Mobile Movies with HTTP Live Streaming (CocoaConf Columbus, Aug '12)

Mobile Movies with
HTTP Live Streaming
Chris Adamson • @invalidname
CocoaConf
Aug 10, 2012 • Columbus, OH

Sides and code available on my blog:
http://www.subfurther.com/blog

Saturday, August 11, 12

So Many Streaming
Apps!


Netﬂix


Flixter


ABC


PBS


NBC Olympics Live
Extra


DirecTV


UStream


Crunchyroll


TwitchTV


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


Sounds good? How
do I get in on that?


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


HLS: What It Is (and
isn't)


Good Ol' Broadcast


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.


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.).


Impedence Mismatch!


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.


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.


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?


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.


Serving up HLS

• Client URL is an .m3u8 playlist ﬁle

• Playlist points to the media segment ﬁles


The HLS playlist
#EXTM3U
#EXT-X-TARGETDURATION:10
#EXT-X-VERSION:3
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PLAYLIST-TYPE:VOD
#EXTINF:9.975,!
fileSequence0.ts
#EXTINF:9.975,!
fileSequence1.ts
#EXTINF:9.975,!
fileSequence2.ts
#EXTINF:9.9767,!
fileSequence3.ts
#EXTINF:9.975,!

[...]

#EXT-X-ENDLIST


The HLS playlist
#EXTM3U Format: .m3u8 format,
#EXT-X-VERSION:3
just a list of ﬁles to play
#EXT-X-PLAYLIST-TYPE:VOD
#EXTINF:9.975,!
fileSequence0.ts
#EXTINF:9.975,!
fileSequence1.ts
#EXTINF:9.975,!
fileSequence2.ts
#EXTINF:9.9767,!
fileSequence3.ts
#EXTINF:9.975,!

[...]

#EXT-X-ENDLIST


The HLS playlist
#EXT-X-VERSION:3
#EXT-X-PLAYLIST-TYPE:VOD Metadata tags describe
#EXTINF:9.975,!
fileSequence0.ts the contents
#EXTINF:9.975,!
fileSequence1.ts
#EXTINF:9.975,!
fileSequence2.ts
#EXTINF:9.9767,!
fileSequence3.ts
#EXTINF:9.975,!

[...]

#EXT-X-ENDLIST


The HLS playlist
#EXT-X-VERSION:3
#EXTINF:9.975,!
#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,!

[...]

#EXT-X-ENDLIST


The HLS playlist
#EXT-X-VERSION:3
#EXTINF:9.975,!
#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

Web Demo


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

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


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)


Serving up HLS


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


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.


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


Demo


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.


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


Encoding the variants


TN2224
Recommendations


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

mediafilesegmenter -I -f variants/wifi
source/IMG_0254_WiFi.m4v

mediafilesegmenter -I -f variants/
cellular source/IMG_0254_Cellular.m4v


Creating variant playlist
variantplaylistcreator -o variants/
variants.m3u8 variants/broadband/
prog_index.m3u8 source/
IMG_0254_Broadband.plist variants/wifi/
IMG_0254_WiFi.plist variants/cellular/
IMG_0254_Cellular.plist


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


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.


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
Documents/HTTP Live Streaming tests/encrypted/cellular/
fileSequence0.ts
Jun 24 2012 18:59:47.160: segment bitrate 271257 is new max


Encrypted .ts ﬁles


Protect those keys

/www/protected

/www/hls


Live Streaming

• mediastreamsegmenter mostly works like the
ﬁle version, but takes its input from UDP
stream or a Unix pipe

• How the heck do you create a UDP A/V
stream?


VLC streams .ts/UDP

http://stackoverﬂow.com/questions/3846145

VLC streams .ts/UDP

mediastreamsegmenter -s 3 -D -f /Library/
WebServer/Documents/httplivestreaming/live
127.0.0.1:1234

http://stackoverﬂow.com/questions/3846145

Demo (Or Not)


Client-side HLS


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


MPMoviePlayerController

// create new movie player
self.moviePlayer = [[MPMoviePlayerController alloc]
! ! ! ! ! ! ! ! initWithContentURL:streamURL];
[self.moviePlayer prepareToPlay];
[self.moviePlayer.view setFrame:
! ! ! ! ! ! ! self.movieContainerView.bounds];
[self.movieContainerView addSubview:
! ! ! ! ! ! ! ! self.moviePlayer.view];
self.moviePlayer.scalingMode =
! ! ! ! ! ! ! ! MPMovieScalingModeFill;


MPMovieScalingMode
AspectFit


MPMovieScalingMode
AspectFill


MPMovieScalingMode
Fill


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"


Setting credentials (1)

NSURLProtectionSpace *protectionSpace =
! [[NSURLProtectionSpace alloc]
! ! initWithHost:host
! ! port:port
! ! protocol:protocol
! ! realm:realm
! ! authenticationMethod:
! ! ! NSURLAuthenticationMethodDefault];


Setting credentials (2)

NSURLCredential *credential =
! [NSURLCredential credentialWithUser:username
! ! ! ! ! ! ! ! ! password:password
! ! ! ! ! ! ! ! ! ! ! persistence:
! ! ! NSURLCredentialPersistenceForSession];

[[NSURLCredentialStorage
! sharedCredentialStorage]
! ! setDefaultCredential:credential
! ! forProtectionSpace:protectionSpace];


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


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


Let's Get Practical

• What devices do you have to be on?

• What devices will you get for free?

• How to encode and deliver to the devices you
need?


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


MPEG-DASH
• Attempt at a standardized approach to HTTP
adaptive-bitrate streaming. ISO/IEC 23009-1.

http://xkcd.com/927/

Emerging Consensus

• Flash for PCs

• HTTP Live Streaming for iOS

• Plus whatever other devices you need to
support


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?


Content Delivery
Networks

http://en.wikipedia.org/wiki/Content_delivery_network

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


Buy or Build


Outsourcing HLS

Ads from "Streaming Media" June/July 2012

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

• Client-side software requirements are fairly
simple


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

@invalidname


Mobile Movies with HTTP Live Streaming (CocoaConf Columbus, Aug '12)

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