To understand the Timing view it's helpful to understand the timing model. The figure
is meant to visualise SMPTE ST 2110-21 standard.
The figure above illustrates the timing model, which puts constraints on the timing of
packets on the output of the sending device. The network compatibility model (C),
Virtual receiver buffer (VRX) and packet read schedule (PRS) all ensure that the
delivery timing is overheld by shaping the transmission.
The packet read schedule specifies the interval the packets are to be drained from
the Virtual Receiver Buffer. There are two different read schedules, the
Gapped
illustrated in the figure and the
Linear
. As opposed to the Linear which sends equally
spaced packets throughout the whole frame interval, the Gapped packet read
schedule is set to model the SDI signal and thereby contains a gap between the last
packet of a frame and the first packet of the consecutive frame.
The alignment point (referred to as “N * T
FRAME
since epoch” in the standard).
N
meaning the number of frames since Epoch and T
FRAME
is the time period between
succeeding frames. N*T
FRAME
will depend on the prevailing frame rate.
B Appendix: 2110 Timing model
58
VB440 Studio Probe User’s Manual v6.0
© Bridge Technologies Co AS
