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HTTP Live Streaming (HLS)
Sanchayan Maity
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Who

  • Who am I?
    • Embedded Systems background
    • Prefer C, Haskell and Rust
    • Organize and speak at Rust and Haskell meet-ups in Bangalore
  • Work?
    • Software Engineer @ asymptotic
    • Open source consulting firm based out of Bangalore and Toronto
    • Work on low level systems software centred around multimedia
    • GStreamer, PipeWire, PulseAudio
    • Language Polyglots

Open source contributions

Agenda

  • Whirlwind tour of GStreamer
  • What's HTTP Live Streaming (HLS)
  • HLS implementation

GStreamer

  • Multiplatform Pipeline based multimedia framework
  • Bindings for various languages
  • Allows building complex media processing workflows
  • Some applications
    • PiTiVi (Video Editor)
    • amaroK, Banshee, Clementine (audio players)
    • Empathy (VOIP and video conferencing)
    • GstLAL (gravitational wave data analysis)
    • Rygel (DLNA streaming server and renderer)
    • Totem (movie player for the GNOME desktop)

Simple pipeline

gst-launch-1.0 videotestsrc ! autovideosink
gst-launch-1.0 audiotestsrc ! autoaudiosink

Media pipeline1

Simple Player{width=80%}

HLS

  • HTTP-based adaptive bit-rate streaming communications protocol
  • Developed by Apple and released in 2009
  • Standardised in RFC 8216
  • HTTP traffic, unlike UDP-based protocols such as RTP
  • Content can be offered from conventional HTTP servers
  • Delivered over widely available HTTP-based content delivery networks

Motivation

  • Video on demand content
    • HLS is better than just serving media directly over HTTP
    • Can describe metadata
    • Variants using a bit rate ladder
    • Alternate media renditions
  • Live content
    • Reuse the same mechanism
    • Trading off lower cost distribution via CDN at the cost of latency over real time

Playlist2

   #EXTM3U
   #EXT-X-TARGETDURATION:10
   #EXT-X-VERSION:3
   #EXTINF:9.009,
   http://media.example.com/first.ts
   #EXTINF:9.009,
   http://media.example.com/second.ts
   #EXTINF:3.003,
   http://media.example.com/third.ts
   #EXT-X-ENDLIST

Master playlist3

   #EXTM3U
   #EXT-X-STREAM-INF:BANDWIDTH=1280000,AVERAGE-BANDWIDTH=1000000
   http://example.com/low.m3u8
   #EXT-X-STREAM-INF:BANDWIDTH=2560000,AVERAGE-BANDWIDTH=2000000
   http://example.com/mid.m3u8
   #EXT-X-STREAM-INF:BANDWIDTH=7680000,AVERAGE-BANDWIDTH=6000000
   http://example.com/hi.m3u8
   #EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5"
   http://example.com/audio-only.m3u8

Master playlist4

   #EXTM3U
   #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="English", \
      DEFAULT=YES,AUTOSELECT=YES,LANGUAGE="en", \
      URI="main/english-audio.m3u8"
   #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="Deutsch", \
      DEFAULT=NO,AUTOSELECT=YES,LANGUAGE="de", \
      URI="main/german-audio.m3u8"
   #EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="...",AUDIO="aac"
   low/video-only.m3u8
   #EXT-X-STREAM-INF:BANDWIDTH=2560000,CODECS="...",AUDIO="aac"
   mid/video-only.m3u8
   #EXT-X-STREAM-INF:BANDWIDTH=7680000,CODECS="...",AUDIO="aac"
   hi/video-only.m3u8
   #EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5",AUDIO="aac"
   main/english-audio.m3u8

Implementation

Demo

Using

  • videojs
  • python3 -m http.server
  • Sample GStreamer Rust Code5

References

Questions