359 lines
11 KiB
Plaintext
359 lines
11 KiB
Plaintext
This file contains information about the implementation of the
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multimedia layer of WINE.
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The libraries consist of MMSYSTEM.DLL (win16), WINMM.DLL (win32) and
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some (abstracted, not Windows compatible) lowlevel drivers. The
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implementation can be found in the multimedia/ subdirectory.
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The multimedia stuff is split into 3 layers. The lowlevel (device
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drivers), midlevel (MCI commands) and highlevel abstraction layers.
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The lowlevel may depend on current hardware and OS services (like
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OSS). Mid-level and high-level must be written independantly from the
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hardware and OS services.
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1. Lowlevel layers
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==================
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Please note that native low-level drivers are not currently
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supported in WINE, because they either access hardware composants
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or require VxDs to be loaded; WINE does not correctly supports
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those two so far.
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Following lowlevel layers are implemented:
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1.1 (Waveform) Audio
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--------------------
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MMSYSTEM and WINMM call the real lowlevel audiodriver using
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the wodMessage/widMessage function in multimedia/audio.c, which
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handles the different requests.
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1.1.1 OSS implementation
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The lowlevel audio driver is currently only implemented for the
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OpenSoundSystem (OSS) as supplied in the Linux and FreeBSD kernels
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by 4Front Technologies (http://www.4front-tech.com/). The presence
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of this driver is checked by configure (depends on the
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<sys/soundcard.h> file).
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The implementation contains all features commonly used, but has
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several problems (see TODO list).
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TODO:
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- add asynchronous reads (must use threads) as done for writes
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- verify all functions for correctness
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- add drivers for other soundsystems (Sun Audio, remote audio
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systems (using X extensions, ...), ALSA
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- WaveHdr must be sent though mmsystem.c to get the linear
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address set correctly. An application calling directly
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(wod|wid)Message will fail
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1.1.2 Wave mapper
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The Wave mapper device allows to load on-demand codecs to perform
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software conversion for the types the actual low level driver
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(hardware) does not support. Those codecs are provided thru the
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standard ACM drivers.
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Wave mapper driver implementation has not started. Core DLL for ACM
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support can be found in dlls/msacm
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TODO:
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- implement wave mapper
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- don't forget to fix builtin ms acm drivers loading which has
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been disabled.
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1.2 MIDI
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--------
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MMSYSTEM and WINMM call the lowlevel driver functions in
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multimedia/midi.c using the midMessage and the modMessage
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functions.
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1.2.1 OSS driver
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The lowlevel audio driver is currently only implemented for the
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OpenSoundSystem (OSS) as supplied in the Linux and FreeBSD kernels
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by 4Front Technologies (http://www.4front-tech.com/). The presence
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of this driver is checked by configure (depends on the
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<sys/soundcard.h> file, and also some specfic defines because MIDI
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is not supported on all OSes by OSS).
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Both Midi in and Midi out are provided. The type of MIDI devices
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supported is external MIDI port (requires an MIDI capable device -
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keyboard...) and OPL/2 synthesis (the OPL/2 patches for all
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instruments are in midiPatch.c).
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TODO:
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- Do not implement a software synthesizer. This should be done
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using MIDI loopback devices in an external program (like
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timidity). The only trouble is that timidity is GPL'ed...
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- use better instrument definition for OPL/2 (midiPatch.c) or
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use existing instrument definition (from playmidi or kmid)
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with a .winerc option
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- have a look at OPL/3 ?
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- MidiHdr must be sent though mmsystem.c to get the linear
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address set correctly. An application calling directly
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(wod|wid)Message will fail
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- implement asynchronous playback of MidiHdr (regular and/or
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stream)
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- use a more accurate read mechanism than the one of snooping
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on timers
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1.2.2 MIDI mapper
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Midi mapper allows to map each one of 16 MIDI channels to a
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specific instrument on an installed sound card. This allows for
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example to support different MIDI instrument definition (XM,
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GM...). It also permits to output on a per channel basis to
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different MIDI renderers.
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TODO:
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- implement the Midi mapper
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1.3 Mixer
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---------
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MMSYSTEM and WINMM call the lowlevel driver functions in
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multimedia/mixer.c using the mixMessage function.
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1.3.1 OSS implementation
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The current implementation uses the OpenSoundSystem mixer.
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TODO:
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- implement mixing mute functionality for OSS.
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- implement mixing lowlevel drivers for other mixers (ALSA...)
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- implement notification mechanism when state of mixer's
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controls change
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- handlers used for mixer are currently poorly implemented
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1.4 AUX
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-------
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The API consists of the aux* functions found in
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multimedia/mmsystem.c. They call auxMessage in multimedia/mmaux.c.
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The aux* functions are the predecessor of the mixer* functions.
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1.4.1 OSS driver
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The implementation uses the OSS mixer API, and is incomplete.
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TODO:
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- verify the implementation
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- check with what is done in mixer
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- open question: shall we implement it on top of the low level
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mixer functions ?
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1.7 JOYSTICK
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------------
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The API consists of the joy* functions found in
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multimedia/joystick.c. The implementation currently uses the Linux
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joystick device driver API. It is lacking support for enhanced
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joysticks and has not been extensively tested.
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TODO:
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- better support of enhanced joysticks
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- support more joystick drivers (like the XInput extension)
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2. Midlevel drivers (MCI)
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=========================
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The midlevel drivers are represented by some common API functions,
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mostly mciSendCommand and mciSendString.
