Moved wine_anon_mmap to loader.c.

[wine] / documentation / multimedia.sgml

  <chapter id="multimedia">
    <title>Wine and Multimedia</title>

    <para>
      This file contains information about the implementation of the
      multimedia layer of Wine.
    </para>

    <para>
      The implementation can be found in the dlls/winmm/ directory (and in
      many of its subdirectories), but also in dlls/msacm/ (for the
      audio compression/decompression manager) and dlls/msvideo/ (for the
      video compression/decompression manager).
    </para>

    <para>
      Written by &name-eric-pouech; <email>&email-eric-pouech;</email>
      (Last updated: 02/16/2001)
    </para>

    <sect1 id="mm-overview">
      <title>Overview</title>

      <para>
        The multimedia stuff is split into 3 layers. The low level (device
        drivers), mid level (MCI commands) and high level abstraction layers.
        The low level layer has also some helper DLLs (like the MSACM/MSACM32
        and MSVIDEO/MSVFW32 pairs).
      </para>

      <para>
        The low level layer may depend on current hardware and OS services
        (like OSS on Unix). Mid level (MCI) and high level layers must be
         written independently from the hardware and OS services.
      </para>

      <para>
        There are two specific low level drivers (one for wave input/output,
        another one for MIDI output only), whose role is:
        <itemizedlist>
          <listitem>
            <para>help choosing one low level driver between many</para>
          </listitem>
          <listitem>
            <para>
              add the possibility to convert streams (ie ADPCM =&gt; PCM)
            </para>
          </listitem>
          <listitem>
            <para>
              add the possibility to filter a stream (adding echo, equalizer...
              to a wave stream), or modify the instruments that have to be
              played (MIDI).
            </para>
          </listitem>
        </itemizedlist>
      </para>

      <para>
        All of those components are defined as DLLs (one by one).
      </para>

    </sect1>

    <sect1 id="mm-low">
      <title>Low level layers</title>

      <para>
        Please note that native low level drivers are not currently supported
        in Wine, because they either access hardware components or require
        VxDs to be loaded; Wine does not correctly supports those two so far.
      </para>

      <para>
        The following low level layers are implemented (as built-in DLLs):
      </para>

      <sect2>
        <title>(Wave form) Audio</title>

        <para>
          MMSYSTEM and WINMM call the real low level audio driver using the
          wodMessage/widMessage which handles the different requests.
        </para>

        <sect3>
          <title>OSS implementation</title>

          <para>
            The low level audio driver is currently only implemented for the
            OpenSoundSystem (OSS) as supplied in the Linux and FreeBSD kernels by
            <ulink url="http://www.4front-tech.com/">4Front Technologies</ulink>.
            The presence of this driver is checked by configure (depends on the
            &lt;sys/soundcard.h&gt; file). Source code resides in
            dlls/winmm/wineoss/audio.c.
          </para>

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

          <para>
            Note that some Wine specific flag has been added to the wodOpen function,
            so that the dsound DLL can share the /dev/dsp access. Currently, this
            only provides mutual exclusion for both DLLs. Future extension could add
            a virtual mixer between the two output streams.
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  verify all functions for correctness
                </para>
              </listitem>
              <listitem>
                <para>
                  Add virtual mixer between wave-out and dsound interfaces.
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Other sub systems</title>

          <para>
            No other is available. Could think of Sun Audio, remote audio systems
            (using X extensions, ...), ALSA, EsounD, ArTs...
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>MIDI</title>

        <para>
          MMSYSTEM and WINMM call the low level driver functions using the
          midMessage and the modMessage functions.
        </para>

        <sect3>
          <title>OSS driver</title>

          <para>
            The low level audio driver is currently only implemented for the
            OpenSoundSystem (OSS) as supplied in the Linux and FreeBSD kernels by
            <ulink url="http://www.4front-tech.com/">4Front Technologies</ulink>.
            The presence of this driver is checked by configure (depends on the
            &lt;sys/soundcard.h&gt; file, and also some specific defines because
            MIDI is not supported on all OSes by OSS). Source code resides in
            dlls/winmm/wineoss/midi.c
          </para>

