
			A   U   D   l   i   b

			     version 0.8
			     May 2000

                   Copyleft 1998 - 2000 Peter Wang
    		      	 (and contributors)


#include <std_disclaimer.h>

   "I do not accept responsibility for any effects, adverse or otherwise, 
    that this code may have on you, your computer, your sanity, your dog, 
    and anything else that you can think of. Use it at your own risk."


What's new 
----------

version 0.8:
    Thanks to Joseph Morris:
    - new function load_aud_stream_offset() 
      i.e. load an AUD embedded inside larger file
    - doubled default buffer size 

version 0.7:
    - changes for Allegro 4.0 and Unix
    - same version number as loadaud :-)

version 0.6b:
    - changed [un]load_aud to [un]load_aud_stream to prevent namespace 
    conflicts with loadaud (the other aud lib).  restart_aud, etc. have been 
    left for backwards compatibility (even though this is ambiguous)

    - "clicking" problems reduced
    - added pause_aud and resume_aud

version 0.6a:
    - slight changed in audlib.h to support C++ programs

version 0.6:
    - faster code
    - stereo aud support


Introduction
------------

    aud is the sound format used in many Westwood Studios games.  It comes 
    in two flavours: 8 bit and 16 bit.  All normal frequencies and mono / 
    stereo channels are supported.

    AUDlib supports 16 bit auds only.  These use the IMA ADPCM compression 
    algorithm and provide 4:1 compression ratio (16bit -> 4bit) with low 
    loss of quality.

    8 bit auds use a proprietary algorithm and therefore are unsupported.

    The point of writing a library like this is so that you can use .aud 
    music files in your own games, so you can distribute it over the net, 
    or perhaps if you had a lot of music, you could use auds instead CDA.


Coding
------
    Type `make' to make the library and the example.  Type `make install' 
    to copy `libaud.a' and `audlib.h' into the `lib' and `include' 
    directories of your djgpp installation.

    To use the library, #include <audlib.h> in your code, and link -laud.

    Function and variable descriptions:

    int load_aud_stream(char *filename, int loop);
	Ready an AUD file to be played.  If you want the file to be looped 
	give TRUE for loop.  Returns TRUE if load was succesful.

    int load_aud_stream_offset(char *filename, int loop, int foffset);
	Does the same as load_aud_stream(), only the AUD begins at
	position FOFFSET inside the file.

    void unload_aud_stream(void);
	Free the AUD from memory.

    int poll_aud(void);
	Decodes and buffers a few AUD chunks (enough to fill the size 
	defined in BUFFER_SIZE).  It needs to be called as often as 
	possible, otherwise you will have skips in your sound. Returns -1 if 
	there's nothing to play (e.g. music has stopped), 0 if the playback 
	buffer is full (meaning it has enough audio data for the moment), 
	and 1 if data was successfully decoded and buffered.

    void pause_aud(void);
	Pause playback.  Note: you should keep calling poll_aud afterwards.

    void resume_aud(void);
	Take a wild guess.

    void restart_aud(void);
	Does exactly that.

    void set_aud_volume(int vol);
	Set the audio stream volume (0-255, default: 128) 
	Note that set_aud_volume(0) will pause playback.

    int aud_loaded;
	TRUE if an AUD file is currently loaded and ready to play.

    int aud_paused;
	TRUE if paused.  FALSE if not.

    int aud_freq;
	Frequency of the current file.

    int aud_stereo;
	TRUE if it is a stereo AUD file.

    char *aud_error;
	If load_aud() fails, check this for a human readable error string.

    You may also like to edit the #define BUFFER_SIZE in audlib.c


Example
-------
    Look at example.c.  If you don't have any AUD files, there is a *very* 
    exciting one included (welcome.aud).


To do and bugs
--------------
    Seeking functions.  Maybe.

    The first time an aud is loaded it seems to need to "warm up" (on my 
	laptop with a Yamaha OPL3SAx anyway).

    Looping doesn't work correctly on some auds (e.g. welcome.aud) [FIXED]

    Tiny click at the end of files.


Special thanks
--------------
    - The code came from loadaud, which in turn came from a package which 
    I found at ftp://ftp.cwi.nl/pub/audio/adpcm.zip by Jack Jansen 
    (jack@cwi.nl).

    - The older code and the aud file format description came from 
    aud3.txt by Vladan Bato (bat22@geocities.com). 

    His site is at: http://www.geocities.com/SiliconValley/8682/
    There you can find AUD2WAV and WAV2AUD conversion utilities.  Note 
    that these will not convert stereo wavs, for that you will need to get 
    loadaud (also by me =).  See web address below.

    - As you can probably see, I modelled my API after LibAmp by Ove Kaaven 
    (ovek@arcticnet.no), and grafted some of his docs into mine.  Thanks Ove!

    - Grzegorz Hankiewicz (gah@jet.es) for a LOT of suggestions, and for 
    using the library in Wotan.  Woohoo!

    - Joseph Morris (jpm@it-he.org) for `load_aud_stream_offset' and
    related changes.


Copyright
---------
    (note licence has changed since version 0.5)

    AUDlib is released under the GNU LGPL.  If you are unfamiliar with 
    this licence, go now to www.gnu.org and enlighten yourself.  You may 
    use AUDlib in any way within the LGPL, all that I ask is this: 
    ``credit where credit is due''.  This applies to all code that you 
    use, not specifically this.


Contact
-------
    Psyk Software:
	http://www.psynet.net/tjaden/
	http://members.xoom.com/psyk/

    Email: tjaden@psynet.net


P.S. Don't forget to check out loadaud (web site above) so you can use 
auds as SAMPLEs in your games and save us all download time.
