[gstreamer-bugs] [Bug 540131] New: [textoverlay] no support for displaying multiple text buffers

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS
           Summary: [textoverlay] no support for displaying multiple text
                    buffers
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: vortex at wolpzone.de
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


Please describe the problem:
After receiving a text buffer, textoverlay waits until it has expired before
accepting a new one. That way, textoverlay can only display one text event (or
rather: the contents of one text buffer) at a time.

Several subtitle formats have support for multiple simultaneous lines or text
events, like ASS or SRT.

Steps to reproduce:
Just play some file with ASS or SRT subs, where there are multiple lines of
text to be displayed simultaneously.

Actual results:
Only the text buffer that is received first is actually displayed. All others
that should be displayed simultaneously are DROPPED and not displayed at all.

Expected results:
Textoverlay should be able to display the contents of more than one text buffer
at a time. Of course, this means that it is also necessary to implement
collision detection, so that multiple lines of text won't overlap. 

Does this happen every time?


Other information:
The direction of the shift for collision detection depends on the current
setting for the vertical alignment.

When subtitles are aligned at bottom, any additional lines of text shall be
shifted upward, so that they won't overlap with what's already being displayed.

When subtitles are aligned at top, additional lines shall be shifted downward.

Not sure what to do with centered subtitles, but who uses that anyway? ;-)


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