Ubuntu – Alsa snd-aloop kernel module for 16.04 or 14.04 server

alsasound

I'm trying to record audio from an application on a server with FFmpeg. Apparently, I need an Alsa loopback driver for this. I've read that this should work on Ubuntu 14.04:

modprobe snd-aloop

Unfortunately, that isn't available on my kernel:

modprobe: FATAL: Module snd-aloop not found.

Is this a difference between server and desktop distributions of Ubuntu?

How can I get this driver installed?

Googling leads me here: https://wiki.ubuntu.com/Audio/InstallingLinuxAlsaDriverModules

That page then says I need to go here: https://wiki.ubuntu.com/Audio/UpgradingAlsa

That page sensibly says to use DKMS: https://wiki.ubuntu.com/Audio/UpgradingAlsa/DKMS

However, the DKMS instructions only list Intel drivers: https://code.launchpad.net/~ubuntu-audio-dev/+archive/ubuntu/alsa-daily/+packages

Am I missing something?

Best Answer

  • Well, I could try loading it in Ubuntu 16.04 Desktop Edition (VirtualBox with disabled audio card). As you can see, it is installed with linux-image-extra package which may be you don't have already.

    ~$ modinfo snd-aloop

filename:       /lib/modules/4.4.0-42-generic/kernel/sound/drivers/snd-aloop.ko
license:        GPL
description:    A loopback soundcard
author:         Jaroslav Kysela <perex@perex.cz>
srcversion:     0A4CE16C028DAB4BC8260D3
depends:        snd-pcm,snd
intree:         Y
vermagic:       4.4.0-42-generic SMP mod_unload modversions 
parm:           index:Index value for loopback soundcard. (array of int)
parm:           id:ID string for loopback soundcard. (array of charp)
parm:           enable:Enable this loopback soundcard. (array of bool)
parm:           pcm_substreams:PCM substreams # (1-8) for loopback driver. (array of int)
parm:           pcm_notify:Break capture when PCM format/rate/channels changes. (array of int)

~$ dpkg -S /lib/modules/4.4.0-42-generic/kernel/sound/drivers/snd-aloop.ko

linux-image-extra-4.4.0-42-generic: /lib/modules/4.4.0-42-generic/kernel/sound/drivers/snd-aloop.ko

~$ sudo modprobe snd-aloop
~$ alsa-info.sh --stdout

upload=true&script=true&cardinfo=
!!################################
!!ALSA Information Script v 0.4.64
!!################################

!!Script ran on: Thu Mar 23 10:28:23 UTC 2017


!!Linux Distribution
!!------------------

Ubuntu 16.04 LTS \n \l DISTRIB_ID=Ubuntu DISTRIB_DESCRIPTION="Ubuntu 16.04 LTS" NAME="Ubuntu" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 16.04 LTS" HOME_URL="http://www.ubuntu.com/" SUPPORT_URL="http://help.ubuntu.com/" BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/" UBUNTU_CODENAME=xenial


!!DMI Information
!!---------------

Manufacturer:      innotek GmbH
Product Name:      VirtualBox
Product Version:   1.2
Firmware Version:  VirtualBox


!!Kernel Information
!!------------------

Kernel release:    4.4.0-42-generic
Operating System:  GNU/Linux
Architecture:      x86_64
Processor:         x86_64
SMP Enabled:       Yes


!!ALSA Version
!!------------

Driver version:     k4.4.0-42-generic
Library version:    1.1.0
Utilities version:  1.1.0


!!Loaded ALSA modules
!!-------------------

snd_aloop


!!Sound Servers on this system
!!----------------------------

Pulseaudio:
      Installed - Yes (/usr/bin/pulseaudio)
      Running - Yes


!!Soundcards recognised by ALSA
!!-----------------------------

 0 [Loopback       ]: Loopback - Loopback
                      Loopback 1


!!PCI Soundcards installed in the system
!!--------------------------------------



!!Advanced information - PCI Vendor/Device/Subsystem ID's
!!-------------------------------------------------------



!!Modprobe options (Sound related)
!!--------------------------------

snd_pcsp: index=-2
snd_usb_audio: index=-2
snd_atiixp_modem: index=-2
snd_intel8x0m: index=-2
snd_via82xx_modem: index=-2
snd_atiixp_modem: index=-2
snd_intel8x0m: index=-2
snd_via82xx_modem: index=-2
snd_usb_audio: index=-2
snd_usb_caiaq: index=-2
snd_usb_ua101: index=-2
snd_usb_us122l: index=-2
snd_usb_usx2y: index=-2
snd_cmipci: mpu_port=0x330 fm_port=0x388
snd_pcsp: index=-2
snd_usb_audio: index=-2


!!Loaded sound module options
!!---------------------------

!!Module: snd_aloop
    enable : Y,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N,N
    id : (null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null)
    index : -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
    pcm_notify : 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    pcm_substreams : 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8


!!ALSA Device nodes
!!-----------------

crw-rw----+ 1 root audio 116,  2 Mar 23 11:18 /dev/snd/controlC0
crw-rw----+ 1 root audio 116,  4 Mar 23 11:18 /dev/snd/pcmC0D0c
crw-rw----+ 1 root audio 116,  3 Mar 23 11:18 /dev/snd/pcmC0D0p
crw-rw----+ 1 root audio 116,  6 Mar 23 11:18 /dev/snd/pcmC0D1c
crw-rw----+ 1 root audio 116,  5 Mar 23 11:18 /dev/snd/pcmC0D1p
crw-rw----+ 1 root audio 116,  1 Mar 23 11:18 /dev/snd/seq
crw-rw----+ 1 root audio 116, 33 Mar 23 11:18 /dev/snd/timer

/dev/snd/by-path:
total 0
drwxr-xr-x 2 root root  60 Mar 23 11:18 .
drwxr-xr-x 3 root root 200 Mar 23 11:18 ..
lrwxrwxrwx 1 root root  12 Mar 23 11:18 platform-snd_aloop.0 -> ../controlC0


!!Aplay/Arecord output
!!--------------------

APLAY

**** List of PLAYBACK Hardware Devices ****
card 0: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7

ARECORD

**** List of CAPTURE Hardware Devices ****
card 0: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7

!!Amixer output
!!-------------

!!-------Mixer controls for card 0 [Loopback]

Card hw:0 'Loopback'/'Loopback 1'
  Mixer name    : 'Loopback Mixer'
  Components    : ''
  Controls      : 97
  Simple ctrls  : 1
Simple mixer control 'PCM',0
  Capabilities: pvolume
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 255
  Mono:
  Front Left: Playback 255 [100%] [0.00dB]
  Front Right: Playback 255 [100%] [0.00dB]
...

  • For general solution, look at:

    How do I find the package that provides a file?

  • Just checked a fresh Ubuntu 16.04.1 Server. It has the snd-aloop module. linux-image-extra* package was installed as dependency of linux-image-generic meta package which is also a dependency of linux-generic meta package. So a quick fix:

    sudo apt install linux-generic
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