  Using The DOSEMU Sound System (SBEMU)
  Author: Alistair MacDonald, <A.MacDon-
  ald@slitesys.demon.co.uk>
  version dosemu-0.98.3

  The document describes the use of the DOSEMU Sound code (SBEMU), and
  what you can expect from it.
  ______________________________________________________________________

  Table of Contents


  1. Introduction

  2. What to (and what not to!) expect

     2.1 FM
        2.1.1 Technical Explanation
     2.2 MPU-401
     2.3 SB (Digital)
     2.4 DMA

  3. Using SBEMU

     3.1 DOSEMU Compile-time Configuration
     3.2 DOSEMU Run-time Configuration
        3.2.1 Changing the SBEMU settings
        3.2.2 Configuring Midi
           3.2.2.1 Using Midid
           3.2.2.2 Sending Midi direct to a device
     3.3 Configuring DOS
     3.4 Configuring the Applications
        3.4.1 Midi with Digital Audio
        3.4.2 SB Music with SB Audio
        3.4.3 Midi Music, No Audio

  4. Debugging SBEMU



  ______________________________________________________________________

  1.  Introduction

  It is much better to be pessimistic about the capabilities of DOSEMU's
  sound code. The code itself provides an EMULATION of the popular SB
  cards. The actual level of emulation that can be achieved is dependant
  upon the capabilities of the sound driver on your system. Currently
  the emulation can only talk to the OSS driver (included in the Linux
  kernel) although it has been written in a modular fashion to allow
  other drivers to be written. For more details on the internals please
  see the WWW pages at
  http://www.slitesys.demon.co.uk/a.macdonald/dosemu/sound/.

  It should be pointed out that not all of this information comes from
  my own knowledge and that parts come from the other developers and
  from users who have contributed code & comments. Unfortunately I tend
  to forget names and lose emails, so their names are not included.


  2.  What to (and what not to!) expect

  The emulation consists of a number of parts, and I'll examine these
  separately.


  2.1.  FM

  The FM driver is the least complete. Most of the chip functions are
  there, but no audio output occurs. This means that software which uses
  the presence/operation of the timer should detect the timer presence,
  but if the audio needs/uses FM you will hear nothing.


  2.1.1.  Technical Explanation

  There are a number of problems with the FM emulation:


  1. Any FM output will have to be translated to appropriate OSS
     sequencer calls. These vary according to the SoundCard family
     (mainly between the cards with real FM synthesis and those with
     wavetable synthesis) You actually need to detect the card type and
     program it accordingly.

  2. The OSS sequencer doesn't allow you to change the parameters whilst
     a note is playing. Many games do this to provide their sound.


  2.2.  MPU-401

  This is the MIDI emulation. This should be fairly complete, but relies
  on the external daemon 'midid'. This is supplied and can be built
  easily.


  2.3.  SB (Digital)

  This is the digital aspect of the audio output. It is the most mature,
  and also the buggiest aspect (because it is the most complex!) Most of
  the functionality up to SB-16 is implemented, although some things
  don't work. Note that SB (DSP) MIDI is not implemented, although
  MPU-401 emulation (above) is.


  2.4.  DMA

  Whilst technically not part of the Sound System, the DMA emulation
  routines where developed primarily for SBEMU. These routines may have
  their own problems which may well impact on the running of SBEMU. As
  far as we know the only limitation is that they don't interface with
  the real DMA controller.


  3.  Using SBEMU

  SBEMU needs to be compiled into DOSEMU, AND turned on at run-time.
  Then your DOS applications need to be configured to use the emulation.
  (Just as they need to be configured to use your real sound card). The
  basic steps are given below.


  3.1.  DOSEMU Compile-time Configuration

  By default, DOSEMU is built with SBEMU support.


  3.2.  DOSEMU Run-time Configuration

  The default settings are:


      Base Address:   220
      IRQ:            5
      DMA:            1
      Midi Port:      330 (Not normally needed)




  Note that these do NOT need to be the same as your real sound card.


