My previous commits would rescale the placeholder for output on every
frame which was not CPU efficient. Now we store a copy of the scaled
placeholder and update it any time the resolution / FPS / format
changes.
A new function GetOutputBufferSize was added to allow calculating the
output size when needed. The existing code assumed a 12-bit format if
the placeholder didn't load, which could cause grey / green output.
An optimization was made to only load and scale the placeholder once
the virtual output starts, as many applications load and unload the
filter multiple times during enumeration of devices.
Various comments were also added to help clarify how the filter works.
47fcbdb0c9