I couldn't get an answer nor from Blackmagic support, nor from Blackmagic forum. So I try here.
My Teranex 2D is missing its "audio menu" (page 81 of the Teranex manual), so no audio mapping is possible ("audio menu" is not the same as "setup -> audio" which serves to choose between RCA and DB25).
And audio embedded in the HDMI out has only 2 channels max.
Do other users of the 2D versions have the same problem ? What about the 3D version ?
I wish Blackmagic would acknowledge the problem, and I hope some good folks can help me define if the problem is with my unit, the 2D, or the teranex line-up