Unofficial AirPlay Protocol Specification

1. Introduction

AirPlay is a family of protocols implemented by Apple to view various types of media content on the Apple TV from any iOS device or iTunes. In this documentation, “iOS device” refers to an iPhone, iPod touch or iPad. The following scenarios are supported by AirPlay:

Display photos and slideshows from an iOS device.
Stream audio from an iOS device or iTunes.
Display videos from an iOS device or iTunes.
Show the screen content from an iOS device or OS X Mountain Lion. This is called AirPlay Mirroring. It requires hardware capable of encoding live video without taking too much CPU, so it is only available on iPhone 4S, iPad 2, the new iPad, and Macs with Sandy Bridge CPUs.

Audio streaming is also supported from an iOS device or iTunes to an AirPort Express base station or a 3^rd party AirPlay-enabled audio device. Initially this was called AirTunes, but it was later renamed to AirPlay when Apple added video support for the Apple TV.
This document describes these protocols, as implemented in Apple TV software version 5.0, iOS 5.1 and iTunes 10.6. They are based on well-known standard networking protocols such as Multicast DNS, HTTP, RTSP, RTP or NTP, with custom extensions.
All these information have been gathered by using various techniques of reverse engineering, so they might be somewhat inaccurate and incomplete. Moreover, this document does not explain how to circumvent any kind of security implemented by Apple:

It does not give any RSA keys.
It does not explain how to decode iTunes videos protected with the FairPlay DRM.
It does not explain the FairPlay authentication (SAPv2.5) used by iOS devices and OS X Mountain Lion to protect audio and screen content.

Please don’t e-mail me about this, I won’t reply. In fact, none of this is actually required to be able to view media content on Apple TV.

2. Service Discovery

AirPlay does not require any configuration to be able to find compatible devices on the network, thanks to DNS-based service discovery, based on multicast DNS, aka Bonjour.
An AirPlay device such as the Apple TV publishes two services. The first one is RAOP (Remote Audio Output Protocol), used for audio streaming, and the other one is the AirPlay service, for photo and video content.

2.1. AirTunes service

RAOP service from Apple TV

name: 5855CA1AE288@Apple TV
type: _raop._tcp
port: 49152
txt:
 txtvers=1
 ch=2
 cn=0,1,2,3
 da=true
 et=0,3,5
 md=0,1,2
 pw=false
 sv=false
 sr=44100
 ss=16
 tp=UDP
 vn=65537
 vs=130.14
 am=AppleTV2,1
 sf=0x4

The name is formed using the MAC address of the device and the name of the remote speaker which will be shown by the clients.
The following fields appear in the TXT record:

name	value	description
`txtvers`	1	TXT record version 1
`ch`	2	audio channels: stereo
`cn`	0,1,2,3	audio codecs
`et`	0,3,5	supported encryption types
`md`	0,1,2	supported metadata types
`pw`	false	does the speaker require a password?
`sr`	44100	audio sample rate: 44100 Hz
`ss`	16	audio sample size: 16-bit
`tp`	UDP	supported transport: TCP or UDP
`vs`	130.14	server version 130.14
`am`	AppleTV2,1	device model

Audio codecs

cn	description
0	PCM
1	Apple Lossless (ALAC)
2	AAC
3	AAC ELD (Enhanced Low Delay)

Encryption Types

et	description
0	no encryption
1	RSA (AirPort Express)
3	FairPlay
4	MFiSAP (3rd-party devices)
5	FairPlay SAPv2.5

Metadata Types

md	description
0	text
1	artwork
2	progress

2.2. AirPlay Service

AirPlay service

name: Apple TV
type: _airplay._tcp
port: 7000
txt:
 deviceid=58:55:CA:1A:E2:88
 features=0x39f7
 model=AppleTV2,1
 srcvers=130.14

The following fields are available in the TXT record:

name	value	description
`model`	AppleTV2,1	device model
`deviceid`	58:55:CA:1A:E2:88	MAC address of the device
`features`	0x39f7	bitfield of supported features
`pw`	1	server is password protected

The pw field appears only if the AirPlay server is password protected. Otherwise it is not included in the TXT record.
The features bitfield allows the following features to be defined:

bit	name	description
0	`Video`	video supported
1	`Photo`	photo supported
2	`VideoFairPlay`	video protected with FairPlay DRM
3	`VideoVolumeControl`	volume control supported for videos
4	`VideoHTTPLiveStreams`	http live streaming supported
5	`Slideshow`	slideshow supported
7	`Screen`	mirroring supported
8	`ScreenRotate`	screen rotation supported
9	`Audio`	audio supported
11	`AudioRedundant`	audio packet redundancy supported
12	`FPSAPv2pt5_AES_GCM`	FairPlay secure auth supported
13	`PhotoCaching`	photo preloading supported

Note that the Apple TV does not support VideoVolumeControl. It has probably been introduced for the upcoming Apple television.
The AirPlay server is a HTTP server (RFC 2616). Two connections are made to this server, the second one being used as a reverse HTTP connection. This allows a client to receive asynchronous events, such as playback status changes, from a server.
All HTTP requests share some common headers:

name	value	description
`X-Apple-Session-ID`	1bd6ceeb…	UUID for the session
`X-Apple-Device-ID`	0xdc2b61a0ce79	MAC address

The reverse connection looks like this:

client → server

POST /reverse
Upgrade: PTTH/1.0
Connection: Upgrade
X-Apple-Purpose: event
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 101 Switching Protocols
Date: Thu, 23 Feb 2012 17:33:41 GMT
Upgrade: PTTH/1.0
Connection: Upgrade

The X-Apple-Purpose header makes it clear that this connection is used for sending events to the client, whereas X-Apple-Session-ID is used to link this connection to the other (non-reverse) one. Events are delivered using a POST request for sending an XML property list to the /event location.

3. Photos

Photos are JPEG data transmitted using a PUT request to the AirPlay server. They can be displayed immediately, or cached for future use.

