Mp3tag showing “wrong” metadata on M4B files

[bengalih]

So I’ve done a lot more testing. I don’t think the post you referenced is entirely relevant since that issue was around the chapter managment itself, not just changing a tag as simple as “title”. However three may be relvance between them. There definitely looks like complications due to the MB4 format. I hope @Florian can shed some light on this as he did with the other.

From what I can see, if I use MP4Box on one of these files to export and then re-import the chapter, the issue seems to resolve itself. I notice that when MP4Box writes, it creates a stream like this:

{
"index": 1,
"codec_name": "bin_data",
"codec_long_name": "binary data",
"codec_type": "data",
"codec_tag_string": "tx3g",
"codec_tag": "0x67337874",

Wheras, when FFmpeg creates it, it outputs this:

{
"index": 1,
"codec_name": "bin_data",
"codec_long_name": "binary data",
"codec_type": "data",
"codec_tag_string": "text",
"codec_tag": "0x74786574",

So, effectively it seems like the issue only occurs if the stream that embeds the chapters is of the “text” format AND have more than one chapter. If I use ffmpeg to create the file with only one chapter, it doesn’t seem to cause an issue, but the moment I add more than one the problem occurs.

If I export/import the chapters with MP4Box, it appears to convert them to “tx3g” format, which Mp3tag doesn’t seem to have an issue with. That being said, when I convert them, it doesn’t automatically fix the inconsistency between what Mp3tag shows and what Explorer shows, but if I save the tag once with Mp3tag, I can then seem to change it in either location and it is properly reflected.

I don’t know enough to say what is right/wrong here. All I know is that ffmpeg is heavily used to write chapter data to MB4 files using the ffmetadata1; format file. I also know that of all the tools I am using, Mp3tag seems to be the only one that is not recognizing changes to simple tags in this way.

Could it be a bug in that Mp3tag? The other crazy thing about this is that while Mp3tag apparently has no issues if my chapters are in the “tx3g” format from a tag writing standpoint, is that it does NOT honor those chapters as separate chapters when “List chapters….” is enabled. But it does do it for the TXT tags!!

And again, for what it is worth, other programs like ffmpeg, mediainfo, VLC, do recognize the chapters (for output or playback) with either option.

EDIT - To add on to this, I have done some more poking. It looks like if I use this when I do my ffmpeg conversion “movflags disable_chpl” that the issue is also resolved. That switch presumably doesn’t create Nero chapterization, only the QT.

That appears to be root issue: Mp3tag has issues with writing tags back to files with Nero chapters on MB4, but not to ones with just QT. But, alternatively, it cal only show “List chapters….” if the file has Nero tags.

ANOTHER EDIT - Found this:

MP4 files with chapters ignore all standard tags; create “ghost tags”

First of all: Thank you for your wonderful program that's served me so well all these years! Mp3tag currently creates Nero metadata for any MP4 file with chapters, but also writes to the standard metadata. This seems fine in theory, but apparently, it also means that Nero copies are created for every standard metadata tag that's set in that file, meaning that if the standard tags are changed with another program, Mp3tag cannot see the change, and the unchanged tags remain in the file a…

Apparently this is a realy issue that Mp3tag can’t deal with, which does make it unsuable in many respects on its own due to it’s reliance/forcing of this Nero data. I suppose that using it for MB4/MP4 chapterized files is simply not the use case for this application unless you don’t want to use any other program.