This file contains information about the implementation of the
multimedia layer of WINE.

The libraries consist of MMSYSTEM.DLL (win16), WINMM.DLL (win32) and
some (abstracted, not Windows compatible) lowlevel drivers. The
implementation can be found in the multimedia/ subdirectory.

The multimedia stuff is split into 3 layers. The lowlevel (device
drivers), midlevel (MCI commands) and highlevel abstraction layers.

The lowlevel may depend on current hardware and OS services (like
OSS). Mid-level and high-level must be written independantly from the
hardware and OS services.

1. Lowlevel layers
==================

   Please note that native low-level drivers are not currently
   supported in WINE, because they either access hardware composants
   or require VxDs to be loaded; WINE does not correctly supports
   those two so far. 

   Following lowlevel layers are implemented:

1.1 (Waveform) Audio
--------------------

   MMSYSTEM and WINMM call the real lowlevel audiodriver using
   the wodMessage/widMessage function in multimedia/audio.c, which
   handles the different requests.

1.1.1 OSS implementation

   The lowlevel audio driver is currently only implemented for the 
   OpenSoundSystem (OSS) as supplied in the Linux and FreeBSD kernels
   by 4Front Technologies (http://www.4front-tech.com/). The presence
   of this driver is checked by configure (depends on the
   <sys/soundcard.h> file). 

   The implementation contains all features commonly used, but has
   several problems (see TODO list).

   TODO:
   	- add asynchronous reads (must use threads) as done for writes
	- verify all functions for correctness
	- add drivers for other soundsystems (Sun Audio, remote audio
          systems (using X extensions, ...), ALSA
	- WaveHdr must be sent though mmsystem.c to get the linear
          address set correctly. An application calling directly
          (wod|wid)Message will fail

1.1.2 Wave mapper
 
   The Wave mapper device allows to load on-demand codecs to perform
   software conversion for the types the actual low level driver
   (hardware) does not support. Those codecs are provided thru the
   standard ACM drivers. 

   Wave mapper driver implementation has not started. Core DLL for ACM
   support can be found in dlls/msacm

   TODO:
	- implement wave mapper
	- don't forget to fix builtin ms acm drivers loading which has 
          been disabled.

1.2 MIDI
--------

   MMSYSTEM and WINMM call the lowlevel driver functions in
   multimedia/midi.c using the midMessage and the modMessage
   functions. 

1.2.1 OSS driver
	
   The lowlevel audio driver is currently only implemented for the 
   OpenSoundSystem (OSS) as supplied in the Linux and FreeBSD kernels
   by 4Front Technologies (http://www.4front-tech.com/). The presence
   of this driver is checked by configure (depends on the
   <sys/soundcard.h> file, and also some specfic defines because MIDI
   is not supported on all OSes by OSS).
   Both Midi in and Midi out are provided. The type of MIDI devices
   supported is external MIDI port (requires an MIDI capable device -
   keyboard...) and OPL/2 synthesis (the OPL/2 patches for all
   instruments are in midiPatch.c). 

   TODO:
	- Do not implement a software synthesizer. This should be done
	  using MIDI loopback devices in an external program (like
          timidity). The only trouble is that timidity is GPL'ed...
        - use better instrument definition for OPL/2 (midiPatch.c) or
          use existing instrument definition (from playmidi or kmid)
          with a .winerc option
        - have a look at OPL/3 ?
	- MidiHdr must be sent though mmsystem.c to get the linear
          address set correctly. An application calling directly
          (wod|wid)Message will fail
	- implement asynchronous playback of MidiHdr (regular and/or
          stream) 
	- use a more accurate read mechanism than the one of snooping
          on timers

1.2.2 MIDI mapper

   Midi mapper allows to map each one of 16 MIDI channels to a
   specific instrument on an installed sound card. This allows for
   example to support different MIDI instrument definition (XM,
   GM...). It also permits to output on a per channel basis to
   different MIDI renderers. 

   TODO:
	- implement the Midi mapper

1.3 Mixer
---------

   MMSYSTEM and WINMM call the lowlevel driver functions in
   multimedia/mixer.c using the mixMessage function.

1.3.1 OSS implementation

   The current implementation uses the OpenSoundSystem mixer.
   
   TODO:
   	- implement mixing mute functionality for OSS.
	- implement mixing lowlevel drivers for other mixers (ALSA...)
	- implement notification mechanism when state of mixer's
          controls change
	- handlers used for mixer are currently poorly implemented

1.4 AUX
-------
   
   The API consists of the aux* functions found in
   multimedia/mmsystem.c. They call auxMessage in multimedia/mmaux.c.

   The aux* functions are the predecessor of the mixer* functions.

1.4.1 OSS driver

   The implementation uses the OSS mixer API, and is incomplete.

   TODO:
   	- verify the implementation
	- check with what is done in mixer
	- open question: shall we implement it on top of the low level 
	  mixer functions ?

1.7 JOYSTICK
------------
   
   The API consists of the joy* functions found in
   multimedia/joystick.c. The implementation currently uses the Linux
   joystick device driver API. It is lacking support for enhanced
   joysticks and has not been extensively tested.

   TODO:
   	- better support of enhanced joysticks
	- support more joystick drivers (like the XInput extension)

2. Midlevel drivers (MCI)
=========================
   
   The midlevel drivers are represented by some common API functions, 
   mostly mciSendCommand and mciSendString.
   See status in chapter 3 for more information.