3.1. HTTP requests

GET /slideshow-features

A client can fetch the list of available transitions for slideshows. Then it can let the user pick one, before starting a slideshow. The Accept-Language header is used to specify in which language the transition names should be.

client → server

GET /slideshow-features HTTP/1.1
Accept-Language: English
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: cdda804c-33ae-4a0b-a5f2-f0e532fd5abd

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:41 GMT
Content-Type: text/x-apple-plist+xml
Content-Length: 6411




 
  themes
  
   
    key
    Reflections
    name
    Reflections
   
   ...

PUT /photo

Send a JPEG picture to the server. The following headers are supported:

name	description
`X-Apple-AssetKey`	UUID for the picture
`X-Apple-Transition`	transition that should be used to show the picture
`X-Apple-AssetAction`	specify a caching operation

Example 1: show a picture without any transition (for the first time)

client → server

PUT /photo HTTP/1.1
X-Apple-AssetKey: F92F9B91-954E-4D63-BB9A-EEC771ADE6E8
Content-Length: 462848
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:42 GMT
Content-Length: 0

Example 2: show a picture using the dissolve transition

client → server

PUT /photo HTTP/1.1
X-Apple-AssetKey: F92F9B91-954E-4D63-BB9A-EEC771ADE6E8
X-Apple-Transition: Dissolve
Content-Length: 462848
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:42 GMT
Content-Length: 0

PUT /slideshows/1

Start or stop a slideshow session. When starting, slideshow settings such as the slide duration and selected transition theme are transmitted. The following parameters are sent in an XML property list:

key	type	description
settings.slideDuration	integer	slide duration in seconds
settings.theme	string	selected transition theme
state	string	`playing` or `stopped`

Example: send slideshow settings

client → server

PUT /slideshows/1 HTTP/1.1
Content-Type: text/x-apple-plist+xml
Content-Length: 366
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 98a7b246-8e00-49a6-8765-db57165f5b67




 
  settings
  
   slideDuration
   3
   theme
   Classic
  
  state
  playing

server → client

HTTP/1.1 200 OK
Date: Thu, 08 Mar 2012 16:30:01 GMT
Content-Type: text/x-apple-plist+xml
Content-Length: 181

POST /stop

Stop a photo or slideshow session.

client → server

POST /stop HTTP/1.1
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:55 GMT
Content-Length: 0

3.2. Events

Photo

This event notifies a client that a photo session has ended. Then the server can safely disconnect.

key	type	description
category	string	`photo`
sessionID	integer	session ID
state	string	`stopped`

Example: stop photo session

server → client

POST /event HTTP/1.1
Content-Type: text/x-apple-plist+xml
Content-Length: 277
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c




 
  category
  photo
  sessionID
  38
  state
  stopped

client → server

HTTP/1.1 200 OK
Content-Length: 0

Slideshow

Slideshow events are used to notify the server about the playback state.

key	type	description
category	string	`slideshow`
lastAssetID	integer	last asset ID
sessionID	integer	session ID
state	string	`loading`, `playing` or `stopped`

Example: slideshow is currently playing

server → client

POST /event HTTP/1.1
Content-Type: text/x-apple-plist+xml
Content-Length: 371
X-Apple-Session-ID: f1634b51-5cae-4384-ade5-54f4159a15f1




 
  category
  slideshow
  lastAssetID
  5
  sessionID
  4
  state
  playing

client → server

HTTP/1.1 200 OK
Content-Length: 0

3.3. Photo Caching

AirPlay supports preloading picture data to improve transition latency. This works by preloading a few pictures (most likely the ones before and after the current picture) just after displaying one.
Preloading is achieved using the cacheOnly asset action. Upon receiving this request, a server stores the picture in its cache. Later, a client can request the display of this picture using the displayCached asset action and the same asset key. This is much faster than a full picture upload because no additional data is transmitted.
When asked for a picture which is no longer in the cache, a server replies with an HTTP 412 error code (Precondition Failed).
Example 1: cache a picture for future display

client → server

PUT /photo HTTP/1.1
X-Apple-AssetAction: cacheOnly
X-Apple-AssetKey: B0DDE2C0-6FDD-48F8-9E5B-29CE0618DF5B
Content-Length: 462848
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:45 GMT
Content-Length: 0

Example 2: show a cached picture

client → server

PUT /photo HTTP/1.1
X-Apple-AssetAction: displayCached
X-Apple-AssetKey: B0DDE2C0-6FDD-48F8-9E5B-29CE0618DF5B
X-Apple-Transition: Dissolve
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:45 GMT
Content-Length: 0

3.4. Slideshows

Slideshows are using the reverse HTTP connection for asynchronous loading of pictures. Three connections are performed in parallel. The X-Apple-Purpose header is set to slideshow. A GET request to the /slideshows/1/assets/1 location is issued to fetch a new picture from the AirPlay client. A binary property list with the following parameters is expected as reply:

key	type	description
data	data	JPEG picture
info.id	integer	asset ID
info.key	integer	1

Example: fetch a new picture

server → client

GET /slideshows/1/assets/1 HTTP/1.1
Content-Length: 0
Accept: application/x-apple-binary-plist
X-Apple-Session-ID: 98a7b246-8e00-49a6-8765-db57165f5b67

client → server

HTTP/1.1 200 OK
Content-Type: application/x-apple-binary-plist
Content-Length: 58932






 
  data
  
  ...
  
  info
  
   id
   1
   key
   1

4. Video

In order to play a video on an AirPlay server, HTTP requests are used to send a video URL, perform scrubbing, change the playback rate and update the timeline.

