We have an ATEM TV Studio Switcher (https://www.blackmagicdesign.com/hk/products/atemtelevisionstudio) in the shop, which allows us to connect up to 9 cameras at the same time with a neat IP based control interface. It sounds like perfect solution for live streaming and event (HDMIs->ATEM TV Studio->Youtube), but challenges surfaced quickly.
The ATEM TV Studio has a USB connector which sends the mixed feed as an H.264 stream, in order to stream a video feed to youtube, we can choose from Wirsecast/FlashMediaLiveEncode (FMLE). Unfortunately, none of them works with the BM ATEM TV Studio Switcher.
Luckily, livestream.com provide a free livestreaming software called Procaster (http://www.livestream.com/userguide/?title=Procaster), which supports the BM interface out of the box!
We ended up stream the feed through livestream.com and use OBS (https://obsproject.com/download#obs2_dl), an opensource broadcasting program as the ultimate solution.
Because the unverified livestream.com channel can only serve up to 50 people, we use the screen/window capturing function of OBS to capture and re-broadcast the stream to youtube to work around this. Soundflower is being used for redirecting sound from the programme to OBS.
Cameras —HDMI/SDI—>BM ATEM TV Studio—USB—>iMac—->Livestream Procaster—>livestream.com channel
Mirrored stream (through another computer)
Chrome (Opening livestream.com as a popup)–>OBS–>Youtube
Another challenge we had was to mix the sound from the sound panel with the SDI video feed supplied by the video company. As the sound panel only provides XLR output and we didn’t have any USB sound capturing device, we used the Sony HDV camera as a XLR->HDMI convertor to the BM ATEM interface. Which worked pretty well.