Mirroring Service

After the pairing process has been finished successfully, the sender can start request the screen mirroring service. The diagram below describes the interaction flow of starting screen mirroring.


Mirroring Service Interaction Flow

We will not talk about pairing process again, please refer to the previous content.

  1. The sender delivers SETUP rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    SETUP rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 535
Content-Type: application/x-apple-binary-plist
CSeq: 3
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1   
bplist00...........	
..
.................RetSeiv^timingProtocol[sessionUUIDVosName^osBuildVersion]sourceVersionZtimingPort_.   isScreenMirroringSessionYosVersionTekeyXdeviceIDUmodelTnameZmacAddress. O..0......FTRM.H.R^SNTP_   $48FE92D4-3786-4D24-8270-752ACCCF8A47XMac OS XV19H524U425.1...	W10.15.7O.HFPLY.......<....%V.&..&k....}..........n.t...   A.Z.8......f....Q....]iuh._..88:66:5A:15:D7:E1^MacBookPro16,1_..SHEENTIAN-MBP00_..88:66:5A:15:D7:E1...).,.0.?.K.R.a.o.z...   .............................%.p......................................

    This request contains a binary plist data in the body and the plist consist of the following structure:

    {
    deviceID = "4C:57:CA:46:07:FC";
    diagnosticsAndUsage = 1;
    eiv = <5e830184 fea012b8 3bbd456d b761f798>;  // AES initial vector
    ekey = <data>;                                // AES key
    et = 32;
    internalBuild = 1;
    isScreenMirroringSession = 1;
    macAddress = "4C:57:CA:46:07:FA";
    model = "iPhone8,4";
    name = "hr\U7684 iPhone";
    osBuildVersion = 16B92;
    osName = "iPhone OS";
    osVersion = "12.1";
    sessionUUID = "42CD0A19-2E4B-4355-BED6-575FA83A60DA";
    sourceVersion = "373.9.1";
    timingPort = 63254;                         // NTP server port in the sender
    timingProtocol = NTP;
}

    The sever needs to store the eiv and ekey for initializing the AES crypto module, and then launches a time syncing client with the sender IP and timingPort. The time syncing client is actually a TCP client. The detailed implementation of the time syncing client will be discussed in the following sections.

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 3
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 83
Content-Type: application/x-apple-binary-plist

bplist00.....YeventPort.........ZtimingPort....
. +................................

    To reply this request, just construct a binary plist with the following structure:

    {
    eventPort: 0;
    timingPort: xxxx    // The local port of time syncing client
}

  2. The sender delivers GET /info RTSP/1.0 request to server

    Request: 

    GET /info RTSP/1.0
X-Apple-ProtocolVersion: 1
CSeq: 4
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

    This request is querying the capacities of the server and no data need to pares in the request.

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 4
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 952
Content-Type: application/x-apple-binary-plist

bplist00.......	.
......"-....
........#.XdeviceID\AABBCCDDEEFFXfeatures.R..._..keepAliveLowPower.._..keepAliveSendStatsAsBody..ZmacAddress_..AA:BB:CC:DD:EE:FFUmodelZAppleTV3,2Tname_..APS[AA:BB:CC:DD:EE:FF]]sourceVersionV220.68[statusFlags.DRpi_.$b08f5a79-db29-4384-b456-a4784d9e6055RpkO.@99FD4299889422515FBD27949E4E1E21B2AF50A454499E3D4BE75A4E0F55FE63Rvv..\audioFormats..... ..!Ttype.`_..audioInputFormats....._..audioOutputFormats.....^audioLatencies.$.%')+&(*,Ttype.`YaudioTypeWdefault_..inputLatencyMicros........._..outputLatencyMicros.........Xdisplays./.02468:<>@BD13579;=?ACEXfeatures..Vheight..8\heightPixels..8^heightPhysical.........Uwidth...[widthPixels...]widthPhysical.........[refreshRate#......N@[overscanned.Xrotation.Tuuid_.$e5f7a68d-7b0f-4305-984b-974f677a150b...).2.?.H.M.a.c.~.............................a.d.f.s.u.|.................................&./.1.H.Q.S.Z.].j.m.|...........................................F................

