The Linux Sound HOWTO

The Linux Sound HOWTO
Jeff Tranter, [email protected]
v1.10, 3 December 1994

This document describes sound support for Linux. It lists the sup-
ported sound hardware, describes how to configure the kernel drivers,
and answers frequently asked questions. The intent is to bring new
users up to speed more quickly and reduce the amount of traffic in the
usenet news groups.

1. Introduction

This is the Linux Sound HOWTO document. It is intended as a quick
reference covering everything you need to know to install and
configure sound support under Linux. Frequently asked questions about
sound under Linux are answered, and references are given to some other
sources of information on a variety of topics related to computer
generated sound and music.

The scope is limited to the aspects of sound cards pertaining to
Linux. See the other documents listed in the Other Sources of
Information section for more general information on sound cards and
computer sound and music generation.

1.1. Acknowledgments

Much of this information came from the Readme files provided with the
sound driver source code, by Hannu Savolainen ([email protected]).
Thanks go to Hannu and the many other people who developed the Linux
kernel sound drivers and utilities.

Thanks to the Linuxdoc-SGML package, this HOWTO is now available in
several formats, including HTML hypertext (Mosaic), PostScript, and
plain ASCII, all generated from a common source file.

1.2. Revision History

Version 1.1
first version; posted to SOUND channel of Linux activists
mailing list only

Version 1.2
minor updates; first version available on archive sites

Version 1.3
converted to SGML; now available in several formats using Matt
Welsh's Linuxdoc-SGML tools; appearance changed due to new
format, only minor changes to content

Version 1.4
minor tweaking of SGML; added answer on PAS16 and Adaptec1542A
SCSI adaptor incompatibilities

Version 1.5
2.5a sound driver is now in 1.1 kernel distribution; note on
GUS-MAX support; other minor updates

Version 1.6
added info on "no space on device" error; added note that
Hacker's Guide is in a "hidden" directory; added question on
bidirectional mode; info on "device busy" errors; other minor
changes

Version 1.7
added info on ASP and AWE32; VoxWare 2.9 is available; answer to
question on using IRQ2; references to Sound and SCSI HOWTOs

Version 1.8
added question on errors under DOS; many minor things updated to
match the version 2.90 sound driver; info on DOOM; answer on
reducing noise

Version 1.9
questions on recording and clone cards

Version 1.10
mentioned that HOWTO is available on WWW, as printed copies, and
translations; info on DMA conflict with QIC tape driver; info on
Sound Galaxy NX Pro and Logitech BusMouse

1.3. New versions of this document

New versions of this document will be periodically posted to
comp.os.linux.announce. They will also be uploaded to various
anonymous ftp sites that archive such information including
sunsite.unc.edu:/pub/Linux/docs/HOWTO.

Hypertext versions of this and other Linux HOWTOs are available on
many World-Wide-Web sites. You can also buy printed copies from
several vendors.

If your native language is not English, you may be able to obtain a
translation of this document (French and Japanese translations are in
progress).

1.4. Feedback

If you have any suggestions, corrections, or comments on the HOWTO,
please send them to the author and I will try to incorporate them in
the next release.

If you have sound related problems that are not answered in this
HOWTO, feel free to send me a mail message and I will try to help.

1.5. Other Sources of Information

The Linux Sound User's Guide covers all of the user visible aspects of
using sound under Linux in much more detail (approximately 40 pages).
If you are interested in sound under Linux you should definitely get
this document. The current version is ALPHA 0.1, and is available on
tsx-11.mit.edu in the directory /pub/linux/ALPHA/LDP. I will continue
to maintain the Sound-HOWTO as a concise guide for users who want to
get sound up and running, or just find out what is required, without
having to read the full user's guide.

If you have a sound card that supports a CD-ROM or SCSI interface, the
Linux SCSI HOWTO and the Linux CD-ROM HOWTO have additional
information that may be useful to you.

Hannu Savolainen has written a draft version of the Hacker's Guide to
VoxWare. The latest version is draft 2, and can be found on
nic.funet.fi in /pub/OS/linux/ALPHA/sound.

