How to use softvol to control the master volume

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This howto describes a workaround if your master volume doesn't work. This happens if your sound card can't control the volume on the hardware side or the driver doesn't support this feature of your sound card. Maybe updating ALSA or using another module will fix the problem. If nothing works, you can define a new virtual pcm device in the.asoundrc file, which controls the volume on the software side.

Contents

• 1 Preparations

• 2 Editing the asoundrc file

  • 2.1 Creating a new softvol device
  • 2.2 Make applications use it

• 3 Common example with dmix

• 4 More complex example
• 5 See also

Preparations

Find out on which existing PCM device you can base your setup. In this device, the audio data will be processed the last on its way to the sound card. In a simple stereo setup, this is problably just thehw:0,0 device. If your card doesn't support hardware mixing, you may have to use a dmix plugin first (seeexample below). In a typical 5.1 surround sound setup, you are probably using the predefinedsurround51 device.

To get a list of possible devices, you may use:

aplay -L

To test this device, use:

speaker-test -D<device name> -c<channel count> -twav

If that command produces sound on the correct channels and you can use it on two different consoles simultaneously, you can use this device. If simultaneous usage doesn't work, seedmix andHardware mixing, software mixingto enable software mixing.

Editing the asoundrc file

Creating a new softvol device

Open the asoundrc file in your favorite editor. E.g. like this:

nano ~/.asoundrc

Now we create a new softvol device be typing:

pcm.softvol {    type            softvol    slave {        pcm         "<device name>"    }    control {        name        "<control name>"        card        0    }}

This will create a new PCM device called softvol, which is controlled by a volume control<control name> and which will pass the sound data with the changed volume to itsslave <device name>.

You have to replace <device name> with the name of the device you determined above and<control name> with what you want to call your new volume control, e.g.SoftMaster. If your card does not have a master volume control at all, you're lucky, because you can name your new volume controlMaster and your new control works like a master volume control is supposed to. To find out, whether such a control exists, run:

amixer controls | grep Master

If this command lists a control named Master, you should not name your new control like this. Unfortunately, existing controls can't be overwritten, so you have to pick a name like SoftMaster. This control will now control everything, but as it is not calledMaster, mixers (likeKMix) won't use it to control master volume, unless you can make them choose another control (likeGMix).

The name you give to your control matters a lot. Some suffixes have special meanings. For example, if you want your softvol to control the playback volume only, the control name must end withPlayback Volume. Such a name prevents the mixer from showing it as a capture control.

Now test your new device with:

speaker-test -Dsoftvol -c<channel count> -twav

Note: The new volume control won't appear immediately! Only after the first usage of the newly defined device (e.g. with the command above), shouldamixer controls | grep <control name> display your new control. Mixers that were already started before the first usage (like KMix) have to be restarted to adopt the changes. If you still don't see the new control, try restarting ALSA or your PC.

Make applications use it

Finally, we'll have to make all applications use this new device. In a simple stereo setup, we can redefine the default device and route it to oursoftvol device (with aplug device, so rate is converted automatically). In that case, add this to your asoundrc file:

pcm.!default {    type             plug    slave.pcm       "softvol"}

With this configuration, our softvol device controls both playback and capture. This may not work properly for some setups. If you prefer thatsoftvol controls the playback only, you must define a new default device which is of typeasym: you can then decide that the playback is controlled by the softvol, and let the capture unchanged. In that case, you should add this to your asoundrc file:

pcm.!default {    type            asym    playback.pcm {        type        plug        slave.pcm   "softvol"    }    capture.pcm {        type        plug        slave.pcm   "<device name>"    }}

If you have a multi channel sound card, you may want to upmix these stereo signals first (seeSurroundSound). It is useful to redefine the surround40,surround51... devices in the same way, so everything is passed through our new softvol device by default.Note that you should not overwrite the device <device name> from above!

Make sure that every application uses a device that is redirected to your softvol device because everything else will not be controlled and may be too loud! If you can't redefine the default devices, you have to configure your applications separately.

Note, if your <device name> happened to be named "default" literally, you will have to go back to the first step, and use "cards.pcm.default" instead of just "default" in pcm.softvol slave pcm block. Otherwise, when trying to replace default output, you will get error

ALSA lib conf.c:4049:(snd1_config_check_hop) Too many definition levels (looped?)Playback open error: -22,Invalid argument

Common example with dmix

In the latest ALSA versions (after 1.0.9)dmix has been enabled by default for the boards that need it, so in order to benefit for both features (softvol+dmix) you must have in \~/.asoundrc something like this:

pcm.!default {    type            plug    slave.pcm       "softvol"   #make use of softvol}pcm.softvol {    type            softvol    slave {        pcm         "dmix"      #redirect the output to dmix (instead of "hw:0,0")    }    control {        name        "PCM"       #override the PCM slider to set the softvol volume level globally        card        0    }}

In this case, the device called dmix is the device<device name> the whole setup is based on (see above).