    To reply this request we need to return a binary plist with the following content:

    auto_plist info = plist_object_dict(15,
  "deviceID", plist_object_string(config_->deviceID().c_str()),
  "features", plist_object_integer(config_->features()),
  "keepAliveLowPower", plist_object_integer(1),
  "keepAliveSendStatsAsBody", plist_object_integer(1),
  "macAddress", plist_object_string(config_->macAddress().c_str()),
  "model", plist_object_string(config_->model().c_str()),
  "name", plist_object_string(config_->name().c_str()),
  "sourceVersion", plist_object_string(config_->serverVersion().c_str()),
  "statusFlags", plist_object_integer(config_->statusFlag()),
  "pi", plist_object_string(config_->pi().c_str()),
  "pk", plist_object_data((uint8_t *)config_->pk().c_str(), (uint32_t)config_->pk().length()),
  "vv", plist_object_integer(config_->vv()),
  "audioFormats",
  plist_object_array(1,
      plist_object_dict(3,
          "type", plist_object_integer(96),
          "audioInputFormats", plist_object_integer(0x01000000),
          "audioOutputFormats", plist_object_integer(0x01000000))),
  "audioLatencies", plist_object_array(1,
      plist_object_dict(4,
          "type", plist_object_integer(96),
          "audioType", plist_object_string("default"),
          "inputLatencyMicros", plist_object_integer(0),
          "outputLatencyMicros", plist_object_integer(0)
      )
  ),
  "displays", plist_object_array(1,
      plist_object_dict(11,
          "features", plist_object_integer(14),
          "height", plist_object_integer(config_->display().height()),
          "heightPixels", plist_object_integer(config_->display().height()),
          "heightPhysical", plist_object_integer(0),
          "width", plist_object_integer(config_->display().width()),
          "widthPixels", plist_object_integer(config_->display().width()),
          "widthPhysical", plist_object_integer(0),
          "refreshRate", plist_object_real(config_->display().refreshRate()),
          "overscanned", plist_object_true(),
          "rotation", plist_object_true(),
          "uuid", plist_object_string(config_->display().uuid().c_str())
      )
  )
);

  3. The sender delivers GET_PARAMETER rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    GET_PARAMETER rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 8
Content-Type: text/parameters
CSeq: 5
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

volume

    This request is simply querying the current volume value of the server.

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 5
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 18
Content-Type: text/parameters

volume: 0.000000

    Just return a text with the above format to tell the sender the volume value.

  4. The sender delivers RECORD rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    RECORD rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
CSeq: 6
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

    This request tells the server to start audio syncing process. After receive this request, the sever needs to send a query request from the time sync client to the sender.

    Response

    RTSP/1.0 200 OK
Audio-Latency: 0
CSeq: 6
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0

    In response of this request we need to add an HTTP header Audio-Latency, the value can be set to 0.

  5. The sender delivers SET_PARAMETER rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    SET_PARAMETER rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 20
Content-Type: text/parameters
CSeq: 7
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

volume: -20.000000

    This request tells the sever to set the volume value, note that the volume value range is [-144.0f ~ 0.0f]. We need to convert this value to the ratio which is recognized to the platform the server is running on.

    Response

    RTSP/1.0 200 OK
CSeq: 7
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0

    Just rely it with status code 200, no extra data.

  6. The sender delivers SETUP rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    SETUP rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 188
Content-Type: application/x-apple-binary-plist
CSeq: 8
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

bplist00...Wstreams.........Ttype]timestampInfo_..streamConnectionID.n.	.....
.TnameUSubSu.

UBePxT.
.UAfPxT.
.UBefEn.
.UEmEnc.j.^..MLr.....!/DFLOTZ]cfloux~................................

    This request tells the server the video stream information.

    {
  streams = [{
    type = 110;
    streamConnectionID = 3873339193950750702;
    timestampInfo = [
      { name = SubSu; },
      { name = BePxT; },
      { name = AfPxT; },
      { name = BefEn; },
      { name = EmEnc; }
    ];
  }];
}

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 8
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 102
Content-Type: application/x-apple-binary-plist

bplist00.....YeventPort...Wstreams......	Ttype.nXdataPort....
.."$).09...............
...............<

  7. The sender delivers SET_PARAMETER rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    This is the same process with the step 5.

