On pg. 149 in 1.5 spec, and pg. 127 in 1.4 2nd edition spec:
The "Details" section states to derive the aspect_ratio as the ratio between the angle xFov and yFov (aspect = xFov/yFov). This, however, is mathematically not correct. The correct formula should be:
aspect_ratio = tan(xFov/2) / tan(yFov/2)
This accounts for both, 1.4 2nd edition and 1.5 specification. The bug reporter does not allow multiple selections, therefore I selected the most recent.