Konkreet, the frames are scaled with a high-quality filter and the stream is re-encoded, since resolution is a property of the coded picture; the aspect ratio is preserved unless you deliberately override it. You give it a target width, a target height or a percentage, and it works from the original rather than from a previously resized copy.
Ndinogona here kuchengeta kuratidzwa kwechifananidzo, kana kumanikidza zvakajeka zviyero?
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Both. Lock the ratio and one dimension follows from the other, which is what you want almost always. Unlock it and you get exactly the numbers you typed, at the cost of stretching — which on video means every face in the frame is slightly too wide. When you need a different shape, crop or letterbox rather than stretch.