    Request: 

    SET_PARAMETER rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 20
Content-Type: text/parameters
CSeq: 9
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

volume: -20.000000

    Response

    RTSP/1.0 200 OK
CSeq: 9
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0

  8. The sender delivers SETUP rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    SETUP rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 265
Content-Type: application/x-apple-binary-plist
CSeq: 10
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

bplist00...Wstreams........	
..
..............[usingScreen[audioFormat_..supportsDynamicStreamID^redundantAudioYaudioModeRctSspfZlatencyMaxTtype[controlPortWisMediaZlatencyMin	.....	..Wdefault.........`...	.....:F`oy|................................................

    This request tells the server the video stream information

    {
  streams = ({
    audioFormat = 262144;
    audioMode = default;
    controlPort = 54956;
    ct = 2;
    latencyMax = 88200;
    latencyMin = 11025;
    spf = 352;
    type = 96;
  });
}

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 10
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 104
Content-Type: application/x-apple-binary-plist

bplist00...Wstreams........	Ttype.`XdataPort..l[controlPort..m.....!#,/;...............
...............>

  9. The sender delivers SET_PARAMETER rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    SET_PARAMETER rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 20
Content-Type: text/parameters
CSeq: 11
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

volume: -20.000000

    Response

    RTSP/1.0 200 OK
CSeq: 11
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0

  10. The sender delivers FLUSH rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server Request: 

    FLUSH rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
RTP-Info: seq=58942;rtptime=1054215198
CSeq: 12
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 12
Date: Wed May  5 02:31:29 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0
Content-Type: application/x-apple-binary-plist

After the flush request, the session moves into media data transfer state. The sender will push the audio/video data to the server, and also the sender will deliver feedback request periodically with 2 seconds interval.

>>>>>>>>>>>>>>>> Media Data Transfer >>>>>>>>>>>>>>>>

<<<<<<<<<<<<<<<< Media Feedback <<<<<<<<<<<<<<<<

>>>>>>>>>>>>>>>> Media Data Transfer >>>>>>>>>>>>>>>>

<<<<<<<<<<<<<<<< Media Feedback <<<<<<<<<<<<<<<<

>>>>>>>>>>>>>>>> Media Data Transfer >>>>>>>>>>>>>>>>

<<<<<<<<<<<<<<<< Media Feedback <<<<<<<<<<<<<<<<

The sender delivers POST /feedback RTSP/1.0 request to server

**Request:** 
```
POST /feedback RTSP/1.0
CSeq: 13
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1
```

For this feedback request, the server needs do nothing, just give an empty response.

**Response**
```
RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 13
Date: Wed May  5 02:31:31 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0
```

  1. The sender delivers TEARDOWN rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    TEARDOWN rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 84
Content-Type: application/x-apple-binary-plist
CSeq: 15
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

bplist00...Wstreams.......XstreamIDTtype...`.....#(*...............................,

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 15
Date: Wed May  5 02:31:34 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0

  2. The sender delivers TEARDOWN rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    TEARDOWN rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 69
Content-Type: application/x-apple-binary-plist
CSeq: 16
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

bplist00...Wstreams.....Ttype.n......................................

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 16
Date: Wed May  5 02:31:34 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0

  3. The sender delivers TEARDOWN rtsp://xxx.xxx.xxx.xxx/xxxxxxxxxx RTSP/1.0 request to server

    Request: 

    TEARDOWN rtsp://192.168.31.82/5259802854977588516 RTSP/1.0
Content-Length: 42
Content-Type: application/x-apple-binary-plist
CSeq: 17
DACP-ID: 7136391BB370A579
Active-Remote: 354444643
User-Agent: AirPlay/425.1

bplist00.................................

    Response

    RTSP/1.0 200 OK
Audio-Jack-Status: Connected; type=digital
CSeq: 17
Date: Wed May  5 02:31:34 2021 GMT
Server: AirTunes/220.68
Session: CAFEBABE
Content-Length: 0