Wirebook › Glossary › Adaptive bitrate streaming
What is adaptive bitrate streaming (ABR)?
In one sentence: How video apps keep a film at several sizes and switch between them chunk by chunk to match your connection, so it starts quickly and rarely freezes.
A little more
Streaming services encode each film or show at several sizes, from small and soft (240p, a few hundred kilobits a second) to large and sharp (1080p around 5 Mbps, 4K around 15 to 25 Mbps). Each version is cut into short chunks of a few seconds, and a list called a manifest tells the player where every chunk lives. The common formats are HLS and MPEG-DASH.
The player times how long each chunk takes to arrive, estimates your throughput, and picks the biggest size it can safely keep up with. It usually starts low so playback begins quickly, climbs a rung at a time, and drops down fast when the buffer runs low. That's why a video can start blurry and sharpen a few seconds later.
See it in action
- BonusWhy does a video go blurry, then sharp?You press play and the picture is smudgy for a second, then it snaps sharp.8 min · interactive
- BonusWhy does a video call go blurry when the connection is slow?Dial a pretend video call's bandwidth thinner, spend a tiny 10-bit budget on eyes vs mouth vs wallpaper to still read a facial expression, then reveal the clear face.7 min · interactive
- BonusWhy does the internet slow down in the evening?Picture the internet as water: your house's pipe, one shared pipe under the street and a big main from far away.9 min · interactive
Do it for real
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