MP3 and ID3 size.

[TooNice]

I keep a backup of my music, and every now and then, I will make a check between what I have in my backup and what I have in my 'active' drive. Whenever I change the tag from my active drive, the file size will, obviously, change a little. For some reason though, I find that the file size of an MP3 after being added a rating (using Foobar2k) is consistantly smaller than the original file by a little.

I would very much appreciate if someone could just make a little test which should take no more than 2 minutes:

1. Take an MP3 you have with some ID3v2 tags in it and note the file size.

2. Make copy of the file, add a meta tag 'RATING=5' and note the file size.

3. Make a copy of it the file, strip the recently added tag, and note the file size.

I would expect 1. and 3. to be of the same size, and to a lesser extent, 2. to be larger than 1. and 3.; yet the file with the most metadata ended up being the smallest. Well, here is an example of my results:

1. Original file: 11,074,958 bytes
2. With the rating tag: 11,073,184 bytes
3. After the rating tag is stripped: 11,073,168 bytes

[The above are actual size, not space on disk]

Minor differences, but consistent, most of my files get smaller as soon as I add that field. If this occurs to others, then I'll just accept it. Otherwise, I'll have to look to see if my player is not actually eating away my files =/

Cheers.

[Funkstar]

I take it you are using FooBar2000 to add and remove the tags?

It is probably re-writing the entire ID3 data and removing some padding while it is at it. Either that or it is stripping sone non-valid data that was included during the initial ripping and tagging.

[directhex]

i suspect you'd need an mp3 frame viewer to confirm it, but here's my hypothesis:

ID3v2 tags can appear anywhere in a file - and in multiple places in a file (e.g. musicmusicmusicmusictagmusicmusictagmusicmusictag). this is one reason why getting tag info from v2 files takes longer than v1 - because your media player needs to scan the whole file

foobar is probably removing all previous tag values, then sticking them together into a single frame (rather than spread through the file)