MP3 Diags
In May 2008 I decided to improve my MP3 collection, by properly tagging all the files (including composer data), adding album cover art, fixing VBR headers, re-ripping albums that have poor sound quality, and more. I tried several programs, but I wasn't happy with how they worked. None of them did all the things that I wanted, and some corrupted the files. Worse, none allowed me to "look inside" an MP3 file, so the best way to see what was wrong with a file was to open it with a hex editor and try to see how some specifications mapped to the various pieces of the file. After a while I decided to give up on the tools I was experimenting with and write my own. The result is MP3 Diags.
There are many programs that create and edit MP3 files, and many of them are broken. As a result, many MP3 files have various issues, ranging from values that are not standards-conforming but that are tolerated by all players and tools (so they look perfectly fine to the end user) to files that play correctly only on some players or even cause players and tools to crash. Many of the tools are quite tolerant of errors in an MP3 file, but some are less so. Also, there are reasons to change a file even if it technically doesn't have errors; for example you may want to add the picture from the album cover, or the lyrics.
What is MP3 Diags and what does it do?
In a few words, MP3 Diags is a GUI-based application that allows end-users to identify issues with their MP3 files, fix some of the issues and make other changes, like adding track information. It also lets you "look inside" an MP3 file.
Unlike some programs that are designed to deal with a single topic (like fixing VBR headers or adding cover art), MP3 Diags is a one stop solution that identifies more than 50 different issues in MP3 files and provides the means to fix many of them (well, not everything is fixable; you can't make a 64kbps file sound like a 256kbps one.)
Some of the more important issues that are found:
Some of the fixes and changes that MP3 Diags can do:
Intended target: this program is not really meant for those who want to push a button and have everything fixed automatically, but rather for people who have some technical background, who are rather picky about what's in their MP3 files, and who are willing to spend some time to get them right. Automatic fixing of non-ID3V2 issues can be done using the 4th custom transformation list, which is as close to "fix all" as MP3 Diags can get, but some may not be so happy with it. Automatic tagging is neither implemented nor planned.
Reviews, opinions, mentions
Some sites notified me that they reviewed the program (or, well, copied the home page and changed a few words here and there), but this list is mainly based on the web traffic they generated: (There seems to be a relatively large Italian following.)
If you want to use those parts of MP3 Diags functionality that alter existing files, it is highly advisable to back up your files first, because there is a real chance of data loss. It can be caused by both user error and bugs in the program.
Now if you wonder just how big this chance is, I don't have any answer. As far as I know, there are no bugs that may cause data corruption, but there may be some that I don't know about. I didn't lose any data in my own files, but you'll have to try it for yourself.
I guess the biggest risk is in a mismatch between what you expect MP3 Diags to do and what it was designed to do. So reading the documentation could help.
Getting the program
MP3 introduction
User's guide
Suggested usage
First run
Scanning MP3 files
Main window
Main window - Tools
Transformations - Details
Main window - All notes
Main window - Tag details
Note filter
Folder filter
Tag editor
Querying Discogs or MusicBrainz
Tag editor - Assigning images
Tag editor - Patterns
File renamer
Config - Files
Config - Ignored notes
Config - Custom transformations
Config - Transformation parameters
Config - Visible transformations
Config - Audio quality
Config - Colors
Config - Shell integration
Config - External tools
Config - Others
Advanced features
Feedback and support
Notes for programmers
Licence and acknowledgements
I'd appreciate feedback about your experience with MP3 Diags (things like if it compiles or not, if it crashes, if it corrupts files, if you'd like a binary available for some platform, parts that you like or dislike, new features ... )