If your iOS app streams video, then you're going to be using HTTP Live Streaming. Between the serious support for it in iOS, and App Store rules mandating its use in some cases, there realistically is no other choice. But where do you get started and what do you have to do? In this session, we'll take a holistic look at how to use HLS. We'll cover how to encode media for HLS and how to get the best results for all the clients and bitrates you might need to support, how to serve that media (and whether it makes sense to let someone else do it for you), and how to integrate the HLS stream into your app.

1. Mobile Movies with
HTTP Live Streaming
Chris Adamson • @invalidname
March 9, 2013 • Chicago, IL
Sides and code available on my blog:
http://www.subfurther.com/blog

2. So Many Streaming
Apps!

3. Netflix

4. Flixter

5. ABC

6. PBS

7. NBC Olympics Live
Extra

8. DirecTV

9. UStream

10. Crunchyroll

11. TwitchTV

12. iTunes Festival

13. Apple Events

14. Oh, and it can be embedded
in the <video> tag

15. Sounds good? How
do I get in on that?

16. What You'll Learn
• What streaming is (and isn't)
• Setting up HLS on the server
• Using HLS streams in iOS apps
• Real-world deployment

17. HLS: What It Is (and
isn't)

18. Good Ol' Broadcast

19. Broadcast Media
• Always live on some channel (a band of EM
spectrum).
• Every client tuned to that channel sees the
same thing, at the same time.
• One-way, one-to-many model.

20. Internet
• Generally one-to-one (host to host).
• Multicast IP is an exception, but is rare on
the public Internet.
• Two-way communication over sockets.
• Routing can take many hops, via multiple
transport media (wire, wifi, cellular, etc.).

21. Impedence Mismatch!

22. Ye Olde Streaming
• Client makes socket connection and keeps it
open for duration of program.
• Server sends media at playback speed (plus
buffering).
• Shoutcast: MP3 files served slowly over HTTP.
• Typically use a special port number and special
server software.

23. Streaming Problems
• Difficult and expensive to scale.
• Special port numbers routinely blocked by
businesses, ISPs, firewalls, etc.
• Competing standards: Real Player, Windows
Media, QuickTime (all with their own plugins).
• No wonder Flash won.
• Good luck holding a socket connection on cellular.

24. What If…
• We didn't need an always-on socket
connection?
• We could just run over port 80?
• We could just adopt industry standards like
H.264 and AAC instead of cooking custom
codecs?

25. HTTP Live Streaming
• Serves media as a series of short flat files, via
HTTP, usually on port 80.
• Any web server will do.
• Client software reassembles the data into a
continuous media stream.
• Spec does not specify contents, but Apple uses
H.264 and AAC, just like all their media apps.

26. Serving up HLS
• Client URL is an .m3u8 playlist file
• Playlist points to the media segment files

28. The HLS playlist
#EXTM3U
Format: .m3u8 format,
#EXT-X-TARGETDURATION:10
#EXT-X-VERSION:3
just a list of files to play
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PLAYLIST-TYPE:VOD
Metadata tags describe
#EXTINF:9.975,
fileSequence0.ts
the contents
#EXTINF:9.975,
fileSequence1.ts
#EXTINF:9.975,
Each segment file
fileSequence2.ts
#EXTINF:9.9767,
preceded by metadata
fileSequence3.ts
(e.g., duration)
#EXTINF:9.975,
[...]
If no end tag, client
#EXT-X-ENDLIST
refreshes periodically

29. <video src="prog_index.m3u8" width="640" height="480"
controls autoplay>No video tag support</video>

30. How is this better than
a flat .m4v file?
• Streams can provide variants for different
bandwidths (as we’ll see…)
• Segments make it easier to scrub into the
video
• Streams can be live video

31. The “Live” in HLS
• A playlist is a live stream if it doesn’t have an
#EXT-X-ENDLIST tag
• Live playlist will generally just contain the last
minute or so of segments
• Client will refresh playlist every minute or so,
download whatever segments it doesn’t
already have, queue them locally
• “Live” isn’t really “live” (often a minute behind)

32. Serving up HLS

34. mediafilesegmenter
• Splits an A/V file into segment files, creates
the .m3u8 playlist
• Source must be .mov or .m4v with H.264 video,
AAC audio
• Output segments will be MPEG-2 Transport
Stream (.ts) files, or .aac if audio-only
• Segment paths are relative, use -b to prepend
URL stub

35. Technical Note TN2224
The following audio and video formats are supported:
• Video: H.264 Baseline Profile Level 3.0 (iPhone/iPod Touch),
Main Profile Level 3.1 (iPad 1,2)
• Audio: HE-AAC or AAC-LC up to 48 kHz, stereo audio OR
MP3 (MPEG-1 Audio Layer 3) 8 kHz to 48 kHz, stereo audio
Note: iPhone 3G supports Baseline Profile Level 3.1. If your
app runs on older iPhones, however, you should use H.264
Baseline Profile 3.0 for compatibility.

