Below diagram is an example to show how to connect SDI ports (Dual Link) for Fill and Key output from Reality Engine. As an example, we have choose AJA Corvid 88 for Video Out.

Since we know that 1 pair of SDI fill signal and SDI key signal makes 1 mixed alpha channel source, we must use video I/O board ports in groups only (Dual link or Quad link). As shown above with orange dotted line which links, 1-2, 3-4, 5-6 and 7-8, these are valid groups.

Ports grouped 2-3, 4-5, 6-7 are invalid pairs and fill and key signals cannot be achieved with such combinations.

In the example above, we have paired 5-6 (Dual link) ports for sending fill and key signals respectively, which means 5th port is sending Fill signal and 6th port is sending Key signal. With any combination of group, first port of the group is always considered to be Fill source and second port as Key source. 

Once the hardware connection is done, there are some properties which needs to be set in order to send proper fill and key signals. As an example, we will launch a project which contains UMG for online graphics having alpha channel transparency. Then on the node graph, we will add the nodes as explained below:

  • Add AJA CARD and AJA OUTPUT node on the node graph.

  • Add LOWER THIRD UMG node for the example in this article.

  • Connect the LOWER THIRD node' OUTPUT > AJA OUTPUT node VIDEO.

The output from AJA card will not yet send fill and key signals as alpha channel until the required properties are set to this node.

Select AJA OUTPUT node, in the properties section, select as shown below:

  • Dual Link (5-6): Fill and key output will be sent from these ports respectively.

  • Standard: Select desired output.

  • Framerate: Select fps based on your program frame rate.

  • PixelFormat: YCbCrA8-4:2:2:4 is the most important setting to get alpha channel signal.

Below diagram is an example to show how to connect SDI ports (Dual Link) for Fill and Key input to Reality Engine. As an example, we have choose AJA Corvid 88 for Video In.

In the example above, we have grouped 1-2 ports for receiving fill and key signals respectively, which means 1st  port is receiving Fill signal and 2nd port is receiving Key signal. With any combination of group, first port of the group is always considered to be Fill source and second port as Key source.

Once the hardware connection is done, there are some properties which needs to be set in order to receive proper fill and key signals. Run your desired graphics (in HD resolution) from external device, e.g. CG online graphics having alpha channel transparency. Then on Reality Engines node graph, we will add the nodes as explained below:

For input, add AJA CARD and AJA INPUT node on the node graph. Connect AJA INPUT node VIDEO pin > MIXER DEFAULTOVERLAY pin.

Select AJA INPUT node, considering that we are working with dual link source, in the properties section, select as shown below:

  • Dual Link (1-2): Fill and key input will be received to these ports respectively.

Port 2 will be set to receive Key signals automatically. There is no need to do any settings for selecting Key channels.

  • PixelFormat: YCbCrA8-4:2:2:4 is the most important setting to get alpha channel signal.

  • QuadLink Mapping: Select between SQD (Square Division) and 2SI (2 Sample Interleave).

Since we want the CG to be shown as overlay DSK, we must connect it to OVERLAY pin of MIXER DEFAULT node.

Connecting it to any other pin will not receive alpha channel transparency.

Anything connected to pin will render on top of all the other channels in the Mixer.

On the MIXER DEFAULT nodes' channels, you can connect your CAMERA node render or other compositing nodes.