Wikipedia:Reference desk/Archives/Computing/2026 September 5

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September 5

mp3 size

When I download new music, I use DOS's DIR command to get a snapshot of the file's name, date, and size in bytes, which I then transfer to an Excel file that lets me manage my media file as flexibly as I'd like. All good. Today, I was performing that action as usual when I realized I hadn't cleaned the file metadata first: I like to go in and correct the file's year/genre/track/etc. and I also usually remove any cover art attached to the file as it's often some stupid "3000 Hits from the 1970s!" type garbage anyway. So, out of curiousity, I kept the original data and compared it to the data reflecting the corrected files and noticed some oddities: removing the album art does not change the file size by a single byte and correcting the metadata, including blanking or filling in fields may affect the file size, but in other situations doesn't. In short, what's happening here? Why wouldn't the file size change when an image is deleted from it? If it matters, I'm doing the clean up in old-school Winamp. Matt Deres (talk) 15:39, 5 September 2026 (UTC)

It really depends on the details of how winamp works. For example, to delete an ID3 tag containing an image, they might choose to just overwrite it with a comment tag rather than actually removing it from the file, which would require writing an entire new copy of the file. Of course, overwriting the original file would be risky and I'd be surprised if they actually did that, but even if they write a new file, it might be simpler to modify the picture tag rather than removing it, if other data in the file depends on the file size or the location of other data. By just modifying the content of the original tag, none of that would change. This is all just a guess though; I don't know how winamp works. If your curiosity is high enough, you might try some other mp3 tag editors and see how they behave. CodeTalker (talk) 03:38, 7 September 2026 (UTC)

Just as an FYI, posts on Wikipedia are highly visible, so if you're downloading music, you might want to avoid revealing any details that could get you in trouble with the law if discovered. (I'm not a lawyer and this is not legal advice.) GrinningIodize (you just lost the game) (talk) 20:57, 8 September 2026 (UTC)

Just out of interest, when's the last time anyone got convicted of illegally downloading .mp3 / .avi files? Asking for a friend, who incidentally refuses to talk about Fight Club. MinorProphet (talk) 18:33, 10 September 2026 (UTC)

Not sure, but I wouldn't be surprised if it could get you into hot water legally. If an ISP finds out, they'll most likely be able to react quicker than the courts, so that's something to consider too. GrinningIodize (you just lost the game) (talk) 18:48, 10 September 2026 (UTC)

I have no idea, but just suppose the metadata portion has a fixed maximum field size (e.g. 4096 bytes, just guessing) which could be either an image or valid characters or blanks - have you tried filling a test file with {{lorem ipsum}} garbage, for example? Adding an inappropriately-sized image? Or you could wade your way through this. Quote:

Frames
Each frame is used for storing one information - eg. Artist or Album.
Frame consists of header and body.
Header(10 Bytes)
Bytes  Content
0-3    Frame identifier
4-7    Size             ←-- NB 4 bytes... 
8-9    Flags

Frame identifier consists of four characters. There are many predefined values you can use. But eg. current version of WinAmp displays only these ones:
Ident. Description
TRCK   Track number
TENC   Encoded By
WXXX   URL
TCOP   Frame identifier
TOPE   Original Artist
TCOM   Composer
TCON   Genre
COMM   Comments
TYER   Year
TALB   Album
TPE1   Artist
TIT2   Song name
 You can freely define you own frame, eg. with identifier "CUNT" but you can't expect that some player will be able to display that. Anyway you can store any information into MP3 file without limits."

Lol, MinorProphet (talk) 18:33, 10 September 2026 (UTC)