Re: [Libcdio-devel] CD-Text patches

[Leon Merten Lohse]

Hi Thomas,

On Thu, Dec 01, 2011 at 09:49:07AM +0100, Thomas Schmitt wrote:
> Hi,
> 
> i logged parts of the data traffic between wodim and the drive,
> while it performed the CD-TEXT test:
>   wodim dev=... -dao -text cuefile=cdtext.cue
> 
> The result is that i seem to understand what's going on, but that
> it does not resemble much the "Sample CUE SHEET" tables in MMC-3
> to MMC-6.
> All CD-TEXT goes to Lead-In, whereas in the MMC example, the CD-TEXT
> is written to a track.

I am unsure which example you are refering to. CD-TEXT is exclusively
written to Lead-In.
The original specification allowed a second method, where it was written
to the whole disc but I do not know of any implementations nor can I
think of a use case.

> Does anybody know an occasion or a way how CD-TEXT is written into
> tracks ? (I.e is this in any way important ?)

No.

> Do we have CD-TEXT input files from other sources which one could
> compare with cdtext.cdt ?

You can easily create your own. All you need is a disc with CD-TEXT on
it. The git version of libcdio has a function get_cdtext_raw (in disc.h)
that gives you an exact copy of the CD-TEXT on the disc. Just write it
to a file and feed it to wodim.

> I found this stumblestone:
> The fourth bytes of each pack in cdtext.cdt seem not to comply to
> MMC-3 Appendix J:
> "Bit 0 to Bit 3, indicate the Character Position. It is the number
>  of character in the strings that belongs to the Text Data Field in
>  the previous Pack."
> But in cdtext.cdt this nibble seems rather to count the characters
> which have been written to the current text by the previous pack.

Maybe CDRWIN's CD-TEXT editor, the one I used to create cdtext.cdt
is worse than I expected. We should not
rely on that file too much.
I now have a Windows 95 machine running *yay*. That gives me access to
Sony's original CD-TEXT authoring tool. I will try to create a new
cdtext.cdt over the weekend with it. Hopefully we can rely on that.
Remark: I hoped it would also feature Japanese CD-TEXT. Unfortunately
you need the Japanese version of the tool for that and that is not
available anymore.

> (It would be interesting to see what happens if bytes 1, 2, 3 are
>  plain 0. They seem to be quite redundant. MMC-3 Appendix J defines
>  that the texts end by a 0-byte and that they get attribyted to
>  whole disc, track 1, track 2, ... in the sequence of their appearance.)

It is indeed redundant. libcdio's implementation does not need them
at all (whereas cdda2wav does, as far as I remember).

> ------------------------------------------------------------------
> Technical details of wodim's operation:
> ------------------------------------------------------------------

Really interesting!

Regards
Leon