4.1. HTTP requests

GET /server-info

Fetch general informations about the AirPlay server. These informations are returned as an XML property list, with the following properties:

key	type	value	description
deviceid	string	58:55:CA:1A:E2:88	MAC address
features	integer	14839	0x39f7
model	string	AppleTV2,1	device model
protovers	string	1.0	protocol version
srcvers	string	120.2	server version

The model, deviceid, srcvers and features properties are the same as broadcasted by the mDNS AirPlay service.
Example: fetch server informations

client → server

GET /server-info HTTP/1.1
X-Apple-Device-ID: 0xdc2b61a0ce79
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 1bd6ceeb-fffd-456c-a09c-996053a7a08c

server → client

HTTP/1.1 200 OK
Date: Thu, 23 Feb 2012 17:33:41 GMT
Content-Type: text/x-apple-plist+xml
Content-Length: 427




 
  deviceid
  58:55:CA:1A:E2:88
  features
  14839
  model
  AppleTV2,1
  protovers
  1.0
  srcvers
  120.2

POST /play

Start video playback. The body contains the following parameters:

name	type	description
`Content-Location`	URL	URL for the video
`Start-Position`	float	starting position between 0 and 1

MP4 movies are supported using progressive download. HTTP Live Streaming might be supported as well, as indicated by the VideoHTTPLiveStreams feature flag. The relative starting position, a float value between 0 (beginning) and 1 (end) is used to start playing a video at the exact same position as it was on the client.
A binary property list can also be used instead of text parameters, with content type application/x-apple-binary-plist.
Example 1: video playback from iTunes

client → server

POST /play HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 163
Content-Type: text/parameters

Content-Location: http://192.168.1.18:3689/airplay.mp4?database-spec='dmap.persistentid:0x63b5e5c0c201542e'&item-spec='dmap.itemid:0x21d'
Start-Position: 0.174051

server → client

HTTP/1.1 200 OK
Date: Mon, 08 Mar 2012 18:08:25 GMT
Content-Length: 0

Example 2: video playback from iPhone

client → server

POST /play HTTP/1.1
X-Transmit-Date: 2012-03-16T14:20:39.656533Z
Content-Type: application/x-apple-binary-plist
Content-Length: 491
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 368e90a4-5de6-4196-9e58-9917bdd4ffd7






 
  Content-Location
  http://redirector.c.youtube.com/videoplayback?...
  Start-Position
  0.024613151326775551

server → client

HTTP/1.1 200 OK

POST /scrub

Seek at an arbitrary location in the video. The position argument is a float value representing the location in seconds.
Example: seek to about 20 seconds

client → server

POST /scrub?position=20.097000 HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 0

server → client

HTTP/1.1 200 OK
Date: Mon, 08 Mar 2012 18:08:42 GMT
Content-Length: 0

POST /rate

Change the playback rate. The value argument is a float value representing the playback rate: 0 is paused, 1 is playing at the normal speed.
Example: pause playback

client → server

POST /rate?value=0.000000 HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 0

server → client

HTTP/1.1 200 OK
Date: Mon, 08 Mar 2012 18:08:37 GMT
Content-Length: 0

POST /stop

Stop playback.
Example: stop playback

client → server

POST /stop HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 0

server → client

HTTP/1.1 200 OK
Date: Mon, 08 Mar 2012 18:09:06 GMT
Content-Length: 0

GET /scrub

Retrieve the current playback position. This can be called repeatedly to update a timeline on the client. The following parameters are returned:

name	type	description
`duration`	float	duration in seconds
`position`	float	position in seconds

Example: fetch current playback progress

client → server

GET /scrub HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 0

server → client

HTTP/1.1 200 OK
Date: Mon, 08 Mar 2012 18:08:31 GMT
Content-Type: text/parameters
Content-Length: 40

duration: 83.124794
position: 14.467000

GET /playback-info

Retrieve playback informations such as position, duration, rate, buffering status and more. An XML property list is returned with the following parameters:

key	type	description
`duration`	real	playback duration in seconds
`position`	real	playback position in seconds
`rate`	real	playback rate
`readyToPlay`	boolean	ready to play
`playbackBufferEmpty`	boolean	buffer empty
`playbackBufferFull`	boolean	buffer full
`playbackLikelyToKeepUp`	boolean	playback likely to keep up
`loadedTimeRanges`	array	array of loaded time ranges
`seekableTimeRanges`	array	array of seekable time ranges

Ranges are defined as dictionaries with the following keys:

key	type	description
`start`	real	range start time in seconds
`duration`	real	range duration in seconds

Example: get playback info

client → server

GET /playback-info HTTP/1.1
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 24b3fd94-1b6d-42b1-89a3-47108bfbac89

server → client

HTTP/1.1 200 OK
Date: Fri, 16 Mar 2012 15:31:42 GMT
Content-Type: text/x-apple-plist+xml
Content-Length: 801
X-Transmit-Date: 2012-03-16T15:31:42.607066Z




 
  duration 1801
  loadedTimeRanges
  
   
    duration 51.541130402
    start 18.118717650000001
   
  
  playbackBufferEmpty 
  playbackBufferFull 
  playbackLikelyToKeepUp 
  position 18.043869775000001
  rate 1
  readyToPlay 
  seekableTimeRanges
  
   
    duration
    1801
    start
    0.0

PUT /setProperty

Set playback property. The property name is sent as query argument. The following properties are defined:

argument	description
`forwardEndTime`	forward end time
`reverseEndTime`	reverse end time

Example: set forward end time

client → server

PUT /setProperty?forwardEndTime HTTP/1.1
Content-Type: application/x-apple-binary-plist
Content-Length: 96
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 24b3fd94-1b6d-42b1-89a3-47108bfbac89





 
  value
  
   epoch 0
   flags 0
   timescale 0
   value 0

server → client

HTTP/1.1 200 OK
Date: Fri, 16 Mar 2012 15:23:11 GMT
Content-Type: application/x-apple-binary-plist
Content-Length: 58






 
  errorCode
  0

GET /getProperty

Get playback property. The property name is sent as query argument. The following properties are defined:

argument	description
`playbackAccessLog`	playback access log
`playbackErrorLog`	playback error log

Example: get playback access log

client → server

POST /getProperty?playbackAccessLog HTTP/1.1
Content-Type: application/x-apple-binary-plist
Content-Length: 0
User-Agent: MediaControl/1.0
X-Apple-Session-ID: 24b3fd94-1b6d-42b1-89a3-47108bfbac89

server → client

HTTP/1.1 200 OK
Date: Fri, 16 Mar 2012 15:31:42 GMT
Content-Type: application/x-apple-binary-plist
Content-Length: 530






 
  errorCode
  0
  value
  
   
    bytes 1818336
    c-duration-downloaded 70
    c-duration-watched 18.154102027416229
    c-frames-dropped 0
    c-observed-bitrate 14598047.302367469
    c-overdue 0
    c-stalls 0
    c-start-time 0.0
    c-startup-time 0.27732497453689575
    cs-guid B475F105-78FD-4200-96BC-148BAB6DAC11
    date 2012-03-16T15:31:24Z
    s-ip 213.152.6.89
    s-ip-changes 0
    sc-count 7
    uri http://devimages.apple.com/iphone/samples/bipbop/gear1/prog_index.m3u8

