Why does my car stereo display text differently in day and night modes?
May 6, 2014 11:44 AM   Subscribe

I admit up front this is an odd question, and it won't kill me if I never get an authoritative answer, but it's been bugging me. My car's stereo has an LCD display that gives the artist's name in fairly large letters and the track title below that in smaller letters. It can only display so many letters of course, and so it has to truncate most names and titles. But it truncates text differently in its daytime and nighttime modes. Why does it do that?

The car's daytime mode shows black letters against a white background. (It's not really white, it's just... blank I guess, but I'll use white for simplicity's sake). But when it's dark outside it flips to a nighttime display mode that reverses white letters out of a black background.

I noticed this mainly because I've been listening to Donald Fagen's most recent solo record, Sunken Condos (which is really good stuff by the way - song snippets here) in my car a lot. And I noticed that in daytime mode the LCD display truncates him to "Donald Fag." And I thought, well that's inappropriate.

But here's the odd part. When I pull into a parking garage, or something switches the display into nighttime mode, his name now truncates as "Donald Fage." Which, of course, is a brand of yogurt. Donald Fagen can't catch a break from my car. But the point is that it's not just flipping all the pixels when it switches modes. It's actually displaying text differently, showing more letters in the same space.

Why can it do that? Why couldn't it show that extra "e" in daytime mode? Is there any research to suggest that we don't need as much stroke weight for letters when they're reversed out of a dark background, and so it can make the letters narrower while maintaining readability? Basically, why would designers make the display do anything more complicated than just flipping the pixels?
posted by Naberius to Technology (7 answers total) 1 user marked this as a favorite
Weird, but not entirely surprising, as car stereos and information/entertainment displays aren't exactly known for their brilliant user interfaces. My guess is that instead of just inverting the colors on a single display, it's switching to an entirely different display, that for some reason is displaying one extra character in the artist name field. Who knows why - maybe different people programmed each display, or a single not-so-consistent programmer did both.
posted by Venadium at 11:52 AM on May 6, 2014 [1 favorite]

Poor programming practices. That's par for the course in aftermarket stereo headers; they've almost always got aggressively bad interfaces. There's no good reason for it, it's just that nobody cared enough to do more than the shoddiest of jobs in programming the display.
posted by Scientist at 12:57 PM on May 6, 2014

My guess is that the elements of the display which can glow (or turn white?) are physically distinct from the ones that can turn black, and the two do not overlap; in the example case, you should be able to observe that the letters in the night mode either start further to the left or end further to the right when truncation occurs.
posted by jamjam at 1:18 PM on May 6, 2014 [3 favorites]

The stereo in my dads car is utterly stupid like this, but hidden within the menus are like twenty possibly display modes for the main screen. A giant animated flip clock, multiple variations of font sizes/weights/styles for the text, etc.

I'd go download the PDF for the manual and see if you can't just reconfigure it.
posted by emptythought at 2:17 PM on May 6, 2014

Could be there are different width fonts for day and night mode. The night mode one is narrower and thus can fit more letters.
posted by ShooBoo at 4:17 PM on May 6, 2014

I think to truly get to the bottom of this you should take photos of the display in both modes. Then we could really take a look at fonts, positioning etc.
posted by cincinnatus c at 1:53 AM on May 7, 2014

I usually just listen to NPR in the car. Now that I've noticed this though, I've been experimenting with more music and paying more attention, and it looks like daytime mode displays 10 characters, including spaces, and nighttime mode consistently displays 11.

It doesn't just use more screen space as jamjam suggested, but appears to do it with tighter character spacing. It's particularly noticeable when you have a lot of wide characters next to each other.

Narrow vertical characters, on the other hand, appear to render at the right edge of their allotted area, which increases their visual spacing. One band I tried is a former Austin, Texas-based French cabaret swing band (I know!) called 8 1/2 Souvenirs. It renders like that: 8[space]1/2[space]Souvenirs. And between the space character and the 1 appearing at the right of its box, the visual separation between the 8 and the 1 is pretty huge. And sure enough, it truncates at "Souv" in daytime mode and "Souve" in nighttime mode.

So yeah, the processor really must be using different text display code to handle the two different modes. As I suggested in the question, I was sort of hoping there was some good reason for doing this instead of simply reversing all the pixels, something about ergonomics and years of readability experiments. But it sounds like you guys are saying nope, just sloppy programming.

This is the factory sound system on a 2011 Volvo, for what that's worth, but I have no idea where Volvo sources them.
posted by Naberius at 6:04 AM on May 7, 2014

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