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Calibir GXM640 IR Camera User's Manual
Features and Configuration Options
69
PTP Configuration Features
Features are available to configure PTP behavior and compensate for network topologies
that include standard Ethernet switches (without PTP tranparent mode support) which
can introduce large, non-deterministic variations in the reception of PTP packets. These
features provide more tolerance to variations in network transmission time of PTP
packets.
Outlier Detection
When the camera receives a PTP sync messages from the master, if the difference in
timestamps
(Master
to
Slave
difference)
is
outside
acceptable
limits
(ptpServoStepThreshold), it is flagged as an “outlier” and ignored.
If the camera receives a large number of outliers, it is assumed that an event has
occurred on the ethernet network that makes it temporarily too unstable for the PTP
algorithm to run. In this case, the Calibir reverts its clock speed to its normal, non-
adjusted value and restarts acquiring statistics on the PTP master, that is, it enters the
synchronization state.
The ptpSyncHistorySize feature determines the number of PTP sync messages saved,
both valid and outlier; if the number of valid PTP sync in the history falls below the
minimum number of valid PTP sync messages (ptpSyncMinCount) required, the camera
reverts back to the Synchronizing state.
To reduce the impact of large adjustments that are still within the outlier threshold, a
user-configurable fraction of the timestamp difference (ptpClockOffsetAdjustFactor and
ptpClockSpeedAdjustFactor) can be used to perform the slave clock offset and speed
corrections. In addition, an upper limit to the size of the corrections can be applied
(ptpClockOffsetMaxAdjust and ptpClockSpeedMaxAdjust).
Related GigE Vision Features
PTP-related features are part of the Event Control feature category; for complete feature
descriptions refer to the Event Control Feature Descriptions.