4.2. Events

This event is used to send the playback state to the client:

key	type	description
category	string	`video`
sessionID	integer	session id
state	string	`loading`, `playing`, `paused` or `stopped`

Example: notify the client that video playback is paused

server → client

POST /event HTTP/1.1
Content-Type: application/x-apple-plist
Content-Length: 321
X-Apple-Session-ID: 00000000-0000-0000-0000-000000000000




 
  category
  video
  sessionID
  13
  state
  paused

client → server

HTTP/1.1 200 OK
Content-Length: 0
Date: Mon, 08 Mar 2012 18:07:43 GMT

5. Audio

Audio streaming is supported using the RTSP protocol (RFC 2326).

5.1. RTSP requests

OPTIONS

The OPTIONS request asks the RTSP server for its supported methods. Apple TV supports the following methods: ANNOUNCE, SETUP, RECORD, PAUSE, FLUSH, TEARDOWN, OPTIONS, GET_PARAMETER, SET_PARAMETER, POST and GET.

client → server

OPTIONS * RTSP/1.0
CSeq: 3
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
Public: ANNOUNCE, SETUP, RECORD, PAUSE, FLUSH, TEARDOWN, OPTIONS,
GET_PARAMETER, SET_PARAMETER, POST, GET
Server: AirTunes/130.14
CSeq: 3

ANNOUNCE

The ANNOUNCE request tells the RTSP server about stream properties using SDP (RFC 4566). Codec informations and encryption keys are of particular interest.
Example 1: ANNOUNCE for Apple Lossless audio from iTunes

client → server

ANNOUNCE rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 3
Content-Type: application/sdp
Content-Length: 348
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

v=0
o=iTunes 3413821438 0 IN IP4 fe80::217:f2ff:fe0f:e0f6
s=iTunes
c=IN IP4 fe80::5a55:caff:fe1a:e187
t=0 0
m=audio 0 RTP/AVP 96
a=rtpmap:96 AppleLossless
a=fmtp:96 352 0 16 40 10 14 2 255 0 0 44100
a=fpaeskey:RlBMWQECAQAAAAA8AAAAAPFOnNe+zWb5/n4L5KZkE2AAAAAQlDx69reTdwHF9LaNmhiRURTAbcL4brYAceAkZ49YirXm62N4
a=aesiv:5b+YZi9Ikb845BmNhaVo+Q

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 3

Example 2: ANNOUNCE for AAC audio from an iOS device

client → server

ANNOUNCE rtsp://192.168.1.45/2699324803567405959 RTSP/1.0
X-Apple-Device-ID: 0xa4d1d2800b68
CSeq: 16
DACP-ID: 14413BE4996FEA4D
Active-Remote: 2543110914
Content-Type: application/sdp
Content-Length: 331

v=0
o=AirTunes 2699324803567405959 0 IN IP4 192.168.1.5
s=AirTunes
c=IN IP4 192.168.1.5
t=0 0
m=audio 0 RTP/AVP 96
a=rtpmap:96 mpeg4-generic/44100/2
a=fmtp:96
a=fpaeskey:RlBMWQECAQAAAAA8AAAAAOG6c4aMdLkXAX+lbjp7EhgAAAAQeX5uqGyYkBmJX+gd5ANEr+amI8urqFmvcNo87pR0BXGJ4eLf
a=aesiv:VZTaHn4wSJ84Jjzlb94m0Q==
a=min-latency:11025

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 16

Example 3: ANNOUNCE for AAC-ELD audio and H.264 video from an iOS device

client → server

ANNOUNCE rtsp://192.168.1.45/846700446248110360 RTSP/1.0
X-Apple-Device-ID: 0xa4d1d2800b68
CSeq: 27
DACP-ID: 14413BE4996FEA4D
Active-Remote: 2543110914
Content-Type: application/sdp
Content-Length: 415

v=0
o=AirTunes 846700446248110360 0 IN IP4 192.168.1.5
s=AirTunes
c=IN IP4 192.168.1.5
t=0 0
m=audio 0 RTP/AVP 96
a=rtpmap:96 mpeg4-generic/44100/2
a=fmtp:96 mode=AAC-eld; constantDuration=480
a=fpaeskey:RlBMWQECAQAAAAA8AAAAAKKp+t27A+686xfviEphhw8AAAAQE/3LSqv9MHgnEKxkbKh1buE9+ylKg0YuqcyAC7fT0EqJNtdq
a=aesiv:i/a3nUKYNDSIPP2fC+UKGQ==
a=min-latency:4410
m=video 0 RTP/AVP 97
a=rtpmap:97 H264
a=fmtp:97

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 27

SETUP

The SETUP request initializes a record session. It sends all the necessary transport informations. Three UDP channels are setup:

channel	description
server	audio data
control	sync and retransmit requests
timing	master clock sync

Example: setup a record session

client → server

SETUP rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 4
Transport: RTP/AVP/UDP;unicast;interleaved=0-1;mode=record;control_port=6001;timing_port=6002
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
Transport: RTP/AVP/UDP;unicast;mode=record;server_port=53561;control_port=63379;timing_port=50607
Session: 1
Audio-Jack-Status: connected
Server: AirTunes/130.14
CSeq: 4

RECORD

The RECORD request starts the audio streaming. The RTP-Info header contains the following parameters:

name	size	description
`seq`	16-bit	initial RTP sequence number
`rtptime`	32-bit	initial RTP timestamp

Example: start audio stream

client → server

RECORD rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 5
Session: 1
Range: npt=0-
RTP-Info: seq=20857;rtptime=1146549156
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
Audio-Latency: 2205
Server: AirTunes/130.14
CSeq: 5