The following FAQs are regularly posted to the usenet newsgroup
news.announce as well as being archived at the site rtfm.mit.edu in
the directory /pub/usenet/news.answers:

PCsoundcards/generic-faq (Generic PC Soundcard FAQ)
PCsoundcards/soundcard-faq (comp.sys.ibm.pc.soundcard FAQ)
PCsoundcards/gravis-ultrasound/faq (Gravis UltraSound FAQ)
audio-fmts/part1 (Audio file format descriptions)
audio-fmts/part2 (Audio file format descriptions)

The FAQs also list several product specific mailing lists and archive
sites. The following Usenet news groups discuss sound and/or music
related issues:

alt.binaries.sounds.* (various groups for posting sound files)
alt.binaries.multimedia (for posting Multimedia files)
alt.sb.programmer (Soundblaster programming topics)
comp.multimedia (Multimedia topics)
comp.music (Computer music theory and research)
comp.sys.ibm.pc.soundcard.* (various IBM PC soundcard groups)

The Linux Activists mailing list has a SOUND channel. To find out how
to join the mailing list, send mail to linux-activists-
[email protected].

The files Readme, Readme.linux, and CHANGELOG included with the kernel
sound driver source code contain useful information about the sound
card drivers. These can typically be found in the directory
/usr/src/linux/drivers/sound.

The Linux Software Map (LSM) is an invaluable reference for locating
Linux software. Searching the LSM for keywords such as sound is a good
way to identify applications related to sound hardware. The LSM can be
found on various anonymous FTP sites, including
sunsite.unc.edu:/pub/Linux/docs/LSM.gz.

1.6. Version Information

At time of writing the latest Linux sound driver was version 2.90-2
and was included in the Linux kernel version 1.1.50 (and should be the
same in Linux 1.2.0). This is a pre-release version of the upcoming
version 3.0 driver which has a number of new features not in previous
versions, some of which are disabled. While version 2.90 appears to be
quite reliable, if you want a more stable driver you may prefer to use
the version 2.5a sound driver provided in kernel revisions 1.1.10
through 1.1.30.

The author of the sound driver, Hannu Savolainen, typically also makes
available newer BETA releases of the sound driver as kernel patches
before they are included as part of the standard Linux kernel
distribution.

2. Supported Sound Hardware

2.1. Sound Cards

The following sound cards are supported by the Linux kernel:

o Roland MPU-401 MIDI interface

o AdLib

o SoundBlaster (version 1 and 2) and compatibles, including
ThunderBoard and ATI Stereo F/X

o SoundBlaster Pro (version 1 and 2)

o Sound Galaxy NX Pro (in its compatibility mode with SoundBlaster
Pro 2.0 and support for its special mixer)

o SoundBlaster 16

o ProAudioSpectrum 16 (and the compatible Logitech SoundMan 16)

o Advanced Gravis UltraSound (GUS)

o GUS MAX (2.9 driver and later)

o Microsoft Sound System (2.9 driver and later)

o Personal Sound System (2.9 driver and later)

Other sound cards that are claimed to be compatible with one of the
supported sound cards may work if they are hardware (i.e. register
level) compatible. Some cards described as "100% SoundBlaster
compatible" are not register compatible.

The Sound Galaxy NX Pro is supported as a SoundBlaster compatible.
Answer "yes" to the question "Do you want support for the mixer of SG
NX Pro" when the sound driver is configured (in versions prior to 2.9
you must manually add #define __SGNXPRO__ to the sound driver local.h
file).

Note that if you have a Sound Galaxy NX Pro and a Logitech Busmouse,
you must configure the card (using the SGPFIG utility on the driver
diskettes) to use base address 0x240 in order to operate your mouse.
The SGNXPRO has a Covox Speech Thing compatibility mode which has its
control register at the base+0x01C which is the Logitech Busmouse
control register address when the SGNXPRO base address is set to 0x220
(thanks to Matti Aarnio ([email protected]) for this information).

The Linux kernel supports the SCSI port provided on some sound cards
(e.g. ProAudioSpectrum 16). There is also support for CD-ROM drives
attached to the Soundblaster Pro and SoundBlaster 16 CD-ROM port (see
the file /usr/src/linux/drivers/block/README.sbpcd).

A loadable kernel module to support joystick ports, including those
provided on some sound cards, is also available.

Note that the kernel SCSI, CD-ROM, and sound drivers are completely
independent of each other.

