VideoOverlayRectangle.getSeqnum

Returns the sequence number of this rectangle. Sequence numbers are monotonically increasing and unique for overlay compositions and rectangles (meaning there will never be a rectangle with the same sequence number as a composition).

Using the sequence number of a rectangle as an indicator for changed pixel-data of a rectangle is dangereous. Some API calls, like e.g. [gstvideo.video_overlay_rectangle.VideoOverlayRectangle.setGlobalAlpha], automatically update the per rectangle sequence number, which is misleading for renderers/ consumers, that handle global-alpha themselves. For them the pixel-data returned by gst_video_overlay_rectangle_get_pixels_*() won't be different for different global-alpha values. In this case a renderer could also use the GstBuffer pointers as a hint for changed pixel-data.