About a month ago I bought a Sony NW-A45 music player from eBay to replace my failed 160GB iPod Classic (2007) whose hard disk failed on 21 June 2018. My main reason for picking this replacement was its battery life - I struggled to find any portable music players on the market that come close to the 40hrs playtime of my iPod, despite 12 years of progress. I discovered that the reason some of my album artwork was not appearing on it was due to it not supporting progressive JPEG images so I had to re-tag the embedded cover art in a few of my FLAC files.
GIMP can remove the progressive overlay by unticking the option on the JPEG export advanced options page, although I prefer to use the command line. The ever reliable image toolkit ImageMagick can both tell me if an image is a progressive JPEG (output will be
Interlace: JPEG if it is or
Interlace: None if not):
identify -verbose cover.jpg | grep Interlace
and turn it into a non-progressive JPEG:
convert -interlace none cover.jpg cover_new.jpg
For use on websites, progressive JPEGs are a good thing for user experience (they allow the image to be displayed at gradually increasing fidelity as the file is loaded) so this is only helpful in cases like this where an older device does not support them.