Encoding ladder / bitrate ladder
An encoding ladder (also called a bitrate ladder) is the set of resolution and bitrate pairs that one video is encoded into for adaptive streaming. A typical ladder might run from 360p at a low bitrate up to 1080p or 4K at a high bitrate. The player climbs up or down the ladder as the viewer's network speed changes.
Why it matters
The ladder decides what every viewer can actually receive. Too few or poorly spaced steps cause buffering on weak networks or soft pictures on good ones. Too many steps raise encoding and storage costs. A well designed ladder balances viewer experience against what the business pays to encode, store and deliver each video.
How it works
- The team picks a set of resolutions, such as 360p, 720p and 1080p, to cover target screens.
- Each resolution gets a bitrate high enough to look good and low enough to suit real networks.
- The video is encoded once per step, producing a set of renditions with aligned keyframes.
- A manifest lists every step so the player can move up or down as bandwidth changes.
What does a typical bitrate ladder look like?
A typical H.264 ladder runs from a small, low bitrate step for weak mobile networks up to 1080p or 4K for fast connections. Apple's HLS guidance, for example, starts at 416x234 around 145 kbps and reaches 1920x1080 at 7,800 kbps. The table below shows a simplified example ladder, not a fixed rule.
How many renditions should a bitrate ladder have?
Most bitrate ladders have between four and eight renditions. Fewer steps save encoding and storage costs but force bigger quality jumps when the player switches. More steps give smoother switching but cost more to produce. A common rule is to space neighboring steps so each bitrate is roughly 1.5 to 2 times the one below it. The ladder size does not change the encoding bill on FastPix, which charges once per source minute, while AWS Elemental MediaConvert bills each output rendition separately.
Where it's used
OTT services, short video apps and online learning platforms use ladders to decide which quality levels to offer, so TV viewers get crisp pictures and mobile users avoid buffering.
Where it usually goes wrong, and how FastPix handles it
Ladders are often set once and never checked against real viewing, so teams do not see when viewers are stuck on low steps or watching stretched, upscaled pictures.
How the ladder performs for real viewers shows up in FastPix Video Data as upscale and downscale percentage, rendition changes and time-weighted average bitrate for every view. These feed the render quality score, which shows whether the ladder fits real screens and networks. Real viewing then shows which screens and networks get a soft picture.
By the numbers
- Apple's example H.264 ladder for 16:9 video ranges from 416x234 at 145 kbps to 1920x1080 at 7,800 kbps. (HLS Authoring Specification for Apple Devices)
