Since the adoption of the Pulse Audio system into many Gnu/Linux distributions, the reliable operation of the Robust Audio Tool (rat) has been problematic. Additionally, using rat with the default ALSA driver has resulted in poorer quality audio for many rat users. Below is described a step by step process which enables rat to select the OSS audio device driver (this is actually a compatibility driver built into ALSA).
The steps outlined in the method below pertain to an Access Grid installation on Ubuntu 9.04 (Jaunty Jackalope). This method may, or may not, work on other Linux distributions.
Method
- in the user's home directory, remove the file .RATdefaults file.
- reboot the machine.
- log in and run rat independently of any other applications e.g. Access Grid. The easiest way to do this is by typing into a terminal:
rat 233.45.67.89/45678
(the numbers are not important, any valid multicast address will do)
- press rat's Options button; this will open a new Preferences panel. In the Preferences panel, select Audio from the Category tab selector button. In the Audio tab, the Audio Device will probably have "ALSA default: Pulse Audio" selected; this is what we want to change. Change the Audio Device setting exactly as follows - taking any short cuts will almost certainly result in failure!
- Select "No Audio Device"
- Press the Apply button. The Preferences panel will disappear and you may see the name of rat's input (under the Talk button) change from Capture to Microphone (this is a good sign).
- Open the Preferences panel again with rat's Options button and select the the Audio category tab as before. Hopefully it will this time show "No Audio Device" as being selected.
- Now change the Audio Device selection to "OSS: Analog Devices AD 1984". The exact text will vary, depending on what audio device is actually installed on your machine. The important part is the "OSS:" part of the label.
- This is also a good time to select 16 kHz as the sample rate and Off for Silence Supression.
- Now press the Apply button (the Preferences panel will disappear) and shutdown rat immediately with its Quit button.
*audioDevice: OSS: Analog Devices AD1984
(again, this will vary depending what audio hardware you have - the important part is that it includes OSS:)
If the *audioDevice entry doesn't look right e.g. includes ALSA: instead of OSS:, then you may as well start all over again, being sure to follow each step above exactly.
Hopefully the .RATdefaults file is correct and you can now run rat successfully, either by itself or from within the Access Grid.
Issues
No OSS device available to select as Audio Device
- ensure you have the alsa-oss package installed
- reboot machine
Contact
Please send any questions, comments, advice etc., to Chris Willing <c.willing _at_ uq.edu.au>