They're usually flipping the least important bit, so the video compressor will probably ignore the dithering. It does turn a perfectly stable image into an unst

They're usually flipping the least important bit, so the video compressor will probably ignore the dithering. It does turn a perfectly stable image into an unstable image, though, so it could potentially be harmful if you're compressing video of static text and geometry - I haven't tested this before, so it's an interesting point.