When the sink does not know the window size (e.g not created yet)
it will not add any param to the the composition meta. This is no
reason not to forward this meta API. Fixes issue where it could not
attach until we resize the window.
https://bugzilla.gnome.org/show_bug.cgi?id=745107
Adds an GST_VIDEO_OVERLAY_COMPOSITION_META_API_TYPE query to glupload
and glimagesink. Detects the query from the downstream elements, so
it is executed only when downstream supports the overlay API.
This makes pipelines with textoverlay ! glupload ! gldownload ! xvimagesink possible.
Uses allocation meta struct for passing the window size upstream.
https://bugzilla.gnome.org/show_bug.cgi?id=745107
I notice that if you stop the pipeline during a renegotiation
the upload may be NULL while an allocation query is being run.
In that scenario, returning FALSE to the allocation query is the
best thing.
In some upload implementations the out buffer has more than one references,
turning the buffer not writable, so it won't be possible to modify its
meta-data.
This patch moves the meta-data copy before increasing the reference of the out
buffer.
https://bugzilla.gnome.org/show_bug.cgi?id=746173
