Video Out to TV Issue

Question

My AluMacbook recently stopped filling the screen of my TV and macbook screen when in mirror mode. I have it connected to my Sharp LC-32D50U (max resolution, 1360x768) via the DVI input. When set at 1360x768 i get black borders on the sides of the TV and i also get a single black borders on the top of my macbook. When i set the macbook to 1280x720 the lower portion of picture is cut off on both the TV and the Macbook. I had it working flawlessly yesterday with the TV displaying a beautiful 1360x768 image and the Macbook maintaining its 1280x800 while in mirror mode but now it's randomly not working. Nothing has changed. Any ideas? Already zapped PRAM and issue persists. There is no overscan option on Display settings for me to select and the TV is set to 1360x768. Already reset TV settings and issue still persists as well. Looking for help here. Thanks!

Answer 1

Of course your TV does scaling. That's how a 720P signal fills the entire physical resolution of your TV (which you state as being 1360x768). Thus the original signal into the TV is 1280x720 and the TV upscales that to something near to 1360x768 (the full physical resolution of your LCD display). In this case (by design) the image looks about as good as it can (for your TV) and the image aspect ratios fit exactly which means that there is no distortion in the final image.
If you input a non-standard resolution into your TV it will try to scale the image as best as it can but it is possible that some combinations will result in black bars or overscan (parts of the image will be missing) or distortion in the final image (stretched vertically or horizontally). Your TV could offer some combination of settings that will get you closer to full screen without too much distortion but it's probably not going to handle every input it receives in the best possible way.
Remember also that LCD, DLP, and plasma TVs run at a fixed physical resolution. The only way they can support other "resolutions" is through scaling or by accepting overscan (you lose part of the image) or by placing black bars around the image (the latter to support input resolutions lower than your TV's physical resolution). Typically when inputing a non-standard resolution you will get some type of scaling which may also result in a distortion of the image (if the aspect ratios aren't the same).
The inputs that your TV will probably handle the best ("standard" resolutions) are standard definition NTSC and PAL, 480p, 720p, and 1080i. You can consider NTSC to be equivalent to 640x480. Your TV may also handle some of the standard PC video resolutions (such as VGA, SVGA, and XGA -- 640x480, 800x600, 1024x768 respectively). Anything other than these (or less) is probably supported only at the discretion of the particular TV manufacturer (or by pure "dumb luck").
Of course Apple is also figuring into this as in the "Mirror Displays" mode they apparently adjust the output resolution depending upon the settings for the MacBook's internal LCD (and vice versa). They may do this to try to keep the aspect ratios into reasonably close agreement (there may also be limitations in what Apple's video driver can support and also in what the graphics card can support).
I also would not completely trust what is shown in the MacBook's Displays control panel (for resolution) when in the mirrored display mode. What is shown there may only be approximate, the video driver probably does what it wants in order to achieve what it thinks is best in the mirrored display mode.
I guess what I'm saying after all of this verbiage is that your mileage may vary. However, I still think that setting the MacBook's external (DVI to the TV) resolution to 1280x720 and leaving the MacBook's LCD set to 1280x800 is your best option. With this setting you'll have small black bars on the top and bottom of your MacBook's LCD but the image aspect ratios will match (no distortion in the images) and your TV should run in full screen at near to its best image quality.