          <para>
            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).
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  use better instrument definition for OPL/2 (midiPatch.c) or use
                  existing instrument definition (from playmidi or kmid) with a
                  .winerc option
                </para>
              </listitem>
              <listitem>
                <para>
                  have a look at OPL/3 ?
                </para>
              </listitem>
              <listitem>
                <para>
                  implement asynchronous playback of MidiHdr
                </para>
              </listitem>
              <listitem>
                <para>
                  implement STREAM'ed MidiHdr (question: how shall we share the code
                  between the midiStream functions in MMSYSTEM/WINMM and the code
                  for the low level driver)
                </para>
              </listitem>
              <listitem>
                <para>
                  use a more accurate read mechanism than the one of snooping on
                  timers (like select on fd)
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Other sub systems</title>

          <para>
            Could support other MIDI implementation for other sub systems (any
            idea here ?)
          </para>

          <para>
            Could also implement a software synthesizer, either inside Wine or
            using using MIDI loop back devices in an external program (like
            timidity). The only trouble is that timidity is GPL'ed...
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>Mixer</title>

        <para>
          MMSYSTEM and WINMM call the low level driver functions using the
          mxdMessage function.
        </para>

        <sect3>
          <title>OSS implementation</title>

          <para>
            The current implementation uses the OpenSoundSystem mixer, and resides
            in dlls/winmm/wineoss/mixer.c
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  implement notification mechanism when state of mixer's controls
                  change
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Other sub systems</title>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  implement mixing low level drivers for other mixers (ALSA...)
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>Aux</title>

        <para>
          The AUX low level driver is the predecessor of the mixer driver
          (introduced in Win 95).
        </para>

        <sect3>
          <title>OSS driver</title>

          <para>
            The implementation uses the OSS mixer API, and is incomplete.
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  verify the implementation
                </para>
              </listitem>
              <listitem>
                <para>
                  check with what is done in mixer
                </para>
              </listitem>
              <listitem>
                <para>
                  open question: shall we implement it on top of the low level mixer
                  functions ?
                </para>
              </listitem>
            </itemizedlist>

          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>Wine OSS</title>

        <para>
           All the OSS dependent functions are stored into the WineOSS DLL. It still
           lack a correct installation scheme (as any multimedia device under Windows),
           so that all the correct keys are created in the registry. This requires
           an advanced model since, for example, the number of wave out devices can
           only be known on the destination system (depends on the sound card driven
           by the OSS interface). A solution would be to install all the multimedia
           drivers through the SETUPX DLL; this is not doable yet (the multimedia
           extension to SETUPX isn't written yet).
        </para>

      </sect2>

      <sect2>
        <title>Joystick</title>

        <para>
          The API consists of the joy* functions found in dlls/winmm/joystick/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.
        </para>

        <para>TODO:
          <itemizedlist>
            <listitem>
              <para>
                better support of enhanced joysticks (Linux 2.2 interface is available)
              </para>
            </listitem>
            <listitem>
              <para>
                support more joystick drivers (like the XInput extension)
              </para>
            </listitem>
            <listitem>
              <para>
                should load joystick DLL as any other driver (instead of hardcoding)
                the driver's name, and load it as any low lever driver.
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

      <sect2>
        <title>Wave mapper (msacm.drv)</title>

        <para>
          The Wave mapper device allows to load on-demand codecs in order to
          perform software conversion for the types the actual low level driver
          (hardware). Those codecs are provided through the standard ACM
          drivers.
        </para>

        <sect3>
          <title>Built-in</title>

          <para>
            A first working implementation for wave out as been provided (wave in
            exists, but doesn't allow conversion).
          </para>

          <para>
            Wave mapper driver implementation can be found in dlls/winmm/wavemap/
            directory. This driver heavily relies on MSACM and MSACM32 DLLs which
            can be found in dlls/msacm and dlls/msacm32. Those DLLs load ACM
            drivers which provide the conversion to PCM format (which is normally
            supported by low level drivers). ADPCM, MP3... fit into the category
            of non PCM formats.
          </para>

          <para>
            There is currently no built-in ACM driver in Wine, so you must use
            native ones if you're looking for non PCM playback.
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  check for correctness and robustness
                </para>
              </listitem>
            </itemizedlist>
          </para>
        </sect3>

