The Datavideo DAC-70 converter is one handy dandy converter. It will allow you to convert HDMI or VGA video input into SDI. It's got a bunch of other nifty little features that are highlighted in this video.
Datavideo DAC-70 up/down/cross converter is designed to convert video signals from VGA, HDMI, SDI with Audio input to 3G/HD/SD SDI outputs.
Perfect for connecting a VGA/HDMI output from computer to SDI devices over long distance SDI cable. Solutons like lecture theater, church, auditorium room and conference hall.
3G/HD/SD Up/Down/Cross convert
3G/HD/SD SDI and HDMI output
Can be rackmounted using optional RMK-2 2RU Rack solution