A reader wrote to me the other day with an intriguing question: why was some of his album art not syncing to his iOS devices? He had ripped John Eliot Gardiner’s Bach cantatas pilgrimage CDs in Apple Lossless format, and scanned all the covers at 600 pixels. Yet none of these covers showed up on his iOS devices. However, all his other music displayed album art on iOS devices.
I asked him to send me one of the files, and I found that he had actually added album art at 2900 pixels wide; perhaps he had set the scanner for 600 dpi, and not resized the images to 600 pixels. When I added the track to my iTunes library and synced it to my iPhone, the album art didn’t display.
So, I set out to do some testing. I tried changing the size of the album art to see if that had an effect; sure enough, it did. I did some more testing, using the same track and the same album art. I tried at different sizes, to see where the cut-off would be. I named each file with the pixel size of the artwork, and the size of the graphic file that I was adding.
It turned out that the files up to 2200 pixels displayed album art; the 2400 and 2900 pixel artwork did not display.
There are two possibilities; I need to do more testing to figure out which variable iTunes uses to decide whether to sync album art with music. It could be either the pixel size, or the graphic file size. In other words, it’s possible that iTunes has a limit of 2200 (or up to 2399) pixels, or that the limit is 10 MB (or up to just under 12 MB). My guess is that it’s the latter; I don’t think iTunes can calculate the pixel size of an embedded image, but it probably can figure out how much space it takes up. The 10 MB file size was rounded up; I think the actual file was 9.8 MB.
It makes sense that iTunes would strip album art if it’s very large when syncing to an iOS device. You might accidentally add a huge file as album art for an album, much larger than the size of the music file itself. (That was the case with the original file I received from my reader; the music file was around 5 MB.) To save space on an iOS device, iTunes may simply strip it. It would be nice, however, if iTunes could tell users when this happens.
So if you’re having problems with iOS devices not displaying album art for specific tracks or albums, select one of these files in iTunes, press Command-I, then click the Artwork tab. Drag the artwork to the Finder, then select it and press Command-I. The info window will show you the file size and the pixel size of the artwork, as you can see in the screenshot to the left.
If the artwork is larger than the sizes I mentioned above, try reducing it to see if it still doesn’t display. I don’t guarantee that my limited test will work all the time; in fact, if it doesn’t work for you, post a comment.
Update: French website iGen did some tests, and found that the limit is around 10 MB for the album art file. They found that pixel size didn’t matter, but they also found that a graphic of 10.3 MB was synced, and another of 10.1 MB didn’t sync. My guess is that those are the Finder sizes, and include the amount of space taken up by thumbnails; it looks like the limit is around 10 MB per file.