2.2. PC Speaker

An alternate sound driver is available that requires no additional
sound hardware; it uses the internal PC speaker. It is mostly software
compatible with the sound card driver, but, as might be expected,
provides much lower quality output and has much more CPU overhead. The
results seem to vary, being dependent on the characteristics of the
individual loudspeaker. For more information, see the documentation
provided with the release.

The current version is 0.7, and can be found at site sunsite.unc.edu
in the file /pub/Linux/kernel/patches/console/pcsndrv-0.7.tar.gz.

2.3. Parallel Port

Another option is to build a digital to analog converter using a
parallel printer port. This provides better sound quality but still
has a lot of CPU overhead. The PC sound driver package mentioned above
supports this, and includes instructions for building the necessary
hardware.

3. Configuring Linux for Sound Support

Configuring Linux to support sound involves the following steps:

1. Installing the sound card.

2. Configuring and building the kernel for sound support.

3. Creating the device files.

4. Testing the installation.

3.1. Installing the Sound Card

To install the card, follow the instructions provided by the
manufacturer. Be sure to note down the jumper settings for IRQ, DMA
channel, etc. If you are unsure, use the factory defaults. Try to
avoid conflicts with other devices (e.g. ethernet cards, SCSI host
adaptors, serial and parallel ports) if possible.

3.2. Configuring the Kernel

If you are using a recent kernel (0.99pl14 or later), the sound
drivers are included with the kernel release. Follow the usual
procedure for building the kernel. When you run make config, a
configuration program will ask you what sound card options you want.
Carefully read the information displayed by this program.

If you are upgrading from an older sound driver, make sure that the
files /usr/include/sys/soundcard.h and /usr/include/sys/ultrasound.h
are symbolic links to the corresponding files in /usr/include/linux,
or that they simply contain the lines #include <linux/soundcard.h> and
#include <linux/ultrasound.h>, respectively.

It's good idea to read the Readme files in the kernel drivers/sound
directory since there could be some last minute information. The file
CHANGELOG contains a list of enhancements and new features since the
previous version.

Particularly with the 2.90 sound driver, read this documentation to be
aware of potential incompatibilities with the older versions of sound
drivers.

3.3. Creating the Device Files

The first time the kernel sound driver is configured, you need to
create the sound device files. The easiest way to do this is to cut
the short shell script from the end of the file Readme.linux (or
possibly Readme) in the directory /usr/src/linux/drivers/sound, and
run it as root.

If your device entries already exist, you might want to ensure they
are correct, e.g. /dev/audio should have major and minor device
numbers 14 and 4. If they are not, or if you are in doubt, run the
above script and it will replace any existing entries with correct
ones.

Some older Linux distributions provided install scripts which created
incorrect sound device files. You may also have a /dev/MAKEDEV script
for creating device files. Using the script included with the kernel
sound driver is preferred since it should always be up to date with
the latest supported sound devices.

3.4. Testing the Installation

You can now follow these steps to verify the sound hardware and
software:

1. Reboot with the new kernel.

Follow your usual procedure for installing and rebooting the new
kernel (keep the old kernel around in case of problems, of course).

2. Verify that the sound card is recognized during kernel
initialization.

Check for a message such as the following on powerup (if they scroll
by too quickly to read, you may be able to retrieve them with the
"dmesg" command):

______________________________________________________________________
snd2 <SoundBlaster Pro 3.2> at 0x220 irq 5 drq 1
snd1 <Yamaha OPL-3 FM> at 0x388 irq 0 drq 0
______________________________________________________________________

This should match your sound card type and jumper settings.

The driver may also display some error messages and warnings during
boot. Watch for these when booting the first time after configuring
the sound driver.

If no sound card is detected when booting, here are some possible
reasons:

o the configuration of the driver is incorrect and the driver was not
able to detect your card in the given I/O address

o the sound driver was configured to be inactive or you booted with
an old kernel (a common error).

3. Check the device file /dev/sndstat.

Reading the sound driver status device file should provide additional
information on whether the sound card driver initialized properly.
Sample output should look something like this:

______________________________________________________________________
% cat /dev/sndstat

Sound Driver:2.90-2 (Fri Aug 26 20:08:45 EDT 1994 [email protected])
Config options: 31402

Installed drivers:
Type 1: OPL-2/OPL-3 FM
Type 2: SoundBlaster

Card config:
SoundBlaster at 0x220 irq 5 drq 1
OPL-2/OPL-3 FM at 0x388 irq 0 drq 0

PCM devices:
0: SoundBlaster Pro 3.2

Synth devices:
0: Yamaha OPL-3

Midi devices:

MIDI Timers:
0: System Timer

1 mixer(s) installed
______________________________________________________________________

If the cat command displays "No such device", the sound driver is not
active in the kernel. Make sure that you booted with the newly
compiled kernel.

