I was looking forward to being able to fit 12 320x240 webcams inside of 1 1280x720 mix-mode encode, as it fits perfectly mathematically. I was also hoping to be able to fit 12 480x360 webcams inside of 1920x1080 mix mode.
However, I find that if I set the json layout to "left: 0", the software assumes the video is in widescreen, so a black bar is placed to the left.
If I must pretend all media is widescreen, that only leaves 9 videos capable at 240p inside of the 720p mix.
Perhaps this may be something to consider allowing as an option for in a future version. I tried using a negative number for "left" but it was deemed invalid.
4:3 is actually quite desirable in the context of conference meetings as usually it is beneficial to not show empty background space to the sides of a person.
Just an idea :). I have decided to go with a 1080p mix due to this limitation, as that way I can fit 16 270p cameras within the mix. That is more than I require, but the resolution is lower than the 360p I would have otherwise been able to achieve.
edit: also being able to set more custom webcam input resolutions would be very helpful. 360p is what i was aiming for but it seems I have to choose between either 240p or 480p.