Today’s media landscape is radically more diverse than just a few years ago. The delivery of consistently acceptable image and sound quality is taken for granted by viewers, despite uncertain or fluctuating bandwidth. Adaptive-bit-rate (ABR) streaming technology makes this possible.
What is ABR streaming?
ABR streaming is a delivery technology designed to provide consistent, high-quality viewing in situations where bandwidth may fluctuate, and where viewers may be on a wide range of devices.
Prior to ABR streaming, Web or mobile video delivery was typically done by encoding a single downloadable file or stream at a fixed bit rate and frame size. Viewers could buffer some of the video, and then simultaneously download and play it back. This delivery model was similar to cable transmission, where a single bit rate is transmitted over a reliable medium.
Unfortunately, transmission mediums for Web and mobile devices are unreliable, and bandwidths vary. During fixed-rate video playback, viewers with low bandwidth suffer from excessive buffering (delaying playback). To compensate, providers have tended to encode at lower bit rates, punishing viewers with high bandwidth. Even then, any fluctuations in bandwidth can cause buffering delays.
To solve this problem, ABR streaming content is encoded into multiple layers, each potentially a different bit rate, frame size and/or frame rate. These layers are combined into a single package that represents the original content. ABR players switch between layers depending upon the device and available bandwidth, to ensure consistent high-quality playback.
For example, a single ABR package might include six layers, each encoded at progressively higher bit rates. As a viewer watches content on his/her mobile phone during a train ride, the player will adaptively switch between low bit rates and high bit rates, depending upon the connectivity of the device.