Announcement

Info updated: 22 Apr 97




From: Martin Blom lcs@lysator.liu.se
Subject: AHI Audio System Release 4
Date: Thu, 24 Apr 97 01:21:01

TITLE

     AHI Audio System

VERSION

     Release 4

AUTHOR

     Martin Blom lcs@lysator.liu.se

DESCRIPTION

Retargetable Audio for AmigaOS

     (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!'.)

     Starting with version 3 of AHI, the MC68000 processor is also
     supported.  However, many features are lacking:

     * 16 bit samples are converted to 8 bits before they are mixed.
     * No HiFi mixing routines are available.
     * No stereo samples
     * No DSP effects are available.
     * Less precision on some calculations
     * Slower

     As you can see, this version is very primitive.  Get yourself an
     accelerator!  I cannot guarantee that I will continue to support
     this processor in the future.

     Quick overview

     * 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)
     * Delfina
     * DraCo Motion
     * Paula (8/14/14c bit)
     * Prelude
     * Toccata
     * Wavetools
     * 8SVX (mono) and AIFF/AIFC (mono & stereo) sample render

     * 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 16-bit
     mono or stereo (with stereo panning if desired) data, using any
     number of channels (as long as 'any' means less than 128...).
     Tables can be used speed the mixing up (especially when using
     8-bit samples).  The samples can have any length (including odd)
     and can have any number of loops.

     * 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 not.

SPECIAL REQUIREMENTS

     AmigaOS release 2.
     MC68020 processor strongly recommended.

AVAILABILITY

     Aminet, for example:
     ftp://ftp.germany.aminet.org/pub/aminet/dev/misc/ahidev.lha
     ftp://ftp.germany.aminet.org/pub/aminet/mus/misc/ahiusr.lha
     ftp://ftp.germany.aminet.org/pub/aminet/docs/misc/ahiman.lha

     WWW:
     http://www.lysator.liu.se/~lcs/ahi.html

PRICE

     Free.  But if you use it in a shareware of commercial product, I
     would like a registered copy for me and each of the audio driver
     authors (this is merely a wish, you don't have to do it if you
     don't think we deserve it).  See the AHI User's Guide for more
     information.

DISTRIBUTABILITY

     Copyright 1994-1997 Martin Blom.
     Freely distributable in unmodified form.
     See the AHI User's Guide for more information.

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