decklink: Add support for extracting/embedding KLV metadata in SDI
WIP implementing SMPTE RP 214 for KLV embedded in VANC of SDI. Not tested with an actual device yet, only loopback. Also only supports KLV on a single line, though KLV ANC packets can extend on multiple lines.
Will close #1108 Depends on this KLV meta merge request, for expediency it's included in my WIP branch.
Edited by Joshua M. Doe