        <sect3>
          <title>Native</title>

          <para>
            Seems to work quite ok (using of course native MSACM/MSACM32 DLLs)
            Some other testings report some issues while reading back the registry
            settings.
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>MIDI mapper</title>

        <para>
          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.
        </para>

        <sect3>
          <title>Built-in</title>

          <para>
            A built-in MIDI mapper can be found in dlls/winmm/midimap/. It partly
            provides the same functionnality as the Windows' one. It allows to pick up
            destination channels (you can map a given channel to a specific playback
            device channel (see the configuration bits for more details).
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  implement the Midi mapper features (instrument on the fly modification)
                  if it has to be done as under Windows, it required parsing the midi
                  configuration files (didn't find yet the specs)
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Native</title>

          <para>
            The native midimapper from Win 98 works, but it requires a bunch of
            keys in the registry which are not part of the Wine source yet.
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  add native midimapper keys to the registry to let it run. This
                  will require proper multimedia driver installation routines.
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

      </sect2>

    </sect1>

    <sect1 id="mm-mci">
      <title>Mid level drivers (MCI)</title>

      <para>
        The mid level drivers are represented by some common API functions,
        mostly mciSendCommand and mciSendString. See status in chapter 3 for
        more information. Wine implements several MCI mid level drivers
        (status is given for both built-in and native implementation):
      </para>

      <para>TODO: (apply to all built-in MCI drivers)
        <itemizedlist>
          <listitem>
            <para>
              use MMSYSTEM multitasking caps instead of the home grown
            </para>
          </listitem>
        </itemizedlist>
      </para>


      <sect2>
        <title>CDAUDIO</title>

        <sect3>
          <title>Built-in</title>

          <para>
            The currently best implementation is the MCI CDAUDIO driver that can
            be found in dlls/winmm/mcicda/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 similar, but are not implemented.)
          </para>

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

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  add support for other cdaudio drivers (Solaris...)
                </para>
              </listitem>
              <listitem>
                <para>
                  add support for multiple cdaudio devices (plus a decent
                  configuration scheme)
                </para>
              </listitem>
              <listitem>
                <para>
                  The DLL is not cleanly separated from the NTDLL DLL. The CDROM
                  interface should be exported someway (or stored in a Wine only DLL)
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Native</title>

          <para>
            Native MCICDA works also correctly... It uses the MSCDEX traps (on int
            2f). However, some commands (like seeking) seem to be broken.
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>MCIWAVE</title>

        <sect3>
          <title>Built-in</title>

          <para>
            The implementation is rather complete and can be found in
            dlls/winmm/mciwave/audio.c. It uses the low level audio API (although
            not abstracted correctly).
          </para>

          <para>FIXME:
            <itemizedlist>
              <listitem>
                <para>
                  The MCI_STATUS command is broken.
                </para>
              </listitem>
            </itemizedlist>
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  check for correctness
                </para>
              </listitem>
              <listitem>
                <para>
                  better use of asynchronous playback from low level
                </para>
              </listitem>
              <listitem>
                <para>
                  better implement non waiting command (without the MCI_WAIT flag).
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Native</title>

          <para>
            Native MCIWAVE works also correctly.
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>MCISEQ (MIDI sequencer)</title>

        <sect3>
          <title>Built-in</title>

          <para>
            The implementation can be found in dlls/winmm/mciseq/mcimidi.c. Except
            from the Record command, should be close to completion (except for non
            blocking commands, as many MCI drivers).
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  implement it correctly
                </para>
              </listitem>
              <listitem>
                <para>
                  finish asynchronous commands (especially for reading/record)
                </para>
              </listitem>
              <listitem>
                <para>
                  better implement non waiting command (without the MCI_WAIT flag).
                </para>
              </listitem>
              <listitem>
                <para>
                  implement the recording features
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Native</title>

          <para>
            Native MCIMIDI has been working but is currently blocked by scheduling
            issues (mmTaskXXX no longer work).
          </para><para>FIXME:
            <itemizedlist>
              <listitem>
                <para>
                  midiStreamPlay get from time to time an incorrect MidiHdr when
                  using the native MCI sequencer
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>MCIANIM</title>

