ID3 - Revision history

AmigoJack: adding informal formats; more correct way to skip ID3v2

2023-10-20T12:18:45Z

adding informal formats; more correct way to skip ID3v2

Eiim: Missed one

2023-09-16T15:36:47Z

Missed one

Eiim: Add Kaitai Struct links under specifications

2023-09-16T15:36:01Z

Add Kaitai Struct links under specifications

Eiim: Add Kaitai Struct, Wikidata

2023-09-16T15:33:48Z

Add Kaitai Struct, Wikidata

Azertus: add link

2022-06-08T14:42:39Z

add link

Marco at 08:01, 31 December 2019

2019-12-31T08:01:22Z

Marco at 08:00, 31 December 2019

2019-12-31T08:00:19Z

Jsummers: /* Identification */

2018-10-26T15:20:10Z

‎Identification

Jsummers at 13:57, 26 October 2018

2018-10-26T13:57:46Z

Jsummers at 16:16, 25 February 2018

2018-02-25T16:16:23Z

@@ Line 20: / Line 20: @@
 == Identification ==
-For an MP3 file with an ID3v1 tag, ASCII "{{magic|TAG}}" appears beginning 128 bytes from the end of the file.
+* For an MP3 file with an ID3v1 tag, ASCII "{{magic|TAG}}" appears beginning 128 bytes from the end of the file.
+* An MP3 file with an ID3v2 tag usually begins with ASCII "{{magic|ID3}}".
-An MP3 file with an ID3v2 tag usually begins with ASCII "{{magic|ID3}}".
+* Alternatively, the signature "{{magic|3DI}}" could appear 10 bytes from the ''end'' of the file, or 138 bytes from the end of the file if there is also an ID3v1 tag. This is much less likely.
-−
 Alternatively, the signature "{{magic|3DI}}" could appear 10 bytes from the ''end'' of the file, or 138 bytes from the end of the file if there is also an ID3v1 tag. This is much less likely.
 There are other (rare) ways to use ID3v2, not covered by the above identification logic.
@@ Line 30: / Line 28: @@
 === How to skip past an ID3v2 segment ===
 To identify an audio file's format, it is best to skip past any ID3v2 segment at the beginning of the file before looking for a magic signature, and not just assume that ID3 implies MP3. Unfortunately, doing so is not trivial. Here is an attempt to summarize the algorithm:
-* Let OFFSET = 0.
+# Let OFFSET = 0.
-* Read and remember the first 10 bytes of the file.
+# Read and remember the first 10 bytes of the file.
-* If bytes 0-2 are not ASCII "ID3", stop. An ID3v2 segment is not present.
+# If bytes 0-2 are not ASCII "ID3", stop. An ID3v2 segment is not present.
-* Let OFFSET = 10 (for the 10-byte header).
+# Let OFFSET = 10 (for the 10-byte header).
-* Decode bytes 6-9 as a 32-bit "synchsafe int" (refer to any ID3v2 spec). Let OFFSET = OFFSET + this decoded int.
+# Decode bytes 6-9 as a 32-bit "synchsafe int" (which are 28 bit of size, because you only read 7 bit of each 4 bytes, refer to any ID3v2 spec). Let OFFSET = OFFSET + this decoded int.
-* If the 0x10 bit of byte 5 is set, let OFFSET = OFFSET + 10 (for the footer).
+# If the 0x10 bit of byte 5 is set, the file's last 10 bytes have an ID3 footer, which is not audio data.
-OFFSET is now the file offset of the payload audio data.
+# OFFSET is now behind the ID3v2 tag. Although uncommon, the docs nowhere forbid to have multiple ID3v2 tags (f.e. v2.2 and v2.3 following), so the whole scannings may start anew at the current offset and you should go back to 1. while your true exit condition is 3. when not seeing the "ID3" magic.
 == Specifications ==

@@ Line 51: / Line 51: @@
 * [https://formats.kaitai.io/id3v1_1/ Kaitai Struct: ID3v1.1]
 * [https://formats.kaitai.io/id3v2_3/ Kaitai Struct: ID3v2.3]
 == Software ==

@@ Line 49: / Line 49: @@
 * [http://wiki.hydrogenaud.io/index.php?title=ID3v1.1 Hydrogenaudio Knowledgebase: ID3v1.1]
 * [http://wiki.hydrogenaud.io/index.php?title=ID3v2 Hydrogenaudio Knowledgebase: ID3v2]
 == Software ==

@@ Line 5: / Line 5: @@
 |locfdd={{LoCFDD|fdd000106}}, {{LoCFDD|fdd000107}}, {{LoCFDD|fdd000108}}
 |released=1996
 }}
 '''ID3''', or '''ID3 tag''', is a metadata format, mainly used in [[MP3]] audio files. It stores information such as the song title, artist, and album.

@@ Line 59: / Line 59: @@
 * [[Wikipedia:ID3|Wikipedia article]]
 * [http://www.codinghorror.com/blog/2006/08/a-spec-tacular-failure.html Coding Horror: A Spec-tacular Failure]
 [[Category:Audio and Music]]

@@ Line 51: / Line 51: @@
 * [http://id3lib.sourceforge.net/ id3lib]
 * [http://taglib.github.com/ TagLib]
-* [https://www.logipole.com/metadata++-en.htm/ Metadata++]
+* [https://www.logipole.com/metadata++-en.htm Metadata++]
 ''[Ed. note: There are many utilities that can read and write ID3 tags, including Windows Explorer to some extent. We suggest searching the web.]''

← Older revision		Revision as of 15:20, 26 October 2018
Line 25:		Line 25:

	There are other (rare) ways to use ID3v2, not covered by the above identification logic.		There are other (rare) ways to use ID3v2, not covered by the above identification logic.
		+
		+	=== How to skip past an ID3v2 segment ===
		+	To identify an audio file's format, it is best to skip past any ID3v2 segment at the beginning of the file before looking for a magic signature, and not just assume that ID3 implies MP3. Unfortunately, doing so is not trivial. Here is an attempt to summarize the algorithm:
		+	* Let OFFSET = 0.
		+	* Read and remember the first 10 bytes of the file.
		+	* If bytes 0-2 are not ASCII "ID3", stop. An ID3v2 segment is not present.
		+	* Let OFFSET = 10 (for the 10-byte header).
		+	* Decode bytes 6-9 as a 32-bit "synchsafe int" (refer to any ID3v2 spec). Let OFFSET = OFFSET + this decoded int.
		+	* If the 0x10 bit of byte 5 is set, let OFFSET = OFFSET + 10 (for the footer).
		+	OFFSET is now the file offset of the payload audio data.

	== Specifications ==		== Specifications ==

@@ Line 2: / Line 2: @@
 |formattype=electronic
 |subcat=Metadata
 |locfdd={{LoCFDD|fdd000106}}, {{LoCFDD|fdd000107}}, {{LoCFDD|fdd000108}}
 |released=1996
@@ Line 7: / Line 8: @@
 '''ID3''', or '''ID3 tag''', is a metadata format, mainly used in [[MP3]] audio files. It stores information such as the song title, artist, and album.
-Although usually associated with MP3, an ID3 tag is a single self-contained blob of bytes, so it can theoretically be used in most any format that is designed to be extensible. For example, [https://samples.libav.org/asf-wmv/wma_with_cover_art/wma_with_ID3_APIC.wma here] is a [[WMA]] file with ID3 data.
+Although designed for use with (and named after) MP3, ID3 is sometimes used with other audio formats. This can be done in two fundamental ways:
 == Format details ==