[Mike Dehmlow]

Thank you that was in fact the problem, for those in a similar situation to parse close captioning from the video output of the Decklink card, the bit layout can be found here:
https://developer.apple.com/quicktime/icefloe/dispatch019.html#v210

It’s a little tricky because the luma and chroma data positions alternate every four byte word. I chunked out the stream as an array of int’s alternating between extracting one bye and two byte based on the modulo of the position.

One other thing is that in order to get every byte its fairly hardware intensive I modified my graph so that no video is displayed and I still drop frames when I move a window or basically anything else.