User:SwifT/Wikified but not merged documents/ALSA guide
What is ALSA?
ALSA, which stands for Advanced Linux Sound Architecture , provides audio and MIDI ( Musical Instrument Digital Interface ) functionality to the Linux operating system. ALSA is the default sound subsystem in the 3.x and 2.6 kernels, thereby replacing OSS ( Open Sound System ), which was used in the 2.4 kernels.
ALSA's main features include efficient support for all types of audio interfaces ranging from consumer sound cards to professional sound equipment, fully modularized drivers, SMP and thread safety, backward compatibility with OSS and a user-space library
alsa-lib to make application development a breeze.
Before you proceed
First, you need to know what drivers your sound card uses. In most cases, sound cards (onboard and otherwise) are PCI based and
lspci will help you in digging out the required information. Please
emerge sys-apps/pciutils to get
lspci , if you don't have it installed already. In case you have a USB sound card,
sys-apps/usbutils might be of help. For ISA cards, try using
sys-apps/isapnptools . Also, the following pages may help users with ISA based sound cards:
For ease of use/explanation, we assume the user has a PCI based sound card for the remainder of this guide.
We now proceed to find out details about the sound card.
# lspci -v | grep -i audio 0000:00:0a.0 Multimedia audio controller: Creative Labs SB Live! EMU10k1 (rev 06)
We now know that the sound card on the machine is a Sound Blaster Live! and the card manufacturer is Creative Labs. Head over to the ALSA Soundcard Matrix page and select Creative Labs from the list. You will be taken to the Creative Labs matrix page where you can see that the SB Live! uses the
emu10k1 module. That is the information we need for now. If you are interested in detailed information, you can click on the link next to the "Details" and that will take you to the
emu10k1 specific page.
If you intend to use MIDI, then you should add
midi to your USE flags in /etc/portage/make.conf before emerging any ALSA packages. Later in the guide, we will show you how to set up .
Configuring the kernel
Let us now configure the kernel to enable ALSA.
genkernelusers should now run
genkernel --menuconfig alland then follow the instructions in .
# cd /usr/src/linux # make menuconfig
The above example assumes that /usr/src/linux symlink points to the kernel sources you want to use. Please ensure the same before proceeding.
Now we will look at some of the options we will have to enable in the kernel to ensure proper ALSA support for our sound card.
Please note that for ease of use, all examples show ALSA built as modules. It is advisable to follow the same as it then allows the use of
alsaconf which is a boon when you want to configure your card. Please do not skip the section of this document. If you still like to have options built-in, ensure that you make changes to your config accordingly.
Device Drivers ---> Sound ---> ## (This needs to be enabled) <M> Sound card support ## (Make sure OSS is disabled) Open Sound System ---> < > Open Sound System (DEPRECATED) ## (Move one step back and enter ALSA) Advanced Linux Sound Architecture ---> <M> Advanced Linux Sound Architecture ## (Select this if you want MIDI sequencing and routing) <M> Sequencer support ## (Old style /dev/mixer* and /dev/dsp* support. Recommended.) <M> OSS Mixer API <M> OSS PCM (digital audio) API ## (You now have a choice of devices to enable support for. Generally, you will have one type of device and not more. If you have more than one sound card, please enable them all here.) ## (Mostly for testing and development purposes, not needed for normal users unless you know what you are doing.) Generic devices ---> ## (For ISA Sound cards) ISA devices ---> ## (IF you had the Gravis, you would select this option) <M> Gravis UltraSound Extreme ## (Move one level back and into PCI devices. Most sound cards today are PCI devices) PCI devices ---> ## (We now select the emu10k1 driver for our card) <M> Emu10k1 (SB Live!, Audigy, E-mu APS) ## (Or an Intel card would be) <M> Intel/SiS/nVidia/AMD/ALi AC97 Controller ## (Or if you have a VIA Card) <M> VIA 82C686A/B, 8233/8235 AC97 Controller ## (Move one level back and select in case you have an USB sound card) USB Devices --->
Now that your options are set, you can (re)compile the kernel and ALSA support for your card should be functional once you reboot into the new kernel. Don't forget to update your GRUB configuration to use the newly built kernel. You can now proceed to and see if everything is working as it should.
alsa-utils forms an integral part of ALSA as it has a truckload of programs that are highly useful, including the ALSA Initscripts. Hence we strongly recommend that you install
# emerge alsa-utils
If you did not compile ALSA as modules, please proceed to the section. The rest of you need to configure ALSA. This is made very easy by the existence of the
alsaconftool provided by
Recent versions of
>=udev-103 ) provide some degree of kernel-level autoconfiguration of your sound card. If possible, try to rely on just letting your kernel automatically setup your sound card for you. Otherwise, use
alsaconf to configure your card, as shown below.
