Telestream Lightspeed Live Capture User Manual page 261

Timecode Source—Specifies the default timecode source. Choose from the following
timecode source signals:
– Source—For H.264 or H.265 the source's SEI data is used; for MPEG2 the source's
GOP header timecode is used. If no valid source timecode is available, see Free
Run Timecode below.
– Computer Clock— by the Lightspeed Live Capture Server. When selected, also
configure Compensate for Computer Clock Drift.
Caution: If your Lightspeed Live Server's Time Zone Setting is set to a time zone
that does not have Daylight Savings Time, computer clock use UTC time, due to a
Windows limitation.
– None—Specifies zero-based timecode recording. When recording begins, the
timecode is set to 00:00:00:00. If Free Run Timecode is enabled, then the
timecode inserted into a QuickTime or MXF file auto-increments. Otherwise,
every frame in the output file contains timecode 00:00:00:00. Capture displays N/
A on the workflow thumbnail, indicating that there is no applicable timecode
available, and 00:00:00:00 displays in Capture's Preview timecode window.
Free Run Timecode—Enabling Free Run Timecode when Compensate for Computer
Clock Drift is enabled has no effect. When enabled, and the desired timecode is not
detected or goes away, the timecode seamlessly free-runs from the last good timecode
received. When Free Run Timecode is not enabled and the desired timecode is not
detected or goes away, the timecode reverts to zero (00:00:00:00) and stays at zero.
Compensate for Computer Clock Drift—Only applies when Computer Clock is
specified as Timecode Source.
Regardless of how Compensate for Computer Clock Drift is set, if packets are lost and
frames are dropped the Live Source process adds frames using the last good timecode
in order to compensate for the lost frames. This may cause timecode values to be
repeated where a frame was lost. If your Transport Stream signal is strong, this problem
should not occur.
When Compensate for Computer Clock Drift is enabled
Computer Clock Time is monitored and compared to the timecode being added to
the captured file. Since the Computer Clock is not gen-locked with a true time
source associated with the incoming frames it can drift over time and get out of
sync with the incoming stream. When a drift of one second is reached the timecode
being added to the file is re-synced to the system's Computer Clock time. This
means there may be a discontinuity in the file's timecode at the point where the re-
sync occurred. Enabling Free Run Timecode when Compensate for Computer Clock
Drift is enabled has no effect on the process described here.
When Compensate for Computer Clock Drift is Disabled
The source process uses the Computer Clock time without compensating for drift.
Over time the timecode may drift several seconds compared to the 'real' time. For
example—if a recording is 6 hours long the Computer Clock drift might be many
Lightspeed Live Capture User Guide
Managing Video Sources
Creating & Configuring SRT Sources
263