Feature: Ability to trigger a camera's built-in tally light via CGI.

Use Case: I have a Panasonic AW-HE40/70 that has a tally light built into it. It can be turned on/off/statused via CGI commands.

Approach: Under the Tally Lights tab on an Input, add a place to enter an HTTP request to turn on, turn off, and status the associated camera's built in tally light. Of course, there'd probably have to be an enable/disable tick box, too, so vMix will know whether or not to execute the request. Perhaps status is not necessary, but perhaps a little dot could be added to the camera's input display that reflects the status of the tally light.

Work Around: I've come up with a work-around to get this functionality, but it isn't the best approach. Here's what I do.
1. Create a browser input. I called mine "Tally State". For the URL, I just use the CGI command to "enable" the tally light functionality: http://{Camera IP}/cgi-bin/aw_ptz?cmd=%23TAE1&res=1. This input will never get used, but could be reloaded if the camera's tally light was ever disabled. The only purpose of this input is to act like a web client and to interact with a web server (i.e. the camera).
2. Add a transition in trigger to each input that will affect the camera's tally light. On the respective input, click the cog wheel to open the settings and navigate to the triggers tab. Select transition in for the trigger, browser navigate for the function, select "Tally State" for the input, add a delay of 1001ms (to overcome the longest transition that exists - I'll explain below), and finally use the CGI command that turns the tally light on (e.g. http://{camera IP}/cgi-bin/aw_ptz?cmd=%23DA1&res=1) for the value field.
3. Add a transition out trigger to each input that will affect the camera's tally light. Follow the same steps as #2 except the delay should be 0 and the URL should be the CGI command that turns the tally light off (e.g. http://{camera IP}/cgi-bin/aw_ptz?cmd=%23DA0&res=1).
When the respective input is transitioned to, it will trigger the respective transition trigger using the browser input as a web client to effectively send an HTTP request to the camera.

Explanation of Delay Value: Since I use a PTZ camera, I have several virtual inputs with specific PTZ position and zoom settings. If I transition from one virtual input to another virtual input on the same camera, the tally light gets turned off. Without a delay, the transition in trigger occurs before the transition out trigger. The transition out trigger seems to be affected by the transition time. My longest transition time is 1000ms, so I set the delay for the transition in trigger to 1001ms. While this does cause the tally light to toggle off and then on again, at least it ensures that the light is in the proper state. NOTE: This may be a vMix bug, but if I use the T-bar to perform the transition, the triggers are not invoked.