If the output contains no devices (PCM, Synth or MIDI), your soundcard
was not detected. Verify that the "HW config" section contains correct
information.

4. Play a simple sound file.

Get hold of a sample sound file, and send it to the sound device as a
basic check of sound output, e.g.

______________________________________________________________________
% cat endoftheworld >/dev/dsp
% cat crash.au >/dev/audio
______________________________________________________________________

(Make sure you don't omit the ">" in the commands above).

Some sample sound files can be obtained from the file snd-
data-0.1.tar.Z.

5. Verify sound recording.

If you have sound input capability, you can do a quick test of this
using commands such as the following:

______________________________________________________________________
# record 4 seconds of audio from microphone
% dd bs=8k count=4 </dev/audio >sample.au
# play back sound
% cat sample.au >/dev/audio
______________________________________________________________________

If these tests pass, you can be reasonably confident that the sound
hardware and software are working. If you experience problems, read
the FAQ section of this document.

4. Applications Supporting Sound

Because The Linux Sound User's Guide describes the available Linux
applications in detail, I will only give here a sample of the types of
applications that you likely want if you have a sound card under
Linux.

As a minimum, you will likely want to obtain the following sound
applications:

o audio file format conversion utility (e.g. Sox)

o mixer utility (e.g. aumix or xmix)

o digitized file player/recorder (e.g. play or wavplay)

o MOD file player (e.g. tracker)

o MIDI file player (e.g. mp)

There are text-based as well as GUI-based versions of most of these
tools. There are also some more esoteric applications (e.g. speech
synthesis) that you may wish to try.

5. Answers To Frequently Asked Questions

This section answers some of the questions that have been commonly
asked on the Usenet news groups and mailing lists.

5.1. What are the various sound device files?

These are the most "standard" device file names, some Linux
distributions may use slightly different names.

/dev/audio
Sun workstation compatible audio device (only a partial
implementation, does not support Sun ioctl interface, just u-law
encoding)

/dev/dsp
digital sampling device

/dev/mixer
sound mixer

/dev/mixer1
second sound mixer

/dev/patmgr0
Patch Manager (not implemented)

/dev/patmgr1
Patch Manager (not implemented)

/dev/sequencer
low level MIDI, FM, and GUS access

/dev/sequencer2
high level sequencer interface (partially implemented)

/dev/midi00
1st raw MIDI port

/dev/midi01
2nd raw MIDI port

/dev/midi02
3rd raw MIDI port

/dev/midi03
4th raw MIDI port

/dev/sndstat
displays sound driver status when read

/dev/audio1
for second sound card

/dev/dsp1
for second sound card

The PC speaker driver provides the following devices:

/dev/pcaudio
equivalent to /dev/audio

/dev/pcsp
equivalent to /dev/dsp
/dev/pcmixer
equivalent to /dev/mixer

5.2. How can I play a sound sample?

Sun workstation (.au) sound files can be played by sending them to the
/dev/audio device. Raw samples can be sent to /dev/dsp. Using a
program such as play is preferable, as it will recognize most file
types and set the sound card to the correct sampling rate, etc.

5.3. How can I record a sample?

Reading /dev/audio or /dev/dsp will return sampled data that can be
redirected to a file. A program such as vrec makes it easier to
control the sampling rate, duration, etc. You may also need a mixer
program to select the appropriate input device.

5.4. Can I have more than one sound card?

Up to two sound cards is supported. It's possible to install a Gravis
UltraSound or MPU-401 with a SoundBlaster, SoundBlaster Pro,
SoundBlaster16 or ProAudioSpectrum16. It's not possible to have a
ProAudioSpectrum16 and SoundBlaster at the same time (the PAS16 has an
SB emulator in it). It's also not possible to have more than one card
of the same type at the same time -- for example, a GUS + GUS
combination is not possible.

You can change the sound card configuration parameters at boot time
using command line options from a boot loader such as LILO. See the
kernel sound driver file Readme.linux for details.

