Resolution: how many pixels
Resolution is the size of each frame in pixels. "1080p" means 1920×1080 — about 2 million pixels per frame; 4K (2160p) is 3840×2160, four times as many. More pixels can carry more detail, but only can: resolution sets the ceiling on sharpness, not the sharpness itself. A frame's pixels still have to be described by data, and that is the bitrate's job.
Two practical notes. First, playback devices scale video to fit the screen anyway, so resolution beyond what the viewer's screen and viewing distance can resolve is spent for nothing — on a phone, the difference between 1080p and 4K is essentially invisible. Second, upscaling never adds detail: converting 720p footage to a 1080p file just spreads the same information over more pixels and a bigger file. Good converters, Mediamorphy included, only ever scale down.
Frame rate: how many frames
Frame rate (fps) is how many frames are shown per second. Film tradition uses 24, broadcast and web video mostly 25–30, and gaming or sports footage often 60. Higher frame rates make motion smoother — but they matter only when there is motion. A screen recording of a presentation, a talking-head interview, or a product demo gains nothing from 60 fps; it just carries twice the frames of a 30 fps version.
Halving the frame rate does not halve the file size, incidentally. Modern codecs store most frames as differences from their neighbors, and consecutive frames at high fps are very similar — cheap to encode. Dropping 60 to 30 typically saves some 20–40%, not 50%. It is still one of the easiest savings available for low-motion content, and 30 fps looks perfectly natural for almost everything that is not gameplay or sport.
Bitrate: how much data per second
Bitrate is the amount of data used per second of video, measured in megabits per second (Mbps). It is the number most directly tied to both file size and quality: size is simply bitrate × duration, and quality is what the encoder can afford to keep within that budget. A 10-minute video at 8 Mbps is roughly 600 MB regardless of what is in it.
The key insight is that bitrate is spread across every pixel of every frame. Think of it as bits per pixel per second: raise the resolution or frame rate without raising the bitrate, and each pixel gets a thinner slice of the budget. This is why a 4K video at 4 Mbps looks worse than a 1080p video at the same 4 Mbps — the 4K version must describe four times the pixels with the same data, so fine detail dissolves into smearing and blocky artifacts exactly where you hoped 4K would shine.
| Resolution | Comfortable range | 10 minutes weighs about |
|---|---|---|
| 720p | 2–4 Mbps | 150–300 MB |
| 1080p | 4–8 Mbps | 300–600 MB |
| 1440p | 8–16 Mbps | 600 MB–1.2 GB |
| 4K | 16–40 Mbps | 1.2–3 GB |
How the three trade against each other
Because the bitrate budget is shared, the three numbers form a triangle: fix any two and the third determines how good the result can look. That leads to a few rules that resolve most real decisions:
- Sharp beats big. Well-fed 1080p looks better than starved 4K on almost any screen. If total size is constrained, lower the resolution before strangling the bitrate.
- Match frame rate to motion. 60 fps for gameplay and sport; 30 fps (or the source's native rate) for everything else. Never convert upward — 30 fps footage gains nothing from a 60 fps container.
- Don't spend pixels the viewer can't see. Video destined for chat apps or embedding in a page can drop to 720p with no perceived loss on the screens it will be watched on.
Where does CRF fit in? Modern encoders let you skip bitrate arithmetic entirely: constant-quality mode picks a varying bitrate automatically to hold visual quality steady. You choose resolution and frame rate; CRF handles the bits. That is usually the better workflow — our CRF guide explains it fully.
Diagnosing problems with the right lever
The triangle also works backwards as a troubleshooting map. Blocky, smeary motion scenes mean the bitrate is too low for the pixels being pushed — raise quality (lower CRF) or reduce resolution. Softness even in still scenes usually means low source resolution or heavy previous compression, which no re-encode can undo. Juddery motion points at frame rate — often a mismatch between source and output rates rather than a low rate as such. And a file far too large means more bits are being spent than the content needs; our size-reduction guide covers the fix step by step.
None of this requires an engineering degree. Resolution says how many pixels, frame rate says how often they change, bitrate says how much data describes it all — and quality lives or dies by whether the third number is adequate for the first two.