While this creates a circular reference between the pipeline and the
context, this ensures that the context stays alive for as long as any
callbacks could be called on it. The circular reference is broken once
the conversion is finished (or error, or timeout), which will then cause
everything to be freed.
Previously it was possible that a callback could be called on the
context right after it was freed already.
Also use only a single context structure, the second structure does not
simplify anything and duplicates storage.
The GSource for dealing with timeouts in
gst_video_convert_sample_async() might be attached to a non-default
context, so we should not be using g_source_remove() on the returned ID.
The correct thing to do is to keep a reference to the actual GSource and
then call g_source_destroy() on it.
https://bugzilla.gnome.org/show_bug.cgi?id=780297
Add private replacements for deprecated functions such as
g_mutex_new(), g_mutex_free(), g_cond_new() etc., mostly
to avoid the deprecation warnings. We'll change these
over to the new API once we depend on glib >= 2.32.
Replace g_thread_create() with g_thread_try_new().
Make appsink return a GstSample. Remove the pull_buffer_list method because it
is not very useful anymore.
Pass GstSample to the conversion function.
Update playbin2 and examples
Binding generators apparently need this as they can't really know
that the callback is guaranteed to be called exactly once and that
the user_data can be freed at the end of it.
There will always be only a single output buffer and if the
target caps have a different framerate than the input there
will be a negotiation error during conversion.
