Characters in title can cause final phase of bind to silently fail

[ehcloninger]

m4b-util version 2025.4.16
Windows 11 under Powershell.
Python 3.13.5

Input files were .m4b in a folder.
Issuing the command
m4b-util bind '.\input' -o .\output\ --keep-temp-files

Would convert all the .m4b to .m4a and combine into a .m4a in the /tmp folder. The final step of converting to .m4b in the output folder would show success. The output file was 0 bytes in size and did not have the correct name.

The problem was the name of the file was generated from the metadata, namely the TITLE. The title contained a colon character (':') which is not a valid character for a file name in Windows. I suspect in the function suggested_file_name() needs some platform-specific scrub functions to remove such characters that are valid in the TITLE metadata, but not in the output file name.

Example:

input file name(s): input\01-book.m4b, input\02-book.m4b, input\03-book.m4b
Metadata title: This Great Author: His Great Book
The output stream shows
Writing 'output\This Great Author: His Great Book.m4b'

The actual file is: outputThis Great Author.m4b` but the file size is 0 bytes. There was no indication of error.

[Tsubashi]

Good catch. I use it primarily on Macintosh so I hadn't run into the issue. Let me see what I can do.

[ehcloninger]

This was the first of the books I was trying to convert, so it really sent me down in the weeds for a while. I've since used mp3tag to change the metadata for that particular book, so it was easy to move past this one.

I have a Macbook, but it runs Ubuntu these days (2014 MBP). I'm pretty platform agnostic, but Windows is my daily driver out of necessity.