It's pretty safe to use.. and it doesn't try to fix REALLY BAD files.

The --repair option (fix VBR headers) looks for an existing VBR header
and "repairs" it if necessary by recalculating the data for it.

I wrote/use the utility to strip the ID3V2 (--remove option) tags from all
of my .mp3 files prior to downloading the the empeg player -- they just
waste space on the empeg, and some of the tags are rather large image
files and text lyrics and whatnot.

Then I noticed that the FF/REW functions didn't work on my latest batch
of encodings.. the newest RealPlayer+ software from RealNetworks
(owners of Xing) writes broken headers to the files it creates.
Broken, as in all-zeros, for the 1/256 offsets in the VBR header.
So, I recently added code to decode .mp3 headers, recalculate the
VBR info, and repair it if specified.

As a bonus, the software looks for other errors (bad headers,
excess data, etc..) and reports it (but does not try to "fix" it).

As a side effect of this work, the program now reports the average
playback bitrate of VBR encoded files. Say you use "128kb VBR" to
encode some tunes: this is just a guideline to the encoding s/w,
which may actually use rates as low as 24kb/sec or as high as 160kb/sec
(or more). The mp3tool utility will compute the average overall rate
and dump it out to satisfy curiosity -- if you see your "128kb" files
are only averaging "110kb", then you know it's time to turn up the
quality setting a notch or two on your encoding software.

Cheers

Mark