Input-Bridge

Bridge Inputs between vMix instances

Allow one to bridge/tunnel an arbitrary number of inputs between two vMix instances with the help of two NDI streams in order to perform load offloading between two vMix instances.

See the corresponding demonstration video for details.

Problem

Sometimes a single vMix instance is overloaded, even on a very powerful computer. One solution is to offload a bunch of inputs, e.g., camera inputs and their chroma-key filtering and virtual PTZ positioning, to a second vMix instance. For instance, when you have 4 cameras and 7 virtual PTZ, you would want to offload the corresponding 28 inputs. Unfortunately, on a 1 Gbps network link you can transmit just a maximum of eight 1080p30, or six 1080p60, or four 2160p30, or two 2160p60, NDI streams between the two vMix instances. You would need at least a 10 Gbps network link and use not more than 2160p30 if all the 28 inputs should be used on both vMix instances in parallel.

Solution

Usually, even if you could bridge all 28 inputs, the primary vMix instance uses just a single one in its output/program and potentially another single one in its preview. So, in practice it is usually sufficient to bridge the arbitrary number of inputs over just two NDI streams, as long as all bridged inputs are singletons and do not occur as a pair in any scene and at any time.

Usage

Suppose you you want to offload inputs named VPTZ - XXX from the vMix instance on COMPUTER2 (10.0.0.12) to a pre-processing vMix instance on COMPUTER1 (10.0.0.11). Then setup COMPUTER1 as following:

• add the VPTZ - XXX inputs as usual (perhaps as the leaves of a complex input hierarchy like Camera / Virtual Input / VirtualSet).

• add two inputs of type Mix named BRIDGE1 and BRIDGE2 and under their Settings / Outputs enable NDI for the outputs #3 and #4 and set these two inputs.

Then setup COMPUTER2 as following:

• add the input-bridge script to COMPUTER2 and adjust its configuration to:

dim peerAPI          as String  = "http://10.0.0.11:8088/API/"
dim bridge1MixNum    as String  = "1"
dim bridge2MixNum    as String  = "2"
dim bridge1InputName as String  = "BRIDGE1"
dim bridge2InputName as String  = "BRIDGE2"
dim timeSlice        as Integer = 50
dim debug            as Boolean = true

• add two inputs of type NDI named BRIDGE1 and BRIDGE2. Their NDI streams should be set to COMPUTER1 (vMix - Output 3) and COMPUTER1 (vMix - Output 4).

• for all the to be bridged inputs VPTZ - XXX (from COMPUTER1) add inputs of type Blank and set their layer 1 initially to just BRIDGE1. The actually used bridge input (BRIDGE1 or BRIDGE2) is automatically selected afterwards and hence you can use any bridge input initially.

Finally, on COMPUTER2, start the script input-bridge and bring any of the VPTZ - XXX inputs into preview (and then potentially cut it to output/program) and observe that the script automatically adjusts the layer 1 on the VPTZ - XXX inputs (it switches between BRIDGE1 and BRIDGE2 when necessary) and it automatically adjusts the Mix inputs BRIDGE1 and BRIDGE2 on COMPUTER1 to have the particular VPTZ - XXX inputs as their active input.