Informational                                                 M. Nilsson
Document: id3v2.4.0-changes.txt                       21st December 2000


                    ID3 tag version 2.4.0 - Changes

Status of this document

   This document describes the changes between ID3v2.3.0 [ID3v2.3.0] and
   ID3v2.4.0 [ID3v2.4.0-strct][ID3v2.4.0-frames]. This document does not
   claim to be complete nor correct. 

   Distribution of this document is unlimited.


Abstract

   This document outlines the more important differences between
   ID3v2.3.0 and ID3v2.4.0. In general ID3v.2.4.0 can be said to be more
   consistent and easier to implement and more suitable to real world
   conditions than the previous versions.


1.   Table of contents

        Status of this document
        Abstract
   1.   Table of contents
   2.   Conventions in this document
   3.   Tag structure changes
   4.   Deprecated ID3v2 frames
   5.   New frames
   6.   References


2.   Conventions in this document

   References to sections in the ID3v2.4.0 Main Structure
   [ID3v2.4.0-strct] document will be given as [S:x.y] where x is the
   section and y is the subsection. In a similar fashion references to
   sections in the ID3v2.4.0 Native Frames [ID3v2.4.0-frames] document
   will be given as [F:x.y].


3.   Tag structure changes

   The location of tags in a file as well as methods to find and merge
   tags are far better defined in ID3v2.4.0 [S:5] than previous
   versions. A reverse search for tags are improved by the addition of a
   tag footer [S:3.4]. A tag footer flag has been added to the header
   flags to indicate the presence of a ID3v2 footer, hence the size
   field is not affected by the footer [S:3.1].

   The extended header has been completely rewritten [S:3.2] and can not
   produce false synchs. It is also possible to indicate artificial tag
   restrictions in the extended header, for use with thinner clients.
   
   Unsynchronisation [S:6.1] is done on frame level, instead of on tag
   level, making it easier to skip frames, increasing the streamability
   of the tag. The unsynchronisation flag in the header [S:3.1]
   indicates if all frames has been unsynchronized, while the new
   unsynchronisation flag in the frame header [S:4.1.2] indicates
   unsynchronisation. To avoid false synchronisations in the frame
   header the size description and flag field has been rewritten [S:4].
   Resynchronisation of the complete tag when the unsynchronisation flag
   in the tag header is set might result in a corrupt tag.

   The character encodings UTF-16BE and UTF-8 has been added to the list
   of valid encodings [S:4].


4.   Deprecated ID3v2 frames

  EQUA - Equalization
    This frame is replaced by the EQU2 frame, 'Equalisation (2)'
    [F:4.12].

  IPLS - Involved people list
    This frame is replaced by the two frames TMCL, 'Musician credits
    list' [F:4.2.2], and TIPL, 'Involved people list' [F:4.2.2].

  RVAD - Relative volume adjustment
    This frame is replaced by the RVA2 frame, 'Relative volume
    adjustment (2)' [F:4.11].
    
  TDAT - Date
    This frame is replaced by the TDRC frame, 'Recording time'
    [F:4.2.5].
    
  TIME - Time
    This frame is replaced by the TDRC frame, 'Recording time'
    [F:4.2.5].
    
  TORY - Original release year
    This frame is replaced by the TDOR frame, 'Original release time'
    [F:4.2.5].
    
  TRDA - Recording dates
    This frame is replaced by the TDRC frame, 'Recording time'
    [F:4.2.5].
    
  TSIZ - Size
    The information contained in this frame is in the general case
    either trivial to calculate for the player or impossible for the
    tagger to calculate. There is however no good use for such
    information. The frame is therefore completely deprecated.
    
  TYER - Year
    This frame is replaced by the TDRC frame, 'Recording time'
    [F:4.2.5].


5.   New frames

   ASPI Audio seek point index [F:4.30]
   EQU2 Equalisation (2) [F:4.12]
   RVA2 Relative volume adjustment (2) [F:4.11]
   SEEK Seek frame [F:4.29]
   SIGN Signature frame [F:4.28]
   TDEN Encoding time [F:4.2.5]
   TDOR Original release time [F:4.2.5]
   TDRC Recording time [F:4.2.5]
   TDRL Release time [F:4.2.5]
   TDTG Tagging time [F:4.2.5]
   TIPL Involved people list [F:4.2.2]
   TMCL Musician credits list [F:4.2.2]
   TMOO Mood [F:4.2.3]
   TPRO Produced notice [F:4.2.4]
   TSOA Album sort order [F:4.2.5]
   TSOP Performer sort order [F:4.2.5]
   TSOT Title sort order [F:4.2.5]
   TSST Set subtitle [F:4.2.1]


6.   References

      [ID3v2.3.0] Martin Nilsson, "ID3v2 informal standard".
   
         http://www.id3lib.org/id3/id3v2.3.0.txt
   
      [ID3v2-frames] Martin Nilsson,
      "ID3 tag version 2.4.0 - Native Frames"
      
         http://www.id3lib.org/id3/id3v2.4.0-frames.txt

      [ID3v2-strct] Martin Nilsson,
      "ID3 tag version 2.4.0 - Main Structure"
      
         http://www.id3lib.org/id3/id3v2.4.0-structure.txt