Video Fundamentals

Resolution is simply the pixel count of the image. 1080p is 1920 by 1080 pixels; UHD, the format people loosely call "4K," is 3840 by 2160 — four times as many pixels. The catch is that more pixels only help if the display genuinely has them and the signal is feeding them natively. Send a lower-resolution signal to a high-resolution screen and it gets scaled up to fill the panel, and you lose the sharpness you thought you were paying for. Aspect ratio is the shape of the image. 16:9 is today's standard, so feeding a square-ish 4:3 source into a 16:9 system leaves black pillarbox bars on the sides — or, if someone stretches it to fill, a distorted picture. Frame rate is how motion is rendered: 24 fps has a cinematic feel, 25 and 30 are common broadcast rates, and 50 and 60 look smoother while carrying twice the data.

There is one more wrinkle hiding inside frame rate. Each frame can be progressive, drawn all at once and labelled "p," or interlaced, drawn as alternating odd and even lines and labelled "i." Mixing the two forces a conversion called deinterlacing. And that points at the rule that quietly prevents most show-day disasters: every device in the chain — source, switcher, scaler, and display — has to agree on resolution, frame rate, and scan type. The moment two of them disagree, something has to convert the signal, and every conversion costs a little quality and adds a little latency.