        <sect3>
          <title>Built-in</title>

          <para>
            The implementation is in dlls/winmm/mcianim/.
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  implement it, probably using xanim or something similar.
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Native</title>

          <para>
            Native MCIANIM is reported to work (but requires native video DLLs
            also, even though the built-in video DLLs start to work correctly).
          </para>

        </sect3>

      </sect2>

      <sect2>
        <title>MCIAVI</title>

        <sect3>
          <title>Built-in</title>

          <para>
            The implementation is in dlls/winmm/mcianim/. Basic features are present,
            simple playing is available, even if lots remain to be done. It rather
            heavily relies on MSVIDEO/MSVFW32 DLLs pair to work.
          </para>

          <para>TODO:
            <itemizedlist>
              <listitem>
                <para>
                  finish the implementation
                </para>
              </listitem>
              <listitem>
                <para>
                  fix the audio/video synchronisation issue
                </para>
              </listitem>
            </itemizedlist>
          </para>

        </sect3>

        <sect3>
          <title>Native</title>

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

        </sect3>

      </sect2>

    </sect1>

    <sect1 id="mm-high">
      <title>High level layers</title>

      <para>
        The rest (basically the MMSYSTEM and WINMM DLLs entry points). It also
        provides the skeleton for the core functionality for multimedia
        rendering. Note that native MMSYSTEM and WINMM do not currently work
        under Wine and there is no plan to support them (it would require to
        also fully support VxD, which is not done yet).
        Moreover, native DLLs require 16 bit MCI and low level drivers. Wine
        implements them as 32 bit drivers.
        MCI and low level drivers can either be 16 or 32 bit for Wine.
      </para>

      <para>TODO:
        <itemizedlist>
          <listitem>
            <para>
              it seems that some program check what's installed in registry
              against value returned by drivers. Wine is currently broken
              regarding this point.
            </para>
          </listitem>
          <listitem>
            <para>
              add clean-up mechanisms when process detaches from MM DLLs
            </para>
          </listitem>
          <listitem>
            <para>
              prepare for the 16/32 big split
            </para>
          </listitem>
          <listitem>
            <para>
              check thread-safeness for MMSYSTEM and WINMM entry points
            </para>
          </listitem>
          <listitem>
            <para>
              unicode entry points are badly supported
            </para>
          </listitem>
        </itemizedlist>
      </para>

      <sect2>
        <title>MCI skeleton</title>

        <para>
          Implementation of what is needed to load/unload MCI drivers, and to
          pass correct information to them. This is implemented in
          dlls/winmm/mci.c. The mciSendString function uses command strings,
          which are translated into normal MCI commands as used by
          mciSendCommand with the help of command tables. The API can be found
          in dlls/winmm/mmsystem.c and dlls/winmm/mci.c. The functions there
          (mciOpen,mciSysInfo) handle mid level driver allocation and calls. The
          implementation is not complete.
        </para>

        <para>
          MCI drivers are seen as regular Wine modules, and can be loaded (with
          a correct load order between built-in, native, elfdll, so), as any
          other DLL. Please note, that MCI drivers module names must bear the
          .drv extension to be correctly understood.
        </para>

        <para>
          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, supersedes the mci key in
          c:\windows\system.ini
       </para>

        <para>
          Note that native VIDEODISC crashes when the module is loaded, which
          occurs when the MCI procedures are initialised. Make sure that this is
          not in the list from above. Try adding:
          mci=CDAUDIO:SEQUENCER:WAVEAUDIO:AVIVIDEO:MPEGVIDEO
          to the [options] section of the wine config file.
        </para>

        <para>TODO:
          <itemizedlist>
            <listitem>
              <para>
                correctly handle the MCI_ALL_DEVICE_ID in functions.
              </para>
            </listitem>
            <listitem>
              <para>
                finish mapping 16 <=> 32 of MCI structures and commands
              </para>
            </listitem>
            <listitem>
              <para>
                MCI_SOUND is not handled correctly (should not be sent to MCI
                driver =&gt; same behavior as MCI_BREAK)
              </para>
            </listitem>
            <listitem>
              <para>
                implement auto-open feature (ie, when a string command is issued
                for a not yet opened device, MCI automatically opens it)
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