This works for my crappy C-Media Electronics CMI 9739 - nforce2 integrated 'soundcard' that lacks both volume control and mixing in hardware. I think it will do for many other similar 'soundcards'.

More complex example

I am using an SBLive! Platinum [CT4760P] and theasoundrc file below. Maybe you can solve your problems by understanding this example and maybe copy parts of it.

On the lowest level, I have two softvol devices that pass their data to the predefined devicesfront andrear controlling their volume with the controlsFront Master andRear Master. Amulti plugin merges those two stereo devices into a four channel device. Mymultidevice would be the<device name> device in the text above. The device calledsoftvol controls the volume with a control calledSoftMasterusing themulti device as slave. I then define an upmix device to upmix stereo streams to 4.0 and some downmix devices to downmix 4.1, 5.0, 5.1 and 7.1 streams to 4.0.

To enable recording with multiple applications, I define some dsnoopdevices.dsnoop does the same thing with recording asdmix does with playback. The devicerecording is a regular stereo recording device, whereasrecleft andrecright are mono devices recording only one channel of the stereo stream. If you want to plug two mono mics into the stereo mic plug of your sound card (with an adapter) and record from them separately, this is quite handy, otherwise, this part is not necessary.

Finally I replace the default device with aasym device, redirecting its playback to the upmixing device and its recording to the recording device. This way, thedefault device is playback and recording device at the same time (full duplex). I also create thesurroundX devices redirecting to the corresponding downmix devices.

What I didn't consider yet in my file are devices needed for compatibility withOSS and similar. If I need them one day and change my config file locally, I'll post an update here.

#-------------------------------#  Volume#-------------------------------# volume of all channelspcm.softvol {    type        softvol    slave.pcm   "multi"    control {        name    "SoftMaster"        card    0    }}# splitting the channels in front and rearpcm.multi {    type    multi    slaves {        a.pcm        "frontvol"        a.channels   2        b.pcm        "rearvol"        b.channels   2    }    bindings {        0.slave      a        0.channel    0        1.slave      a        1.channel    1        2.slave      b        2.channel    0        3.slave      b        3.channel    1    }}# frontpcm.rearvol {    type        softvol    slave.pcm   "rear"    control {        name    "Rear Master"        card    0    }}# rearpcm.frontvol {    type        softvol    slave.pcm   "front"    control {        name    "Front Master"        card    0    }}#-------------------------------#  Recording#-------------------------------pcm.recording {    type        dsnoop    ipc_key     2589    slave {        pcm     "hw:0,0"        format  "S16_LE"    }}pcm.recleft {    type        dsnoop    ipc_key     2589    slave {        pcm     "hw:0,0"        format  "S16_LE"    }    bindings.0 0}pcm.recright {    type        dsnoop    ipc_key     2589    slave {        pcm     "hw:0,0"        format  "S16_LE"    }    bindings.0 1}#-------------------------------#  Upmix#-------------------------------# upmix stereo to 40pcm.upmix {    type        route    slave.pcm   "softvol"    slave.channels    4    ttable {        0.0    1        0.2    1        1.1    1        1.3    1    }}#-------------------------------#  Downmix#-------------------------------pcm.downmix41 {    type        route    slave.pcm   "softvol"    slave.channels    4    ttable {        0.0    1        1.1    1        2.2    1        3.3    1    }}pcm.downmix51 {    type        route    slave.pcm   "softvol"    slave.channels    4    ttable {        0.0    0.67        1.1    0.67        2.2    1        3.3    1        4.0    0.33        4.1    0.33    }}pcm.downmix71 {    type        route    slave.pcm    "softvol"    slave.channels    4    ttable {        0.0    0.34        1.1    0.34        2.2    0.67        3.3    0.67        4.0    0.33        4.1    0.33        6.0    0.33        6.2    0.33        7.1    0.33        7.3    0.33    }}#-------------------------------#  Overwrite existing devices#-------------------------------pcm.!default {    type           asym    playback.pcm   "plug:upmix"    capture.pcm    "plug:recording"}pcm.!surround40 {    type         plug    slave.pcm    "softvol"}pcm.!surround41 {    type         plug    slave.pcm    "downmix41"}pcm.!surround50 {    type         plug    slave.pcm    "downmix51"}pcm.!surround51 {    type        plug    slave.pcm    "downmix51"}pcm.!surround71 {    type         plug    slave.pcm    "downmix71"}

See also

• asoundrc
• SurroundSound
• dmix

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