Hey all,
The IEEE specs for 12G add support for a 4th channel, to be used for Alpha or Ancillary data.
Alpha is very convenient for running live lower thirds (instead of green screen or luma keying), and since the Constellation and other 12G switchers support the spec, how do they handle the extra channel? Do they now support Alpha over SDI? I was going to ask support directly, but this is useful for general knowledge to others too, so better to add somewhere it can be found.
Here's the technical overview from IEEE, and it looks like Alpha is added in ST 2082-10.
https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7565450