Mobile Movies with HTTP Live Streaming (CocoaConf Portland, Oct. '12)

Mobile Movies with
HTTP Live Streaming
Chris Adamson • @invalidname
Oct 26, 2012 • Portland, OR

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

Saturday, October 27, 12

So Many Streaming
Apps!


Netﬂix


Flixter


ABC


PBS


NBC Olympics Live
Extra


DirecTV


UStream


Crunchyroll


TwitchTV


iTunes Festival


Apple Events


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

<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


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


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


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:


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];


Live Streaming


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?


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?


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: Encoders


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.


invalidstream

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


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.


Bandwidth Costs

Prices from ScaleEngine, UStream, and LiveStream as of
October 2012

Wrap Up


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


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 Portland, Oct. '12)

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