5.5. Error: No such file or directory for sound devices

You need to create the sound driver device files. See the section on
creating device files. If you do have the device files, ensure that
they have the correct major and minor device numbers (some older CD-
ROM distributions of Linux may not create the correct device files
during installation).

5.6. Error: No such device for sound devices

You have not booted with a kernel containing the sound driver or the
I/O address configuration doesn't match your hardware. Check that you
are running the newly compiled kernel and verify that the settings
entered when configuring the sound driver match your hardware setup.

5.7. Error: No space left on device for sound devices

This can happen if you tried to record data to /dev/audio or /dev/dsp
without creating the necessary device file. The sound device is now a
regular file, and has filled up your disk partition. You need to run
the script described in the Creating the Device Files section of this
document.

5.8. Error: device busy for sound devices

Only one process can open a given sound device at one time. Most
likely some other process is using the device in question. One way to
determine this is to use the fuser command:

______________________________________________________________________
% fuser -v /dev/dsp
/dev/dsp: USER PID ACCESS COMMAND
tranter 265 f.... tracker
______________________________________________________________________

In the above example, the fuser command showed that process 265 had
the device open. Waiting for the process to complete or killing it
will allow the sound device to be accessed once again.

5.9. I still get device busy errors!

According to Brian Gough, for the SoundBlaster cards which use DMA
channel 1 there is a potential conflict with the QIC-02 tape driver,
which also uses DMA 1, causing "device busy" errors. If you are using
FTAPE, you may have this driver enabled. According to the FTAPE-HOWTO
the QIC-02 driver is not essential for the use of FTAPE; only the
QIC-117 driver is required. Reconfiguring the kernel to use QIC-117
but not QIC-02 allows FTAPE and the sound-driver to coexist.

(the following explanation was supplied by Harald Albrecht
[email protected])

Some soundcards support using DMA channel 0. The sound driver
configuration program allows this, and the kernel compiles properly,
but accessing the sound device results in a "device busy" error
message.

The reason is that the Linux kernel reserves DMA channel 0 for DRAM
refresh. This is no longer true for modern 386/486 boards which use
their own refresh logic. You can correct it by changing this line in
the file /usr/src/linux/kernel/dma.c:

______________________________________________________________________
static volatile unsigned int dma_chan_busy[MAX_DMA_CHANNELS] = {
1, 0, 0, 0, 1, 0, 0, 0
};
______________________________________________________________________

Replace the first 1 with a 0; this enables DMA channel 0. Don't do the
same with DMA channel 4 as this is cascade and won't work! The code
should now look like this:

______________________________________________________________________
static volatile unsigned int dma_chan_busy[MAX_DMA_CHANNELS] = {
0, 0, 0, 0, 1, 0, 0, 0
};
______________________________________________________________________

Recompile and reboot with the new kernel.

5.10. Partial playback of digitized sound file

The symptom is usually that a sound sample plays for about a second
and then stops completely or reports an error message about "missing
IRQ" or "DMA timeout". Most likely you have incorrect IRQ or DMA
channel settings. Verify that the kernel configuration matches the
sound card jumper settings and that they do not conflict with some
other card.

Another symptom is sound samples that "loop". This is usually caused
by an IRQ conflict.

5.11. There are pauses when playing MOD files

Playing MOD files requires considerable CPU power. You may have too
many processes running or your computer may be too slow to play in
real time. Your options are to:

o try playing with a lower sampling rate or in mono mode

o eliminate other processes

o buy a faster computer

o buy a more powerful sound card (e.g. Gravis UltraSound)

If you have a Gravis UltraSound card, you should use one of the mod
file players written specifically for the GUS (e.g. gmod).

5.12. Compile errors when compiling sound applications

The version 1.0c and earlier sound driver used a different and
incompatible ioctl() scheme. Obtain newer source code or make the
necessary changes to adapt it to the new sound driver. See the sound
driver Readme file for details.

Also ensure that you have used the latest version of soundcard.h and
ultrasound.h when compiling the application. See the installation
instructions at beginning of this text.

5.13. SEGV when running sound binaries that worked previously

This is probably the same problem described in the previous question.

5.14. What known bugs or limitations are there in the sound driver?

See the Readme and CHANGELOG files included with the sound driver
kernel source.

