A2dp sink的初始化流程和A2dp 的初始化流程,基本一样,这里做简单分析.这里分析的android的版本是Android O.

我们先从service的启动说起吧.

下面 是启动的时候的log:

  1. D/BluetoothAdapterService( ): setProfileServiceState() - Starting service com.android.bluetooth.a2dpsink.A2dpSinkService
  1. - ::22.042 D/A2dpSinkService( ): Received start request. Starting profile...
  2. - ::22.045 D/A2dpSinkService( ): start()
  3. - ::22.054 I/BluetoothA2dpSinkServiceJni( ): classInitNative: succeeds

我们看看 A2dpSinkService.java的start函数的实现:

  1.     protected boolean start() {
  2.         if (DBG) {
  3.             Log.d(TAG, "start()");
  4.         }
  5.         // Start the media browser service.
  6.         Intent startIntent = new Intent(this, A2dpMediaBrowserService.class);
  7.         startService(startIntent);//启动service
  8.         mStateMachine = A2dpSinkStateMachine.make(this, this);//启动状态机
  9.         setA2dpSinkService(this);//设置sA2dpSinkService = this
  10.         return true;
  11.     }

这里比较重要的地方就是 sink 状态机的启动,我们进一步看看:

  1.     static A2dpSinkStateMachine make(A2dpSinkService svc, Context context) {
  2.         Log.d("A2dpSinkStateMachine", "make");
  3.         A2dpSinkStateMachine a2dpSm = new A2dpSinkStateMachine(svc, context);//新建状态机
  4.         a2dpSm.start();
  5.         return a2dpSm;
  6.     }

我们看看这个类的构造函数实现:

  1.     static {
  2.         classInitNative();
  3.     }
  1.     private A2dpSinkStateMachine(A2dpSinkService svc, Context context) {
  2.         super("A2dpSinkStateMachine");
  3.         mService = svc;
  4.         mContext = context;
  5.         mAdapter = BluetoothAdapter.getDefaultAdapter();
  6.  
  7.         initNative();//初始化
  8.  
  9.         mDisconnected = new Disconnected();
  10.         mPending = new Pending();
  11.         mConnected = new Connected();
  12.  
  13.         addState(mDisconnected);
  14.         addState(mPending);
  15.         addState(mConnected);
  16.  
  17.         setInitialState(mDisconnected);
  18.  
  19.         PowerManager pm = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
  20.  
  21.         mIntentBroadcastHandler = new IntentBroadcastHandler();
  22.     }

上面  主要做了初始化,然后 新建三个状态,然后设置初始状态.这里主要分析一下初始化相关的流程： classInitNative()和initNative()

我们先看前者：

  1.  private native static void classInitNative();

这是本地实现的函数,在com_android_bluetooth_a2dp_sink.cpp中:

  1. static void classInitNative(JNIEnv* env, jclass clazz) {
  2.   method_onConnectionStateChanged =
  3.       env->GetMethodID(clazz, "onConnectionStateChanged", "(I[B)V");
  4.  
  5.   method_onAudioStateChanged =
  6.       env->GetMethodID(clazz, "onAudioStateChanged", "(I[B)V");
  7.  
  8.   method_onAudioConfigChanged =
  9.       env->GetMethodID(clazz, "onAudioConfigChanged", "([BII)V");
  10.  
  11.   ALOGI("%s: succeeds", __func__);
  12. }

主要就是 从上层 索取了一些函数调用的"句柄",我们继续看initNative:

  1. static void initNative(JNIEnv* env, jobject object) {
  2.   const bt_interface_t* btInf = getBluetoothInterface();
  3.   if (btInf == NULL) {
  4.     ALOGE("Bluetooth module is not loaded");
  5.     return;
  6.   }
  7.  
  8.   if (sBluetoothA2dpInterface != NULL) {
  9.     ALOGW("Cleaning up A2DP Interface before initializing...");
  10.     sBluetoothA2dpInterface->cleanup();
  11.     sBluetoothA2dpInterface = NULL;
  12.   }
  13.  
  14.   if (mCallbacksObj != NULL) {
  15.     ALOGW("Cleaning up A2DP callback object");
  16.     env->DeleteGlobalRef(mCallbacksObj);
  17.     mCallbacksObj = NULL;
  18.   }
  19.  
  20.   sBluetoothA2dpInterface =
  21.       (btav_sink_interface_t*)btInf->get_profile_interface(
  22.           BT_PROFILE_ADVANCED_AUDIO_SINK_ID);
  23.   if (sBluetoothA2dpInterface == NULL) {
  24.     ALOGE("Failed to get Bluetooth A2DP Sink Interface");
  25.     return;
  26.   }
  27.  
  28.   bt_status_t status = sBluetoothA2dpInterface->init(&sBluetoothA2dpCallbacks);
  29.   if (status != BT_STATUS_SUCCESS) {
  30.     ALOGE("Failed to initialize Bluetooth A2DP Sink, status: %d", status);
  31.     sBluetoothA2dpInterface = NULL;
  32.     return;
  33.   }
  34.  
  35.   mCallbacksObj = env->NewGlobalRef(object);
  36. }