  3.2.1.  Changing the SBEMU settings

  The DOSEMU Sound settings are controlled by the following entries in
  /etc/dosemu.conf (-- Note that there is some overlap here with the
  configuration notes in the README. This will be addressed at a later
  stage--) :


  $_sound = (off)         # sound support on/off
  $_sb_base = (0x220)
  $_sb_irq = (5)
  $_sb_dma = (1)
  $_sb_dsp = "/dev/dsp"
  $_sb_mixer = "/dev/mixer"
  $_mpu_base = "0x330"




  Note that these are the default values. $_sb_dsp and $_sb_mixer are
  pre-configured to work with the standard OSS-Free driver. You are
  unlikely to need to change these values unless you have multiple
  drivers in your kernel.( eg such as the Ultra project drivers).


  3.2.2.  Configuring Midi

  The midi driver can be used in two way. It is possible to direct the
  output of the SBEMU midi driver directly to a sound card, or through
  the midid daemon. All midi traffic is directed at
  ~/.dosemu/run/dosemu-midi. You will need to create this, or link it to
  the appropriate device, according to your configuration. Details about
  this are given below.


  3.2.2.1.  Using Midid

  This is the preferred method of producing MIDI output. The midid is
  NOT built at the same time as DOSEMU, but it is simple to build:



       % make midid





  This will create src/arch/linux/dosext/sound/midid/midid. You will
  probably want to copy this somewhere on your path, such as /usr/bin.
  Next you will need to create the output pipe for the SBEMU driver:




  % mkdir -p ~/.dosemu/run
  % rm -f ~/.dosemu/run/dosemu-midi
  % mknod ~/.dosemu/run/dosemu-midi p




  If you already have a ~/.dosemu/run directory then the mkdir will
  fail. This is not a problem.


  Finally, you need to start the midid program:



       % midid < ~/.dosemu/run/dosemu-midi &





  This will run the driver in the background, giving you your prompt
  back.You should now run DOSEMU. Midid will terminate when DOSEMU
  terminates.


  Note that midid currently only supports the Ultra driver (autodetected
  when DOSEMU is configured), OSS/Free (partially) and a NULL driver
  (which just outputs the data stream as text). Midid should detect
  which is applicable. Running midid with the argument -h will list the
  options.


  3.2.2.2.  Sending Midi direct to a device

  This will ONLY work if your Midi device accepts raw midi data and you
  have either preloaded instruments patches, or it has hardware patches.
  Use this method ONLY if you cannot use the previous method, and do not
  EXPECT support.


  To use this method you simply need to link the SBEMU midi output file
  to the input of your MIDI device. The simplest method of doing this
  is:



       % mkdir -p ~/.dosemu/run
       % rm -f ~/.dosemu/run/dosemu-midi
       % ln -s /dev/MyMidiDevice ~/.dosemu/run/dosemu-midi




  Where /dev/MyMidiDevice is the path to your midi device. If you
  already have a ~/.dosemu/run directory then the mkdir will fail. This
  is not a problem.


  3.3.  Configuring DOS

  You should set your BLASTER environment variable to match your DOSEMU
  settings. Note that these don't need to correspond to your real sound
  card. For a base SB with the values above, use the following DOS
  command:

  set BLASTER=A220 I5 D1 T1




  The T1 identifies this as a Type 1 SB device eg old! The precise
  version of 'SB' is up to you, but the lower the model, the more likely
  it is to work.


  3.4.  Configuring the Applications

  Bearing in mind what was stated above, the following are the
  recommended methods for configuring applications to use SBEMU. The
  first is the preferred method. If you need to manually set any
  parameters remember to use those you configured DOSEMU with.


  3.4.1.  Midi with Digital Audio

  Configure the applications to use 'General Midi' for Music, and 'SB'
  for Digital Audio.


  3.4.2.  SB Music with SB Audio

  Configure the application with 'SB' for Music & Audio. Note that if
  the system plans to use FM for the music you will not get music.


  3.4.3.  Midi Music, No Audio

  Configure the application with 'General Midi' for Music and no Audio.


  4.  Debugging SBEMU

  The debugging output for SBEMU is enabled in the same way as all
  DOSEMU debug, and collected in the same manner. The debug flag for
  sound is 'S'. Because the DMA controller is hardware it uses the debug
  flag 'h'. To get basic debugging information into a file called
  sound.out use:



       % dos -D-a+Sh -o sound.out




  You can get slightly more verbose output is you use level 2 debugging
  (eg use -D-a+2Sh). If you need someone else to look at the debug
  output then feel free to send it to the list, but PLEASE, remove any
  unnecessary debug output, and give a DETAILED description of the
  problem. Ideally, use the bug reporting toolsubmit-bug-report.











