Adaptive bitrate (ABR) streaming is the technique of encoding a single video into multiple quality renditions — for example 1080p at 4 Mbps, 720p at 2 Mbps, 480p at 1 Mbps, and 360p at 500 kbps — and packaging them so the player can switch renditions mid-stream as network conditions change. The two dominant ABR protocols are HLS (HTTP Live Streaming), which uses an M3U8 manifest and short MPEG-TS or fMP4 segments, and MPEG-DASH, which uses an MPD manifest; HLS has near-universal device support and is the default for most learning platforms. The player measures available bandwidth and buffer health every few seconds and selects the highest rendition it can sustain without rebuffering, switching down if throughput drops. For learning video, ABR is the primary mechanism that keeps a course watchable on a mobile learner's LTE connection or a corporate laptop on shared Wi-Fi; without it, a single high-bitrate file will stall and the learner will abandon. Transcoding the source file into the rendition ladder is a separate prerequisite step, typically handled by a cloud transcoding service such as AWS Elemental MediaConvert, Mux, or FFmpeg pipelines. The practical trade-off is storage and CDN egress cost: a five-rendition ladder multiplies storage roughly four-fold compared to a single file. Choosing the right bitrate ladder for educational content — which is typically screen recordings or talking-head video with moderate motion — allows lower top-end bitrates than entertainment video.