Please shut down any programs that might access the sound card while running
To configure your sound card just type
alsaconf in a shell as root.
You will now see a neat menu guided interface that will automatically probe your devices and try to find out your sound card. You will be asked to pick your sound card from a list. Once that's done, it will ask you permission to automatically make required changes to /etc/modprobe.d/alsa.conf . It will then adjust your volume settings to optimum levels, run
update-modules and start the /etc/init.d/alsasound service. Once
alsaconf exits, you can proceed with setting up the ALSA initscript.
We're now almost all setup. Whichever method you chose to install ALSA, you'll need to have something load your modules or initialize ALSA and restore your volume settings when your system comes up. The ALSA Initscript handles all of this for you and is called
alsasound . Add it to the boot runlevel.
# rc-update add alsasound boot * alsasound added to runlevel boot * rc-update complete.
Next, just check the /etc/conf.d/alsasound file and ensure that SAVE_ON_STOP variable is set to yes. This saves your sound settings when you shutdown your system.
Before we move on to testing, there's one last important thing that needs to be setup. Rule of thumb in a *nix OS: Do not run as root unless needed. This applies here as well ;) How? Well, most of the times you should be logged in as a user and would like to listen to music or access your soundcard. For that to happen, you need to be in the "audio" group. At this point, we'll add users to the audio group, so that they won't have any issues when they want to access sound devices. We'll use
gpasswd here and you need to be logged in as root for this to work.
## (Substitute <username> with your user) # gpasswd -a <username> audio Adding user <username> to group audio
We've completed all the setups and prerequisites, so let's fire up ALSA. If you ran
alsaconf , you can skip this step, since
alsaconf already does this for you.
# /etc/init.d/alsasound start
Now that the required things have been taken care of, we need to check up on the volume as in certain cases, it is muted. We use
alsamixer for this purpose.
## (Opens up a console program. Only required settings are shown) # alsamixer
This is how the ALSA Mixer might look the first time you open it. Pay attention to the Master and PCM channels which both have an MM below them. That means they are muted. If you try to play anything with
alsamixer in this state, you will not hear anything on your speakers.
Now, we shall unmute the channels, and set volume levels as needed.
Both Master and PCM need to be unmuted and set to audible volume levels if you want to hear some output on your speakers.
- To move between channels, use your left and right arrow keys. (<- & ->)
- To toggle mute, move to the specific channel, for example Master and press the m key on the keyboard.
- To increase and decrease the volume levels, use the up and down arrow keys respectively.
Be careful when setting your Bass and Treble values. 50 is usually a good number for both. Extremely high values of Bass may cause jarring on speakers that are not designed to handle them.
After you're all done, your ALSA Mixer should look similar to the one below. Note the 00 instead of the MM and also the volume levels for some optimum settings.
Finally. Some music. If everything above is perfect, you should now be able to listen to some good music. A quick way to test is to use a command line tool like
media-sound/madplay . You could also use something more well known like
mpg123 . If you are an ogg fan, you could use
ogg123 provided by
media-sound/vorbis-tools . Use any player you are comfortable with. As always,
emerge what you need.
## (Install the applications you want) # emerge madplay mpg123 ## (To play .ogg files) # emerge vorbis-tools
And then play your favorite sound track...
# madplay -v /mnt/shyam/Music/Paul\ Oakenfold\ -\ Dread\ Rock.mp3 MPEG Audio Decoder 0.15.2 (beta) - Copyright (C) 2000-2004 Robert Leslie et al. Title: Dread Rock Artist: Paul Oakenfold Album: Matrix Reloaded Year: 2003 Genre: Soundtrack Soundtrack 00:04:19 Layer III, 160 kbps, 44100 Hz, joint stereo (MS), no CRC # ogg123 Paul\ Oakenfold\ -\ Dread\ Rock.ogg Audio Device: Advanced Linux Sound Architecture (ALSA) output Playing: Paul Oakenfold - Dread Rock.ogg Ogg Vorbis stream: 2 channel, 44100 Hz Genre: Soundtrack Transcoded: mp3;160 Title: Dread Rock Artist: Paul Oakenfold Date: 2003 Album: Matrix Reloaded Time: 00:11.31 [04:28.75] of 04:40.06 (200.6 kbps) Output Buffer 96.9%
ALSA and USE
You can now add the
alsa use flag to /etc/portage/make.conf to ensure that your applications that support ALSA get built with it. Some architectures like x86 and amd64 have the flag enabled by default.
