[vlc-devel] Re: How is CD-Text (or CDDB, Musicbrainz) supposed to work with the new infrastructure?

R. Bernstein rocky at panix.com
Wed Aug 25 06:52:34 CEST 2004

=?iso-8859-15?Q?Cl=E9ment?= Stenac writes:
 > Glad to see that we might have an improved CD plugin back

We're really not there yet. I've compiled something locally but I haven't
been able to get back in meta information, let alone move forward.

 > You can use p_input->input.p_item 

Could you give a detailed example? Is this documented? 

 > and store meta information here (not
 > sure if you are allowed to use input_Control( INPUT_ADD_INFO ) in an
 > access module)

input_Control() is what I was using before in the cdda plugin. But at
that point the data type was input_thread_t)

 > These are stored as "titles" (look in the navigation menu), at the
 > moment. As anyway, this plugin does not get any meta-information, 

Actually in a sense, it does. It knows how many tracks are on the CD
and I suppose the length of the CD (the leadout). At the least it
could add that to the media info. 

 > I am currently working on an improved playlist core which allows for
 > tree structure, so you could have the original CD playlist item which
 > contains one child item for each track.

As is said in Yiddish, Oy. Maybe I should wait until after this is
done.  I'm not really all that enthusiastic about working on something
then finding it's been changed so either the work I spent was
superflous (as in the OGT and CVD subtitles) or that I need to change
it again as in CDDA and VCD. I have other projects I'd like to move
forward on. (For example, bash 3.0 is out and it has the debugging
support that I put in the patched 2.05b.)

 > (It would be fine, if we could have a probing system, with a part of a
 > CD module that would remain loaded and check when a CD is inserted and
 > add the playlist items automatically)

The 0.70 release of libcdio will add a generic interface to give SCSI
MMC commands. In later releases I'll try to package common useful SCSI
MMC commands in a way that may be generally useful.  Actually in 0.70
things like "get drive capability" (MODE SENSE 10) is already there.

I believe there is a MODE SENSE flag reported back which will let one
know if media has changed. SCSI MMC often has a couple ways of doing
the same thing (Hurray for standards!) and there is another set of
commands to get all "features" supported by a drive, one of these is
something which tells you if the drive supports indicating whether
media has changed.

So in cases where a drive supports indicating whether media has
changed (which I'm assuming is all the more modern drives), it should
be possible in libcdio to give that status back and add a common
interface so you don't have to know about the SCSI MMC MODE SENSE 10
and GET CONFIGURATION commands and flags.

OSX seems to have its own unique and complicated mechanism, but no
matter how wonderful the OSX mechanism is, unless it can be replicated
with good probability to other OS's it's probably not going to get
added in libcdio.

 > I'm not sure I quite understand what you mean. You can set the psz_name
 > field of the input item, can't you ?

I'm probably wrong and one can probably set that field. (But I don't
remember -- did it work in cddax on 0.7.2?) Right now though I'm not sure
exactly how to set that field. Detailed code or documentation would be
nice. Failing that another access plugin that in fact uses this would
be nice.

 > anyway, don't hesitate to come on the irc channel for a more live
 > discussion about these issues.

I'd like to take you up on that. Right now too I'm pressed for time on
too many projects. If I can get something working, without too much
hassle I'll do it. If it's too much hassle, I think I have to shelve
it and go onto something where progress can be more easily made.

 > Good luck

Thanks. I think I'm going to need not just luck but probably a little
bit of help. Which reminds me, thanks everyone for the help so far!

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