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ALSA how-to (en版)

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发表于 2004-8-29 18:18:16 | 显示全部楼层 |阅读模式
Make a directory to store the alsa source code in.

        cd /usr/src
        mkdir alsa
        cd alsa
        cp /downloads/alsa-* .

Now unzip and install the alsa-driver package

        bunzip2 alsa-driver-xxx
        tar -xf alsa-driver-xxx
        cd alsa-driver-xxx
        ./configure --with-cards=au8820 -withsequencer=yes;make;make install

NB. If you are using drivers before 0.9.4 then you need to run

        ./snddevices

If you use devfs then you should not run the snddevices script

The snddevices script sets the permissions for the devices it creates to root. You should

chmod     a+rw /dev/dsp /dev/mixer /dev/sequencer /dev/midi

Now unzip and install the alsa-lib package

        cd ..
        bunzip2 alsa-lib-xxx
        tar -xf alsa-lib-xxx
        cd alsa-lib-xxx
        ./configure;make;make install

Now unzip and install the alsa-utils package

        cd ..
        bunzip2 alsa-utils-xxx
        tar -xf alsa-utils-xxx
        cd alsa-utils-xxx
        ./configure;make;make install

Now insert the modules into the kernel.

modprobe snd-au8820;
modprobe snd-pcm-oss;
modprobe snd-mixer-oss;
modprobe snd-seq-oss

NB. For drivers older than 0.9.0beta11 use:

        modprobe snd-card-au8820

Now adjust your soundcards volume levels. All mixer channels are muted by default. You must use a native mixer program to unmute appropriate channels, for example alsamixer from the alsa-utils package. Note that some usb-audio devices do not have internal mixer controls.

        alsamixer


You can also look at the utils/alsasound file. This script is designed for the RedHat distribution, but it can be used with other distributions which use System V style rc init scripts. This will allow you to load your modules at boot time. If you want to do this you could just compile them into the kernel instead and save yourself the hassle of coming to terms with the rc init scripts.

Setting up modprobe and kmod support

Before you send a mail complaining that "I don't have /etc/modules.conf, where do I find it ....." ,The /etc/conf.modules has been deprecated with a few distro's so in your case, it may still be /etc/conf.modules. Basically they are both the same, but recent version of modutils uses /etc/modules.conf instead. Nothing to worry about as such, optionally please update to latest version of modutils. This should solve your problem.

Here's the example for this card. Copy and paste this to the bottom of your /etc/modules.conf file.


Note to debian users: You need to save this information into a file in the /etc/modutils/ directory (Eg. /etc/modutils/alsa) and run update-modules

        # ALSA portion
        alias char-major-116 snd
        alias snd-card-0 snd-au8820
        # module options should go here

        # OSS/Free portion
        alias char-major-14 soundcore
        alias sound-slot-0 snd-card-0
       
        # card #1
        alias sound-service-0-0 snd-mixer-oss
        alias sound-service-0-1 snd-seq-oss
        alias sound-service-0-3 snd-pcm-oss
        alias sound-service-0-8 snd-seq-oss
        alias sound-service-0-12 snd-pcm-oss
  

NB. For drivers older than 0.9.0beta11 use:

        snd-card-au8820

To copy and paste the above to your /etc/modules.conf file follow these instructions.

A short explanation of what happens in the /etc/modules.conf file

Native Devices

After the main multiplexer is loaded, its code requests top level sound card module. String snd-card-%i is requested for native devices where %i is sound card number from zero to seven. String sound-slot-%i is requested for native devices where %i is slot number for ALSA owner this means sound card number. The options line allows you to set various config options before the module is loaded. String snd_id lets you set the name of the card which is returned in the /proc/asound/cards file. Other options may be available which are card specific. The options for these are found in the INSTALL file or above.

        xyz@localhost#pico /etc/modules.conf

        # ALSA portion
        alias snd-card-0 snd-interwave
        alias snd-card-1 snd-cmipci
        options snd-cmipci id="first" enable_midi="1"
       
        # OSS/Free portion
        alias sound-slot-0 snd-card-0
        alias sound-slot-1 snd-card-1
       

NB. For drivers older than 0.9.0rc5 use:

        options snd-cmipci snd_id="first" snd_enable_midi="1"

The "snd_" prefix has been removed from the "module options" to fit with the kernel standard.

Autoloading OSS/free emulation

We are finished at this point with the configuration for ALSA native devices, but you may also need autoloading for ALSA add-on OSS/Free emulation modules. At this time only one module does not depend on any others, thus must be loaded separately, snd-pcm1-oss.o. String sound-service-%i-%i is requested for OSS/Free service where first %i means slot number e.g. card number and second %i means service number.

        xyz@localhost#pico
        /etc/modules.conf

        # OSS/Free portion - card #1
        alias sound-slot-0 snd-card-0
        alias sound-service-0-0 snd-mixer-oss
        alias sound-service-0-1 snd-seq-oss
        alias sound-service-0-3 snd-pcm-oss
        alias sound-service-0-8 snd-seq-oss
        alias sound-service-0-12 snd-pcm-oss
       
        # OSS/Free portion - card #2 (cmipci)
        alias sound-slot-1  snd-card-1
        alias sound-service-1-0 snd-mixer-oss
        alias sound-service-1-3 snd-pcm-oss
        alias sound-service-1-12 snd-pcm-oss

The alias for snd-seq-oss is not necessary on the second device, because there is only one /dev/sequencer, regardless how many devices you have.

The .asoundrc file

Find out more about this file here.

This file allows the you to have more advanced control over your card/device. Some very useful applications will not work without it. The .asoundrc file consists of definitions of the various cards available in your system. It also gives you access to the pcm plugins in alsa-lib. These allow you to do tricky things like combine your cards into one or access multiple i/o's on your mulitchannel card.

Below is the most basic definition.

Make a file called .asoundrc in your home and/or root directory.

        vi /home/xxx/.asoundrc

copy and paste the following into the file then save it.

        pcm.au8820 {
           type hw
           card 0
        }

        ctl.au8820 {
           type hw
           card 0
        }
 楼主| 发表于 2004-8-29 23:19:54 | 显示全部楼层
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发表于 2004-8-30 00:52:02 | 显示全部楼层

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 楼主| 发表于 2004-9-4 12:05:57 | 显示全部楼层
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