Telestream PRISM MPI, User Manual

Page: 198 / 304

Application Information
Timing Application
PRISM MPI-MPX User Manual
198
Additional offset displays are available for Quad Link SDI signals.
•
Link Offsets: Time delays of Links B, C, and D relative to Link A. These time delays are
also shown graphically under the timing display window.
•
Max Link Offset: Maximum time delay between any two links.
Timing Offsets for IP Signals
Because ST2022-6 streams are complete SDI signals encapsulated in IP, the timing
measurement treats these IP signals as if they were SDI. So the timing system detects
the start of the IP frame, then extrapolates to the 0h point of the encapsulated SDI.
Then using PTP as the reference, the ideal alignment point for that frame rate is
calculated based on the PTP epoch. Finally, the offset between the ST2022-6 signal and
the ideal alignment is displayed. The display shows both absolute time and the time
parsed into lines or horizontal delay as time and pixels.
For ST2110-20 streams, the Timing application displays the time of the first packet of
the frame. Since ST2110 does not include blanking, the first packet is nominally
coincident with the first active line in the SDI raster. This means it is normal for the
ST2110 streams to be delayed by the lines in the vertical blanking of a given format.This
value varies by format: HD (21 lines), 3G (42 lines), 4K/UHD (84 lines). According to
ST2110-21, both gapped and linear flows should have the start of frame delayed by the
equivalent of vertical blanking.
Use Cases for Measuring Timing
One use case for the Timing application is to measure the delay in a gateway and
network. If a properly timed SDI signal is applied to a gateway, then the timing
measurement on the resulting IP flow displays the combined latency in the gateway
and the network.
Each ST2110 stream also carries time stamps. The Stream Timing application allows for
the analysis of these time stamps.