      <sect2>
        <title>MCI multi-tasking</title>

        <para>
          Multi-tasking capabilities used for the MCI drivers are provided in
          dlls/winmm/mmsystem.c.
        </para>

        <para>TODO:
          <itemizedlist>
            <listitem>
              <para>
                mmTaskXXX functions are currently broken because the 16 loader does
                not support binary command lines =&gt; provide Wine's own mmtask.tsk not
                using binary command line.
              </para>
            </listitem>
            <listitem>
              <para>
                the Wine native MCI drivers should use the mmThreadXXX API (but since
                all built-in MCI drivers are 32 bit, this would require a special
                flag to mark 32 bit entry points)
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

      <sect2>
        <title>Timers</title>

        <para>
          It currently uses a service thread, run in the context of the calling
          process, which should correctly mimic Windows behavior.
        </para>

        <para>TODO:
          <itemizedlist>
            <listitem>
              <para>
                Check if minimal time is satisfactory for most programs.
              </para>
            </listitem>
            <listitem>
              <para>
                current implementation may let a timer tick (once) after it has
                been destroyed
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

      <sect2>
        <title>MMIO</title>

        <para>
          The API consists of the mmio* functions found in mdlls/winmm/mmio.c.
          Seems to work ok in most of the cases. There's some linear/segmented
          issues with 16 bit code. There are also some bugs when writting MMIO
          files.
        </para>

      </sect2>

      <sect2>
        <title>sndPlayXXX functions</title>

        <para>
          Seem to work correctly.
        </para>

      </sect2>

    </sect1>

    <sect1 id="mm-conf">
      <title>Multimedia configuration</title>

      <para>
        Currently, multimedia configuration heavily relies on Win 3.x
        configuration model.
      </para>

      <sect2>
        <title>Drivers</title>

        <para>
          Since all multimedia drivers (MCI, low level ones, ACM drivers,
          mappers) are, at first, drivers they need to appear in the [mci] or
          [mci32] section of the system.ini file.
          Since all drivers are, at first, DLLs, you can choose to load their
          Wine's (built-in) or Windows (native) version.
        </para>

      </sect2>

      <sect2>
        <title>MCI</title>

        <para>
          A default [mci] section (in system.ini) looks like (see the note above
          on videodisc):
        </para>

        <screen>
   [mci]
   cdaudio=mcicda.drv
   sequencer=mciseq.drv
   waveaudio=mciwave.drv
   avivideo=mciavi.drv
   videodisc=mcipionr.drv
   vcr=mcivisca.drv
   MPEGVideo=mciqtz.drv
        </screen>

        <para>
          By default, the list of loadable MCI drivers will be made of those
          drivers (in the [mci] section).
        </para>

        <para>
          The list of loadable (recognized) MCI drivers can be altered in the
          [option] section of the wine config file, like:
          mci=CDAUDIO:SEQUENCER:WAVEAUDIO:AVIVIDEO:MPEGVIDEO
        </para>

        <para>TODO:
          <itemizedlist>
            <listitem>
              <para>
                use a default registry setting to bypass this (ugly) configuration
                model
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

      <sect2>
        <title>Low level drivers</title>

        <para>
           Configuration of low level drivers is done with the Wine configuration file.
           Default keys are provided in winedefault.reg.
        </para>

        <para>
          The registry keys used here differ from the Windows' one. Using the Windows' one
          would require implementing something equivalent to a (real) driver installation.
          Even if this would be necessary in a few cases (mainly using MS native multimedia)
          modules, there's no real need so far (or it hasn't been run into yet).
        </para>

        <para>
          See the configuration part of the User's Guide for more details.
        </para>