上面的逻辑 就是先获取蓝牙的接口,再获取sink 的接口,然后对sink 接口进行初始化.我们主要看初始化的过程:

实现是在btif_av.cc中:

  1. static const btav_sink_interface_t bt_av_sink_interface = {
  2.     sizeof(btav_sink_interface_t),
  3.     init_sink,
  4.     sink_connect_src,
  5.     disconnect,
  6.     cleanup_sink,
  7.     update_audio_focus_state,
  8.     update_audio_track_gain,
  9. }

这里的init 对应的接口就是init_sink,我们继续看:

  1. /*******************************************************************************
  2.  *
  3.  * Function         init_sink
  4.  *
  5.  * Description      Initializes the AV interface for sink mode
  6.  *
  7.  * Returns          bt_status_t
  8.  *
  9.  ******************************************************************************/
  10.  
  11. static bt_status_t init_sink(btav_sink_callbacks_t* callbacks) {
  12.   BTIF_TRACE_EVENT("%s()", __func__);
  13.  
  14.   bt_status_t status = btif_av_init(BTA_A2DP_SINK_SERVICE_ID);
  15.   if (status == BT_STATUS_SUCCESS) bt_av_sink_callbacks = callbacks;
  16.  
  17.   return status;
  18. }

这里的核心是btif_av_init,这里和之前src的初始化很相似,由于Android版本的演化,这里的btif_av_init 接口已经有了参数,:

  1. /*******************************************************************************
  2.  *
  3.  * Function         btif_av_init
  4.  *
  5.  * Description      Initializes btif AV if not already done
  6.  *
  7.  * Returns          bt_status_t
  8.  *
  9.  ******************************************************************************/
  10.  
  11. bt_status_t btif_av_init(int service_id) {
  12.   if (btif_av_cb.sm_handle == NULL) {
  13.     alarm_free(av_open_on_rc_timer);
  14.     av_open_on_rc_timer = alarm_new("btif_av.av_open_on_rc_timer");
  15.  
  16.     switch (service_id) {
  17.       case BTA_A2DP_SOURCE_SERVICE_ID:
  18.         if (!btif_a2dp_source_startup())
  19.           return BT_STATUS_FAIL;  // Already running
  20.         break;
  21.       case BTA_A2DP_SINK_SERVICE_ID:
  22.         if (!btif_a2dp_sink_startup())
  23.           return BT_STATUS_FAIL;  // Already running
  24.         break;
  25.     }
  26.  
  27.     /* Also initialize the AV state machine */
  28.     btif_av_cb.sm_handle = btif_sm_init(
  29.         (const btif_sm_handler_t*)btif_av_state_handlers, BTIF_AV_STATE_IDLE);//初始化 av 状态机
  30.  
  31.     btif_enable_service(service_id);//enable 某个service
  32.  
  33.   }
  34.  
  35.   return BT_STATUS_SUCCESS;
  36. }

从上面的代码结构可以看出,此接口是sink 和src 共享的.

上面的代码的执行任务分为3个部分：

  1. btif—a2dp-sink的线程启动btif_sm_init
  2. btif_sm_init
  3. btif_enable_service(sink)

我们发现根据传入的参数不同，如果是src，那么执行btif_a2dp_source_startup，如果是sink 执行：btif_a2dp_sink_startup，看了下两者的实现也是大致相同，都是先设置相应的状态，然后新建线程，然后绑定线程队列，然后调用thread_post 去执行 剩下的流程：

  1. bool btif_a2dp_sink_startup(void) {
  2.   if (btif_a2dp_sink_state != BTIF_A2DP_SINK_STATE_OFF) {
  3.     APPL_TRACE_ERROR("%s: A2DP Sink media task already running", __func__);//先判断状态机的状态
  4.     return false;
  5.   }
  6.  
  7.   memset(&btif_a2dp_sink_cb, , sizeof(btif_a2dp_sink_cb));
  8.   btif_a2dp_sink_state = BTIF_A2DP_SINK_STATE_STARTING_UP;//设置状态机
  9.  
  10.   APPL_TRACE_EVENT("## A2DP SINK START MEDIA THREAD ##");
  11.  
  12.   /* Start A2DP Sink media task */
  13.   btif_a2dp_sink_cb.worker_thread = thread_new("btif_a2dp_sink_worker_thread");
  14. ...
  15.  
  16.   btif_a2dp_sink_cb.rx_focus_state = BTIF_A2DP_SINK_FOCUS_NOT_GRANTED;
  17.   btif_a2dp_sink_cb.audio_track = NULL;
  18.   btif_a2dp_sink_cb.rx_audio_queue = fixed_queue_new(SIZE_MAX);//新建audio 队列
  19.  
  20.   btif_a2dp_sink_cb.cmd_msg_queue = fixed_queue_new(SIZE_MAX);//新建cmd msg队列
  21.   fixed_queue_register_dequeue(
  22.       btif_a2dp_sink_cb.cmd_msg_queue,
  23.       thread_get_reactor(btif_a2dp_sink_cb.worker_thread),
  24.       btif_a2dp_sink_command_ready, NULL);绑定命令队列以及命令处理函数
  25.  
  26.   APPL_TRACE_EVENT("## A2DP SINK MEDIA THREAD STARTED ##");
  27.  
  28.   /* Schedule the rest of the startup operations */
  29.   thread_post(btif_a2dp_sink_cb.worker_thread, btif_a2dp_sink_startup_delayed,
  30.               NULL);//接下来的流程放置到btif_a2dp_sink_worker_thread的work_queue里面去
  31.  
  32.   return true;
  33. }

