[gstreamer-bugs] [Bug 324162] New: Add gst_buffer_make_meta_writable or similar

[GStreamer (bugzilla.gnome.org)]

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 GStreamer | gstreamer (core) | Ver: HEAD CVS

           Summary: Add gst_buffer_make_meta_writable or similar
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: thaytan at mad.scientist.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
                CC: all-bugs at bugzilla.gnome.org


It is dangerous to do modifications to the metadata of a buffer like:
http://freedesktop.org/cgi-bin/viewcvs.cgi/gstreamer/gst-plugins-base/gst/playback/gstplaybin.c.diff?r1=1.73&r2=1.74

Because buffers are refcounted, only the creator of a buffer can be sure that
the metadata can be safely modified. One option is to call
gst_buffer_make_writable, but that will copy the data block unnecessarily. 

I'dlike to add a core utility function called something like
gst_buffer_make_meta_writable that will check the refcount on the MiniObject. If
the refcount is 1, then the metadata is modifiable, otherwise create a subbuffer
of the entire contents and return that instead.

This would also remove the ugly bit of code in basetransform that checks the
refcount itself.

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