5.15. What version of the sound driver I should use?

If you are using version 1.0c or earlier, you definitely need to
upgrade. Version 1.0c is not compatible with the applications written
for version 2.0 or later.

There have been no significant changes after version 2.0, so if you
don't have problems and that particular version fulfills your
requirements, there are no compelling reasons to move to a more recent
version (this should be true at least until September 1994).

The latest official version is in the latest Linux kernel
distribution. There may also be some test and prototype versions lying
around. If the version number is smaller than 2.9, the version should
be quite safe. Any driver release having a version number of the form
2.99.XX is an incompletely implemented and experimental test release.

If you run DOOM under Linux, see the related question later in this
document.

If you are interested in development of the sound driver, join the
linux activists SOUND channel.

5.16. What do all the sound driver configuration options mean?

During configuration of the sound driver, a configure program is
compiled and executed. This program asks you some questions and then
generates the header file local.h that defines the sound card
configuration.

The configuration file defines (or undefines) the following symbols:

Symbol Meaning
====== =======
KERNEL_SOUNDCARD enable/disable sound driver
EXCLUDE_PAS ProAudioSpectrum support
EXCLUDE_SB SoundBlaster support
EXCLUDE_ADLIB AdLib support
EXCLUDE_GUS Gravis UltraSound support
EXCLUDE_MPU401 MPU-401 MIDI interface support
EXCLUDE_UART6850 6850 MIDI UART support
EXCLUDE_PSS Professional Sound System support
EXCLUDE_GUS16 Gravis UltraSound support
EXCLUDE_GUSMAX Gravis UltraSound Max support
EXCLUDE_MSS Microsoft Sound System support
EXCLUDE_SBPRO SoundBlaster Pro support
EXCLUDE_SB16 SoundBlaster 16 support
EXCLUDE_AUDIO Digitized voice support
EXCLUDE_MIDI MIDI interface support
EXCLUDE_YM3812 FM synthesizer (YM3812/OPL-3) support
EXCLUDE_SEQUENCER MIDI sequencer support
EXCLUDE_PRO_MIDI SoundBlaster Pro MIDI support
EXCLUDE_CHIP_MIDI MIDI on CHIP support
SBC_BASE 0x220 SoundBlaster I/O base address
SBC_IRQ SoundBlaster IRQ number
SBC_DMA SoundBlaster DMA channel
SB16_DMA SoundBlaster 16 DMA channel
SB16_MIDI_BASE base address of SoundBlaster 16 MIDI port
PAS_IRQ ProAudioSpectrum IRQ number
PAS_DMA ProAudioSpectrum DMA channel
GUS_IRQ Gravis UltraSound IRQ number
GUS_DMA Gravis UltraSound DMA channel
GUS_BASE base address of Gravis UltraSound
MPU_IRQ MPU-401 IRQ number
MPU_BASE base address of MPU-401 port
DSP_BUFFSIZE DMA buffer size

Several other defines are also created, setting such things as the
sound driver revision level and the time and date when configure was
run.

There are other parameters that are not set by the configure program.
If you need to change these, edit the file sound_config.h.

To disable the sound driver, run make config and answer "no" to the
"Sound card support?" question.

5.17. What future enhancements are planned for the sound driver?

The sound driver is not just for Linux, it also supports several other
Intel-based Unix operating systems. The package is now called
"VoxWare". Some of the enhancements being considered are:

o implementing full MIDI support

o patch manager support

o document sound card driver (Hacker's Guide)

o support for new sound cards

o miscellaneous bug fixes

5.18. Where are the sound driver ioctls() etc. documented?

These are documented in the Hacker's Guide to VoxWare, currently
available in draft form. The latest version is draft 2, and can be
found on nic.funet.fi in /pub/OS/linux/ALPHA/sound. Note that this
directory is "hidden" and will not appear in directory listings. If
you "cd" to the directory and use the FTP "dir" command, the files are
there.

5.19. What CPU resources are needed to play or record without pauses?

There is no easy answer to this question, as it depends on:

o whether using PCM sampling or FM synthesis

o sampling rate and sample size

o which application is used to play or record

o Sound Card hardware

o disk I/O rate, CPU clock speed, cache size, etc.

In general, any 386 machine should be able to play samples or FM
synthesized music on an 8 bit soundcard with ease.

