ReferenceTimestampMeta can be used to attach alternative timestamps and possibly durations to a Buffer.
These are generally not according to the pipeline clock and could be e.g. the NTP timestamp when the media was captured.
The reference is stored as a Caps in reference. Examples of valid references would
be
* `timestamp/x-drivername-stream`: for timestamps that are locally generated by some driver named `drivername` when generating the stream, e.g. based on a frame counter * `timestamp/x-ntp, host=pool.ntp.org, port=123`: for timestamps based on a specific NTP server. Note that the host/port parameters might not always be given. * `timestamp/x-ptp, version=IEEE1588-2008, domain=1`: for timestamps based on a given PTP clock. * `timestamp/x-unix`: for timestamps based on the UNIX epoch according to the local clock.