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See status in chapter 3 for more information.
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WINE implements several MCI midlevel drivers (status is given for
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both builtin and native implementation):
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TODO: (apply to all builtin MCI drivers)
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- move mci drivers as regular DLLs (loading in wine,
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elfglue...)
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2.1 CDAUDIO
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-----------
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2.1.1 Builtin
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The currently best implementation is the MCI CDAUDIO driver that can
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be found in multimedia/mcicda.c. The implementation is mostly
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complete, there have been no reports of errors.
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It makes use of misc/cdrom.c Wine internal cdrom interface. This
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interface has been ported on Linux, FreeBSD and NetBSD.
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(Sun should be similair, but are not implemented.)
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A very small example of a cdplayer consists just of the line
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mciSendString("play cdaudio",NULL,0,0);
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2.1.2 Native
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Native MCICDA works also correctly... It uses the mscdex traps (on
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int 2f).
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TODO:
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- add support for other cdaudio drivers (Solaris...)
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2.2 MCIWAVE
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-----------
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2.2.1 Builtin
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The implementation is rather complete and can be found in
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multimedia/audio.c.
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It uses the lowlevel audio API (although not abstracted
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correctly).
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FIXME:
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- The MCI_STATUS command is broken.
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TODO:
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- check for correctness
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- better use of asynchronous playback from low level
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- record has to be checked
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- MCI_CUE command is broken
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- better implement non waiting command (without the MCI_WAIT
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flag).
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2.2.2 Native
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Native MCIWAVE works also correctly.
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2.3 MCISEQ (MIDI sequencer)
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---------------------------
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2.3.1 Builtin
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The implementation can be found in multimedia/midi.c. Except from
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the Record command, should be close to completion (except for non
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blocking commands).
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TODO:
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- implement it correctly
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- finish asynchronous commands (especially for reading/record)
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- better implement non waiting command (without the MCI_WAIT
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flag).
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2.3.2 Native
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Native MCIMIDI has been working but is currently blocked by
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scheduling issues (mmTaskXXX no longer work).
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2.4 MCIANIM
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-----------
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2.4.1 Builtin
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The implementation consists of stubs and is in
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multimedia/mcianim.c.
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TODO:
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- implement it, probably using xanim or something similair.
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2.4.2 Native
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Native MCIANIM is reported to work (but requires native video DLLs
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also).
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2.5 MCIAVI
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----------
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2.5.1 Builtin
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The implementation consists of stubs and is in multimedia/mciavi.c.
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TODO:
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- implement it, probably using xanim or something similair.
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2.5.2 Native
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Native MCIAVI is reported to work (but requires native video DLLs
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also). Some files exhibit some deadlock issues anyway.
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3 High-level layers
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===================
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The rest (basically the MMSYSTEM and WINMM DLLs entry points).
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It also provides the skeletton for the core functionnalites for
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multimedia rendering.
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Note that native mmsystem and WINMM do not currently under WINE
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and there is no plan to support them (it would require to also
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fully support VxD, which is not done yet).
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TODO:
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- allow a dynamic loading of low level driver (should have one
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for OSS, another one for ALSA...)
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- add clean-up mechanisms when process detach from MM DLLs
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- reimplement the sndPlay??? functions using MCI commands
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rather than rewriting everything from scratch.
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- prepare for the 16/32 bit split
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- check thread-safeness for MMSYSTEM and WINMM entry points
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3.1 MCI skeletton
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-----------------
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Implementation of what is needed to load/unload MCI drivers, and
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to pass correct information to them. This is implemented in
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multimedia/mci.c and multimedia/mcistring.c
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The mciSendString function uses commandstrings, which are
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translated into normal MCI commands as used by mciSendCommand.
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The API can be found in multimedia/mmsystem.c and
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multimedia/mcistring.c. The functions there (mciOpen,mciSysInfo)
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handle midlevel driver allocation and calls.
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The implementation is not complete.
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MCI drivers are seen as regular WINE modules, and can be loaded
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(with a correct loadorder between builtin, native, elfdll, so), as
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any other DLL. Please note, that MCI drivers module names must
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bear the .drv extension to be correctly understood.
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The list of available MCI drivers is obtained as follows:
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1/ key 'mci' in [option] section from .winerc (or wineconf)
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mci=CDAUDIO:SEQUENCER
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gives the list of MCI drivers (names, in uppercase only) to
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be used in WINE.
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2/ This list, when defined, supercedes the mci
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key in c:\windows\system.ini
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TODO:
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- MCI command loading support mci(Load|Free)Command
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- implement other stuff as yet unknown
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- in mciString(), make use of hiword from mciSendMessage
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return value to convert value into string...
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- mmTaskXXX functions are currently broken because the 16
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loader does not support binary command lines.
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3.2 MCI multi-tasking
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---------------------
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Multi-tasking capabilities used for the MCI drivers are provided
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in multimedia/mmsystem.c
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3.3 Timers
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----------
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It currently uses a service thread, run in the context of the calling
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process, which should correctly mimic Windows behaviour.
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TODO:
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- Check if minimal time is satisfactory for most programs.
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3.4 MMIO
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--------
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The API consists of the mmio* functions found in multimedia/mmio.c.
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Seems to work ok in most of the cases.
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TODO:
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- ...
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@------------------------------------@
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@ Last updated: 12, May 1999 @
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@ Eric Pouech <eric.pouech@lemel.fr> @
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@------------------------------------@
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