Playing MOD files, however, requires considerable CPU resources. Some
experimental measurements have shown that playing at 44kHz requires
more than 40% of the speed of a 486/50 and a 386/25 can hardly play
faster than 22 kHz (these are with an 8 bit card sound such as a
SoundBlaster). A card such as the Gravis UltraSound card performs more
functions in hardware, and will require less CPU resources.

These statements assume the computer is not performing any other CPU
intensive tasks.

Converting sound files or adding effects using a utility such as Sox
is also much faster if you have a math coprocessor. The kernel driver
itself does not do any floating point calculations, though.

5.20. Problems with a PAS16 and an Adaptec 1542 SCSI host adaptor

(the following explanation was supplied by [email protected])

Linux only recognizes the 1542 at address 330 (default) or 333, and
the PAS only allows the MPU-401 emulation at 330. Even when you
disable the MPU-401 under software, something still wants to conflict
with the 1542 if it's at its preferred default address. Moving the
1542 to 333 makes everyone happy.

Additionally, both the 1542 and the PAS-16 do 16-bit DMA, so if you
sample at 16-bit 44KHz stereo and save the file to a SCSI drive hung
on the 1542, you're about to have trouble. The DMAs overlap and there
isn't enough time for RAM refresh, so you get the dread ``PARITY ERROR
- SYSTEM HALTED'' message, with no clue to what caused it. It's made
worse because a few second-party vendors with QIC-117 tape drives
recommend setting the bus on/off times such that the 1542 is on even
longer than normal. Get the SCSISEL.EXE program from Adaptec's BBS or
several places on the internet, and reduce the BUS ON time or increase
the BUS OFF time until the problem goes away, then move it one notch
or more further. SCSISEL changes the EEPROM settings, so it's more
permanent than a patch to the DOS driver line in CONFIG.SYS, and will
work if you boot right into Linux (unlike the DOS patch). Next
problem solved.

Last problem - the older Symphony chipsets drastically reduced the
timing of the I/O cycles to speed up bus accesses. None of various
boards I've played with had any problem with the reduced timing except
for the PAS-16. Media Vision's BBS has SYMPFIX.EXE that's supposed to
cure the problem by twiddling a diagnostic bit in Symphony's bus
controller, but it's not a hard guarantee. You may need to:

o get the motherboard distributor to replace the older version bus
chip,

o replace the motherboard, or

o buy a different brand of sound card.

Young Microsystems will upgrade the boards they import for around $30
(US); other vendors may be similar if you can figure out who made or
imported the motherboard (good luck). The problem is in ProAudio's
bus interface chip as far as I'm concerned; nobody buys a $120 sound
card and sticks it in a 6MHz AT. Most of them wind up in 25-40MHz
386/486 boxes, and should be able to handle at least 12MHz bus rates
if the chips are designed right. Exit soapbox (stage left).

The first problem depends on the chipset used on your motherboard,
what bus speed and other BIOS settings, and the phase of the moon.
The second problem depends on your refresh option setting (hidden or
synchronous), the 1542 DMA rate and (possibly) the bus I/O rate. The
third can be determined by calling Media Vision and asking which
flavor of Symphony chip is incompatible with their slow design. Be
warned, though - 3 of 4 techs I talked to were brain damaged. I would
be very leery of trusting anything they said about someone else's
hardware, since they didn't even know their own very well.

5.21. Problems with the FM synthesizer on a SoundBlaster Pro 1

The newer SB Pro has an OPL-3 FM chip, but the older version 1 used
the OPL-2. The sound driver assumed the presence of an OPL-3. Version
2.5 of the sound driver corrects this problem.

5.22. Is the GUS-MAX supported?

With the 2.5a sound driver the GUS-MAX is not explicitly supported but
it will work partially. The driver does not know about the additions
such as the mixer or 16 bit sampling. Booting your system and
initializing the card under MS-DOS and then booting Linux (using ctrl-
alt-del) should allow it to work.

There is support for the GUS-MAX starting with the 2.9 sound driver.

5.23. What if my sound card is not supported?

First, make sure you really have an unsupported sound card. A few
cards are compatible with supported cards (e.g. Logitech SoundMan 16
is compatible with ProAudioSpectrum 16). Post your question to the net
or the Linux activists SOUND channel.