If for some reason you're unable to hear sound, the first thing to do would be to check your settings. 80% of the issues lie with muted channels or low volume. Also check your Window Manager's sound applet and verify that volumes are set to audible levels.
/proc is your friend. And in this case, /proc/asound is your best friend. We shall just take a short look at how much info is made available to us there.
## (First and foremost, if /proc/asound/cards shows your card, ALSA has picked up your sound card fine.) # cat /proc/asound/cards 0 [Live ]: EMU10K1 - Sound Blaster Live! Sound Blaster Live! (rev.6, serial:0x80271102) at 0xb800, irq 11 ## (This displays the current running ALSA version) # cat /proc/asound/version Advanced Linux Sound Architecture Driver Version 1.0.8 (Thu Jan 13 09:39:32 2005 UTC). ## (ALSA OSS emulation details) # cat /proc/asound/oss/sndstat Sound Driver:3.8.1a-980706 (ALSA v1.0.8 emulation code) Kernel: Linux airwolf.zion 2.6.11ac1 #2 Wed May 4 00:35:08 IST 2005 i686 Config options: 0 Installed drivers: Type 10: ALSA emulation Card config: Sound Blaster Live! (rev.6, serial:0x80271102) at 0xb800, irq 11 Audio devices: 0: EMU10K1 (DUPLEX) Synth devices: NOT ENABLED IN CONFIG Midi devices: 0: EMU10K1 MPU-401 (UART) Timers: 7: system timer Mixers: 0: SigmaTel STAC9721/23
The other most common issue users face is the dreaded "Unknown symbol in module" error. An example of the same is shown below.
# /etc/init.d/alsasound start * Loading ALSA modules ... * Loading: snd-card-0 ... [ ok ] * Loading: snd-pcm-oss ... WARNING: Error inserting snd_mixer_oss (/lib/modules/2.6.12-gentoo-r6/kernel/sound/core/oss/snd-mixer-oss.ko): Unknown symbol in module, or unknown parameter (see dmesg) FATAL: Error inserting snd_pcm_oss (/lib/modules/2.6.12-gentoo-r6/kernel/sound/core/oss/snd-pcm-oss.ko): Unknown symbol in module, or unknown parameter (see dmesg) [ !! ] * Loading: snd-mixer-oss ... FATAL: Error inserting snd_mixer_oss (/lib/modules/2.6.12-gentoo-r6/kernel/sound/core/oss/snd-mixer-oss.ko): Unknown symbol in module, or unknown parameter (see dmesg) [ !! ] * Loading: snd-seq ... [ ok ] * Loading: snd-emu10k1-synth ... [ ok ] * Loading: snd-seq-midi ... [ ok ] * Restoring Mixer Levels ... [ ok ]
And when you take a look at
dmesg as suggested, you're quite likely to see:
## (Only relevant portions are shown below) # dmesg | less ACPI: PCI Interrupt 0000:02:06.0[A] -> Link [APC3] -> GSI 18 (level, low) -> IRQ 209 snd_mixer_oss: Unknown symbol snd_unregister_oss_device snd_mixer_oss: Unknown symbol snd_register_oss_device snd_mixer_oss: Unknown symbol snd_mixer_oss_notify_callback snd_mixer_oss: Unknown symbol snd_oss_info_register snd_pcm_oss: Unknown symbol snd_unregister_oss_device snd_pcm_oss: Unknown symbol snd_register_oss_device snd_pcm_oss: Unknown symbol snd_mixer_oss_ioctl_card snd_pcm_oss: Unknown symbol snd_oss_info_register snd_mixer_oss: Unknown symbol snd_unregister_oss_device snd_mixer_oss: Unknown symbol snd_register_oss_device snd_mixer_oss: Unknown symbol snd_mixer_oss_notify_callback snd_mixer_oss: Unknown symbol snd_oss_info_register
The above issue is caused when you switch from the
alsa-driver to in-kernel ALSA because when you unmerge
alsa-driver the module files are config protected and hence get left behind. So, when you switch to in-kernel drivers, running
modprobe gives you a mix of
alsa-driver and in-kernel modules thus causing the above errors.
The solution is quite easy. We just need to manually remove the problem causing directory after you unmerge
alsa-driver . Be sure to remove the correct kernel version and not the current one!
# rm -rf /lib/modules/$(uname -r)/alsa-driver
Another reason for error messages similar to the ones above could be a file in /etc/modprobe.d supplying a
device_mode parameter when it isn't required. Confirm that this is indeed the issue and find out which file is the culprit.
## (Check dmesg to confirm) # dmesg | grep device_mode snd: Unknown parameter `device_mode' ## (Now, to get to the source of the issue) # grep device_mode /etc/modprobe.d/*
Usually it is a file called alsa with the line
options snd device_mode=0666 . Remove this line and restart the
alsasound service and that should take care of this issue.
