For me, the issue is that I actually have a number of 4:3 videos which
do not have black sidebars, but have a static image encoded into the video instead - which is 100x worse.
Black bars are actually not an issue for my set, and what I would prefer to see.
It probably wouldn't help much to set the background color of a 4:3 video to something other than black, since most 4:3 videos do not fill the frame entirely, and a number of them are now 16:9 with sidebars encoded into them. (whether that is black or a static image)
A solution which addresses all of this would be to have a control that enables Media Center to draw its own pillarboxing on top of the video.
You could set a color in the options menu (black for me, a shade of gray for you) and then you need a slider to adjust the width of it, since not all content is exactly 4:3 (1.33:1) and it applies to other aspect ratios like 1.66:1 as well.
And ideally we would see independent X/Y scaling options added to Media Center, since they compliment each other.
Once you start drawing 4:3 bars on top of the image, you realize that the video's aspect ratio was often not quite correct.
Here's a recent example. Someone thought it would be cute to put up rusted pillarboxing on the side of this horror footage:
So now there is a static image stuck on either side of the screen.
If we draw
perfect 4:3 pillarboxing over the image, you see that there is a problem - the footage is not exactly 4:3
This would actually make any burn-in from these static images
much worse than the original image.
With independent X/Y scaling, it's possible to correct the video aspect ratio to a proper 4:3
Now in this example, I know that the footage itself is
supposed to be exactly 4:3, so a horizontal stretch fixes the issue.
In other footage, however, the footage itself is the correct aspect ratio, but that aspect ratio is either wider or narrower than 4:3 - which is why you would need an option to adjust the width of the pillarboxing that MC draws on top of the image, rather than it just drawing pillarboxing which is exactly 4:3.
And another issue that I have run into, which makes itself known if you are drawing pillarboxing over the image, is that the current X/Y image positioning and zoom controls are very coarse in MC, so it's not always possible to center the image.
Now personally I would prefer to draw black bars on the sides rather than gray, but it makes things stand out more to use gray for this comparison.
If this were saved to the "Playback Info" tag, you would just need to spend 30 seconds fixing this at the start of the first video, and then copy that tag to every other video in the series.
I probably have something in the region of 300-400 videos where this would apply. (across a number of different video series')