我们看看 btif_a2dp_sink_startup_delayed  的实现：

  1. static void btif_a2dp_sink_startup_delayed(UNUSED_ATTR void* context) {
  2.   raise_priority_a2dp(TASK_HIGH_MEDIA);
  3.   btif_a2dp_sink_state = BTIF_A2DP_SINK_STATE_RUNNING;//更新sink的状态
  4. }

下面我们看看btif_sm_init的实现：

这里是新建了一个状态机，为后续的状态转换作准备：该函数将会传入以下的参数，我们发现是一个个的处理handler

  1. static const btif_sm_handler_t btif_av_state_handlers[] = {
  2.     btif_av_state_idle_handler, btif_av_state_opening_handler,
  3.     btif_av_state_opened_handler, btif_av_state_started_handler,
  4.     btif_av_state_closing_handler};
  1. /*****************************************************************************
  2.  *
  3.  * Function     btif_sm_init
  4.  *
  5.  * Description  Initializes the state machine with the state handlers
  6.  *              The caller should ensure that the table and the corresponding
  7.  *              states match. The location that 'p_handlers' points to shall
  8.  *              be available until the btif_sm_shutdown API is invoked.
  9.  *
  10.  * Returns      Returns a pointer to the initialized state machine handle.
  11.  *
  12.  *****************************************************************************/
  13.  
  14. btif_sm_handle_t btif_sm_init(const btif_sm_handler_t* p_handlers,
  15.                               btif_sm_state_t initial_state) {
  16.  
  17.   btif_sm_cb_t* p_cb = (btif_sm_cb_t*)osi_malloc(sizeof(btif_sm_cb_t));
  18.   p_cb->state = initial_state;//设置初始状态
  19.   p_cb->p_handlers = (btif_sm_handler_t*)p_handlers;//将这个handler赋值到pcb里面
  20.  
  21.   /* Send BTIF_SM_ENTER_EVT to the initial state */
  22.   p_cb->p_handlers[initial_state](BTIF_SM_ENTER_EVT, NULL);
  23.  
  24.   return (btif_sm_handle_t)p_cb;
  25. }

最后会执行 进如idle 的状态机的流程:这里不作具体分析了

  1. static bool btif_av_state_idle_handler(btif_sm_event_t event, void* p_data) {
  2.   BTIF_TRACE_DEBUG("%s event:%s flags %x", __func__,
  3.                    dump_av_sm_event_name((btif_av_sm_event_t)event),
  4.                    btif_av_cb.flags);
  5.  
  6.   switch (event) {
  7.     case BTIF_SM_ENTER_EVT:
  8.       /* clear the peer_bda */
  9.       memset(&btif_av_cb.peer_bda, , sizeof(bt_bdaddr_t));
  10.       btif_av_cb.flags = ;
  11.       btif_av_cb.edr = ;
  12.       bta_av_co_init(btif_av_cb.codec_priorities);
  13.       btif_a2dp_on_idle();
  14.       break;

下面我们在看看btif_enable_service 的流程:

  1. /*******************************************************************************
  2.  *
  3.  * Function         btif_enable_service
  4.  *
  5.  * Description      Enables the service 'service_ID' to the service_mask.
  6.  *                  Upon BT enable, BTIF core shall invoke the BTA APIs to
  7.  *                  enable the profiles
  8.  *
  9.  * Returns          bt_status_t
  10.  *
  11.  ******************************************************************************/
  12. bt_status_t btif_enable_service(tBTA_SERVICE_ID service_id) {
  13.   tBTA_SERVICE_ID* p_id = &service_id;
  14.  
  15.   /* If BT is enabled, we need to switch to BTIF context and trigger the
  16.    * enable for that profile
  17.    *
  18.    * Otherwise, we just set the flag. On BT_Enable, the DM will trigger
  19.    * enable for the profiles that have been enabled */
  20.  
  21.   btif_enabled_services |= ( << service_id);//设置标志位
  22.  
  23.   BTIF_TRACE_DEBUG("%s: current services:0x%x", __func__,
  24.                    btif_enabled_services);
  25.  
  26.   if (btif_is_enabled()) {
  27.     btif_transfer_context(btif_dm_execute_service_request,
  28.                           BTIF_DM_ENABLE_SERVICE, (char*)p_id,
  29.                           sizeof(tBTA_SERVICE_ID), NULL);//开启该profile
  30.   }
  31.  
  32.   return BT_STATUS_SUCCESS;
  33. }

我们需要开始的profile 隐藏在p_id 参数中,那我们也可以看出,这里其他的profile 也应该是走的这个流程.

