Genlocking output on a DeckLink SDI 4K

Hi we're starting to use a decklink SDI card for development on linux and we're asking ourselve if there is any special instructions to get our signal to be genlocked.

We already have a blackmagick clock generator plugged in in the REF connector but i can't seems to find any other instructions beside plugging the cable. I also went through the sample code and SDK documentation there doesn't seems to be any mention of genlocked output.

Alex

[Nicholas Gill]

Hi Alex,

When performing a playback operation, a compatible genlock signal will be used automatically to time the output.

The DeckLink API provides interfaces to determine the genlock status, and to configure an offset with respect to genlock.

The relevant attributes[1] which can be queried via the IDeckLinkAttributes[2] interface are:

BMDDeckLinkHasReferenceInput - Identifies if the particular device has a reference input connector.

BMDDeckLinkSupportsFullFrameReferenceInputTimingOffset - normal range for the adjustable reference offset is +-511 pixels, if this flag is supported then the range is expanded to +- half the total pixels in the video frame.

The IDeckLinkOutput::GetReferenceStatus[3] method can be used to determine the current genlock status. It returns a bitmask from the BMDReferenceStatus[4] enumeration.

The relevant configuration[5] items available via the IDeckLinkConfiguration[6] interface are:

bmdDeckLinkConfigReferenceInputTimingOffset - a configurable offset with respect to reference. Use the BMDDeckLinkSupportsFullFrameReferenceInputTimingOffset attribute to determine the range.

The status of the reference input can also be monitored from the IDeckLinkStatus[7] interface.

The relevant status information[8] items are:

bmdDeckLinkStatusReferenceSignalMode - The detected reference input mode (BMDDisplayMode), available on devices which support reference input format detection.
bmdDeckLinkStatusReferenceSignalLocked - True if the reference input signal is locked.

The status of the reference input can be observed in the Desktop Video Utility, as "REF INPUT".

Cheers,

-nick

[1] 2.7.17 DeckLink Attribute ID
[2] 2.5.17 IDeckLinkAttributes Interface
[3] 2.5.3.26 IDeckLinkOutput::GetReferenceStatus method
[4] 2.7.40 Genlock reference status
[5] 2.7.18 DeckLink Configuration ID
[6] 2.5.15 IDeckLinkConfiguration Interface
[7] 2.5.39 IDeckLinkStatus Interface
[8] 2.7.59 DeckLink Status ID