I've had problems with BG scaling on all tables.
If you could check what the captured BG file looks like in an external viewer, that would determine whether the capture is grabbing the wrong screen area or the playback is scaling it wrong.
I can't tell what your physical monitor setup looks like, but is there any chance that you're in Full Screen mode with the PBY window but not with the B2S window, or vice versa? I'm still thinking this is the issue - the PBY and B2S backglass windows need to have the same display coverage for the sizing to work.
Could go to this program...
<your visual pinball install folder>\Tables\B2S_ScreenResEditor.exe
...run it, and see what it says for Backglass Width, Height, X Pos, Y Pos? Then go to your <pinballY>\Settings.txt file and see what it says for BackglassWindow.Position = left,top,right,bottom. The X Pos and Y Pos from B2S should match up with the left and right in your PBY settings, and you'll have to do the math to figure the right/bottom that correspond to X Pos + Width and Y Pos + Height. If those don't match up, that's got to be the answer.
If they don't match, you can just plug in the numbers from B2S by hand in the PBY Settings.txt file. That should guarantee that they're exactly right.
If they do already match, the next thing to check is the log file to find the screen location that ffmpeg is being told to capture. You'll need to start a new session and do a fresh capture, since the log file gets overwritten on each run. The ffmpeg capture area is given in some fairly self-evident parameters:
ffmpeg ... -offset_x 123 -offset_y 456 -video_size 789x543
So check that against the areas from the two sets of settings and see if that matches.
Edited by mjr, 23 August 2018 - 10:17 PM.