View source for CD-Text

{{Short description|CD-based format that allows for song information to be stored alongside audio data}}
{{multiple issues|
{{More citations needed|date=September 2013}}
{{More footnotes|date=October 2009}}
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{{infobox media
| logo = [[File:CD-Text (logo).svg|class=skin-invert|upright=0.5|frameless]]
| type = [[Optical disc]]
| encoding = 2 channels of [[LPCM]] audio, plus [[Interactive Text Transmission System|ITTS]] data
| capacity = 
| read = 780&nbsp;nm [[laser diode]]
| standard = [[Rainbow Books|Red Book]]
| owner = [[Philips]] & [[Sony]]
| use = Audio storage
| extended from = [[Compact Disc Digital Audio|CD-DA]]
| extended to = 
}}

'''CD-Text''' is an extension of the [[Red Book (CD standard)|Red Book]] [[Compact Disc]] specifications standard for audio CDs. It allows storage of additional information (e.g. album name, song name, and artist name) on a standards-compliant audio CD.

The specification for CD-Text was included in the [[SCSI Multimedia Commands|Multi-Media Commands Set 3 R01]] (MMC-3) standard, released in September 1996 and backed by [[Sony]].<ref name="faq"/> It was also added to new revisions of the Red Book.<ref>[http://www.edocpublish.com/resources-2/specifications/cd-logos/ Approved Compact Disc Logo configurations].</ref> The actual text is stored in a format compatible with [[Interactive Text Transmission System]] (ITTS), defined in the IEC&nbsp;61866 standard.<ref>[https://webstore.iec.ch/publication/6045 IEC 61866:1997 Audiovisual systems – Interactive text transmission system (ITTS)].</ref> The ITTS standard is also applied in the [[MiniDisc]] format, as well as in [[Digital Audio Broadcasting]] technology and [[Digital Compact Cassette]].

== Storage ==
{{Optical disc authoring}}

The CD-Text information is stored in the [[Compact Disc subcode|subchannels]] ''R'' to ''W'' on the disc. This information is usually stored in the subchannels in the lead-in area of the disc, where there is roughly 5&nbsp;kilobytes of space available. It can also be stored on the main program area of the disc (where the audio tracks are), which can store about 31&nbsp;megabytes.<ref name="faq">[http://web.ncf.ca/aa571/cdtext.htm Unofficial CD Text FAQ].</ref> Since the R to W channels are not used in the Red Book specification of audio CDs, they are not read by all CD players, which prevents some devices from reading CD-Text information.<ref name="faq"/>

== Format ==
CD-text data is defined in a scattered manner between MMC-3 and Sony documentation. The information below uses GNU libcdio's description.<ref name=cdio>[https://www.gnu.org/software/libcdio/cd-text-format.html CD Text Format], in GNU libcdio documentation. Provides references to MMC-3 and Sony standards.</ref>

On the lowest level, CD-text is stored in 18-byte "pack" units; this part is defined in MMC-3 Annex&nbsp;J. Each pack consists of 4&nbsp;bytes of header (type indicator, track number reference, sequential counter, block number and character position indicator [BNCPI]), 12&nbsp;bytes of payload, and 2&nbsp;bytes of [[Cyclic redundancy check|CRC]]. The type indicator ranges from 0x80 to 0x8F, the 13 defined values being:<ref name=3r10g>[http://www.13thmonkey.org/documentation/SCSI/mmc3r10g.pdf MMC-3 Draft R10G]</ref>

{| class="wikitable"
|+ CD-Text keywords
|-
!Type!!Keyword!!Description!!Section!!Format
|-
|0x84||ARRANGER||Name(s) of the arranger(s)||Any||Character
|-
|0x83||COMPOSER||Name(s) of the composer(s)||Any||Character
|-
|0x86||DISK_ID||Disc Identification information||Disk||Binary
|-
|0x87||GENRE||[[Music genre|Genre]] Identification and Genre information||Disk||Binary
|-
|0x8e||ISRC||[[International Standard Recording Code]] of each track||Track||Character
|-
|0x85||MESSAGE||Message from the content provider and/or artist||Any||Character
|-
|0x81||PERFORMER||Name(s) of the performer(s)||Any||Character
|-
|0x82||SONGWRITER||Name(s) of the songwriter(s)||Any||Character
|-
|0x80||TITLE||Title of album name or track titles||Any||Character
|-
|0x88||TOC_INFO||Table-of-content information||Disk||Binary
|-
|0x89||TOC_INFO2||Second table-of-content information||Disk||Binary
|-
|0x8e||UPC_EAN||[[Universal Product Code|UPC]]/[[International Article Number|EAN]] code of the album||Disc||Character
|-
|0x8f||SIZE_INFO||Size information of the block||Any||Binary
|}

The BNPCI is used to define information that does not fit in one pack. This can be text or binary data. The BNCPI also indicates whether the text is single-byte or [[DBCS|double-byte]] data in the top bit. This determines how [[null-terminated string]]s are defined{{snd}} one or two bytes of 0x00.<ref name=cdio/> (Note: the DBCS mode is rarely, if ever, used. Its special null handling is not necessary for computer DBCS code pages, as they are "hybrid" with ASCII and compatible in the NUL behavior. [[UTF-16]] could be the intended use.)

For block types listed above as "character" (per MMC-3), the payload is a simple null-terminated string. (MMC-3 is written confusingly here{{snd}} it describes the encoding as "ASCII" in the pack type table despite mentioning the BNCPI flag modifying its behavior later.) The descriptions of the binary fields are vague, but the developers of GNU libcdio has either matched them to sections of MMC-3 or written new descriptions based on Sony's sample.<ref name=cdio/>

Another layer of encoding specification is found at this payload level, in the SIZE_INFO block. Here the first byte may be used to indicate the encoding, [[ASCII]], [[Latin-1]], or [[Code page 932 (Microsoft Windows)|"MS-JIS"]]. This is supported by the original Sony authoring tools.<ref name=cdio/>

== See also ==
* [[CD+G]]
* [[CDVU+]]
* [[ID3]]
* [[Vorbis comment]]

== References ==
{{Reflist}}

== External links ==
* [http://www.cdrfaq.org/faq03.html#S3-28 CD-Recordable FAQ, question 3-28: How do I add CD-Text information?]

{{Compact disc}}
{{Rainbow Books}}

{{DEFAULTSORT:Cd-Text}}
[[Category:Compact disc]]
[[Category:Metadata]]