Review iOS 10 integration to PJSIP

[nanang]

iOS 10 is coming with new features such as CallKit, framework changes such as in AVFoundation, and also API deprecations. This ticket will review and apply any integrations needed in PJSIP library.

PushKit guide

What your application needs to do:

1. Set up PushKit according to ​Apple's doc.
2. Upon startup, request for push tokens.
3. Send REGISTER to SIP server with additional specific header or header params to tell the SIP server about the PN (Push Notification) info (server URI, tokens, etc). You can use pjsua_acc_config.reg_hdr_list or pjsua_acc_config.reg_contact_params (the later is available in ticket #1965).
   Note: draft ​Push Notifications in the Session Initiation Protocol (SIP) suggests to put it in Contact header params, for example:

   Contact: <sip:alice@alicemobile.example.com;
        pn-type=acme;pn-methods="INVITE";
        pn-uri="https://pn.acme.example.com/ZTY4ZDJlMzODE1NmUgKi0K">
   

4. After a successful registration, SIP client can go background and will be woken up by the OS upon receiving push notification.

Configure your SIP server:

1. Parse the PN info in registration.
2. Upon receiving an incoming SIP INVITE, SIP server should contact PN server as specified via PN URI and tokens.
3. After some interval (assuming the SIP client has been woken up), it then can send/forward the SIP INVITE message to the SIP client.

CallKit support

CallKit requires the call audio to start only when audio session has been activated, thus it's recommended that you use PJSIP with no sound device (by calling pjsua_set_no_snd_dev()) and open the sound device only when necessary (by calling pjsua_set_snd_dev()). Below is an example on how to integrate CallKit with PJSIP, with the delegate functions taken from ​Speakerbox sample app provided by Apple.

To make outgoing call:

    func provider(_ provider: CXProvider, perform action: CXStartCallAction) {
        /* 1. Provide your own implementation to configure
         *    the audio session here.
         */
        configureAudioSession()

        /* 2. Set pjsua_set_no_snd_dev() before making call with
         *    pjsua_call_make_call() since we must not start
         *    call audio here, and can only do so once the audio session
         *    has been activated by the system after having its priority
         *    elevated.
         */
         
        /* 3. Use pjsua's on_call_state() callback to report significant
         *    events in the call's lifecycle, by calling iOS API
         *    CXProvider.reportOutgoingCall(with: startedConnectingAt:) and
         *    CXProvider.reportOutgoingCall(with: ConnectedAt:)
         */
         
        /* 4. If step (2) above returns PJ_SUCCESS, call action.fulfill(),
         *    otherwise call action.fail().
         */
    }

To handle incoming call:

    func provider(_ provider: CXProvider, perform action: CXAnswerCallAction) {
        /* 1. Provide your own implementation to configure
         *    the audio session here.
         */
        configureAudioSession()

        /* 2. We must not start call audio here, so if sound device is
         *    active, you need to call pjsua_set_no_snd_dev() first,
         *    before proceeding with pjsua_call_answer().

        /* 3. Signal to the system that the action has been successfully
         *    performed.
         */
        action.fulfill()
    }

To start sound device:

    func provider(_ provider: CXProvider, didActivate audioSession: AVAudioSession) {
        /* Start call audio media, now that the audio session has been
         * activated after having its priority boosted.
         *
         * Call pjsua API pjsua_set_snd_dev() here.
         */
    }

API/Symbol Deprecations

1. "kCFStreamNetworkServiceTypeVoIP is deprecated (first deprecated in iOS 9.0 - use PushKit for VoIP control purposes."
   See the PushKit guide above.
   If you want to disable the use of kCFStreamNetworkServiceTypeVoIP, set PJ_IPHONE_OS_HAS_MULTITASKING_SUPPORT to 0.

2. AVFoundation API deprecation:
   "warning: 'devices' is deprecated: first deprecated in iOS 10.0 - Use AVCaptureDeviceDiscoverySession instead."
   Done in r5454.

Reference:

• ​What's new in iOS 10.

[ming]

In 5453:

Re #1941: Add support to specify min iOS versions in configure-iphone and update the default for ipjsua sample app

[ming]

In 5454:

Re #1941: Support for AVCaptureDeviceDiscoverySession to replace the deprecated [AVCaptureDevice devices] in iOS 10.