      </sect2>

      <sect2>
        <title>Midi mapper</title>

        <para>
          The Midi mapper configuration is the same as on Windows 9x. Under the key
          <screen>
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Multimedia\MIDIMap
          </screen>
          if the 'UseScheme' value is not set, or is set to a null value, the midi
          mapper will always use the driver identified by the 'CurrentInstrument'
          value. Note: Wine (for simplicity while installing) allows to define
          'CurrentInstrument' as "#n" (where n is a number), whereas Windows only
          allows the real device name here. If UseScheme is set to a non null value,
          'CurrentScheme' defines the name of the scheme to map the different channels.
          All the schemes are available with keys like
          <screen>
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\MediaProperties\PrivateProperties\Midi\Schemes\%name_of_scheme%
          </screen>
          For every scheme, under this key, will be a sub-key (which name is usually
          a two digit index, starting at 00). Its default value is the name of the
          output driver, and the value 'Channels' lists all channels (of the 16
          standard MIDI ones) which have to be copied to this driver.
        </para>

        <para>
          To provide enhanced configuration and mapping capabilities, each driver
          can define under the key
          <screen>
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\MediaProperties\PrivateProperties\Midi\Ports\%driver_name%
          </screen>
          a link to and .IDF file which allows to remap channels internally (for
          example 9 -&gt; 16), to change instruments identification, event
          controlers values. See the source file dlls/winmm/midimap/midimap.c
          for the details (this isn't implemented yet).
        </para>
      </sect2>

      <sect2>
        <title>ACM</title>

        <para>
          To be done (use the same mechanism as MCI drivers configuration).
        </para>

      </sect2>

      <sect2>
        <title>VIDC</title>

        <para>
          To be done (use the same mechanism as MCI drivers configuration).
        </para>

      </sect2>

    </sect1>

    <sect1 id="mm-arch">
      <title>Multimedia architecture</title>

      <sect2>
        <title>Windows 9x multimedia architecture</title>

        <screen>
             |
Kernel space |                    Client applications
             |
             |           | |         ^ ^       | |          | |
             |        16>| |<32   16>| |<32 16>| |<32    16>| |<32
             |           | v         | |       | v          | v
             |      +----|-----------|---------|------------|-------+
             |      |    |           |         |            |       |  WinMM.dll
             |      |    |           |         |            |       |   32 bit
             |      +----|-----------|---------|------------|-------+
             |           | |         | ^       | |          |
             |  +------+ | |<16      | |       | |<16       |
             |  |   16>| | |         | |       | |          |
             |  |      v v v         | |       v v          v
             |  |   +---------------+---+-------------+-------------+
             |  |   | waveInXXX     |   | mciXXX      | *playSound* |
             |  |   | waveOutXXX    |   |             | mmioXXX     |
             |  |   | midiInXXX     |   |             | timeXXX     |
             |  |   | midiOutXXX    |   |             | driverXXX   |
             |  |   | midiStreamXXX |   |             |             |  MMSystem.dll
             |  |   | mixerXXX      |   |             |             |     16 bit
 +--------+  |  |   | auxXXX    +---+   +---+ mmThread|             |
 |MMDEVLDR|<------->| joyXXX    | Call back | mmTask  |             |
 +--------+  |  |   +-----------+-----------+---------+-------------+
     ^       |  |          |       ^    ^     | ^
     |       |  |       16>|       |<16>|  16>| |<16
     v       |  |          v       |    |     v |
 +--------+  |  |   +-------------+    +----------+
 |  VxD   |<------->|    *.drv    |    | mci*.drv |
 +--------+  |  |   +--------------+   +-----------+
             |  |    |  msacm.drv  |    | mciwave  |
             |  |    +--------------+   +-----------+
             |  |     | midimap.drv |    | mcimidi  |
             |  |     +-------------+    +-----------+
             |  |    Low-level drivers    |    ...   | MCI drivers
             |  |                         +----------+
             |  |                               |
             |  |                               |<16
             |  +-------------------------------+
             |
        </screen>

        <para>
          The important points to notice are:
          <itemizedlist>
            <listitem>
              <para>
                all drivers (and most of the core code) is 16 bit
              </para>
            </listitem>
            <listitem>
              <para>
                all hardware (or most of it) dependant code reside in the kernel
                space (which is not surprising)
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