FLUSH

The FLUSH request stops the streaming.
Example: pause the audio stream

client → server

FLUSH rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 31
Session: 1
RTP-Info: seq=25009;rtptime=1148010660
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
RTP-Info: rtptime=1147914212
Server: AirTunes/130.14
CSeq: 31

TEARDOWN

The TEARDOWN request ends the RTSP session.
Example: close session 1

client → server

TEARDOWN rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 32
Session: 1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 32

5.2. RTP Streams

Audio packets are fully RTP compliant. Control and timing packets, however, do not seem to be fully compliant with the RTP standard.
The following payload types are defined:

payload type	port	description
82	`timing_port`	timing request
83	`timing_port`	timing reply
84	`control_port`	time sync
85	`control_port`	retransmit request
86	`control_port`	retransmit reply
96	`server_port`	audio data

Audio packets

Audio data is sent using the DynamicRTP-Type-96 payload type. The Marker bit is set on the first packet sent after RECORD or FLUSH requests. The RTP payload contains optionally encrypted audio data.
Example: encrypted audio packet

client → server

0000   80 e0 b1 91 f7 79 16 c2 e8 bb 6b 2c bb 5c 8e 51
0010   aa 7c d2 96 00 c3 fd 60 eb ae 6e 41 31 38 fe ae
....
03e0   cb 1c 73 bf e7 05 93 30 fa 85 7f 32 77 8d a8 97
03f0   a0 c7 c8 78 7b e5 81 a1 4f b4 3e a3 43 db 7c

Real-Time Transport Protocol
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 .... = Extension: False
    .... 0000 = Contributing source identifiers count: 0
    1... .... = Marker: True
    Payload type: DynamicRTP-Type-96 (96)
    Sequence number: 45457
    Timestamp: 4151908034
    Synchronization Source identifier: 0xe8bb6b2c (3904596780)
    Payload: bb5c8e51aa7cd29600c3fd60ebae6e413138feae909b44f1...

Sync packets

Sync packets are sent once per second to the control port. They are used to correlate the RTP timestamps currently used in the audio stream to the NTP time used for clock synchronization. Payload type is 84, the Marker bit is always set and the Extension bit is set on the first packet after RECORD or FLUSH requests. The SSRC field is not included in the RTP header.

bytes	description
8	RTP header without `SSRC`
8	current NTP time
4	RTP timestamp for the next audio packet

Example: sync packet

client → server

0000   80 d4 00 04 c7 cd 11 a8 83 ab 1c 49 2f e4 22 e2
0010   c7 ce 3f 1f

Real-Time Transport Protocol
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 .... = Extension: False
    .... 0000 = Contributing source identifiers count: 0
    1... .... = Marker: True
    Payload type: Unassigned (84)
    Sequence number: 4
    Timestamp: 3352105384
    Synchronization Source identifier: 0x83ab1c49 (2209029193)
    Payload: 2fe422e2c7ce3f1f

Retransmit packets

AirTunes supports resending audio packets which have been lost. Payload type is 85 for retransmit queries, the Marker bit is always set and the SSRC field is not included in the RTP header.

bytes	description
8	RTP header without `SSRC`
2	sequence number for the first lost packet
2	number of lost packets

Retransmit replies have payload type 86, with a full audio RTP packet after the sequence number.

Timing packets

Timing packets are used to synchronize a master clock for audio. This is useful for clock recovery and precise synchronization of several devices playing the same audio stream.
Timing packets are sent at 3 second intervals. They always have the Marker bit set, and payload type 82 for queries and 83 for replies. The SSRC field is not included in the RTP header, so it takes only 8 bytes, followed by three NTP timestamps:

bytes	description
8	RTP header without `SSRC`
8	origin timestamp
8	receive timestamp
8	transmit timestamp

Example: timing query/reply

server → client

0000   80 d2 00 07 00 00 00 00 00 00 00 00 00 00 00 00
0010   00 00 00 00 00 00 00 00 83 c1 17 cc af ba 9b 32

Real-Time Transport Protocol
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 .... = Extension: False
    .... 0000 = Contributing source identifiers count: 0
    1... .... = Marker: True
    Payload type: Unassigned (82)
    Sequence number: 7
    Timestamp: 0
    Synchronization Source identifier: 0x00000000 (0)
    Payload: 00000000000000000000000083c117ccafba9b32

client → server

0000   80 d3 00 07 00 00 00 00 83 c1 17 cc af ba 9b 32
0010   83 c1 17 cc b0 12 ce b6 83 c1 17 cc b0 14 10 47

Real-Time Transport Protocol
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 .... = Extension: False
    .... 0000 = Contributing source identifiers count: 0
    1... .... = Marker: True
    Payload type: Unassigned (83)
    Sequence number: 7
    Timestamp: 0
    Synchronization Source identifier: 0x83c117cc (2210469836)
    Payload: afba9b3283c117ccb012ceb683c117ccb0141047

5.3. Volume Control

Audio volume can be changed using a SET_PARAMETER request. The volume is a float value representing the audio attenuation in dB. A value of –144 means the audio is muted. Then it goes from –30 to 0.
Example: set audio volume

client → server

SET_PARAMETER rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 6
Session: 1
Content-Type: text/parameters
Content-Length: 20
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

volume: -11.123877

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 6

5.4. Metadata

Metadata for the current track are sent using SET_PARAMETER requests. This allows the Apple TV to show the track name, artist, album, cover artwork and timeline. The RTP-Info header contains a rtptime parameter with the RTP timestamp corresponding to the time from which the metadata is valid.

