[gstreamer-bugs] [Bug 618542] DVB subtitles support

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=618542
  GStreamer | gst-plugins-bad | git

Mart Raudsepp <leio> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |leio at gentoo.org
         Resolution|                            |FIXED

--- Comment #6 from Mart Raudsepp <leio at gentoo.org> 2010-12-16 02:54:43 UTC ---
There is now initial support for DVB subtitles available in the dvbsuboverlay
plugin in gst-plugins-bad development tree (most likely to get included in
gst-plugins-bad-0.10.21).
DVB subtitles are defined in the following specification: ETSI EN 300 743
V1.3.1 - Digital Video Broadcasting (DVB); Subtitle systems

Compared to v1.2.1, v1.3.1 adds a display definition segment to support scaling
and positioning for high definition video content (e.g supporting same dvb
subtitle encoding for SD and HD video streams). This should be supported by the
current code, thanks to Sebastian Dröge (scaling code) and Janne Grunau
(segment parsing and integration).

The RLE subpicture decoder is based on http://github.com/leio/libdvbsub with
modifications, which in turn was a port of mine to glib/GObject with fixes and
some refactoring of LGPL ffmpeg dvbsubdec code.

Manual pipelines with it seem to work good on good transport streams, feel free
to give it a spin.
There is probably some autoplugging work still to be done (soon) for playbin2,
though with some media it works out of the box already, but not for most.

2-bit and 8-bit object data segment RLE encodings have not been tested, as no
media that has been encoded with that method has been found yet. If you
encounter such a media, it currently will spit a g_warning once stating that,
so we'd get to know to verify and get feedback on it. It seems most broadcasts
use 4-bit object data segment RLE encodings, and this has therefore been pretty
extensively tested already.

Text coding object data segments are currently not supported. I have not seen
any media with that encoding yet with many European broadcasts tested, probably
because it is not well defined in the spec and relies on player/broadcast
co-operation to pick correct encoding/font/other properties, so not very
universally usable. Please let me know if you know of any such examples or when
supporting it should be important..

I guess if independent testers find issues with up to date git tree, new bugs
can be filed with the details. I consider the feature implementation complete
enough to close this bug as FIXED now. Further code improvement will get done
in the normal process of getting a plugin from -bad to have good enough quality
to be promoted to -good.


For completeness, some other ways that DVB/MPEG-TS can have some sort of
subtitles support, which are unrelated to DVB subtitles other than the
container type usually used, are:

* Teletext subtitles - tracked in bug 618850 and bug 619739
* Closed captioning - related to teletext (VBI data), didn't find any existing
bug requesting support; but could potentially be hooked up to libzvbi based
implementation of teletext support (bug 619739)

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