  1. void btif_dm_execute_service_request(uint16_t event, char* p_param) {
  2.   bool b_enable = false;
  3.   bt_status_t status;
  4.   if (event == BTIF_DM_ENABLE_SERVICE) {
  5.     b_enable = true;
  6.   }
  7.   status =
  8.       btif_in_execute_service_request(*((tBTA_SERVICE_ID*)p_param), b_enable);
  9.   if (status == BT_STATUS_SUCCESS) {
  10.     bt_property_t property;
  11.     bt_uuid_t local_uuids[BT_MAX_NUM_UUIDS];//新建内存存放uuid
  12.  
  13.     /* Now send the UUID_PROPERTY_CHANGED event to the upper layer */
  14.     BTIF_STORAGE_FILL_PROPERTY(&property, BT_PROPERTY_UUIDS,
  15.                                sizeof(local_uuids), local_uuids);//
  16.     btif_storage_get_adapter_property(&property);//fill property value
  17.     HAL_CBACK(bt_hal_cbacks, adapter_properties_cb, BT_STATUS_SUCCESS, ,
  18.               &property);//上报相关的property
  19.   }
  20.   return;
  21. }

我们知道当 profile启动完成之后,那么 将通过HAL_CBACK 将已经启动的property 上报到JNI 以及以上.

那么我们现在看看btif_in_execute_service_request的实现:

  1. bt_status_t btif_in_execute_service_request(tBTA_SERVICE_ID service_id,
  2.                                             bool b_enable) {
  3.   BTIF_TRACE_DEBUG("%s service_id: %d", __func__, service_id);
  4.   /* Check the service_ID and invoke the profile's BT state changed API */
  5.   switch (service_id) {
  6.     case BTA_HFP_SERVICE_ID:
  7.     case BTA_HSP_SERVICE_ID: {
  8.       btif_hf_execute_service(b_enable);
  9.     } break;
  10.     case BTA_A2DP_SOURCE_SERVICE_ID: {
  11.       btif_av_execute_service(b_enable);
  12.     } break;
  13.     case BTA_A2DP_SINK_SERVICE_ID: {
  14.       btif_av_sink_execute_service(b_enable);
  15.     } break;
  16. ...
  1. /*******************************************************************************
  2.  *
  3.  * Function         btif_av_sink_execute_service
  4.  *
  5.  * Description      Initializes/Shuts down the service
  6.  *
  7.  * Returns          BT_STATUS_SUCCESS on success, BT_STATUS_FAIL otherwise
  8.  *
  9.  ******************************************************************************/
  10. bt_status_t btif_av_sink_execute_service(bool b_enable) {
  11.   if (b_enable) {
  12.     /* Added BTA_AV_FEAT_NO_SCO_SSPD - this ensures that the BTA does not
  13.      * auto-suspend av streaming on AG events(SCO or Call). The suspend shall
  14.      * be initiated by the app/audioflinger layers */
  15.     BTA_AvEnable(BTA_SEC_AUTHENTICATE,
  16.                  BTA_AV_FEAT_NO_SCO_SSPD | BTA_AV_FEAT_RCCT |
  17.                      BTA_AV_FEAT_METADATA | BTA_AV_FEAT_VENDOR |
  18.                      BTA_AV_FEAT_ADV_CTRL | BTA_AV_FEAT_RCTG |
  19.                      BTA_AV_FEAT_BROWSE,
  20.                  bte_av_callback);
  21.     BTA_AvRegister(BTA_AV_CHNL_AUDIO, BTIF_AVK_SERVICE_NAME, ,
  22.                    bte_av_sink_media_callback, UUID_SERVCLASS_AUDIO_SINK);
  23.   } else {
  24.     BTA_AvDeregister(btif_av_cb.bta_handle);
  25.     BTA_AvDisable();
  26.   }
  27.   return BT_STATUS_SUCCESS;
  28. }

这里和src的初始化的流程非常的相似,也是分为两个步骤:

  1. BTA_AvEnable(BTA_SEC_AUTHENTICATE,BTA_AV_FEAT_NO_SCO_SSPD | BTA_AV_FEAT_RCCT |BTA_AV_FEAT_METADATA | BTA_AV_FEAT_VENDOR |BTA_AV_FEAT_ADV_CTRL | BTA_AV_FEAT_RCTG |
    BTA_AV_FEAT_BROWSE,bte_av_callback);

  2. BTA_AvRegister(BTA_AV_CHNL_AUDIO, BTIF_AVK_SERVICE_NAME, 0,bte_av_sink_media_callback, UUID_SERVCLASS_AUDIO_SINK);

我们先看BTA_AvEnable :

  1. #define BTA_SEC_AUTHENTICATE   (BTM_SEC_IN_AUTHENTICATE | BTM_SEC_OUT_AUTHENTICATE) /* Authentication required. */0x12
  1. #define BTM_SEC_IN_AUTHENTICATE 0x0002
  2. #define BTM_SEC_OUT_AUTHENTICATE 0x0010
  1. BTA_AV_FEAT_NO_SCO_SSPD | BTA_AV_FEAT_RCCT | BTA_AV_FEAT_METADATA | BTA_AV_FEAT_VENDOR | BTA_AV_FEAT_ADV_CTRL | BTA_AV_FEAT_RCTG | BTA_AV_FEAT_BROWSE,//0x825B

看看其回调函数:

  1. static void bte_av_callback(tBTA_AV_EVT event, tBTA_AV* p_data) {
  2.   btif_transfer_context(btif_av_handle_event, event, (char*)p_data,
  3.                         sizeof(tBTA_AV), btif_av_event_deep_copy);//基本上是把event 传给状态机
  4. }

现在看看BTA_AvEnable的实现

  1. /*******************************************************************************
  2.  *
  3.  * Function         BTA_AvEnable
  4.  *
  5.  * Description      Enable the advanced audio/video service. When the enable
  6.  *                  operation is complete the callback function will be
  7.  *                  called with a BTA_AV_ENABLE_EVT. This function must
  8.  *                  be called before other function in the AV API are
  9.  *                  called.
  10.  *
  11.  * Returns          void
  12.  *
  13.  ******************************************************************************/
  14. void BTA_AvEnable(tBTA_SEC sec_mask, tBTA_AV_FEAT features,
  15.                   tBTA_AV_CBACK* p_cback) {
  16.   tBTA_AV_API_ENABLE* p_buf =
  17.       (tBTA_AV_API_ENABLE*)osi_malloc(sizeof(tBTA_AV_API_ENABLE));
  18.  
  19.   /* register with BTA system manager */
  20.   bta_sys_register(BTA_ID_AV, &bta_av_reg);
  21.  
  22.   p_buf->hdr.event = BTA_AV_API_ENABLE_EVT;
  23.   p_buf->p_cback = p_cback;//bte_av_callback
  24.   p_buf->features = features;//0x825B
  25.   p_buf->sec_mask = sec_mask;//0x0012
  26.  
  27.   bta_sys_sendmsg(p_buf);
  28. }

发送了BTA_AV_API_ENABLE_EVT  这个事件；

  1. #define BTA_ID_AV 18            /* Advanced audio/video */

这个 event的 主ID 还是BTA_ID_AV，而并不是BTA_ID_AVK

  1. /* register with BTA system manager */
  2.   bta_sys_register(BTA_ID_AV, &bta_av_reg);

我们看看

  1. static const tBTA_SYS_REG bta_av_reg = {bta_av_hdl_event, BTA_AvDisable};

也就是0x18开头的event 都是由bta_av_hdl_event  来统一处理：

  1. /*******************************************************************************
  2.  *
  3.  * Function         bta_av_hdl_event
  4.  *
  5.  * Description      Advanced audio/video main event handling function.
  6.  *
  7.  *
  8.  * Returns          bool
  9.  *
  10.  ******************************************************************************/
  11. bool bta_av_hdl_event(BT_HDR* p_msg) {
  12.   if (p_msg->event > BTA_AV_LAST_EVT) {
  13.     return true; /* to free p_msg */
  14.   }
  15.   if (p_msg->event >= BTA_AV_FIRST_NSM_EVT) {
  16.     APPL_TRACE_VERBOSE("%s: AV nsm event=0x%x(%s)", __func__, p_msg->event,
  17.                        bta_av_evt_code(p_msg->event));
  18.     /* non state machine events */
  19.     (*bta_av_nsm_act[p_msg->event - BTA_AV_FIRST_NSM_EVT])(
  20.         (tBTA_AV_DATA*)p_msg);
  21.   } else if (p_msg->event >= BTA_AV_FIRST_SM_EVT &&
  22.              p_msg->event <= BTA_AV_LAST_SM_EVT) {
  23.     APPL_TRACE_VERBOSE("%s: AV sm event=0x%x(%s)", __func__, p_msg->event,
  24.                        bta_av_evt_code(p_msg->event));
  25.     /* state machine events */
  26.     bta_av_sm_execute(&bta_av_cb, p_msg->event, (tBTA_AV_DATA*)p_msg);
  27.   } else {
  28.     APPL_TRACE_VERBOSE("handle=0x%x", p_msg->layer_specific);
  29.     /* stream state machine events */
  30.     bta_av_ssm_execute(bta_av_hndl_to_scb(p_msg->layer_specific), p_msg->event,
  31.                        (tBTA_AV_DATA*)p_msg);
  32.   }
  33.   return true;
  34. }

从上面的代码实现，我们发现 其讲event 分为了3类，一类是不在状态机中处理的，一类是在状态机中处理，还有一类是在stream 的状态机中处理的，现在我们将这些event 分类一下：

