[Libav-user] interlaced output from BlackMagic decklink Duo 2

[larnold7 at cox.net]

I have a QT  app based on the muxer.c example that creates a live video of text items and streams it out of a DeckLink card.
if I configure the output codec as:

        c->bit_rate = 400000;
        c->width    = 1920;
        c->height   = 1080;
        ost->st->time_base.den = 30000;
        ost->st->time_base.num = 1001;
        c->time_base       = ost->st->time_base;
        c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
        c->pix_fmt       = STREAM_PIX_FMT; //UYVY422

The Decklink card outputs at 1080p29.97. I need to produce 1080i59.94 to match our cameras and feed into an ATEM production switcher for keying onto the camera video. Can anybody tell me what I need to do to make this happen? Thanks in advance.