multibitrate

Multibitrate refers to the practice of encoding media at multiple bitrates and resolutions to support adaptive streaming. The goal is to allow a client to select or switch among representations during playback to accommodate changing network conditions and device capabilities, reducing buffering and improving perceived quality.

In typical implementations, a media file is encoded into a ladder of representations, for example 240p at 300 kbps, 360p at 600 kbps, 720p at 2 Mbps, and 1080p at 4 Mbps. Each representation is divided into small segments (for example, 2–6 seconds). An associated manifest file (such as an HLS master playlist or a DASH MPD) lists all representations. The client begins playback using an initial representation and then adapts by measuring available bandwidth and buffer occupancy and switching to a higher or lower bitrate as needed.

Advantages include smoother playback across fluctuating networks and devices, better use of CDN caches, and more efficient delivery via HTTP-based delivery. They enable streaming services to support a wide range of devices from mobile phones to desktop browsers.

Challenges include the need for additional encoding, storage, and packaging work to create and maintain multiple representations; design of the bitrate ladder affects quality and efficiency; and abrupt switches or high latency in certain environments can impact user experience. Modern ABR schemes use buffer-based and throughput-based metrics to optimize switching.

Multibitrate streaming became widely adopted with HTTP-based streaming protocols in the early 2010s, notably Apple's HLS and MPEG-DASH. It remains a standard approach for professional streaming and on-demand services today.