Bitrate vs resolution: which one you can actually see
File size is bitrate made visible. Once you know that, the download list stops being a menu of numbers and starts being useful.
- Size ÷ duration is your bitrate estimate
- Motion-heavy content needs far more bitrate than static content
- Two files at the same resolution can differ hugely in quality
Reading the size as bitrate
A ten-minute file at 400 MB is running roughly 5 Mbps. That's healthy for 1080p. The same duration at 4K in 400 MB would be starved, and you'd see it in every fast pan.
Why content type changes the answer
A locked-off interview compresses beautifully because most of the frame doesn't change. Sport, gaming and handheld footage change every pixel every frame and need several times the bitrate to hold together.
Where artefacts show up
Look at fast motion, dark gradients and fine texture — foliage, water, confetti. Blocking and banding appear there first, long before the flat areas of the picture suffer.
How to use this at download time
Compare the sizes offered for the same video. If the 4K rung is only marginally bigger than the 1080p one, it's a low-bitrate 4K and the smaller file is the better choice.