Also move processing from the capture thread to the streaming thread.
The NDI SDK can cause frame drops if not reading fast enough from it.
All frame processing is now handled inside the ndisrcdemux.
Also use a buffer pool for video if copying is necessary.
Additionally, make sure to use different stream ids in the stream-start
event for the audio and video pad.
This plugin now requires GStreamer 1.16 or newer.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1365>
The NDI closed captions specifications [1] define a variation where metadata is
attached to the video frame. This requires the AFD buffer to be v210 encoded.
This commit applies this strategy.
Another difference with previous version is that when an error occurs while
encoding or decoding a meta, next meta are also tried instead of failing
immediately.
Receiving closed captions as a standalone metadata is kept for interoperability
purposes. In this case, metadata is also expected to be v210 encoded.
[1]: http://www.sienna-tv.com/ndi/ndiclosedcaptions.html
Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1356>