Track Informations

Informations about the current track are sent in the DAAP (Digital Audio Access Protocol) format, with application/x-dmap-tagged content type.
The following DAAP attributes are displayed on Apple TV:

attribute	description
`dmap.itemname`	track name
`daap.songartist`	artist
`daap.songalbum`	album

Example: send track informations

client → server

SET_PARAMETER rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 8
Session: 1
Content-Type: application/x-dmap-tagged
Content-Length: 3242
RTP-Info: rtptime=1146549156
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 8

Cover Artwork

Artworks are sent as JPEG pictures, with image/jpeg content type.
Example: send cover artwork

client → server

SET_PARAMETER rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 9
Session: 1
Content-Type: image/jpeg
Content-Length: 34616
RTP-Info: rtptime=1146549156
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 9

Playback Progress

Playback progress is sent as text/parameters, with a progress parameter representing three absolute RTP timestamps values: start/curr/end.

timestamp	description
`start`	beginning of the current track
`curr`	current playback position
`end`	end of the current track

The relative position and track duration can be computed as follows:

position = rtptime_to_sec(curr - start)
duration = rtptime_to_sec(end - start)

Example: send playback progress

client → server

SET_PARAMETER rtsp://fe80::217:f2ff:fe0f:e0f6/3413821438 RTSP/1.0
CSeq: 10
Session: 1
Content-Type: text/parameters
Content-Length: 44
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3)
AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 1986535575

progress: 1146221540/1146549156/1195701740

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 10

5.5. AirPort Express Authentication

Sending audio data to the AirPort Express requires a RSA based authentication. All binary data are encoded using Base64 (RFC 4648) without padding.

Client side

In the ANNOUNCE request, the client sends a 128-bit random number in the Apple-Challenge header.
A 128-bit AES key is generated, encrypted with the RSA public key using the OAEP encryption scheme, and sent along with an initialization vector in the rsaaeskey and aesiv SDP attributes.

Server side

The AirPort Express decrypts the AES key with its RSA private key, it will be used to decrypt the audio payload.
The AirPort Express signs the Apple-Challenge number with its RSA private key using the PKCS#1 signature scheme and send the result in the Apple-Response header.

Client side

The client decrypts the Apple-Response value with the RSA public key, and checks that it is the same random number it has previously generated.

Example: AirPort Express challenge/response

client → server

ANNOUNCE rtsp://10.0.1.101/3172942895 RTSP/1.0
CSeq: 1
Content-Type: application/sdp
Content-Length: 567
User-Agent: iTunes/4.6 (Windows; N)
Client-Instance: 9FF35780A8BC8D2B
Apple-Challenge: 09KF45soMYmvj6dpsUGiIg

v=0
o=iTunes 3172942895 0 IN IP4 10.0.1.101
s=iTunes
c=IN IP4 10.0.1.103
t=0 0
m=audio 0 RTP/AVP 96
a=rtpmap:96 AppleLossless
a=fmtp:96 4096 0 16 40 10 14 2 255 0 0 44100
a=rsaaeskey:5QYIqmdZGTONY5SHjEJrqAhaa0W9wzDC5i6q221mdGZJ5ubO6Kg
            yhC6U83wpY87TFdPRdfPQl2kVC7+Uefmx1bXdIUo07ZcJsqMbgtje4w2JQw0b
            Uw2BlzNPmVGQOxfdpGc3LXZzNE0jI1D4conUEiW6rrzikXBhk7Y/i2naw13ayy
            xaSwtkiJ0ltBQGYGErbV2tx43QSNj7O0JIG9GrF2GZZ6/UHo4VH+ZXgQ4NZvP/
            QXPCsLutZsvusFDzIEq7TN1fveINOiwrzlN+bckEixvhXlvoQTWE2tjbmQYhMvO
            FIly5gNbZiXi0l5AdolX4jDC2vndFHqWDks/3sPikNg
a=aesiv:zcZmAZtqh7uGcEwPXk0QeA

server → client

RTSP/1.0 200 OK
CSeq: 1
Apple-Response: u+msU8Cc7KBrVPjI/Ir8fOL8+C5D3Jsw1+acaW3MNTndrTQAeb/a
                5m10UVBX6wb/DYQGY+b28ksSwBjN0nFOk4Y2cODEf83FAh7B
                mkLpmpkpplp7zVXQ+Z9DcB6gC60ZsS3t98aoR7tSzVLKZNgi2X2sC+vGsz
                utQxX03HK008VjcdngHv3g1p2knoETd07T6eVfZCmPqp6Ga7Dj8VIIj/GEP3
                AjjDx3lJnQBXUDmxM484YXLXZjWFXCiY8GJt6whjf7/2c3rIoT3Z7PQpEvPmM
                1MXU9cv4NL59Y/q0OAVQ38foOz7eGAhfvjOsCnHU25aik7/7ToIYt1tyVtap/kA
Audio-Jack-Status: connected; type=analog

5.6. Remote Control

Audio speakers can send commands to the AirPlay client to change the current track, pause and resume playback, shuffle the playlist, and more. This uses a subset of DACP (Digital Audio Control Protocol). An AirPlay client advertises this capability by including a DACP-ID header in its RTSP requests, with a 64-bit ID for the DACP server. An Active-Remote header is included as well, serving as an authentication token.
The AirPlay server needs to browse the mDNS _dacp._tcp services for a matching DACP server. Server names look like iTunes_Ctrl_$ID.

DACP service from iTunes

name: iTunes_Ctrl_56B29BB6CB904862
type: _dacp._tcp
port: 3689
txt:
 txtvers=1
 Ver=131075
 DbId=63B5E5C0C201542E
 OSsi=0x1F5

Once the DACP server has been identified, HTTP requests can be sent to the corresponding service port. The Active-Remote header must be included in these requests, so no additional pairing is required. The location for remote control commands is /ctrl-int/1/$CMD. The following commands are available:

command	description
`beginff`	begin fast forward
`beginrew`	begin rewind
`mutetoggle`	toggle mute status
`nextitem`	play next item in playlist
`previtem`	play previous item in playlist
`pause`	pause playback
`playpause`	toggle between play and pause
`play`	start playback
`stop`	stop playback
`playresume`	play after fast forward or rewind
`shuffle_songs`	shuffle playlist
`volumedown`	turn audio volume down
`volumeup`	turn audio volume up

Example: send a pause command

server → client

GET /ctrl-int/1/pause HTTP/1.1
Host: starlight.local.
Active-Remote: 1986535575

client → server

HTTP/1.1 204 No Content
Date: Tue, 06 Mar 2012 16:38:51 GMT
DAAP-Server: iTunes/10.6 (Mac OS X)
Content-Type: application/x-dmap-tagged
Content-Length: 0

6. Screen Mirroring

Screen mirroring is achieved by transmitting an H.264 encoded video stream over a TCP connection. This stream is packetized with a 128-byte header. AAC-ELD audio is sent using the AirTunes protocol. As for the master clock, it is synchronized using NTP.
Moreover, as soon as a client starts a video playback, a standard AirPlay connection is made to send the video URL, and mirroring is stopped. This avoids decoding and re-encoding the video, which would incur a quality loss.