36. Yuna:HTTP Live Streaming tests cadamson$ mediafilesegmenter
-f basic source/IMG_0251.MOV
Jun 24 2012 10:01:24.203: Using floating point is not
backward compatible to iOS 4.1 or earlier devices
Jun 24 2012 10:01:24.204: Processing file /Users/cadamson/
Documents/HTTP Live Streaming tests/source/IMG_0251.MOV
Jun 24 2012 10:01:24.338: Finalized /Users/cadamson/
Documents/HTTP Live Streaming tests/basic/fileSequence0.ts
Jun 24 2012 10:01:24.375: segment bitrate 3.78028e+06 is
new max
Jun 24 2012 10:01:24.468: Finalized /Users/cadamson/
Documents/HTTP Live Streaming tests/basic/fileSequence1.ts
Jun 24 2012 10:01:24.554: Finalized /Users/cadamson/
Documents/HTTP Live Streaming tests/basic/fileSequence2.ts
Jun 24 2012 10:01:24.631: Finalized /Users/cadamson/
Documents/HTTP Live Streaming tests/basic/fileSequence3.ts
Jun 24 2012 10:01:24.717: Finalized /Users/cadamson/
Documents/HTTP Live Streaming tests/basic/fileSequence4.ts

37. Demo

38. Variant Playlists
• One bitrate does not fit all: Mac on Ethernet
versus iPhone on Edge.
• Solution: encode your video at multiple
bitrates, offer metadata in playlist about what's
available, let client figure out which to use.
• HLS clients automatically switch to best variant
for current network conditions, switch on the
fly.

39. variantplaylistcreator
• Creates a playlist that itself points to playlists
created with mediafilesegmenter.
• Each entry contains metadata describing the
bitrate and encoding of the variant.
• Tool takes argument pairs: file or URL of a
variant .m3u8, and metadata .plist created with
mediafilesegmenter -I flag
• First entry in variant playlist is default; client will try
this one first

40. Encoding the variants

41. TN2224
Recommendations

42. Creating variants
Yuna:HTTP Live Streaming tests cadamson$
mediafilesegmenter -I -f variants/
broadband/ source/IMG_0254_Broadband.m4v
Yuna:HTTP Live Streaming tests cadamson$
mediafilesegmenter -I -f variants/wifi
source/IMG_0254_WiFi.m4v
Yuna:HTTP Live Streaming tests cadamson$
mediafilesegmenter -I -f variants/
cellular source/IMG_0254_Cellular.m4v

43. Creating variant playlist
Yuna:HTTP Live Streaming tests cadamson$
variantplaylistcreator -o variants/
variants.m3u8 variants/broadband/
prog_index.m3u8 source/
IMG_0254_Broadband.plist variants/wifi/
prog_index.m3u8 source/
IMG_0254_WiFi.plist variants/cellular/
prog_index.m3u8 source/
IMG_0254_Cellular.plist

44. Demo

45. That's Great, but…
How do we keep people from stealing our stream?

46. Encryption
• HLS encrypts files, not transport.
• Easy to scale: still serving flat files, but now
they're useless without decryption keys.
• Serving the keys still needs to be secure.
• Necessary, but not sufficient, for DRM.

47. Encrypting a playlist
Yuna:HTTP Live Streaming tests cadamson$ mediafilesegmenter -
I -k keys -f encrypted/cellular source/IMG_0426_Cellular.m4v
Jun 24 2012 18:59:47.115: Using new key/iv rotation period;
this is not backward compatible to iOS 3.1.* or earlier
devices. Use the "-encrypt-iv=sequence" option for
compatibility with those devices.
Jun 24 2012 18:59:47.115: Using floating point is not
backward compatible to iOS 4.1 or earlier devices
Jun 24 2012 18:59:47.115: Processing file /Users/cadamson/
Documents/HTTP Live Streaming tests/source/
IMG_0426_Cellular.m4v
Jun 24 2012 18:59:47.152: changing IV
Jun 24 2012 18:59:47.160: Finalized /Users/cadamson/
Documents/HTTP Live Streaming tests/encrypted/cellular/
fileSequence0.ts
Jun 24 2012 18:59:47.160: segment bitrate 271257 is new max

48. Encrypted .ts files

49. Protect those keys
/www/protected
/www/hls

50. Demo

51. Captions
• HLS supports CEA-608 closed captions in the
MPEG-2 Transport Stream
• If using file segmenter, add a closed-
caption track (type 'clcp') to your source
QuickTime .mov
• Or use Compressor and Sonic Scenarist

52. Client-side HLS

53. Opening an HLS
stream
• Provide the .m3u8 URL to
MPMoviePlayerController or AVPlayer
• Add the movie view or layer to your UI,
customizing size or scaling if necessary

54. Create an
MPMoviePlayerController
// create new movie player
self.moviePlayer = [[MPMoviePlayerController alloc]
initWithContentURL:streamURL];
[self.moviePlayer prepareToPlay];
• This is the same as playing a local file or
any other URL

