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[Libcdio-devel] CD-TEXT documentation

From: Thomas Schmitt
Subject: [Libcdio-devel] CD-TEXT documentation
Date: Sat, 04 Feb 2012 12:27:14 +0100


now that i have released libburn and cdrskin with CD-TEXT features,
i want to contribute to the libcdio docs about that topic.

Are there files to read and update, other than these ?
 doc/glossary.texi item "CD Text"
 doc/libcdio.texi node "CD Text"


Consider to add a pointer which refers to libburn's doc/cdtext.txt.

(The latter triggers on my elderly browser download rather than viewing.)


Some of its aspects go beyond my own CD knowledge.
Nevertheless, i have to question some statements:

> The first place the information can be recorded is in the R-W sub
> codes in the lead in area of the CD giving a data capacity of about
> 5,000 ASCII characters (or 2,500 Kanji or Unicode characters).

How was the payload of 5,000 bytes computed ?

The highest lead-in start for recordable CD media in my list is
97m 49s 00f which means LBA -9975. Lead-in reaches up to LBA -150.
Each sector can take 4 text packs of 12 bytes payload = 471,600 bytes.

MMC command READ TOC/PMA/ATIP could retrieve 65,534 bytes from lead-in.

A CD-TEXT block can have only 253 payload packs of 12 bytes each.
There can be 8 blocks at most. 253 * 12 * 8 = 24,288 bytes.

A single block (i.e. one language) can have 253 * 12 = 3036 bytes.

> The second place the information can be recorded is in the R-W sub
> codes in the program area of the CD giving a data capacity of roughly
> 31MB. This information is stored in a format that follows the
> Interactive Text Transmission System (ITTS) which is the same data
> transmission standard used by such things as Digital Audio
> Broadcasting (DAB), and virtually the same as the data standard for
> the MiniDisc. Traditionally the R-W sub codes have been used for text
> and graphics in applications such as CD+G

Shouldn't the statement about the format be separated in an own paragraph ?
"This information is stored in a format [...] the MiniDisc."

Afaik, the format is the same in lead-in and in program area.

Is the statement about CD+G particularly about program area or does it
apply to lead-in too ?

> In the case of ATAPI drives, the
> SFF8020 spec covers the reading of the RW subcodes.

This is covered by MMC meanwhile.
Reading from lead-in is done by command 43h READP TOC/PMA/ATIP, Format 0101b.
Reading from program area is supposed to be done by BEh READ CD.
(I did not explore the latter yet.)

Are any non-MMC drives still worth to be mentioned ?

How much degree of detail from
would be appropriate for doc/libcdio.texi resp. other libcdio documentation ?

You are of course invited to simply copy the whole thing. But near the
end it contains some libburn specifics.
(Proff-reading would be appreciated, too.)

Have a nice day :)


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