Bitrate and quality
At a given resolution and codec, raising the bitrate improves the picture up to a point, after which the gain becomes invisible. Too low a bitrate shows as blockiness, smeared detail and banding, especially in fast motion and dark scenes.
The right bitrate depends on the content. A talking head or animation compresses far more easily than sport, rain or confetti, so the same number can look excellent on one and poor on another.
Typical video bitrates
These are rough ranges for H.264 at 24 to 30 frames per second. Newer codecs such as H.265 and AV1 reach the same quality at roughly 30% to 50% less. Higher frame rates need more.
- 480p: about 1 to 2 Mbps
- 720p: about 2.5 to 4 Mbps
- 1080p: about 4 to 8 Mbps
- 4K: about 12 to 25 Mbps
Bitrate, file size and cost
Size is bitrate multiplied by duration. One hour at 5 Mbps is 5 megabits × 3,600 seconds = 18,000 megabits, or about 2.25 GB. Every viewer who watches that hour pulls about that much through your CDN.
This is why bitrate is the main control on delivery cost. Trimming the average bitrate across your audience by 20% cuts the delivery bill by the same amount.
Constant and variable bitrate
A constant bitrate (CBR) uses the same amount of data every second, which is predictable and suits live contribution. A variable bitrate (VBR) spends more on complex scenes and less on simple ones, giving better quality for the same average size, and is normal for on-demand.
Last reviewed