KOReader shows garbled text on a specific MOBI file

[stressreader]

Hi all,

I'm new to KOReader and have been testing it recently. Everything looks great, except that for a specific MOBI file (curiously, the first one I tried to open) it shows some garbled text. For example, the first page shows:

Spoiler:

CR!NNEGZG6Y356MHET1K1W0J1HTW0Z3
z$[
z$
}
en
false
Ov?g5A]"?
2QB~r@2K?.b,ඨ!Ɛ9u?[?a
"?
1?B*19
e5=+p3dY?mPCi~+ @U?Q[y?"?
%"?ӣ?K(=7- [??!
>>=ه?
?F4 ?OZ(?)K
Y?*F??J?8 ?O[Q	?̙yU?#?k,&̈
=("??TP)pl%?$1 1̈7oV!?
: &R11%BƠS%C((M"*yo)0W?6*`yǀ&J)

2

(The rest is jibberish)

I'm guessing that some of these should be read as fields pertaining to the MOBI format ("en", "false") rather than the text itself. This happens both on my Kindle and on my PC using the AppImage. I see nothing particularly noteworthy within the logs:

Spoiler:

---------------------------------------------
                launching...
  _  _____  ____                _
 | |/ / _ \|  _ \ ___  __ _  __| | ___ _ __
 | ' / | | | |_) / _ \/ _` |/ _` |/ _ \ '__|
 | . \ |_| |  _ <  __/ (_| | (_| |  __/ |
 |_|\_\___/|_| \_\___|\__,_|\__,_|\___|_|

 It's a scroll... It's a codex... It's KOReader!
[*] Current time: 02/12/25-22:40:04
has monolibtic? no (libs/libkoreader-monolibtic.so: cannot open shared object file: No such file or directory)
lib_search_path: libs/?
lib_basic_format: lib%s.so
lib_version_format: lib%s.so.%s[*] Version: v2024.11

ffi.load: rt.so.1 (RTLD_GLOBAL)
ffi.findlib: utf8proc [3]
ffi.load: libs/libutf8proc.so.3
ffi.findlib: blitbuffer
ffi.load: libs/libblitbuffer.so
ffi.findlib: SDL2-2.0 [0]
ffi.load: libs/libSDL2-2.0.so.0
Starting SDL in /tmp/.mount_koreade7VRsG/
ffi.findlib: lodepng
ffi.load: libs/liblodepng.so
02/12/25-22:40:04 INFO  initializing for device AppImage 
02/12/25-22:40:04 INFO  framebuffer resolution: {
  h = 800,
  w = 600
} --[[table: 0x7efad3a02d98]] 
ffi.findlib: wrap-mupdf
ffi.load: libs/libwrap-mupdf.so
ffi.findlib: sqlite3 [0]
ffi.load: libs/libsqlite3.so.0
ffi.findlib: freetype [6]
ffi.load: libs/libfreetype.so.6
ffi.findlib: harfbuzz [0]
ffi.load: libs/libharfbuzz.so.0
ffi.findlib: zstd [1]
ffi.load: libs/libzstd.so.1
02/12/25-22:40:04 INFO  Loading plugins from directory: plugins 
02/12/25-22:40:04 INFO  Loading plugins from directory: <home>/.config/koreader/plugins/ 
ffi.findlib: leptonica [6]
ffi.load: libs/libleptonica.so.6
ffi.findlib: k2pdfopt [2]
ffi.load: libs/libk2pdfopt.so.2
02/12/25-22:40:24 INFO  opening file <home>/Xerox Corporation. Palo Alto Research Center_Hiltzik, Michael A - Dealers of Lightning_ Xerox PARC and the Dawn of the Computer Age-HarperCollins e-books (2009).mobi 
02/12/25-22:40:24 INFO  Inhibiting user input 
02/12/25-22:40:25 INFO  Restoring user input handling

This same MOBI can be opened with Calibre viewer, foliate, etc. without a problem. The actual file is a 2009 copy of Michael Hiltzik's Dealers of Lightning.

It isn't really a big deal since if I convert to EPUB it reads normally, but I'm actually curious: Is this behaviour somewhat expected due to different versions of MOBI files or is it a bug? If it is a bug, can it be reported without sharing the actual file?

Thanks in advance.

[BionicGecko]

It’s hard to say what went wrong with that specific file, but according to the KOReader User Guide, “MOBI support in KOReader is minimal to nonexistent”.

You can always open a bug report, but my gut feeling is that fine-tuning the MOBI renderer is not very high on the KOReader development team’s priority list.

[Frenzie]

Correct, but occasional fixes do happen: https://github.com/koreader/crengine...3834a3ae681df4

(I link that commit in part because the symptoms sound potentially somewhat similar.)

[stressreader]

Thanks. I'll check out the code and see if I can play around enough to come up with a cause or even a fix.