      <sect2>
        <title>Wine multimedia architecture</title>

        <screen>
             |
Kernel space |                    Client applications
             |
             |           | |         ^ ^       | |          | |
             |        16>| |<32   16>| |<32 16>| |<32    16>| |<32
             |           | |         | |       | |          | |
             |  +------+ | |         | |       | |          | |
             |  |32/16>| | |         | |       | |          | |
             |  |      v v v         | |       v v          v v
             |  |   +---------------+---+-------------+-------------+
             |  |   | waveInXXX     |   | mciXXX      | *playSound* |
             |  |   | waveOutXXX    |   |             | mmioXXX     | WinMM.dll
             |  |   | midiInXXX     |   |             | timeXXX     |   32 bit
             |  |   | midiOutXXX    |   |             | driverXXX   |
             |  |   | midiStreamXXX |   |             |             | MMSystem.dll
             |  |   | mixerXXX      |   |             |             |   16 bit
             |  |   | auxXXX    +---+   +---+ mmThread|             |
             |  |   | joyXXX    | Call back | mmTask  |             |
             |  |   +-----------+-----------+---------+-------------+
             |  |         ||      ^    ^     ||    ^^
             |  |      16>||<32   |<16>|  16>||<32>||<16
             |  |         vv      |<32>|     vv    ||
+---------+  |  |   +-------------+    +----------+
|HW driver|<------->|    *.drv    |    | mci*.drv |
+---------+  |  |   +--------------+   +-----------+
             |  |    |  msacm.drv  |    | mciwave  |
             |  |    +--------------+   +-----------+
             |  |     | midimap.drv |    | mcimidi  |
             |  |     +-------------+    +-----------+
             |  |    Low-level drivers    |    ...   | MCI drivers
             |  |                         +----------+
             |  |                               |
             |  |                               |<32/16
             |  +-------------------------------+
             |
        </screen>

        <para>
          From the previous drawings, the most noticeable differences are:
          <itemizedlist>
            <listitem>
              <para>
                low-level drivers can either be 16 or 32 bit
              </para>
            </listitem>
            <listitem>
              <para>
                MCI drivers can either be 16 or 32 bit
              </para>
            </listitem>
            <listitem>
              <para>
                MMSystem and WinMM will be hosted in a single elfglue library
              </para>
            </listitem>
            <listitem>
              <para>
                no link between the MMSystem/WinMM pair on kernel space shall
                exist. For example, there will be a low level driver to talk to a
                UNIX OSS (Open Sound System) driver
              </para>
            </listitem>
            <listitem>
              <para>
                all built-in drivers (low-level and MCI) will be written as 32 bit
                drivers
              </para>
            </listitem>
            <listitem>
              <para>
                all native drivers will be 16 bits drivers
              </para>
            </listitem>
          </itemizedlist>
        </para>

      </sect2>

    </sect1>

          <sect1 id="msacm">
            <title>MS ACM Dlls</title>

            <sect2>
              <title>Contents</title>

              <para>tbd</para>
            </sect2>

            <sect2>
              <title>Status</title>

              <para>tbd</para>
            </sect2>

            <sect2>
              <title>Caching</title>

              <para>
                The MSACM/MSACM32 keeps some data cached for all known ACM
                drivers. Under the key
                <screen>
                  Software\Microsoft\AudioCompressionManager\DriverCache\&lt;driver
                  name&gt;
                </screen>
                are kept for values:
                <itemizedlist>
                  <listitem>
                    <para>
                      aFormatTagCache which contains an array of
                      DWORD. There are two DWORDs per cFormatTags
                      entry. The first DWORD contains a format tag
                      value, and the second the associated maximum
                      size for a WAVEFORMATEX structure.
                      (Fields dwFormatTag and cbFormatSize from
                      ACMFORMATDETAILS)
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      cFilterTags contains the number of tags supported by the driver
                      for filtering.
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      cFormatTags contains the number of tags support
                      by the driver for conversions.
                    </para>
                  </listitem>
                  <listitem>
                    <para>
                      fdwSupport (the same as the one returned from
                      acmDriverDetails).
                    </para>
                  </listitem>
                </itemizedlist>
              </para>

              <para>
                The cFilterTags, cFormatTags, fdwSupport are the same
                values as the ones returned from acmDriverDetails
                function.
              </para>
            </sect2>
          </sect1>


  </chapter>

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