This document outlines improvements to low-latency HTTP Live Streaming (LL-HLS). It discusses adopting ad insertion, reducing latency through blocking playlist reloads, preload hints, playlist delta updates, and audio experience optimizations. LL-HLS aims to deliver content with minimal delay by simplifying delivery directives, generating CMAF formats, and preloading segments before playback is needed. Blocking playlist reloads allow clients to wait for new segments rather than polling frequently. Playlist delta updates send only changes to reduce bandwidth. These changes bring LL-HLS out of beta status.

1. HLS
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2. Outline
● What’s new in Low-Latency HLS
● Adopt Ad Insertion to Low-Latency HLS
● Reduce Latency with HLS Blocking Playlist Reload
● Discover HLS Blocking Preload Hints
● Optimize Live Streams with HLS Playlist Delta Updates
● Improve stream authoring with HLS Tools
● Deliver a Better HLS Audio Experience

3. What’s New in Low-Latency HLS

8. Important changes
● Replaced HTTP/2 Push with Preloading Hinting
● Simplified Delivery Directives
● Generate CMAF in reference tools
Everything is included in the current HLS spec
Low-Latency HLS comes out of beta this year
● Aim to deliver your service

9. Quick Review of Regular Live HLS works

35. And it has to supply preload hints for both as well

37. What’s Blocking Playlist Reload?
● HLS clients discover new segments by reloading the Playlist

38. What’s Blocking Playlist Reload?
● HLS clients discover new segments by reloading the Playlist
● Original HLS approach (polling) delays discovery

39. What’s Blocking Playlist Reload?
● HLS clients discover new segments by reloading the Playlist
● Original HLS approach (polling) delays discovery
● Low-Latency HLS introduced server Delivery Directives

40. ● HLS clients discover new segments by reloading the Playlist
● Original HLS approach (polling) delays discovery
● Low-Latency HLS introduced server Delivery Directives
● Client asks server to hold reload request until new segment appear
● Response unblocks when Playlist updates
What’s Blocking Playlist Reload?

63. Other exceptional cases
● _HLS_msn and _HLS_part are ignored if Playlists contains EXT-X-ENDLIST

64. Other exceptional cases
● _HLS_msn and _HLS_part are ignored if Playlists contains EXT-X-ENDLIST
● Server unblocks immediately if Playlist is newer than requested
● Requested segment/part is not the most recent
○ It might even have rolled out of the Playlist

65. ● _HLS_msn and _HLS_part are ignored if Playlists contains EXT-X-ENDLIST
● Server unblocks immediately if Playlist is newer than requested
● Requested segment/part is not the most recent
○ It might even have rolled out of the Playlist
● Server may time out if it spends too long blocked
Other exceptional cases

79. Using CMAF Chunks with LL-HLS
● Each resource (URL) corresponds to a Parent Segment
● Each Parent Segment contains multiple CMAF Chunks
● Each CMAF Chunk is a Partial Segment
○ Specified as Parent Segment URL + byte-range

93. Extension Playlist Delta Update

100. Wrap up
● Provide Playlist Delta Updates for livestreams with large windows
● Latest OS offers v2 updates that include EXT-X-DATERANGE tags
● Improves Playlist reload performance, which increases reliability

115. SCORE attribute

118. Thank you!