version 6, the 68000 processor is no longer supported.
68000 owners should use version 4 instead.
Quick overview
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* Driver based
Each supported sound card is controlled by a library-based audio
driver. For a 'dumb' sound card, a new driver should be written in
a few hours. For a 'smart' sound card, it is possible to utilize an
on-board DSP, for example, to maximize performance and sound quality.
For sound cards with own DSP but little or no memory, it is possible
to use the main CPU to mix channels and do the post-processing
with the DSP. Available today are drivers for
· Aura (sampler only)
· Clarity (sampler only)
· Concierto (Picasso IV sound module)
· Delfina DSP and Delfina Lite
· DraCo Motion
· Maestro Pro
· Melody Z2 and 1200
· Paula (8/14/14c bit)
· Prelude and Prelude 1200
· Toccata
· Wavetools
· 8SVX (mono) and AIFF/AIFC (mono & stereo) sample render
· ...and more.
* Fast, powerful mixing routines (yeah, right... haha)
The device's mixing routines mix 8- or 16-bit signed samples, both
mono and stereo, located in Fast-RAM and outputs 32-bit mono or stereo
(with stereo panning if desired) data, using any number of channels
(as long as 'any' means less than 128...). Tables are no longer
used, which might affect performace slightly. Instead, version 6
forcuses slightly more on the quality of the sound.
* Support for non-realtime mixing
By providing a timing feature, it is possible to create high-
quality output even if the processing power is lacking, by saving
the output to disk, for example as an IFF AIFF or 8SXV file.
There are so-called HiFi mixing routines that can be used, which
use linear interpolation and gives 32 bit output.
* Audio database
Uses ID codes, much like Screenmode IDs, to select the many
parameters that can be set. The functions to access the audio
database are not too different from those in 'graphics.library'.
The device also features a requester to get an ID code from the
user.
* Both high- and low-level protocol
By acting both like a device and a library, AHI gives the programmer
a choice between full control and simplicity. The device API allows
several programs to use the audio hardware at the same time, and
the AUDIO: dos-device driver makes playing and recording sound very
simple for both the programmer and user.
* Future Compatible
When AmigaOS gets device-independent audio worth it's name, it should
not be too difficult to write a driver for AHI, allowing applications
using 'ahi.device' to automatically use the new OS interface. At
least I hope it wont.
Funny how things turned out, isn't it? Sigh.
SPECIAL REQUIREMENTS
AmigaOS release 2.
MC68020 processor or better.
AVAILABILITY
Aminet, for example:
ftp://ftp.germany.aminet.org/pub/aminet/dev/misc/ahi6dev.lha
ftp://ftp.germany.aminet.org/pub/aminet/dev/misc/ahi6src.lha
ftp://ftp.germany.aminet.org/pub/aminet/mus/misc/ahi6usr.lha
WWW:
http://www.lysator.liu.se/~lcs/ahi.html
PRICE
Free. As in speech. And beer too! However, should you want to
make a donation, my PayPal account is martin@blom.org.
DISTRIBUTABILITY
Copyright ©1994-2005 Martin Blom.
AHI version 6 is (L)GPL:ed. See COPYING and COPYING.LIB inside the
archive for more information.
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