CPUM

From IRCBotWiki

CPU Killer's Streaming Meta Tags for MP3

I recently came up with this because I like to archive shows from ShoutCast and I would like the title changes to be in the MP3 so it will update as it plays just like the show did... and voila, here it is.

As a MP3 decoder scans for the next MP3 frame, it usually reads a few bytes at a time looking for 0xFF then 0xE0 (or 0xF0 if they are an older decoder that doesn't support MPEG 2.5) in the first two bytes, and here is where my CPUM (CPU Meta) tags come in.

If the 0xFF/0xE0 search fails, check to see if it equals 'CPUM' (0x4D555043 as a Little-endian long), after that there is a status byte which tells which data fields are written to the file.
Data does not have to be null-terminated, but it won't hurt, and DO NOT pad it with spaces!

	MSB	Status Byte						LSB
Bit	7 (0x80)	6 (0x40)	5 (0x20)	4 (0x10)	3 (0x08)	2 (0x04)	1 (0x02)	0 (0x01)
Field Name	Forbidden	Reserved	Reserved	Album	Genre	Artist	URL	Title
Size (in Bytes)	0	NYD	NYD	64	16	64	128	64

The forbidden bit is so MP3 decoders won't mistake the CPUM tag for a valid MP3 frame, also 0xFF should never appear in your data.
Fields will be stored in left-to-right order, ie. if the status byte is 0x03, you would

Read a 64 byte title,
Then a 128 byte URL.

And that is it. Simple yet effective.

• NYD = Not Yet Determined

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