[[http://lists.linuxaudio.org/pipermail/linux-audio-user/2008-November/056243.html|Based on this mail on LAU by Nathanael Anderson]]

~~META:title=Intel-HDA JACK low latency howto~~
~~META:desc=How to get Intel-HDA cards working with low latency, in duplex operation~~

====== Intel-HDA JACK low latency howto ======

I've seen asked many times on the list how to get intel-hda cards working with low latency, in duplex operation. Here is a full, step by step, on how I got 4ms latency. I'm using a Dell M90 with a Quadro fx 1500, attached to a docking station with a Maudio Delta 66 pci card (secondary card) in it, the binary Nvidia drivers and Compiz. So if you were wondering, it is possible. :)

===== Kernel =====

(I'm not going to walk you through how to compile a kernel)

the last kernel before the big kernel lock regression
  wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.24.7.tar.bz2

  tar xvjf linux-2.6.24.7.tar.bz2
  cd linux-2.6.24.7.tar.bz2
  wget http://www.kernel.org/pub/linux/kernel/projects/rt/patch-2.6.24.7-rt21.bz2

if you don't see it here look in the [[http://www.kernel.org/pub/linux/kernel/projects/rt/older/|projects/rt/older/]] directory

  bzcat ../patch-2.6.24.7-rt21.bz2

Download this config: {{:wiki:config-intel-hda.txt}}

  mv config-intel-hda.txt .config.old
  make oldconfig

build and install your kernel

===== Module Options =====

Add the following line to the file your distribution has its module options in
(in ubuntu it is /etc/modules.d/alsa-base)

  options snd-hda-intel model=ref position_fix=1 enable=1 index=0

===== Mixer Options (VERY IMPORTANT ! ! !) =====

enable capture/record elements in mixer

**without this jack can't play nicely with intel-hda cards**

===== RT Permissions =====

In most modern distros /etc/security/limits.conf is where realtime permissions are set, I added these 3 lines to it, and added myself to the @audio group in /etc/group

  @audio          -       memlock         1024000
  @audio          -       nice            -10
  @audio          -       rtprio          99

===== Jack options =====

I use qjackctl to set these

  * put a check in Realtime
  * Priority 89
  * Frames/Period 64
  * Sample Rate 48000
  * Periods/Buffer 3

===== Debian (9 sept 2013) =====
  * Realtime does not have to be compiled anymore into the kernel: it is already by default. I know at least on "Debian 7.1 //Wheezy// amd64" & latest UbuntuStudio, perhaps more.
  * On Debian the location of the config file is **/etc/modprobe.d/alsa-base.conf**
  * Further config files are located at **~/.asoundrc** (userwide) and **/etc/asound.conf** (systemwide). Note that ~/.asoundrc works out as /home/CURRENTUSERNAME/.asoundrc so be aware that using ~ while being root (or su in a terminal) works out as /home/root/.asoundrc, which might not be what you want.
  * The 'index=' setting seems to not work properly, and give errors during boot about //card not ready for slot// or something ( I will try to reproduce later). The solution is to not use the line with 'index=', but instead use '**options snd slots=snd-hda-intel**'. This will put snd-hda-intel in slot 0. If you have more cards, like me, you can sum them all up, 'options snd slots=snd-ca0106,snd-hda-intel' will assign my SB Audigy (ca0106) to slot 0, and my motherboard audio (hda-intel) to slot 1. You can also keep slot 0 'open', and only assign slot 1: 'options snd slots=,snd-hda-intel' will put the hda-intel in slot 1, keeping slot 0 open for any takers. Note the comma.
  * The '**nice**' option is not needed, it is commented out on my setup.
  * Example of /etc/asound.conf that will capture sound from device 0 on 'CA0106', and playbacks sound to device 1 on 'Intel':
  Use '**aplay -l**' to list all playback devices, and '**arecord -l**' to list all capture devices. Results are like '//card 1: **Intel** [HDA Intel], device 1: ALC1200 Digital [ALC1200 Digital]// ', where the part made bold is the name used. Case sensitive.
  pcm.!default {                   # declare the default PCM device
    type asym                      # combine playback and capture devices
    playback.pcm {                 ### Playback object ###
      type plug                    # convert audio to mixer format
      slave.pcm {
        type dmix                  # mix multiple audio streams
        ipc_key 69569              # shared memory key; must be unique, just make one up
        ipc_key_add_uid true       # add UID to shared mem key
        ipc_perm 0600              # shared mem file permissions
        slave {
          pcm {
            type hw                # define the playback hardware
            card "Intel"           # YOUR playback card name
            device 1               # YOUR playback device on that card
          }
          format S32_LE            # YOUR bits per sample format
          rate 48000               # YOUR samples per second
          channels 2               # number of audio channels
        }
      }
    }
    capture.pcm {                  ### Capture object ###
      type plug                    # convert audio format from the hardware
      slave {
        pcm {
          type hw                  # define the capture hardware
          card "CA0106"            # YOUR capture card name 
          device 0                 # YOUR capture device on that card
        }
      }
    }
  }
===== Comments =====

Please comment here if this guide worked for you or what you had to do to get it working:



!-- Comments end here --!
{{tag>Sound_Cards_and_Drivers jack howtos_and_faqs hardware_linux}}