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For historical reasons it was mapped to a musicbrainz prefix,
but it's not really musicbrainz-specific at all.

Conflicts:
	libs/gst/base/gstbasetransform.c

... in the extent that a non-waiting pad (so indicated by newsegment)
turns out to provide the best buffer, which is then forced to waiting
for book-keeping purposes, but that should only be temporary.

See bug #415754.

This handles muxing of sparse/subtitle streams and has
lots of cleanup. Still missing is special support for
live streams but this can be added later without breaking
API/ABI.

Based on the version from the videomixer plugin.
https://bugzilla.gnome.org/show_bug.cgi?id=415754

If you get warnings, use gst_caps_new_empty().

https://bugzilla.gnome.org/show_bug.cgi?id=343346

Conflicts:
	libs/gst/base/gstbasetransform.c

If you get a warning, use gst_structure_empty_new().

https://bugzilla.gnome.org/show_bug.cgi?id=343346

Don't leak peercaps and a ref to the basetransform when returning
the cached caps.