Matching Quality To The Network
Viewers have wildly different bandwidth. Adaptive bitrate streaming encodes the same content at several quality levels so each player picks what its connection can sustain.
The Rendition Ladder
The encoder produces a ladder of renditions, each a full copy at a different bitrate and resolution.
- A manifest lists every rendition and its segments.
- The player measures throughput and chooses a level.
- When the network changes, it switches to a higher or lower rung at the next segment.
Because switches happen at segment boundaries, playback stays smooth.
The Edge Multiplier
Each rendition is a separate set of cacheable segments, so the cache must hold more variants.
- Popular renditions, often the mid quality ones, stay warm at the edge.
- Rare extreme renditions may miss more often and reach the shield.
- The cache key distinguishes renditions so the player always gets the level it asked for.
This multiplies stored objects, which is why cache sizing accounts for the full ladder.
Client Versus Server Logic
The player drives switching, but edge behavior shapes it. If a higher rendition is cached locally, it loads fast and the player may climb sooner. Consistent edge availability across the ladder helps clients reach stable quality rather than oscillating.
Key idea
Adaptive bitrate offers a ladder of renditions as separate cacheable segment sets, letting players switch quality at segment boundaries while the edge keeps popular renditions warm across the ladder.