6.1. HTTP requests

Screen mirroring does not use the standard AirPlay service. Instead it connects to an apparently hard-coded port 7100. This is a HTTP server which supports the following requests:

GET /stream.xml

Retrieve information about the server capabilities. The server sends an XML property list with the following properties:

key	type	value	description
`height`	integer	720	vertical resolution
`width`	integer	1280	horizontal resolution
`overscanned`	boolean	true	is the display overscanned?
`refreshRate`	real	0.01666…	refresh rate 60 Hz (1/60)
`version`	string	130.14	server version

These properties tell us that the AirPlay server is connected to a 1280x720, 60 Hz, overscanned display.
Example: fetch mirroring server informations

client → server

GET /stream.xml HTTP/1.1
Content-Length: 0

server → client

HTTP/1.1 200 OK
Date: Mon, 08 Mar 2012 15:30:27 GMT
Content-Type: text/x-apple-plist+xml
Content-Length: 411




 
  height
  720
  overscanned
  
  refreshRate
  0.016666666666666666
  version
  130.14
  width
  1280

POST /stream

Start the live video transmission. The client sends a binary property list with information about the stream, immediately followed by the stream itself. At this point, the connection is no longer a valid HTTP connection.
The following parameters are sent:

key	type	value	description
deviceID	integer	181221086727016	MAC address (A4:D1:D2:80:0B:68)
sessionID	integer	–808788724	session ID (0xcfcadd0c)
version	string	130.16	server version
param1	data	(72 bytes)	AES key, encrypted with FairPlay
param2	data	(16 bytes)	AES initialization vector
latencyMs	integer	90	video latency in ms
fpsInfo	array
timestampInfo	array

The param1 and param2 parameters are optional.
As soon as the server receives a /stream request, it will send NTP requests to the client on port 7010, which seems hard-coded as well. The client needs to export its master clock there, which will be used for audio/video synchronization and clock recovery.
Example: send stream information

client → server

POST /stream HTTP/1.1
X-Apple-Device-ID: 0xa4d1d2800b68
Content-Length: 503






 
  deviceID
  181221086727016
  fpsInfo
  
    name SubS 
    name B4En 
    name EnDp 
    name IdEn 
    name IdDp 
    name EQDp 
    name QueF 
    name Sent 
  
  latencyMs
  90
  param1
  
  RlBMWQECAQAAAAA8AAAAANvKuDizduszL1hG9IvIk+AAAAAQukdPJ5Jw/gGBAl22WZdF
  m9ujZEGIV7jm3ZByWm51HjpDwjYY
  
  param2
  
  3qpOHtYWbBPyEWPnGt1BuQ==
  
  sessionID
  -808788724
  timestampInfo
  
    name SubSu 
    name BePxT 
    name AfPxT 
    name BefEn 
    name EmEnc 
    name QueFr 
    name SndFr 
  
  version
  130.16

6.2. Stream Packets

The video stream is packetized using 128-byte headers, followed by an optional payload. Only the first 64 bytes of headers seem to be used. Headers start with the following little-endian fields:

size	description
4 bytes	payload size
2 bytes	payload type
2 bytes	0x1e if type = 2, else 6
8 bytes	NTP timestamp

There are 3 types of packets:

type	description
0	video bitstream
1	codec data
2	heartbeat

Codec Data

This packet contains the H.264 extra data in avcC format (ISO/IEC 14496:15). It is sent at the beginning of the stream, each time the video properties might change, when screen orientation changes, and when the screen is turned on or off.

H.264 codec data from iPad

0000   01 64 c0 28 ff e1 00 10 67 64 c0 28 ac 56 20 0d
0010   81 4f e5 9b 81 01 01 01 01 00 04 28 ee 3c b0

The H.264 codec data is interpreted as follows:

size	value	description
1 byte	1	version
1 byte	100	profile (high)
1 byte	0xc0	compatibility
1 byte	40	level (4.0)
6 bits	0x3f	reserved
2 bits	3	NAL units length size - 1
3 bits	0x7	reserved
5 bits	1	number of SPS
2 bytes	16	length of SPS
16 bytes	…	Sequence parameter set
1 byte	1	number of PPS
2 bytes	4	length of PPS
4 bytes	…	Picture parameter set

Codec data packet from iPad

0000   1f 00 00 00 01 00 06 00 1d 9a 9f 59 ef de 00 00
0010   00 00 58 44 00 00 22 44 00 00 00 00 00 00 00 00
0020   00 00 00 00 00 00 00 00 00 00 58 44 00 00 22 44
0030   00 00 50 43 00 00 10 42 00 c0 57 44 00 c0 21 44
0040   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0050   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0060   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0070   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0080   01 64 c0 28 ff e1 00 10 67 64 c0 28 ac 56 20 0d
0090   81 4f e5 9b 81 01 01 01 01 00 04 28 ee 3c b0

Video Bitstream

This packet contains the video bitstream to be decoded. The payload can be optionally AES encrypted. The NTP timestamp found in the header serves as presentation timestamp.

Video bitstream packet from iPad

0000   c8 08 00 00 00 00 06 00 e9 e6 f5 ac 60 e0 00 00
0010   58 37 6e f9 40 01 00 00 00 00 00 00 00 00 00 00
0020   00 00 00 00 00 00 00 00 00 00 58 44 00 00 22 44
0030   00 00 50 43 00 00 10 42 00 c0 57 44 00 c0 21 44
0040   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0050   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0060   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0070   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0080   ...

Heartbeat

Sent every second, this packet does not contain any payload.