一以下是所有的event：

  1. enum {
  2.   /* these events are handled by the AV main state machine */
  3.   BTA_AV_API_DISABLE_EVT = BTA_SYS_EVT_START(BTA_ID_AV),
  4.   BTA_AV_API_REMOTE_CMD_EVT,
  5.   BTA_AV_API_VENDOR_CMD_EVT,
  6.   BTA_AV_API_VENDOR_RSP_EVT,
  7.   BTA_AV_API_META_RSP_EVT,
  8.   BTA_AV_API_RC_CLOSE_EVT,
  9.   BTA_AV_AVRC_OPEN_EVT,
  10.   BTA_AV_AVRC_MSG_EVT,
  11.   BTA_AV_AVRC_NONE_EVT,
  12.  
  13.   /* these events are handled by the AV stream state machine */
  14.   BTA_AV_API_OPEN_EVT,
  15.   BTA_AV_API_CLOSE_EVT,
  16.   BTA_AV_AP_START_EVT, /* the following 2 events must be in the same order as
  17.                           the *API_*EVT */
  18.   BTA_AV_AP_STOP_EVT,
  19.   BTA_AV_API_RECONFIG_EVT,
  20.   BTA_AV_API_PROTECT_REQ_EVT,
  21.   BTA_AV_API_PROTECT_RSP_EVT,
  22.   BTA_AV_API_RC_OPEN_EVT,
  23.   BTA_AV_SRC_DATA_READY_EVT,
  24.   BTA_AV_CI_SETCONFIG_OK_EVT,
  25.   BTA_AV_CI_SETCONFIG_FAIL_EVT,
  26.   BTA_AV_SDP_DISC_OK_EVT,
  27.   BTA_AV_SDP_DISC_FAIL_EVT,
  28.   BTA_AV_STR_DISC_OK_EVT,
  29.   BTA_AV_STR_DISC_FAIL_EVT,
  30.   BTA_AV_STR_GETCAP_OK_EVT,
  31.   BTA_AV_STR_GETCAP_FAIL_EVT,
  32.   BTA_AV_STR_OPEN_OK_EVT,
  33.   BTA_AV_STR_OPEN_FAIL_EVT,
  34.   BTA_AV_STR_START_OK_EVT,
  35.   BTA_AV_STR_START_FAIL_EVT,
  36.   BTA_AV_STR_CLOSE_EVT,
  37.   BTA_AV_STR_CONFIG_IND_EVT,
  38.   BTA_AV_STR_SECURITY_IND_EVT,
  39.   BTA_AV_STR_SECURITY_CFM_EVT,
  40.   BTA_AV_STR_WRITE_CFM_EVT,
  41.   BTA_AV_STR_SUSPEND_CFM_EVT,
  42.   BTA_AV_STR_RECONFIG_CFM_EVT,
  43.   BTA_AV_AVRC_TIMER_EVT,
  44.   BTA_AV_AVDT_CONNECT_EVT,
  45.   BTA_AV_AVDT_DISCONNECT_EVT,
  46.   BTA_AV_ROLE_CHANGE_EVT,
  47.   BTA_AV_AVDT_DELAY_RPT_EVT,
  48.   BTA_AV_ACP_CONNECT_EVT,
  49.   BTA_AV_API_OFFLOAD_START_EVT,
  50.   BTA_AV_API_OFFLOAD_START_RSP_EVT,
  51.  
  52.   /* these events are handled outside of the state machine */
  53.   BTA_AV_API_ENABLE_EVT,
  54.   BTA_AV_API_REGISTER_EVT,
  55.   BTA_AV_API_DEREGISTER_EVT,
  56.   BTA_AV_API_DISCONNECT_EVT,
  57.   BTA_AV_CI_SRC_DATA_READY_EVT,
  58.   BTA_AV_SIG_CHG_EVT,
  59.   BTA_AV_SIGNALLING_TIMER_EVT,
  60.   BTA_AV_SDP_AVRC_DISC_EVT,
  61.   BTA_AV_AVRC_CLOSE_EVT,
  62.   BTA_AV_AVRC_BROWSE_OPEN_EVT,
  63.   BTA_AV_AVRC_BROWSE_CLOSE_EVT,
  64.   BTA_AV_CONN_CHG_EVT,
  65.   BTA_AV_DEREG_COMP_EVT,
  66. #if (AVDT_REPORTING == TRUE)
  67.   BTA_AV_AVDT_RPT_CONN_EVT,
  68. #endif
  69.   BTA_AV_API_START_EVT, /* the following 2 events must be in the same order as
  70.                            the *AP_*EVT */
  71.   BTA_AV_API_STOP_EVT
  72. }

我们发现，不在状态机中处理的event是：

  1.   /* these events are handled outside of the state machine */
  2.   BTA_AV_API_ENABLE_EVT,
  3.   BTA_AV_API_REGISTER_EVT,
  4.   BTA_AV_API_DEREGISTER_EVT,
  5.   BTA_AV_API_DISCONNECT_EVT,
  6.   BTA_AV_CI_SRC_DATA_READY_EVT,
  7.   BTA_AV_SIG_CHG_EVT,
  8.   BTA_AV_SIGNALLING_TIMER_EVT,
  9.   BTA_AV_SDP_AVRC_DISC_EVT,
  10.   BTA_AV_AVRC_CLOSE_EVT,
  11.   BTA_AV_AVRC_BROWSE_OPEN_EVT,
  12.   BTA_AV_AVRC_BROWSE_CLOSE_EVT,
  13.   BTA_AV_CONN_CHG_EVT,
  14.   BTA_AV_DEREG_COMP_EVT,
  15. #if (AVDT_REPORTING == TRUE)
  16.   BTA_AV_AVDT_RPT_CONN_EVT,
  17. #endif
  18.   BTA_AV_API_START_EVT, /* the following 2 events must be in the same order as
  19.                            the *AP_*EVT */
  20.   BTA_AV_API_STOP_EVT

