Genlock System - Adtec RD-71 User Manual

Genlock System

The RD-71 can synchronize its SDI and CVBS outputs to an external sync signal using the
SYNC IN input and the Genlock control system. The SYNC IN input signal's frame
synchronization is used to generate SDI and CVBS output pixel clocks, frame
synchronization and audio clocks that are locked to the SYNC IN reference. The video
decoder will automatically skip or repeat video frames as needed to adjust to differences
between the SYNC IN clock and the decoder source clock (which is synchronized to the
stream's PCR data). The audio system uses a sample rate converter to adjust to differences
between the decoder source clock and the SYNC IN clock.
The Genlock system will automatically cross lock for all resolutions within the 59.94 Hz
standard or all resolutions within the 50 Hz standards. It does not cross lock between 50 Hz
and 59.94 Hz standards at this time. This allows the SYNC IN signal to be valid for
compatible decoded streams (example: An NTSC black burst SYNC IN signal can be used to
Genlock a 1080I59 feed).
The Genlock system can be configured in two modes. Genlock ​ S LAVE mode is used when
the SYNC IN signal is synchronous with the decoded stream, ie, both signals are using the
same 27 MHz source clock. This mode allows two RD-71's to be used for receiving 3D/4K
signals or when the decoded source is using the same clock base as the SYNC IN. This
mode bypasses the need for the audio sample rate converters. Genlock ​ R EMOTE mode is
used when the SYNC IN signal does not use the same 27 MHz clock source as the decoded
stream. This mode enables the audio sample rate converters for audio output.
The SYNC IN input will accept standard analog video sync for NTSC, PAL, 480I/P, 576I/P,
720P, and 1080I/P from Composite Video (CVBS). The input can accept Bi-level and
Tri-level sync signals. The signal is processed to create synchronous audio and video clocks
and to frame align the SDI and CVBS outputs with the input sync signal. Generally, the
output will be automatically aligned within a few pixel clocks of the input.
If the Genlock system is locked, and the SYNC IN is removed, the system will attempt to
maintain the clocks and frame reference with the last known locked frequency. There may
be some clock drift over time. If the decoder is stopped and restarted in this mode, the
Genlock system will use the decode source clock and operate in a 'free-run' mode until the
reference is re-applied. The video and audio will be lost for a short time when the SYNC IN
reference is restored.
When the Genlock mode is changed, the Genlock system will automatically be reset. This
will cause a brief disturbance of the video and audio outputs.
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