This setting in the preferences, what does it do? What do I lose by setting it to Off instead of choosing my video card? When I choose my video card, I get pixelation/glitches in the video preview window at certain places (doesn't appear to be random) in the video.
If you’re still using an Intel Core i7-2600k, as your signature indicates, you could lose preview performance. That depends on how much the GPU is needed to decode your media.
Yes, same system.. the only way I can seem to overcome this issue is by setting it to Off, so I guess I'll just deal with whatever slowdown happens in the preview.
It is OFF for me for a long time (I'm long time AMD user, so only tried different AMD GPU/iGPU). When it ON, the preview performance is better, but stability is suffering (VP crashing often).