Heartbeat packet from iPad

0000   00 00 00 00 02 00 1e 00 00 00 00 00 00 00 00 00
0010   4d d8 1a 41 00 00 00 00 00 00 20 41 86 c9 e2 36
0020   00 00 00 00 80 88 44 4b 00 00 00 00 00 00 00 00
0030   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0040   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0050   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0060   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0070   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

6.3. Time Synchronization

Time synchronization takes place on UDP ports 7010 (client) and 7011 (server), using the NTP protocol (RFC 5905). The AirPlay server runs an NTP client. Requests are sent to the AirPlay client at 3 second intervals. The reference date for the timestamps is the beginning of the mirroring session.

server → client

0000   23 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0010   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0020   00 00 00 00 00 00 00 00 00 00 01 c4 c8 ac 5d b5

Network Time Protocol
    Flags: 0x23
        00.. .... = Leap Indicator: no warning (0)
        ..10 0... = Version number: NTP Version 4 (4)
        .... .011 = Mode: client (3)
    Peer Clock Stratum: unspecified or invalid (0)
    Peer Polling Interval: invalid (0)
    Peer Clock Precision: 1.000000 sec
    Root Delay: 0.0000 sec
    Root Dispersion: 0.0000 sec
    Reference ID: NULL
    Reference Timestamp: Jan 1, 1970 00:00:00.000000000 UTC
    Origin Timestamp: Jan 1, 1970 00:00:00.000000000 UTC
    Receive Timestamp: Jan 1, 1970 00:00:00.000000000 UTC
    Transmit Timestamp: Jan 1, 1900 00:07:32.783880000 UTC

client → server

0000   24 01 02 e8 00 00 00 00 00 00 00 00 41 49 52 50
0010   00 00 00 00 00 00 00 00 00 00 01 c4 c8 ac 5d b5
0020   00 00 01 c4 c9 6a 0b a1 00 00 01 c4 c9 78 73 d2

Network Time Protocol
    Flags: 0x24
        00.. .... = Leap Indicator: no warning (0)
        ..10 0... = Version number: NTP Version 4 (4)
        .... .100 = Mode: server (4)
    Peer Clock Stratum: primary reference (1)
    Peer Polling Interval: invalid (2)
    Peer Clock Precision: 0.000000 sec
    Root Delay: 0.0000 sec
    Root Dispersion: 0.0000 sec
    Reference ID: Unidentified reference source 'AIRP'
    Reference Timestamp: Jan 1, 1970 00:00:00.000000000 UTC
    Origin Timestamp: Jan 1, 1900 00:07:32.783880000 UTC
    Receive Timestamp: Jan 1, 1900 00:07:32.786774000 UTC
    Transmit Timestamp: Jan 1, 1900 00:07:32.786994000 UTC

7. Password Protection

An AirPlay server can require a password for displaying any content from the network. This is implemented using standard HTTP Digest Authentication (RFC 2617), over RTSP for AirTunes, and HTTP for everything else. The digest realms and usernames accepted by Apple TV are the following:

service	realm	username
AirTunes	`raop`	`iTunes`
AirPlay	`AirPlay`	`AirPlay`

Example 1: AirTunes password request

client → server

ANNOUNCE rtsp://fe80::217:f2ff:fe0f:e0f6/3414156527 RTSP/1.0
CSeq: 3
Content-Type: application/sdp
Content-Length: 348
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 448488758

server → client

RTSP/1.0 401 Unauthorized
Server: AirTunes/130.14
WWW-Authenticate: Digest realm="raop", nonce="ddfd59b4aea7bbbcbbb3b60d3b2768b7"
CSeq: 3

client → server

ANNOUNCE rtsp://fe80::217:f2ff:fe0f:e0f6/3414156527 RTSP/1.0
CSeq: 4
Content-Type: application/sdp
Content-Length: 348
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Client-Instance: 56B29BB6CB904862
DACP-ID: 56B29BB6CB904862
Active-Remote: 448488758
Authorization: Digest username="iTunes", realm="raop", nonce="ddfd59b4aea7bbbcbbb3b60d3b2768b7", uri="rtsp://fe80::217:f2ff:fe0f:e0f6/3414156527", response="36f93a97c9038598290729ec0f141b03"

server → client

RTSP/1.0 200 OK
Server: AirTunes/130.14
CSeq: 4

Example 2: AirPlay password request

client → server

POST /play HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 163
Content-Type: text/parameters

Content-Location: http://192.168.1.18:3689/airplay.mp4?database-spec='dmap.persistentid:0x63b5e5c0c201542e'&item-spec='dmap.itemid:0x21e'
Start-Position: 0.317546

server → client

HTTP/1.1 401 Unauthorized
Date: Fri, 09 Mar 2012 15:50:40 GMT
Content-Length: 0
WWW-Authenticate: Digest realm="AirPlay", nonce="MTMzMTMwODI0MCDEJP5Jo7HFo81rbAcKNKw2"

client → server

POST /play HTTP/1.1
User-Agent: iTunes/10.6 (Macintosh; Intel Mac OS X 10.7.3) AppleWebKit/535.18.5
Content-Length: 163
Content-Type: text/parameters
Authorization: Digest username="AirPlay", realm="AirPlay", nonce="MTMzMTMwODI0MCDEJP5Jo7HFo81rbAcKNKw2", uri="/play", response="aa085eea3e66a2e56125a4957e70894a"

Content-Location: http://192.168.1.18:3689/airplay.mp4?database-spec='dmap.persistentid:0x63b5e5c0c201542e'&item-spec='dmap.itemid:0x21e'
Start-Position: 0.317546

server → client

HTTP/1.1 200 OK
Date: Fri, 09 Mar 2012 15:50:40 GMT
Content-Length: 0

8. History

Date	Changes
2012–03–20	Initial version.

9. Resources

9.1. IETF RFCs

RFC 2616: Hypertext Transfer Protocol – HTTP/1.1
RFC 2617: HTTP Authentication: Basic and Digest Access Authentication
RFC 2326: Real Time Streaming Protocol (RTSP)
RFC 4566: SDP: Session Description Protocol
RFC 3550: RTP: A Transport Protocol for Real-Time Applications
RFC 5905: Network Time Protocol Version 4
RFC 4648: The Base16, Base32, and Base64 Data Encodings

9.2. IETF drafts

9.3. Apple Protocols

DAAP: Digital Audio Access Protocol
DACP: Digital Audio Control Protocol
RAOP: Remote Audio Output Protocol