AccessGrid.org

Getting the Sound Working

The following steps provides information on how to get audio working on an Access Grid

Getting the sound working for your Access Grid will probably be the most difficult part of this whole process. The setup will vary, as many computer workstations generally will have different sound cards.

Audio Setup

Since the release of Fedora 8 (in which Fedora is the basis for Scientific Linux), "PulseAudio is now installed and enabled by default. PulseAudio is an advanced sound server compatible with nearly all existing Linux sound systems. PulseAudio allows for hot-switching audio outputs, individual volume controls for each audio stream, networked audio, and more." as quoted from Release Highlights.

For more information about PulseAudio, it is suggested to visit the PulseAudio website.

Removal of alsa-pluggins-pulseaudio

Through testing, it has been found that the package alsa-pluggins-pulseaudio is required to be removed for the AG software to work. (On some systems, not removing this package will cause "rat" issues and may even "lock up" the entire system.)

By executing the command within a terminal session (as super user)

yum remove alsa-plugins-pulseaudio

will remove this package!

For other sound difficulties, it is suggested to visit http://www.pulseaudio.org/wiki/PerfectSetup.

Note: If you do some future updates, you may have to remove "alsa-plugins-pulseaudio" again, as it may get re-installed, especially if updating KDE

ALSA vs OSS Audio Device

In the past, it has always been recommended to use the OSS audio device over the ALSA device for quality reasons. A number of fixes have occurred recently within the kernel and now it is recommended to use the ALSA driver!

Sound Preferences

To ensure that the correct audio device is selected for both input and output channels, this can be configured within Sound preferences (Gnome menu option “System -> Preferences -> Sound”).

By selecting the "Hardware" tab, it allows you to change some settings within each of the audio devices installed.

By selecting the "Input" tab, this allows you to select the default input audio device.

By selecting the "Output" tab, this allows you to select the default output audio device.

Rat Configurations

Before you start to setup the sound, there is an option that needs configuring.

  • In RAT, click on the “Options” button. This will bring up a window similar to the one below.

fc5install-sound-setup1

  • Click on the button “personal” and select “audio”. This will bring up another window.

fc5install-sound-setup2

  • Silence Suppression may be on “Automatic” by default. It is recommended that you configure this option to be “Off”. It is also recommended that the option "Echo Suppression" is turned off as well. Once these options have been selected, click on the "Apply" Button. This will bring you back to the RAT window.
  • Also, ensure that the selected "Audio Device" is the correct device. Simply click on the Device button to change devices.  It has been found that when using the ALSA default: [device] device, audio artefacts are introduced.  It is recommended to select the ALSA #: [device].

    For example, select

    ALSA 1: HDA Intel 

    Rather than

    ALSA Default: HDA Intel

  • To set up the sound you will need to watch the talk and listen meter levels in RAT. You will probably want to see the talk and listen meters move up until about 2-3 bars from the end when someone is talking in their normal voice, as seen below in the second.

fc5install-sound-setup3

fc5install-sound-setup4

  • It is best to get the sound working collaboratively with other people. If the talk levels in RAT are not moving when you talk, you will need to change the input levels. When other people are talking your RAT "Listen" meter should be moving. If the meter in RAT does not move, you will need to adjust the output levels. These setting can be adjusted using "Volume Control" and/or alsamixer.
    • Another possible setting to check and test, is in the options menu within RAT: Category->Audio, check that a Audio Device is present.

Saving Rat Settings

There are times, such as when you want to change the audio device and other options (such as displaying the "Interface -> Powermeters") and want to save these settings to be default options. This would then configure these settings to be used each time rat is started.

To save any changes to "rat", simply hit "quit" button on Rat. This will write the current settings to the ~/.RATdefaults file.

You can then click on the "enable/disable audio button" within the Access Grid Venue Client to first disable, then again to enable. This should now restart rat with the new settings configured.

Additional Settings

If you are experiencing loop-back audio, or you find changing the "talk" gain has no real effect, you may have to change the “force_ac97” setting within the AudioService.

  • This can be achieve by running the VenueClient, then selecting “Preferences” -> “Manage My Node” options within the menu.
  • Then by selecting the audio service and right click and select the "Configure" option, this will display the Audio Config Dialog.

  • Then change the setting to “true” for the force_ac97 option. Click on the “OK” button. You will then need to store the node configuration on the “Access Grid Node Management” for the changes to be saved. Rememeber to ensure this is kept standard by saving the configuration.

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