PowerBook displays black lines when exporting video

"I noticed a problem when using the NTSC output in either S-Video or composite mode where scan lines 10 and 12 (counting from the bottom of the image at 640 x 480 resolution) display only black lines every other frame. In order to recreate the behavior the TV Mirroring Control Strip must be set to Best for Video and Overscan (if available). I've seen this occur on several other PowerBooks that use an ATI RAGE controller. I captured the S-video output of the PowerBook to miniDV and then brought the clip into Final Cut Pro. I exported a second of the video as stills (30 frames) and I could see the lines in alternating interlacing frames. I have posted an example here.

I recently purchased an ATI RADEON PCI card for a dual G4, and it exhibited the exact same problem with the NTSC output. However, it also included several additional pieces of system software that I believe can fix the problem. The ATI Display has a dialog box in the Mac2TV section which permits an on/off toggle of Hard Synch to TV. When it is set the black lines are eliminated and all frames appear correct. I do not believe this fix has been implemented for the PowerBook."