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

Clément Stenac zorglub at via.ecp.fr
Wed Aug 25 15:16:01 CEST 2004

> 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.

My main point is that you indeed want to restore it :)

Anyway, even if meta information is not fully restored, if the plugin
works, it is probably worth commiting it.

>  > You can use p_input->input.p_item 

> Could you give a detailed example? Is this documented? 

I don't know if it is "legal", but you can vlc_object_find the input
thread, and access p_input->input.p_item which is the "input_item" that
stores the uri, the name, and the meta information about the current

But to really store meta information, the best way is to use
input_Control( INPUT_ADD_INFO )

> 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. 

It could indeed, but as gibalou explained, the fact is that we lack an
easy way to add meta-information from an access module. I think adding
ACCESS_GET_META to access_Control should be enough and not that hard.

> As is said in Yiddish, Oy. Maybe I should wait until after this is
> done. 

Well, anyway, it won't change "much" for you. At the moment, you would
set autodeletion flag on your current playlist item and use playlist_Add
to create new items. 

Only that part would change, you will then use playlist_ItemToNode on
the current item and playlist_NodeAddItem for each new item.

And it will be quite easy then to add meta-information to the children

Because, here is the point.

The "parent item" can contain meta-information, but also the children. 

I think you should have a "Audio CD" category in each item or only in
the parent, as you prefre, for general info like number of tracks, total
length, ... + in the "meta-information" category add the track-specific
info, using the meta system. Actually, ACCESS_GET_META wouldn't help
much, beacuse it would only work on the parent item, which is not the
place where you want most of the info, and certainly not info which is
stored in the "meta-information" category IMHO.

You will have to add meta information yourself to the children item
(look at the inline helper functions for this)

> 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) 

I don't think one can say this work was superflous as anyway, some of it
will get reused in the new subtitle filters.

> or that I need to change
> it again as in CDDA and VCD
Well, this API change was needed and affected everything ...

> 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
> [snip]

Ok, I think for this we'll have to add interface capabilities to your
plugin and this part of it will be used to create the items on media
change.. Anyway, this is longer term and only to do after the playlist
change (which will occur after the reelease of 0.7.3)

> 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?) 

I think it did.

once more, ethe meta system would be better, it is more consistent but
needs to be expanded a little.

> Thanks. I think I'm going to need not just luck but probably a little
> bit of help.

I would be quite happy to help you, especially on these meta-information
issues, but at the moment,I don't know much about CD-DA or
libcdio/licddb. Don't hesitate to contact me if you need.

Anyway, I don't think you should consider these issues as blocking for
the release of this plugin, it would anyway be better.

Clément Stenac

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