Concatenating MP3s

[CWuestefeld]

I'm looking for a good way of concatenating MP3s. I know this seems like a stupid question. Out on the intertubes there are n+1 ways of joining MP3s -- writing these seems to be another favorite hobby of those who love to write video converters and file synchronizers.

However, it seems that the obvious way of doing this -- simply concatenating the files -- only partially works. In particular, it seems to me that the block numbers need to be fixed up.

What I'm trying to do is reassemble large audiobooks that have been broken into short pieces. A typical book might be 10 or more hours long, and because most MP3 players don't support bookmarks, they are frequently broken up into song-sized chunks. The latest version of the MS Zune firmware does have bookmarks (for podcasts, anyway), which is a much better way of doing things. I can set the book aside, listen to some music, and resume the book right where I left off. So I'd like to take better advantage of this feature.

The thing is, in the couple of MP3 joiners I've tried, the result is broken. The file plays as an MP3 just fine, but the Zune is unable to hold a bookmark that points beyond the first chunk of the book. In fact, it's not able to even correctly show the length of the book.

So, can anyone recommend a way of taking a set of input files and producing a new single MP3 that is completely according to specifications?

[Renegade]

The problem is that something like 20% of a frame's data can be in the n-1 frame (or n+1 frame -- I forget), so there's no really good way to do this. Yes, it can be done, but it's just much easier to decode, concat, then reencode it. You get a quality loss, but if it's an audio book, it's probably not that important.

This is an issue that I'll be looking at later this year to see if it makes sense to actually implement. So far I've only looked at it very very briefly.

I don't know of any programs that I can recommend that do this. (You can check Blaze though -- Chris puts a good amount of attention to detail, so I'd bet that he's done it right, but you'd need to check for yourself to see if Blaze even does it.)

[yksyks]

To avoid re-encoding you can use copy and paste in mp3DirectCut. You can open multiple instances of it at once. Very fast, the quality is maintained, of course. It's freeware.