Blackmagic & Wirecast – Live Streaming
Simple Thought Productions specializes in streaming live events. Today we are going over our setup for a multi-camera setup for a sporting event. In this setup we utilize two court cameras and a third camera that provides a live clock overlay. A second computer provides a live stats view to mix into the overall stream. First lets take a look at the overall mixed live stream we are trying to create.
The Background is fed by the Blackmagic Television Studio (ATEM). This provides an HD stream where the cameras are frame synced between cuts which means that the cut is clean and there are no black frames between the switch. This also allows us to mix up to 6 cameras over a combination of HDMI and HD-SDI connections without adding load to the computer that is taking care of the live stream. The lower thirds are from the second computer. On top of that is a feed via a Blackmagic Mini Recorder providing a live shot of the clock. The ATEM device does not allow for specific picture in picture layouts, you can create the effect somewhat but not perfectly with a partial transition, which is why the live clock camera comes directly into Wirecast. This setup requires that we do the primary switching on the ATEM and secondary switching (full screen stats) in Wirecast. Utilizing the software control for the ATEM we have both controls on screen at all times.
Video Input is handled by two Blackmagic Mini-Recorders. These are connected via two Thunderbolt connections. One taking the mixed live feed from the ATEM and the other taking the live clock shot. The scoreboard and stats are coming in over the network from the second computer via Desktop Presenter (part of wirecast) These devices allow you to capture from HDMI or HD-SDI. We utilize HD-SDI as it allows for longer cable runs we require. Two USB Ethernet adapters are also in use. One providing a wired connection (no ethernet on the new macbook pros) and the other provides a connection to the ATEM device to control via the software.
Wirecast is set to stream live to a CDN over RTMP as well as record a local copy to disk. For this setup the ingest server is configured to transcode the 720P 3mbit stream into multiple bitrates. This means the local broadcast computer only has to encode one bitrate instead of multiple. It should be noted that Wirecast does not officially support multi-bitrate streaming. You can setup multiple profiles and then link them with a smil or playlist. I have done this with success before when using frequent keyframes. The downside is that the stream switches between bitrates may result in a slight skip ahead or backwards in the stream. It also means your machine has to have enough power to encode all the desired bitrates in addition to having enough bandwidth to upload all versions.
this demo has been transcoded from the original stream which has reduced quality when viewing full screen
1x HDMI Monitor
1x Macbook Pro 2.3Ghz i7 – 16GB RAM
1x Blackmagic Television Studio
2x Blackmagic Ultra Studio Mini Recorder
2x Canon XF 305
1x Canon XF 105
1x Sennheiser Wireless G2 microphone