If your card truly is not supported, here are some options:

o replace it with a supported sound card

o write the driver yourself

o ask Hannu Savolainen to add support to the sound driver

The Hacker's Guide to Voxware has some comments on which sound cards
may be supported in future.

5.24. Is it possible to read and write samples simultaneously?

Due to hardware limitations, this is not possible with most sound
cards. The only supported card that can do this is the
ProAudioSpectrum16. See the section on "bidirectional mode" in the
Hacker's Guide to Voxware for more information.

5.25. My SB16 is set to IRQ 2, but configure does not allow this
value.

On '286 and later machines, the IRQ 2 interrupt is cascaded to the
second interrupt controller. It is equivalent to IRQ 9.

5.26. Are the SoundBlaster AWE32 or SoundBlaster16 ASP supported?

Creative Labs is not willing to release programming information for
the ASP and Emu chips used in these cards. Unless they change their
policy, there will be no support for this under Linux.

The Gravis UltraSound card has capabilities similar to the AWE32, and
is supported under Linux. Cards based on other DSPs such as the
Analog Devices ADSP-21xx may be supported in the future.

5.27. If I run Linux, then boot DOS, I get errors and/or sound appli-
cations do not work properly.

This happens after a soft reboot to DOS. Sometimes the error message
misleadingly refers to a bad CONFIG.SYS file.

Most of the current sound cards have software programmable IRQ and DMA
settings. If you use different settings between Linux and MS-
DOS/Windows, this may cause problems. Some sound cards don't accept
new parameters without a complete reset (i.e. cycle the power or use
the hardware reset button).

The quick solution to this problem it to perform a full reboot using
the reset button or power cycle rather than a soft reboot (e.g. Ctrl-
Alt-Del).

The correct solution is to ensure that you use the same IRQ and DMA
settings with MS-DOS and Linux (or not to use DOS :-).

5.28. You say I need to configure and build a kernel - how do I do
that?

This is not the kernel HOWTO (any volunteers?). Until one is written,
try reading the file /usr/src/linux/README; it is reasonably complete.

If you really don't want to compile a kernel, you may be able to find
a precompiled kernel that has the drivers you need as part of a Linux
distribution (e.g. the Slackware "q" series of disks).

5.29. Problems running DOOM under Linux

Users of the recently released port of ID software's game DOOM for
Linux may be interested in these notes.

For correct sound output you need version 2.90 or later of the sound
driver; it has support for the new the real-time "DOOM mode".

The sound samples are 16-bit. If you have an 8-bit sound card there is
a program called sndcvt available that converts the data from 16 to 8
bits on the fly. You also have to patch the DOOM sound server; the
details are explained in the README file.

If performance of DOOM is poor on your system, disabling sound (by
renaming the file sndserver) may improve it.

At least at time of writing, DOOM for Linux does not have any
background music.

5.30. How can I reduce noise picked up by my soundcard?

Using good quality shielded cables and trying the sound card in
different slots may help reduce noise. If the sound card has a volume
control, you can try different settings (maximum is probably best).

Using a mixer program you can make sure that undesired inputs (e.g.
microphone) are set to zero gain.

Some sound cards are simply not designed with good shielding and
grounding and are prone to noise pickup.

Finally, on my system I found that the kernel command line option no-
hlt reduces the noise level. This tells the kernel not to use the halt
instruction when running the idle process loop. You can try this
manually when booting, or set it up using the command append = "no-
hlt" in your LILO configuration file.

5.31. I can play sounds, but not record.

If you can play sound but not record, try these steps:

o use a mixer program to select the appropriate device (e.g.
microphone)

o use the mixer to set the input gains to maximum

o If you can, try to test sound card recording under MS-DOS to
determine if there is a hardware problem

5.32. My "compatible" sound card only works if I first initialize
under MS-DOS.

Some sound card clones are not 100% register compatible with the real
thing; they sometimes contain extra circuitry such as mixers. You may
be able to use these under Linux if you first initialize under MS-DOS,
then soft boot Linux (i.e. Ctrl-Alt-Delete).

One user also reported that he had better results if he used LOADLIN
rather than LILO to boot Linux after initializing his sound card under
MS-DOS (this was with a Diamond sound card).,

They may or may not function reliably. The real solution is to find
out from the manufacturer what the differences are and have the
support added to the sound driver. This has been done, for example,
for the Sound Galaxy NX Pro.