[SlimDevices: SqueezeCenter] Corrupted EXIF data in folder.jpg interferes with LMS operation

[Martin Gregorie]

This is something I've only noticed recently: if folder.jpg has
corrupted EXIF data it interferes with the way LMS displays the album
details and prevents folder.jpg from being displayed on my Logitech
Touch

Here's the sequence of events:

1) I'm ripping my CD collection on a laptop running Fedora 28 Linux
   X86_64 with Asunder and photographing the CD cover with a Panasonic
   TZ-70 bridge camera.

2) The GIMP is then used to increase the folder.jpg contrast, crop it
   to just the cover and rescale it to 400x400 pixels

3) If needed, I use EasyTag to tweak the album and track names because
   Asunder's album/artist/track catalogue does contain mistakes and
   mis-spellings

4) gftp is then used to move the directory containing the tracks and
   folder.jpg to my music server (a dual Athlon PC running Fedora 28
   Linux X86_64. The m3u playlist is not copies across.

4) LMS then does rescan. Normally everything then works as expected.

However, under some conditions the TZ-70 corrupts the EXIF tagset in
the JPG - I think it may be when the pic is taken on low
light/fluorescent lighting. GIMP reports this as:

==================================
While parsing XMP metadata:
Error on line 46 char 1: End of element <exif:Flash> not expected in
this context
While parsing XMP metadata:
Error on line 63 char 1: End of element <exif:Flash> not expected in
this context

Metadata parasite seems to be corrupt
While parsing XMP metadata:
Error on line 46 char 1: End of element <exif:Flash> not expected in
this context

** (file-jpeg:9125): WARNING **: 14:15:00.816: JPEG - unable to decode
XMP metadata packet
==================================
- though, as the message is sent to stderr, it's not seen unless GIMP
is started from a command line. Inspection if the exif data 
(under File|Properties|Advanced ) doesn't show anything that looks like
<exif:Flash>

This affects LMS as shown:

- if the album is played the 'Play list' part of the web page remains
  blank although the whole album plays

- same happens if the play list is filled by selecting a single track
  or 'all tracks' 

- the Touch does not display the album cover image.

If the exif data is removed the problem can be fixed, i.e. LMS will now
show the playlist for that album and folder.jpg is displayed by the
Touch. I removed the exif data by using GIMP to export the image as
.png and then to load and re-export that as .jpg to overwrite the
original, which reduces it to less than 50% of its original size.

However, just replacing folder.jpg with the exifless copy and doing a
rescan does not fix the problem. The only way to do that is to run
'Clear library and rescsan everything'.

If LMS can be made to explicitly ignore any EXIF data if a 'folder'
image then I think this problem can be avoided entirely, which would be
nice.

I'm running LMS 7.9.1

Apart from this issue I'm not having any problems and am generally
pleased with the way its working.


Martin
 


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