Please Add the Ability to Modify %VBR% field in MP3 Tag

I have discovered a issue in Nero When using Nero Burning ROM to "Save Tracks" and encode audio CD's to MP3 VBR files the %VBR% field is set to CBR in error. This causes song length times to display substantially longer than the actual play time for the given song. The resulting MP3 files play just fine, but the play time is not what it should be.


%VBR% is not a tag, but a property of the file that is determined by a special header. If the header is not present, %VBR% will return false and you cannot change that. Use something like

Then since %VBR% is not a tag, but rather a special property denoted by a special header, does MP3Tag make a assumption that the file is CBR if that special property is not present? If I enable the column VBR in customize columns in MP3Tag a VBR file encoded using Nero 7 "Save tracks" to rip CD's to MP3 VBR shows CBR in that column. I then must run VBRFix on the tracks to get the column to display correctly.

If I do not run VBRFix the file plays just fine (and it plays fine after running VBRFix too), does this imply there's a tag property that Nero 7 should have created, but didn't? I'd see that as a bug.

One other question that this raises is how is it that the file plays just fine when the special property header is not present to inform whatever MP3 (Decoder) player that it's playing a VBR rather than CBR file?

A VBR MP3 file has a special header called "Xing" header or "VBRI" header (latter is used only by Fraunhofer MP3 encoders). The header is only used to inform the decoder how many frames the MP3 file has which is then used to calculate the duration of the file. It also contains an index used for navigating inside the file (fast forward and rewind). Since MP3 files are made of multiple frames that can be decoded individually, a decoder will play VBR files without problems even if no Xing header is present (actually, the Xing header is only a hint as I said, the MP3 specifications do not require this header to be present).

If you want the right duration to be showed in players or other applications, you should use the tool I mentioned. As far as I know, it traverses all frames and then generates the Xing header containing the number of total frames.

Edit: Since Xing / VBRI frames are not mandatory for VBR, I wouldn't call Nero's "inability" to write the respective header a bug, but a limitation of the feature. I will check if Nero 9 writes the respective frame and if not suggest it to the responsible department.

Thanks so much for taking all the time to provide the info on VBR, XING and VBRI! My guess is that if Nero does anything it'll be VBRI since they use the Fraunhofer MP3 encoders (at least they used to in Nero 5, 6 & 7). I'd be curious to know what you find out about Nero 9, I've been debating whether or not to buy it.

If Nero uses the VBRI header is it supposed to denote VBR/CBR? Like I said, files I've encoded with Nero 7 as VBR using FHG encoder are showing CBR in MP3Tag. And they show wildly long song length and extremely low bit rates. Here's a example...

MP3Tag shows before VBRFix - Cat Stevens - The First Cut is the Deepest
Bitrate = 32kBits/s
Length = 23:57

MP3Tag shows after VBRFix - Cat Stevens - The First Cut is the Deepest
Bitrate = 250 kBits/s
Length = 3:03

It's also worth noting that Windows Explorer on Vista Ultimate SP1 comes much closer on the song length before VBRFix than MP3Tag does. On this same track before VBRFix Windows Explorer is showing a length of 3:21 where MP3Tag is showing 23:57. The 3:03 that MP3Tag shows after running the file through VBRFix is the correct length and also Windows Explorer shows the correct length.

Thanks again!

The calculation of the duration depends on how many frames are used. If Mp3tag uses only the first frame and that first frame, because it's silent, is encoded with 32 kbps, Mp3tag will assume that the whole file uses 32 kbps. If you do that and divide the file size by the 32 kbps, you will end up with a lot of frames and therefore a long playtime. It is possible that Explorer either looks at a different spot in the file (in the middle for example) or that it doesn't use just only frame, but more and then divides the file size by the average bitrate it detected.

Nero uses the Thomson MP3 encoder (for MP3 and mp3PRO) and it does not write a VBR header - not even Nero 9. Nero also has a LAME plugin but which also doesn't write a Xing header. :frowning: I'll see what I can do.

Once again, thanks for all the help and clarity on how this all works! I've tried both the LAME and MP3 encoders with Nero and I honestly can't tell a audio difference between the 2 of them (I'm not really a audiofile, so I'm probably missing something. I just enjoy my music on the real home stereo). LAME and MP3 seem to both put out very nice quality at the highest VBR settings, but the big difference I see between the 2 of them is that the MP3 encoder seems to be about twice as fast at doing the encoding work vs the LAME encoder. Back when I decided that I'd use my PC as a music server in 2002 I had just over 600 albums to rip and tag so I could use them with my SB Wireless Music and all it would handle was MP3. To do it all and get the tags all squared away it ended up taking the better part of 3 months to rip it all. The SB Wireless Music has gone by the way side due to a lack of support and it won't work at all on a 64 bit OS. I've now gone with a Logitech Duet setup and if I had it all to do over again I'd go FLAC, the file size is reasonable and it's loseless. The reason for both these units was the fact that the menu is on the remote and doesn't empty your wallet like a Sonos player would. I can't see using something that would either require the TV to see what you're doing or having some little display on the receiver unit at the stereo.

Hope you have some pull with the Nero folks and they're willing to listen to what us users want in their product. I've always considered Nero to be the "Swiss Army Knife" of CD's, DVD's and digital media. They just seem to do their own thing and don't seem to listen much when you say you have a problem. One of the biggest things I miss is that ImageDrive went away with Vista, I used it a bunch with XP!