Blackmagic DeckLink Alpha In

With many of the Blackmagic DeckLink cards a single in/out channel has 2 SDI lines (key and fill). This allows you to easily work with video that has an alpha channel. In Touch I can easily output like this but I can’t seem to figure out how to input a channel of video with with alpha. I only get the RGB fill.

Is this a limitation or am I missing a setting?

I could add another DeckLink card for the key channel and merge them but this leads to sync problems. The DeckLink card buffers can drift leading to the key and fill not lining up.

I don’t need it but the same issue occurs with audio. The audio stream that shows up like a sound card is not synced with the video stream.

As far as I know there is no way to do a Key+Fill input with decklink cards, only output.

Is there anyway this option could be added?

I am processing the output of graphics system and I am losing a lot of quality keying out black instead of using the alpha channel.

I mean, the hardware/drivers don’t support it. It would be something to ask blackmagic to add support for.