HLS (HTTP Live Streaming) is Apple's adaptive streaming protocol and, with DASH, one of the two dominant ways video and its audio reach players over the web. It describes the stream in playlist (.m3u8) files and delivers the media as a series of short segments fetched over ordinary HTTP, so it traverses CDNs and firewalls like any web content. Audio is declared with EXT-X-MEDIA tags that define rendition groups — the available languages, codecs, and channel layouts — which the player associates with the video and switches among per its own logic and the available bandwidth. HLS's reach across Apple devices made it ubiquitous, and its Low-Latency extension (LL-HLS) brings glass-to-glass delay down for live.
The book · Volume 4 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From PCM and Codecs to Loudness, Accessibility, and Real-Time Voice Processing
In HLS the audio track is where multilingual, accessible and surround streams most often break, from wrong codec flags to mismatched loudness. This volume covers the audio side in depth, with AAC and Opus, channel layouts, loudness and accessibility tracks, so the renditions you declare in HLS play correctly on every device. Written by Nikolay Sapunov, CEO at Fora Soft.
Shipping multiple audio tracks in HLS and seeing players pick the wrong one?
Share a playlist and target players and we will audit your HLS audio renditions, codec signaling and loudness with a clear fix list. 250+ video products shipped since 2005.
