Allow the user to select whether to buffer the source or not. The
settings are auto-detect, on, and off. Auto-Detect turns it off for
non-encoded devices, and on for encoded devices.
Webcams, internal devices, and other such things on windows do not
really need to be buffered, and buffering incurs a tiny bit of delay, so
turning off buffering is actually a little better for non-encoded
devices.
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