Re: [xine-devel] On implementing setting Track and Chapter

[R. B. <ro...@pa...>]

Michael Roitzsch writes:
 > On the other hand, the UI_SET_TITLE method is much more flexible, since 
 > it allows arbitrary names for these navigation entities. 

I think I see your point but I am not sure I totally
agree. UI_SET_TITLE is already used to mean "set some sort of title"
in the front end. That's already dedicated.  So I was proposing to use
*another* UI_SET_XXX in *addition* to XINE_STREAM_XXX or
XINE_META_INFO_XXX.  Comparing adding another event or another meta
information, I don't see how one is more flexible than the other.

Here's the difference in coding:

  uevent.type        = XINE_EVENT_UI_SET_XXX;
  uevent.stream      = this->stream;
  uevent.data        = &data;
  uevent.data_length = sizeof(data);

  memcpy(data.str, str, strlen(info) + 1);
  data.str_len = strlen(info) + 1;

  xine_event_send(this->stream, &uevent);

vs. 
  stream->meta_info[XINE_META_INFO_XXX] = strdup(info);

Setting meta is simpler, but with xine_event_send(), the effect is
more immediate. Setting meta info, it's up to the front end to notice
a change. For the information we're talking about here, I don't think
it's all that crucial to the information updated immediately. The
default behavior in the Video CD an CD-DA plugins sets the track name
in the display, and in fact what I see right now is that the title
gets updated before playing because there are audio or video in
buffers that haven't played.

But perhaps by "more flexible" you meant that "title display" contains
a bunch of uninterpreted text. Yes that's flexible, but not all that
helpful and in some skins wasteful of screen real estate. In my CD-DA
and Video plugins you in fact can customize that to show the Track
(which makes sense in both plugins), Segment (which makes sense only
for Video CD's), or CDDB Disc ID (which makes sense only for
CD-DA). Or decide not to show them among many other possibilities. If
you don't want the word "Track" to appear, you can make it say or
"Spur", "Piste", "Pista" or whatever. And as far as I know, these are
the only plugins that do let you customize the display. So you are
preaching to the choir here (my plugins are already 'more flexible.')

But the designer of Celanoma clearly was trying to model the display
of real hardware media players and that's not a bad starting
point. Many of them have a digital display. Also, it might be helpful
in the stream information to have a portion for that digit display.

 > "Track" and 
 > "Chapter" sounds very CDDA/VCD specific. 
 > From the DVD standpoint, these 
 > should be called "Title" and "Part". Other inputs might have even 
 > different names (DVB might want something like "Channel").

Track might be specific to CD-DA and Video CD (and for DVD's it's not
all that unacceptable to call a title a track), but Chapter isn't. The
Video CD word is "Entry."  And there is no such subdivision for
CD-DA. I used the word "Track" and "Chapter" merely because in
Celanoma there is a T field and a CH field (which could mean "chapter"
or "channel"). So would people prefer

#define XINE_STREAM_CH_NUM        27  /* chapter or channel, or ... */
#define XINE_META_INFO_T_NUM      10  /* track or title, or ... */
?

 > So we should be very careful not to make the metainfo too specific for 
 > certain input plugins. 

Actually it already is very specific. There already are fields for
"Genre", "Album", "Year", "Has Chapters" (not "Has Channels" or "Has
Parts" ;-)

But I have a suggestion here. There is no reason that these fields
can't be reused in ways appropriate for that format.  In fact I
already do that in the Video CD plugin. I use the "Genre" field for
the video format (VCD 1.0, VCD 2.0, SVCD). What's missing is the
ability to customize that title for that format so instead of "Genre"
is says "Video Format". And to make it less hoaky on setup one could
change xine.h.in from:

#define XINE_META_INFO_GENRE               3

to:
#define XINE_META_INFO_GENRE               3  /* used by CD-DA */
#define XINE_META_INFO_VIDEO_CD_FORMAT     3  /* used by Video CD's */