   WINE implements several MCI midlevel drivers (status is given for 
   both builtin and native implementation):

   TODO: (apply to all builtin MCI drivers)
	- move mci drivers as regular DLLs (loading in wine,
          elfglue...) 

2.1 CDAUDIO
-----------
   
2.1.1 Builtin

   The currently best implementation is the MCI CDAUDIO driver that can
   be found in multimedia/mcicda.c. The implementation is mostly
   complete, there have been no reports of errors.

   It makes use of misc/cdrom.c Wine internal cdrom interface. This
   interface has been ported on Linux, FreeBSD and NetBSD.
   (Sun should be similair, but are not implemented.)

   A very small example of a cdplayer consists just of the line
   mciSendString("play cdaudio",NULL,0,0);

2.1.2 Native

   Native MCICDA works also correctly... It uses the mscdex traps (on
   int 2f). 

   TODO:
   	- add support for other cdaudio drivers (Solaris...)

2.2 MCIWAVE
-----------
   
2.2.1 Builtin

   The implementation is rather complete and can be found in 
   multimedia/audio.c.
   It uses the lowlevel audio API (although not abstracted
   correctly). 

   FIXME: 
	- The MCI_STATUS command is broken.

   TODO: 
	- check for correctness
	- better use of asynchronous playback from low level
	- record has to be checked
	- MCI_CUE command is broken
	- better implement non waiting command (without the MCI_WAIT
          flag). 
   
2.2.2 Native

   Native MCIWAVE works also correctly.

2.3 MCISEQ (MIDI sequencer)
---------------------------
   
2.3.1 Builtin

   The implementation can be found in multimedia/midi.c. Except from
   the Record command, should be close to completion (except for non
   blocking commands).

   TODO: 
   	- implement it correctly
	- finish asynchronous commands (especially for reading/record) 
	- better implement non waiting command (without the MCI_WAIT
          flag). 

2.3.2 Native

   Native MCIMIDI has been working but is currently blocked by
   scheduling issues (mmTaskXXX no longer work). 

2.4 MCIANIM
-----------

2.4.1 Builtin

   The implementation consists of stubs and is in
   multimedia/mcianim.c. 

   TODO: 
   	- implement it, probably using xanim or something similair.

2.4.2 Native

   Native MCIANIM is reported to work (but requires native video DLLs 
   also).

2.5 MCIAVI
----------

2.5.1 Builtin

   The implementation consists of stubs and is in multimedia/mciavi.c.

   TODO: 
   	- implement it, probably using xanim or something similair.

2.5.2 Native

   Native MCIAVI is reported to work (but requires native video DLLs
   also). Some files exhibit some deadlock issues anyway.

3 High-level layers
===================

   The rest (basically the MMSYSTEM and WINMM DLLs entry points).
   It also provides the skeletton for the core functionnalites for 
   multimedia rendering.

   Note that native mmsystem and WINMM do not currently under WINE
   and there is no plan to support them (it would require to also
   fully support VxD, which is not done yet).

   TODO:
	- allow a dynamic loading of low level driver (should have one 
	  for OSS, another one for ALSA...)
	- add clean-up mechanisms when process detach from MM DLLs
	- reimplement the sndPlay??? functions using MCI commands
          rather than rewriting everything from scratch.
	- prepare for the 16/32 bit split
	- check thread-safeness for MMSYSTEM and WINMM entry points 

3.1 MCI skeletton
-----------------

   Implementation of what is needed to load/unload MCI drivers, and 
   to pass correct information to them. This is implemented in 
   multimedia/mci.c and multimedia/mcistring.c

   The mciSendString function uses commandstrings, which are 
   translated into normal MCI commands as used by mciSendCommand. 
   The API can be found in multimedia/mmsystem.c and 
   multimedia/mcistring.c. The functions there (mciOpen,mciSysInfo) 
   handle midlevel driver allocation and calls.

   The implementation is not complete.
 
   MCI drivers are seen as regular WINE modules, and can be loaded 
   (with a correct loadorder between builtin, native, elfdll, so), as 
   any other DLL. Please note, that MCI drivers module names must
   bear the .drv extension to be correctly understood.

   The list of available MCI drivers is obtained as follows:
	1/ key 'mci' in [option] section from .winerc (or wineconf)
		mci=CDAUDIO:SEQUENCER
	  gives the list of MCI drivers (names, in uppercase only) to 
	  be used in WINE.
	2/ This list, when defined, supercedes the mci
	  key in c:\windows\system.ini

   TODO:
	- MCI command loading support mci(Load|Free)Command
	- implement other stuff as yet unknown
	- in mciString(), make use of hiword from mciSendMessage
          return value to convert value into string...
	- mmTaskXXX functions are currently broken because the 16
          loader does not support binary command lines.

3.2 MCI multi-tasking
---------------------
   Multi-tasking capabilities used for the MCI drivers are provided 
   in multimedia/mmsystem.c

3.3 Timers
----------

   It currently uses a service thread, run in the context of the calling
   process, which should correctly mimic Windows behaviour.

   TODO:
   	- Check if minimal time is satisfactory for most programs.

3.4 MMIO
--------
   
   The API consists of the mmio* functions found in multimedia/mmio.c.

   Seems to work ok in most of the cases.

   TODO:
	- ...

@------------------------------------@
@     Last updated: 12, May 1999     @
@ Eric Pouech <eric.pouech@lemel.fr> @
@------------------------------------@