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Video streaming, explained
The concepts behind shipping video — adaptive bitrate, HLS vs DASH, CDNs, and bitrate ladders — in plain language, with how rehelios handles each.
What is adaptive bitrate streaming (ABR)?
Adaptive bitrate streaming (ABR) delivers the same video at several quality levels and lets the player switch between them in real time to match each viewer's connection and screen. It's why a video starts fast on a phone on 4G and sharpens up on a laptop on wifi, instead of buffering on a single fixed file.
What is the difference between HLS and DASH?
HLS and DASH are the two dominant adaptive-bitrate streaming protocols. Both chop a video into short segments at several quality levels and let the player switch between them on the fly. HLS was created by Apple and is the only format iPhones and iPads play natively; MPEG-DASH is an open standard used widely elsewhere. Serving both covers every device.
What is a video CDN?
A video CDN is a network of edge servers that cache your video segments close to viewers, so playback starts fast and doesn't hammer your origin. When someone hits play, segments are served from a nearby point of presence instead of crossing the internet to wherever the file is stored.
What's the difference between signed URLs, playback tokens, and DRM?
They're three levels of video access control. A signed URL (or playback token) is a time-limited, cryptographically signed link that proves a request is authorized — cheap and enough for most private video. DRM (Widevine, FairPlay, PlayReady) goes further and encrypts the media itself, so even a downloaded file can't be played without a license — heavier, and mainly for premium licensed content.
What is a bitrate ladder?
A bitrate ladder is the set of quality levels — resolution and bitrate pairs — that a video is encoded into for adaptive streaming. A typical ladder runs from 240p at a few hundred kbps up to 1080p at several Mbps. The player climbs and descends this ladder to match each viewer's bandwidth.