Adaptive bitrate (ABR) is the streaming approach where the player chooses a quality level for each short segment in real time, picking a rung of the bitrate ladder by what the network can sustain. It is the mechanism behind the central QoE trade-off: pick a bitrate higher than the network can carry and the buffer drains to zero and the stream stalls; pick one lower and playback is steady but softer than it needed to be. Two logic families split on what they watch, throughput-based estimation that fits startup with an empty buffer, and buffer-based control that reads buffer occupancy to cut stalls in steady state, and many players hand off from one to the other. The catch for measurement is that ABR trades picture quality against rebuffering every segment, so its effects surface across several metrics at once, average bitrate played, bitrate switching, and the rebuffering ratio, rather than in any single number.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
Adaptive bitrate is where quality and rebuffering trade off on every session, so ladder and player choices show up in viewer complaints. We wrote seven volumes covering the whole video stack, and for ABR start with Volume 3: ABR algorithms, bitrate ladders, players and QoE monitoring, with Volume 1 on encoding the rungs and Volume 2 on HLS and DASH delivery. Written by Nikolay Sapunov, CEO at Fora Soft.
Viewers seeing quality drops or rebuffering even with a full ABR ladder?
Share your ladder, player and QoE data: we pinpoint where ABR switching loses quality and give you ladder and player settings to fix it. 250+ video products shipped since 2005.
