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Apple HLS: comparing versions

An introduction to Apple HLS is available as: Apple HLS: introduction. A technical analysis of the versions is available as: Apple HLS: technical in-depth.

Versions and revisions

HLS comes in different versions. As of when this article is written, version numbers from 1 to 7.

Each of the version is covered by one or more revisions. The HLS revisions covered in this analysis range from 0 to 14. The modifications are mostly about clarifications.

Note: if you look closely at the dates in the table, you’ll notice that no revision is separated by more than 6 months from the previous. That’s because the HLS specification has been available as an IETF draft. And IETF drafts automatically expire after 6 months. Thanks to Nicolas Weil for the reminder. Therefore Apple HLS has been available as a draft since May 1, 2009 i.e. for more than five years. We have no information of Apple planning to finalize it.

You can find the correspondence between ‘version’ and ‘revision’ in the table below. You can find the correspondence between revisions and iOS versions in this Apple developer page (thanks to G. Du Pontavice from flashls):

revisionversiondatenew features01May 1, 2009Initial release11June 8, 2009
21October 5, 2009
32April 2, 2010

• Specifying the resolution for video variant streams.
• Improving encryption (initialization vector).
• Introducing version compatibility.

42June 5, 2010
53November 19, 2010Introducing the playlist-type (VOD, Event)63March 31, 2011
74September 30, 2011

• Audio and Video can be specified separately (e.g. unmuxed together), introducing rendition groups.
• Introducing byte-ranges to access the content from a single file.
• Allowing special playlists containing only I-frames (i.e. access points).

84March 23, 2012
95September 22, 2012

• Subtitles (WebVTT).
• Adding a new per-sample encryption scheme.

105October 15, 2012
115April 16, 2013
126October 14, 2013

• Introduce Closed-Captions (in addition to subtitles).
• Error resilience: discontinuity and independence of each segment can be signalled in the playlist.

136April 16, 2014
147October 14, 2014

• Adding alternate renditions signalling.
• Adding session data.
• Closed-Captions: support for CEA-708.

157April 15, 2015

• AC-3 and eAC-3.
• FRAME-RATE attribute in EXT-X-STREAM-INF.

167April 15, 2015

• Bitrate definition clarified: it doesn’t include network (HTTP, TCP, IP) overhead.
• Multiple EXT-X-VERSION are now rejected.
• TYPE attribute of EXT-X-MEDIA is now mandatory.
• Removed FRAME-RATE attribute introduced in revision 16 (the same day 

177October 16, 2015

• Use of MUST and SHOULD keywords as inRFC2119.

187November 19, 2015

• Cosmetics.

197April 4, 2016

• Adding EXT-X-DATERANGE (with SCTE35 specific attributes)

The latest version of the Apple HLS IETF document can be found here.