55. Add it to your UI
[self.moviePlayer.view setFrame:
self.movieContainerView.bounds];
[self.movieContainerView addSubview:
self.moviePlayer.view];
self.moviePlayer.scalingMode =
MPMovieScalingModeFill;
• Can inspect the moviePlayer's naturalSize, though
it may change during playback (listen for
MPMovieNaturalSizeAvailableNotification),
or just setFullscreen:animated:

56. MPMovieScalingMode
AspectFit

57. MPMovieScalingMode
AspectFill

58. MPMovieScalingMode
Fill

59. Accessing Encrypted
Streams
• Media Player and AV Foundation can use
NSURLCredentials that you've provided
• Place credentials in
NSURLCredentialStorage
• Server can provide the keys securely(*) with
HTTP Basic or Digest authentication, an
HTTPS script, etc.
* - For various values of "secure"

60. Setting credentials (1)
NSURLProtectionSpace *protectionSpace =
[[NSURLProtectionSpace alloc]
initWithHost:host
port:port
protocol:protocol
realm:realm
authenticationMethod:
NSURLAuthenticationMethodDefault];

61. Setting credentials (2)
NSURLCredential *credential =
[NSURLCredential credentialWithUser:username
password:password
persistence:
NSURLCredentialPersistenceForSession];
[[NSURLCredentialStorage
sharedCredentialStorage]
setDefaultCredential:credential
forProtectionSpace:protectionSpace];

62. Live Streaming

63. Live Streaming
• mediastreamsegmenter mostly works like the
file version, but takes its input from UDP
stream or a Unix pipe
• Only difference is that .m3u8 file doesn't
have an EXT-X-ENDLIST tag, so client
reloads periodically to fetch new segments
• How the heck do you create a UDP A/V
stream?

64. You Don't
• None of Apple's tools create the required
stream
• This is a "third party opportunity"
• Which begs the question… buy or build?

65. Streaming in the Real
World
It's not all about iPhones…

66. Streaming Clients
• Mobile Devices: iPhone, iPad, iPod Touch…
plus Android, Windows Mobile, etc.
• Mac and Windows PCs
• Over-the-top (OTT) boxes: Apple TV, Roku
• Game consoles

67. Let's Get Practical
• What devices do you have to be on?
• What devices will you get for free?
• HLS is the preferred format for Roku
• How to encode and deliver to the devices
you need?

68. HLS Alternatives
• Flash still rules on the desktop/browser
space, thanks in part to Mozilla's obstinance
about H.264 in <video> (irony alert: H.264 is
the de facto standard for Flash video)
• Adobe Dynamic Streaming and Microsoft
Smooth Streaming are highly similar to HLS:
bitrate-adaptive streams over HTTP

69. MPEG-DASH
• Attempt at a standardized approach to HTTP
adaptive-bitrate streaming. ISO/IEC 23009-1.
http://xkcd.com/927/

70. Emerging Consensus
• Flash for PCs
• HTTP Live Streaming for iOS
• Plus whatever other devices you need to
support

71. Real-World HLS
• Can you competently encode all your media
at all the variant bitrates you need?
• Do you have a way to QC all your streams?
• Can you handle the server load?

72. Build or Buy: Services
• Provide hosting, transcoding, bandwidth
• All-in-one: UStream, LiveStream, Justin.tv /
Twitch.tv (all of which have iOS apps)
• May provide broadcast tools (Flash applet,
Telestream Wirecast, etc.
• Often free with ads; you pay to go ad-free,
embed on your site, etc.

73. invalidstream
http://www.ustream.tv/channel/invalidstream

74. Production Demo
http://www.telestream.net/wirecast/

75. Content Delivery
Networks
http://en.wikipedia.org/wiki/Content_delivery_network

76. Content Delivery
Networks
• CDNs host your media on edge servers that
are closer to your clients. Less strain on your
servers and the backbones.
• Examples: Akamai, Limelight, EdgeCast
• Big media companies may have their own
CDN
• Most already know how to do HLS

77. Buy or Build: Encoders

78. Buy or Build:
Bandwidth
• Each HLS client will consume up to 1GB /
hour, depending on variant bitrates, client
bandwidth, etc.
• Many CDNs charge around $0.20/GB.

79. Bandwidth Costs
Prices from ScaleEngine, UStream, and LiveStream as of
October 2012

80. Self-Hosted Costs
Prices from MacMiniColo and Amazon EC2 as of March 2013

81. Wrap Up

82. Takeaways
• HLS is a very practical streaming solution
• Only part of the picture if you're multi-platform
• Encoding and serving correctly requires
some care and expertise, and a lot of money
• Client-side software requirements are fairly
simple

83. Q&A
Slides and code will be available on my blog:
http://www.subfurther.com/blog
http://www.slideshare.net/invalidname
@invalidname