APEv2

This is how information is laid out in an APEv2 tag:

APE Tags Header 32 bytes
APE Tag Item 1 10.. bytes
APE Tag Item 2 10.. bytes
... 10.. bytes
APE Tag Item n-1 10.. bytes
APE Tag Item n 10.. bytes
APE Tags Footer_ 32 bytes

APE tag items should be sorted ascending by size. When streaming, parts of the APE tags can be dropped to reduce danger of drop outs between titles. This is not a must, but strongly recommended. Actually the items should be sorted by importance/byte, but this is not feasible. Only break this rule if you add less important small items and you don’t want to rewrite the whole tag. An APE tag at the end of a file (strongly recommended) must have at least a footer, an APE tag in the beginning of a file (strongly unrecommended) must have at least a header. When located at the end of an MP3 file, an APE tag should be placed after the the last frame, just before the ID3v1 tag (if any).

Ape Tags Flags

Contains attribute of the tag (bit 31...) and of a item (bit 0...)

Member of APE Tags Header, Footer or Tag item

Note: APE Tags 1.0 do not use any of the APE Tag flags. All are set to zero on creation and ignored on reading.

Bit 31
  • 0: Tag contains no header
  • 1: Tag contains a header
Bit 30
  • 0: Tag contains a footer
  • 1: Tag contains no footer
Bit 29
  • 0: This is the footer, not the header
  • 1: This is the header, not the footer
Bit 28...3
Undefined, must be zero
Bit 2...1
  • 0: Item contains text information coded in UTF-8
  • 1: Item contains binary information*
  • 2: Item is a locator of external stored information**
  • 3: reserved
Bit 0
  • 0: Tag or Item is Read/Write
  • 1: Tag or Item is Read Only

[*] Binary information: Information which should not be edited by a text editor, because

  • Information is not a text.
  • Contains control characters
  • Contains internal restrictions which can’t be handled by a normal text editor
  • Can’t be easily interpreted by humans.

[**] Allowed formats:

Note: Locators are also UTF-8 encoded. This can especially occur when filenames are encoded.

APE Tag Item

An APE tag item is a value assigned by a key.

Member of APE Tag Version 2.0

Note:

  • APE Tags Item Key are case sensitive.
  • Nevertheless it is forbidden to use APE Tags Item Key which only differs in case.
  • And nevertheless Tag readers are recommended to be case insensitive.
  • Every Tag Item Key can only occures (at most) once. It is not possible to transmit a Tag Key multiple time to change it contents.
  • Tags can be partially or complete repeated in the streaming format.
  • This is to make it possible to display artist and title if you missed the start of the transmission.
  • It is recommended to transmit very important information like artist / album / title every 2 minutes and additional 5...10 seconds before the end. Be careful and don’t transmit these information too often or during passages with high bitrate demand to avoid unnecessary drop-outs.
Size of the Item Value, Bits 0...7
Size of the Item Value, Bits 8...15
Size of the Item Value, Bits 16...23
Size of the Item Value, Bits 24...31
 32 bits Length len of the assigned value in bytes
Item Flags, Bits 0...7
Item Flags, Bits 8...15
Item Flags, Bits 16...23
Item Flags, Bits 24...31
 32 bits Item flags
Item Key m bytes Item key, can contain ASCII characters from 0x20 (Space) up to 0x7E (Tilde)
0x00 1byte Item key terminator
Item Value len bytes Item value, can be binary data or UTF-8 string

APE Key

  • An APE tag item key is a key for accessing special meta-information in an audio file.
  • Member of APE Tag Item.
  • APE tag item keys can have a length of 2 (including) up to 255 (including) characters in the range from 0x20 (Space) until 0x7E (Tilde).
  • Typical keys should have a length of 2 ... 16 characters using the following characters: Space (0x20), Slash (0x2F), Digits (0x30...0x39), Letters (0x41...0x5A, 0x61...0x7A).
  • Values can contain binary data, a value or a list of values. See here. List of values can be mixed, i.e. contain UTF-8 strings and external references beginning with file://..., http://www..., ftp://ftp....
  • Not allowed are the following keys: ID3, TAG, OggS and MP+.

Currently the following keys are defined:

TODO