处理他的函数是：bta_av_nsm_act：

  1. /* action functions */
  2. const tBTA_AV_NSM_ACT bta_av_nsm_act[] = {
  3.     bta_av_api_enable,       /* BTA_AV_API_ENABLE_EVT */
  4.     bta_av_api_register,     /* BTA_AV_API_REGISTER_EVT */
  5.     bta_av_api_deregister,   /* BTA_AV_API_DEREGISTER_EVT */
  6.     bta_av_api_disconnect,   /* BTA_AV_API_DISCONNECT_EVT */
  7.     bta_av_ci_data,          /* BTA_AV_CI_SRC_DATA_READY_EVT */
  8.     bta_av_sig_chg,          /* BTA_AV_SIG_CHG_EVT */
  9.     bta_av_signalling_timer, /* BTA_AV_SIGNALLING_TIMER_EVT */
  10.     bta_av_rc_disc_done,     /* BTA_AV_SDP_AVRC_DISC_EVT */
  11.     bta_av_rc_closed,        /* BTA_AV_AVRC_CLOSE_EVT */
  12.     bta_av_rc_browse_opened, /* BTA_AV_AVRC_BROWSE_OPEN_EVT */
  13.     bta_av_rc_browse_closed, /* BTA_AV_AVRC_BROWSE_CLOSE_EVT */
  14.     bta_av_conn_chg,         /* BTA_AV_CONN_CHG_EVT */
  15.     bta_av_dereg_comp,       /* BTA_AV_DEREG_COMP_EVT */
  16. #if (AVDT_REPORTING == TRUE)
  17.     bta_av_rpc_conn, /* BTA_AV_AVDT_RPT_CONN_EVT */
  18. #endif
  19.     bta_av_api_to_ssm, /* BTA_AV_API_START_EVT */
  20.     bta_av_api_to_ssm, /* BTA_AV_API_STOP_EVT */
  21. }

还有一类事件 是在AV的main 的状态机中处理的：

  1.   /* these events are handled by the AV main state machine */
  2.   BTA_AV_API_DISABLE_EVT = BTA_SYS_EVT_START(BTA_ID_AV),
  3.   BTA_AV_API_REMOTE_CMD_EVT,
  4.   BTA_AV_API_VENDOR_CMD_EVT,
  5.   BTA_AV_API_VENDOR_RSP_EVT,
  6.   BTA_AV_API_META_RSP_EVT,
  7.   BTA_AV_API_RC_CLOSE_EVT,
  8.   BTA_AV_AVRC_OPEN_EVT,
  9.   BTA_AV_AVRC_MSG_EVT,
  10.   BTA_AV_AVRC_NONE_EVT,

处理的函数组是：bta_av_sm_execute --->bta_av_action:

  1. /* action functions */
  2. const tBTA_AV_ACTION bta_av_action[] = {
  3.     bta_av_disable,
  4.     bta_av_rc_opened,
  5.     bta_av_rc_remote_cmd,
  6.     bta_av_rc_vendor_cmd,
  7.     bta_av_rc_vendor_rsp,
  8.     bta_av_rc_free_rsp,
  9.     bta_av_rc_free_browse_msg,
  10.     bta_av_rc_meta_rsp,
  11.     bta_av_rc_msg,
  12.     bta_av_rc_close,
  13. };

最后一类是  建立 stream之后的event：

  1. /* these events are handled by the AV stream state machine */
  2.   BTA_AV_API_OPEN_EVT,
  3.   BTA_AV_API_CLOSE_EVT,
  4.   BTA_AV_AP_START_EVT, /* the following 2 events must be in the same order as
  5.                           the *API_*EVT */
  6.   BTA_AV_AP_STOP_EVT,
  7.   BTA_AV_API_RECONFIG_EVT,
  8.   BTA_AV_API_PROTECT_REQ_EVT,
  9.   BTA_AV_API_PROTECT_RSP_EVT,
  10.   BTA_AV_API_RC_OPEN_EVT,
  11.   BTA_AV_SRC_DATA_READY_EVT,
  12.   BTA_AV_CI_SETCONFIG_OK_EVT,
  13.   BTA_AV_CI_SETCONFIG_FAIL_EVT,
  14.   BTA_AV_SDP_DISC_OK_EVT,
  15.   BTA_AV_SDP_DISC_FAIL_EVT,
  16.   BTA_AV_STR_DISC_OK_EVT,
  17.   BTA_AV_STR_DISC_FAIL_EVT,
  18.   BTA_AV_STR_GETCAP_OK_EVT,
  19.   BTA_AV_STR_GETCAP_FAIL_EVT,
  20.   BTA_AV_STR_OPEN_OK_EVT,
  21.   BTA_AV_STR_OPEN_FAIL_EVT,
  22.   BTA_AV_STR_START_OK_EVT,
  23.   BTA_AV_STR_START_FAIL_EVT,
  24.   BTA_AV_STR_CLOSE_EVT,
  25.   BTA_AV_STR_CONFIG_IND_EVT,
  26.   BTA_AV_STR_SECURITY_IND_EVT,
  27.   BTA_AV_STR_SECURITY_CFM_EVT,
  28.   BTA_AV_STR_WRITE_CFM_EVT,
  29.   BTA_AV_STR_SUSPEND_CFM_EVT,
  30.   BTA_AV_STR_RECONFIG_CFM_EVT,
  31.   BTA_AV_AVRC_TIMER_EVT,
  32.   BTA_AV_AVDT_CONNECT_EVT,
  33.   BTA_AV_AVDT_DISCONNECT_EVT,
  34.   BTA_AV_ROLE_CHANGE_EVT,
  35.   BTA_AV_AVDT_DELAY_RPT_EVT,
  36.   BTA_AV_ACP_CONNECT_EVT,
  37.   BTA_AV_API_OFFLOAD_START_EVT,
  38.   BTA_AV_API_OFFLOAD_START_RSP_EVT,

