Album Art does NOT display properly

[AMJF]

I am using the current build of Rockbox on a Sansa Clip Zip with a colour screen, and I've noticed an issue with some album art not showing up correctly.

Most album art shows up fine, even though the resolution is tiny (less than 50x50 pixels!) but I have two albums (a Mozart compilation and a movie soundtrack) that have black areas in most of the picture and a lighter area in the middle, and for some reason they show up on Rockbox as very light grey, and it spoils the look of the image. Why is it showing up grey when it is black everywhere else?

[ZincAlloy]

It's the display's fault. The difference between black and the darkest shade of grey is exaggerated.

The orginal firmware has the same problem, but it makes album art look even worse because it doesn't dither 24bit graphics down as nicely as rockbox.

[AMJF]

The Sandisk Sansa Zip has an OLED display, meaning that it emits light, so on Rockbox when there are black areas on the screen, they are BLACK, ie. no light emitted whatsoever on those pixels.

I don't agree with you either, as other album art with black areas or bits show up totally black in those parts. I think I may be able to show you with photos if I compare the album art on the Sansa with, say, Foobar2000 on my PC with the same album art at the same time. I would take the photos with my Android smartphone which, BTW, displays the album art flawlessly on the standard music player.

[saratoga]

The Sandisk Sansa Zip has an OLED display, meaning that it emits light, so on Rockbox when there are black areas on the screen, they are BLACK, ie. no light emitted whatsoever on those pixels.

I don't see how thats related to the color accuracy. 

FWIW, I don't think album art looks that bad on my device.  I remember multiple models of display are used, perhaps some are better than others, or maybe one of them has buggy color scaling?

[ZincAlloy]

The black is perfect. Not-quite black ist just much too bright. And the color is off, too. A little greenish I think.
Cabbiev2's gradient shows off the problem nicely.

[[Saint]]

I don't see how thats related to the color accuracy.

If its true black, the pixel won't be lit - so, it should indeed be /black/.

FWIW - there is indeed something quite wrong with the display of certain images used for album art - this isn't the first time this has popped up or been discussed so it surprises me that people are telling OP that this isn't an issue when it in fact is.


[Saint]

[ZincAlloy]

To me it sounds more like the quirks of the display.. A photo or the actual album art that has the problem would be quite helpful, though.

[[Saint]]

This has been reported before

I have seen it pop up occasionally in my own art.

I understand the willingness to blame the display, and it could *also* be a contributing factor, but, there's definitely another issue at play here.

Unfortunately the images from that original post (this has also popped up several times on our IRC channel but my Google-fu is weak tonight) have long since fallen into a black hole, but I'm willing to bet they would show OP's issue exactly as the behavior he describes is very specific.


[Saint]

EDIT: Now that I realized this small point - how it is rational to assume that the display is at fault when there are (presumably) other areas of the screen that display color fine? I didn't see OP mention "black looks screwed up *everywhere*"...

[saratoga]

Trying the image in that thread, the background is drawn as kind of a darkish gray color.  This happens on both device and sim.  Changing to 8 bit fixes the problem.  I guess there is some bug in the color conversion. 

[AMJF]

Trying the image in that thread, the background is drawn as kind of a darkish gray color.  This happens on both device and sim.  Changing to 8 bit fixes the problem.  I guess there is some bug in the color conversion.

The problem I have is not the display, it's more related to buggy JPEG decoding, I think. I read somewhere that progressive JPEG album art doesn't work well with Rockbox.

How do I change to 8-bit so I can at least see if that works, Saratoga?

[saratoga]

Progressive jpeg isn't supported at all.

You can can change image formats using an image editor.

[ZincAlloy]

Trying the image in that thread, the background is drawn as kind of a darkish gray color.  This happens on both device and sim.  Changing to 8 bit fixes the problem.  I guess there is some bug in the color conversion.

For me it looks light grey with a white foreground. And parts of it are shown on the right side of the cover instead of the left side.
Simply resaving it fixes the issue for me. No need to convert to 8bit.

[AMJF]

These are pictures I took of both Foobar and my Sansa Clip Zip showing the same albums:

http://img.photobucket.com/albums/v175/Foebane/AA1.jpg
http://img.photobucket.com/albums/v175/Foebane/AA2.jpg
http://img.photobucket.com/albums/v175/Foebane/AA3.jpg

Notice how the Mozart image is all grey and washed out on the Clip, unlike Foobar which has the nice black surrounding the composer.

The Bryan Ferry album looks about right, although it's not quite black, but a very dark shade of green for Ferry himself.

The Cat Stevens cover has a lot of black areas, and this is reflected in the Clip.

Notice the dark blue status bar at the top on the Clip, this is how dark the display can get. Also notice the flicker on the Clip's screen.

[ZincAlloy]

Only the Mozart one has a problem. The others look fine to me.
This version of the cover works flawlessly on my player (other than the black/blue gradient looking really messed up in image viewer): http://ecx.images-amazon.com/images/I/41yV53QAEyL._SL500_AA280_.jpg
So it must be something specific to your file.

Edit: Maybe you have a really large version of that cover on your player and that grey haze that your seeing results from a lot of dithering?

EditEdit: Nope, that's not it. Just tried a 1200x1200px version.

[saratoga]

Trying the image in that thread, the background is drawn as kind of a darkish gray color.  This happens on both device and sim.  Changing to 8 bit fixes the problem.  I guess there is some bug in the color conversion.

For me it looks light grey with a white foreground. And parts of it are shown on the right side of the cover instead of the left side.
Simply resaving it fixes the issue for me. No need to convert to 8bit.

You're right, a simple resave fixes it.  Has anyone figured out a way to make an image that looks odd?  I'm curious what settings are used.