MacBuild Tips 'n Tricks

CD Audio Skip

iMacs/PowerMacs with CPU speeds of 40MHz or less and with older CD drives seem to have problems playing CDs using SoundJuicer and RythmBox, the CD ripper and CD player installed by default with Ubuntu. Playback audio will 'skip', producing gaps of a few seconds, and may even cease altogether. Loren has been able to solve this by replacing CD drives in slot loading iMacs and PowerMac Towers. Replacement drives are not always available for iMacs, however. Another solution is to install gxine from the Applications->Add/Remove menu and modify some of its configuration parameters.

gxine configuration parameters are found in the user's home directory, ~/.gxine/config. There may be a global/default version of this somewhere but I haven't looked for it. The parameters for tweaking are media.audio_cd.drive_slowdown, default 4, revised to 0 or 12, and engine.buffers.audio_num_buffers, default 230, revised to 500 (maybe unnecessary). It turns out there is also a visualization parameter there, which can be set to do nothing: gui.post_plugins.audio_visualisation, default goom, revised to None. These revisions make the default operation permanent.

The remaining issue is how to make gxine do the right thing as the default audio auto-startup application. Default preferred applications can be modified through the System->Preferences->Removeable Drives and Media->Multimedia menu. In the Audio CD Disks command box, replace the existing sound-juicer -d %d entry with gxine vcd://dev/cdrom@ (untested as of 15may07).

The modified sections of ~/.gxine/config look like this:

• for cd_drive.slowdown

# slow down disc drive to this speed factor
# numeric, default: 4
#media.audio_cd.drive_slowdown:4
media.audio_cd.drive_slowdown:12

• for audio_num_buffers

# number of audio buffers
# numeric, default: 230
#engine.buffers.audio_num_buffers:230
engine.buffers.audio_num_buffers:500

• for audio_visualization

# Default audio visualisation plugin
# { None  fftgraph  oscope  fftscope  goom }, default: 1
#gui.post_plugins.audio_visualisation:goom
gui.post_plugins.audio_visualisation:None

<still needs a set of step-by-step cli instructions - tr 15may07>

Video setup on Flower Power iMac

iMacs with 500MHz, 600MHz, and 700MHz processors, the so called Flower Power models, have a 750cx version CPU and ATI Rage 128 Pro Ultra video controller. After a normal Edgy alternate CD install, video response is extremely sluggish. For example, mouse cursor movements lag several seconds behind physical mouse movement.

A fix is suggested in http://ubuntuforums.org/showthread.php?t=191080. It consists of the following changes to /etc/X11/xorg.conf:

• in the Module section

Section "Module"
# Load "i2c"
# Load "bitmap"
# Load "ddc"
Load "dri"
Load "extmod"
Load "freetype"
Load "dbe"
Load "glx"
# Load "int10"
# Load "type1"
# Load "vbe"
EndSection

• in the Device section

Section "Device"
Identifier "ATI Technologies, Inc. Rage 128 Pro Ultra TR"
Driver "ati"
Option "UseFBDev" "false"
Option "SWcursor" "true"
Option "ForcePCIMode" "true"
Option "XAANoOffscreenPixmaps"
EndSection

The normal way to apply these changes is

1. CTL+ALT+F1 to use a virtual terminal (command line interface)
2. login as oem
3. command: sudo /etc/init.d/gdm stop
4. edit /etc/X11/xorg.conf, for example, sudo nano /etc/X11/xorg.conf
5. modify the Module and Device sections as indicated above
6. save the file and exit
7. command: sudo /etc/init.d/gdm start

The normal Ubuntu login page should appear with much better video response.

Note that the original problem is observed in Ubuntu Edgy (Release 6.10).  ATI video
driver installation is different in Ubuntu Feisty (7.04), in that a best driver version
is selected to match the detected video controller.  The problem may not be present with 
Feisty, but that has not been tested as of 15May2007.