We can only reliably use the adaptation field discontinuity flag if our input is properly timestamped on a regular basis (ex: UDP, DVB, RTP, etc...). For HLS and other systems which don't provide that information, we should not reset the base observations. Otherwise we would potentially end up picking a reference time from a long time ago. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8480>