Other things ALSA
Setting up MIDI support
First, check to make sure that you enabled the
midi USE flag in /etc/portage/make.conf . If you didn't, go ahead and add it now. You will also need to re-emerge any ALSA packages that use the
midi flag, such as
If your sound card is one of those that come with on-board MIDI synthesizers and you would like to listen to some .mid files, you have to install
awesfx which is basically a set of utilities for controlling the AWE32 driver. We need to install it first. If you don't have a hardware synthesizer, you can use a virtual one. Please see the section on for more information.
# emerge awesfx
You will need to copy over SoundFont (SF2) files from your sound card's driver CD or a Windows installation into /usr/share/sounds/sf2/ . For example a sound font file for the Creative SBLive! card would be 8MBGMSFX.SF2.
After copying over the Soundfont files, we can then play a midi file as shown. You can also add the
asfxload command to /etc/conf.d/local.start , so that the sound font is loaded every time the system starts up.
/mnt paths mentioned in the code listing(s) below will not be the same in your machine. They are just an example. Please be careful to change the path to suit your machine.
## (First, copy the Soundfont) # cp /mnt/win2k/Program\ Files/CreativeSBLive2k/SFBank/8MBGMSFX.SF2 /usr/share/sounds/sf2/ ## (Or get it from your SoundBlaster CD) # cp /mnt/cdrom/AUDIO/ENGLISH/SFBANK/8MBGMSFX.SF2 /usr/share/sounds/sf2/ ## (We load the specific Soundfont) # asfxload /usr/share/sounds/sf2/8MBGMSFX.SF2
You can now play midi files using a program like
aplaymidi . Run
aplaymidi -l to get a list of available ports and then pick one to play the file on.
## (Check open ports) # aplaymidi -l Port Client name Port name 64:0 EMU10K1 MPU-401 (UART) EMU10K1 MPU-401 (UART) 65:0 Emu10k1 WaveTable Emu10k1 Port 0 65:1 Emu10k1 WaveTable Emu10k1 Port 1 65:2 Emu10k1 WaveTable Emu10k1 Port 2 65:3 Emu10k1 WaveTable Emu10k1 Port 3 ## (Pick a port, and play a mid file) # aplaymidi --port=65:0 /mnt/shyam/music/midi/mi2.mid
If your sound card lacks a hardware synthesizer, you could use a virtual one like
timidity++ . Installation is a breeze.
# emerge timidity++
For timidity to play sounds, it needs a sound font. Fortunately, the ebuild will install some sound font packages for you. There are a few other font packages available in Portage, such as
timidity-eawpatches . You can have multiple sound font configurations installed, and you can place your own in /usr/share/timidity/ . To switch between different timidity configurations, you should use
# eselect timidity list # eselect timidity set eawpatches
Don't forget to add
timidity to the default runlevel.
# rc-update add timidity default # /etc/init.d/timidity start
You can now try out files.
Tools and Firmware
Some specific sound cards can benefit from certain tools provided by the
alsa-firmware packages. You may install either with a simple
# emerge alsa-tools
Multiple sound cards
You can have more than one sound card in your system simultaneously, provided that you have built ALSA as modules in your kernel. You just need to specify which should be started first in /etc/modprobe.d/alsa.conf . Your cards are identified by their driver names inside this file. 0 is the first card, 1 is the second, and so on. Here's an example for a system with two sound cards.
options snd-emu10k1 index=0 options snd-via82xx index=1
Or, if you have two cards that use the same driver, you specify them on the same line, using comma-separated numbers. Here's an example for a system with three sound cards, two of which are the same Intel High Definition Audio card.
options snd-ymfpci index=0 options snd-hda-intel index=1,2
You may want to install some plugins for extra functionality.
alsa-plugins is a collection of useful plugins, which include: PulseAudio output, a sample rate converter, jack (a low-latency audio server), and an encoder that lets you output 6-channel audio through digital S/PDIF connections (both optical and coaxial). You can choose which of its plugins you want installed by adding their USE flags to /etc/portage/package.use .
# emerge -avt alsa-plugins
A big thank you to...
Everyone who contributed to the earlier version of the Gentoo ALSA Guide: Vincent Verleye, Grant Goodyear, Arcady Genkin, Jeremy Huddleston, John P. Davis, Sven Vermeulen, Benny Chuang, Tiemo Kieft and Erwin.
We would like to thank the following authors and editors for their contributions to this guide:
- Shyam Mani
- Joshua Saddler
- Diego Pettenò