[gst-devel] Re: Totem or no Totem was Re: GNOME Development Series Snapshot 2.3.0: "Mighty Atom"

Mario Sergio Fujikawa Ferreira lioux-list at uol.com.br
Wed Apr 23 19:42:06 CEST 2003


On Thu, Apr 24, 2003 at 12:26:22AM +0200, Thomas Vander Stichele wrote:
> > On Wed, 2003-04-23 at 15:36, Bastien Nocera wrote:
> > ...
> > > You didn't get it at all. These are just subtitle formats, you can use
> > > them on top of any video playable by the player. Ie. if I have an MPEG
> > > file, and a subtitle file, I can have the subtitles synchronised with
> > > the video. For all these formats, the specs are available.
> > 
> This may be a stupid question, but who's going to promote this to content 
> creators ? Who are these content creators ? And why aren't they using SMIL 
> already ?
> > If nothing else I would expect that some transformation software between
> > SMIL and these formats could be put together.
> same here - who's going to  write this software ?
> I've been hearing about SMIL for a long time but I've never had to use it 
> and I don't see a lot being done with it.

	I am going to provide a user point of view. I've done
some research on computer based subtitling. I have used all of the
usual subtitling formats available for Windows (and Unix via mplayer):
Subrip, SubViewer, MicroDVD, SubStationAlpha and MPSub. Formats are
chosen based on usability (available applications to edit and to
view the subs) and on capability (changing font faces, styles,
positioning, coloring).

	From the aforementioned, the easiest format to use is
subrip. However, the most feature rich is SubStationAlpha since it
allows you to pick placement on the screen (left, right, top, down),
font assignment, font coloring, font styles, etc. However, none of
these formats has l18n support. Which is a MAJOR drawback from a
developer point of view.  Therefore, we cannot rely on any of them
for wide deployment. SubStationAlpha developers could be contacted
about adding l18n support since their format seems the most flexible.

	Okay, these were just subtitling formats. Using a good
recent video player such as MPlayer, Zoom Player or avifile; you
add subs to a video by simply telling the player where to find a
suitable subtitle file in one of those aforementioned formats.
Therefore, the use of these files does not interfere with the video
in any way. You can use them with MPEG, AVI, OGM, etc.

	What about multimedia containers? Neither MPEG nor AVI have
any support for embedding subtitles in the files. 

		1) A MPEG file can have more than one MP2 audio
		   stream embedded but no subtitle streams.
		2) A SVCD can several MPEG files and subtitles for
		   them. Therefore, a SVCD can have a MPEG with
		   both several MP2 audio streams and several
		   subtitles. SVCD can support DVD-like chapters.
		3) However, one CAN'T tell which stream belongs to
		   which language. You have to check out if
		   audio/subtitle 1 is english, german, french,
	- AVI
		1) An AVI file can have more than one video/audio
		   stream embedded but no subtitle streams. Selecting
		   amongst the multiple video and audio streams
		   require specific software.
	- OGM
		1) Supports multiple audio, video, subtitle streams.
		2) Subtitle streams are currently limitted to
		   SubRipper/subrip format but plan is on the way
		   to add support for other formats.
		3) Supports DVD-like chapters.
		4) One can language identify any kind of stream.
		   Therefore, you can tell the language of an audio,
		   a video or a subtitle stream.

	Of course, I might be missing information here but you can
have an idea. From a user perspective, all current subtitling formats
should be supported. There are several implementations around as
an example (mplayer for instance although not the best implementation
for some of the formats, e.g., SubStationAlpha). Furthermore, there
are many users wishing for such support. These should make it in
the priority list.

	From a developers perspective, we should push the technology
to support the next best thing. Therefore, adding support for OGM
and trying to support/develop l18n capable subtitle formats not to
mention MPEG4 containers (although they're not widely deployed yet
not have been "de facto" established) which should be perfect for
streaming. Not to mention this SMIL we keep hearing about but I
have to yet see a real life example of it. These should make it in
the "wish list". :)

	Well, I hope to have added a bit to the discussion. If you
need more info, ask me and I'll try to answer though I'm just a
small town user. :)


Mario S F Ferreira - DF - Brazil - "I guess this is a signature."
FreeBSD Committer | Unix Developer
lioux at ( freebsd dot org )
flames to beloved devnull at someotherworldbeloworabove.org
feature, n: a documented bug | bug, n: an undocumented feature

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