Audio and MIDI information
--------------------------

The mixer has recently been replaced by using SDL_mixer. This will allow easier 
porting to other platforms and removes the need to maintain the complex mixer 
code. The addition of the SDL_mixer was mainly done so that we could easily 
support OGG/MP3 music, referred to as "Digital Music" in Exult.

All Digital SFX and Digital music currently play at 22Khz. This sample rate
is high enough for the SFX and digital music as they rarely go above 11Khz,
plus SDL_mixer/SDL currently works better at 22khz than 44khz.

SDL_mixer has the ability to play MIDI music directly through MIDI ports 
or by using Timidity. The MIDI support in Exult does not currently make use of 
SDL_mixer but uses tailor made midi drivers in the midi_drivers directory. A 
generic SDL_mixer interface is available in the midi_drivers directory called 
mixer_midiout.

To make use of this mixer_midiout simply use the following in Midi.cc (in the
relevant sections):
-----------------------------------------
#ifdef _WIN32
  #include "midi_drivers/mixer_midiout.h"
#endif
-----------------------------------------
#ifdef _WIN32
  TRY_MIDI_DRIVER(Mixer_MidiOut)
#endif
-----------------------------------------


Sound Effects
-------------
Sound effects were originally played through MIDI but now that the SFX
digital sound packs (jmsfx & sqsfx) are available this has been disabled 
and will not be developed in future. MIDI now only plays the music.
Sound effects are loaded when required from the flx files, each time they
are played, but the last 6, or so, played are cached in memory to save disk
I/O and conversion processing.


MIDI Music
----------
Exult music can be played through MIDI using either MIDI ports or
Timidity. Conversion is usually applied to the MIDI music using the XMIDI
code to convert from the Roland MT-32 voice assignments to General Midi
(GM). It is still possible to play directly to a Roland MT-32 by selecting
the "none" midi conversion setting.

Timidity support works on Linux and should work on Windows. To use it in
Linux the timidity.cfg file must be in the directory where the exult
executable is run. This appears to be a quirk with SDL_mixer.

Linux MIDI out currently uses playmidi or KMIDI.


Digital Music
-------------
Digital Music using OGG is now available in Exult. This uses the Digital
Music pack recorded by Simon Quinn on the Roland MT-32, available on the
Exult sourceforge site. This should work on any platform that supports
SDL_mixer and will give the closest musical experience to the original
Ultima VII games.

Additionally, with the Digital Music support, a number of atmospheric 
SFX tracks are played when no music is playing. The tracks played are 
as follows:
* Day time outside: wind, bird and frog track
* Night time: wind track with randomly generated digital sfx crickets
* Dungeon: dungeon music track (atmospheric SFX and music)
Music tracks always take priority over these SFX tracks and being "music"
tracks they will not play if the music has been switched off.

These SFX "music" tracks are not available with the MIDI support as they 
play Roland MT-32 specific voices that cannot be mapped to GM.

NOTE: OGG was chosen over MP3 as SDL_mixer has better support for OGG and 
has OGG supported compiled into the drivers by default, from v1.2.4. 


Voice/VOC support
-----------------
The VOC decoding is partially customised to Exult and the U7 data files. 
Samples are converted to 22Khz (or to match the audio output sample rate)
and expanded to two channels, and some bytes are cut off each end to 
eliminate harsh clicking.

Sample rate conversion has been left in the VOC decoder as currently,
v1.2.4 of SDL, does not have good sample rate conversion.

The code currently uses a lot of memory as the whole VOC to be played is
loaded and converted in RAM, potentially using many megabytes of memory.