处理的函数是bta_av_ssm_execute ，处理的action 是p_scb->p_act_tbl

我们继续看BTA_AV_API_ENABLE_EVT 的处理，根据上面的分类，处理的函数是bta_av_api_enable：

  1. /*******************************************************************************
  2.  *
  3.  * Function         bta_av_api_enable
  4.  *
  5.  * Description      Handle an API enable event.
  6.  *
  7.  *
  8.  * Returns          void
  9.  *
  10.  ******************************************************************************/
  11. static void bta_av_api_enable(tBTA_AV_DATA* p_data) {
  12.   /* initialize control block */
  13.   memset(&bta_av_cb, , sizeof(tBTA_AV_CB));
  14.  
  15.   for (int i = ; i < BTA_AV_NUM_RCB; i++)
  16.     bta_av_cb.rcb[i].handle = BTA_AV_RC_HANDLE_NONE;
  17.  
  18.   bta_av_cb.rc_acp_handle = BTA_AV_RC_HANDLE_NONE;
  19.  
  20.   /*
  21.    * TODO: The "disable" event handling is missing - there we need
  22.    * to alarm_free() the alarms below.
  23.    */
  24.   bta_av_cb.link_signalling_timer = alarm_new("bta_av.link_signalling_timer");//这里只是新建了一个timer ，还没有启动
  25.   bta_av_cb.accept_signalling_timer =
  26.       alarm_new("bta_av.accept_signalling_timer");
  27.  
  28.   /* store parameters */
  29.   bta_av_cb.p_cback = p_data->api_enable.p_cback;//bte_av_callback
  30.   bta_av_cb.features = p_data->api_enable.features;//0x825B
  31.   bta_av_cb.sec_mask = p_data->api_enable.sec_mask;//0x0012
  32.  
  33.   tBTA_AV_ENABLE enable;
  34.   enable.features = bta_av_cb.features;//0x825B
  35.  
  36.   /* Register for SCO change event */
  37.   if (!(bta_av_cb.features & BTA_AV_FEAT_NO_SCO_SSPD)) {
  38.     bta_sys_sco_register(bta_av_sco_chg_cback);
  39.   }
  40.  
  41.   /* call callback with enable event */
  42.   (*bta_av_cb.p_cback)(BTA_AV_ENABLE_EVT, (tBTA_AV*)&enable);//callback:bte_av_callback
  43. }

这里需要注意的是 上面只是新建了定时器，还么有 启动定时器，我们看看回调函数的实现：

  1. static void bte_av_callback(tBTA_AV_EVT event, tBTA_AV* p_data) {
  2.   btif_transfer_context(btif_av_handle_event, event, (char*)p_data,
  3.                         sizeof(tBTA_AV), btif_av_event_deep_copy);
  4. }
  1. static void btif_av_handle_event(uint16_t event, char* p_param) {
  2.   BTIF_TRACE_EVENT("%s event:%s", __func__,
  3.                    dump_av_sm_event_name((btif_av_sm_event_t)event));
  4.   switch (event) {
  5.     case BTIF_AV_CLEANUP_REQ_EVT:
  6.       btif_a2dp_source_shutdown();
  7.       btif_a2dp_sink_shutdown();
  8.       break;
  9.  
  10.     case BTA_AV_REGISTER_EVT:
  11.       if (btif_av_cb.sm_handle == NULL) {
  12.         btif_av_cb.bta_handle = ((tBTA_AV*)p_param)->registr.hndl;
  13.         BTIF_TRACE_DEBUG("%s: BTA AV Handle updated", __func__);
  14.       }
  15.     /* FALLTHROUGH */
  16.     default:
  17.       btif_sm_dispatch(btif_av_cb.sm_handle, event, (void*)p_param);
  18.       btif_av_event_free_data(event, p_param);
  19.   }
  20. }

上面走到到了 btif_sm_dispatch 里面了：

  1. /*****************************************************************************
  2.  *
  3.  * Function     btif_sm_dispatch
  4.  *
  5.  * Description  Dispatches the 'event' along with 'data' to the current state
  6.  *              handler
  7.  *
  8.  * Returns      BT_STATUS_SUCCESS on success
  9.  *              BT_STATUS_UNHANDLED if event was not processed
  10.  *              BT_STATUS_FAIL otherwise
  11.  *
  12.  *****************************************************************************/
  13. bt_status_t btif_sm_dispatch(btif_sm_handle_t handle, btif_sm_event_t event,
  14.                              void* data) {
  15.   bt_status_t status = BT_STATUS_SUCCESS;
  16.  
  17.   btif_sm_cb_t* p_cb = (btif_sm_cb_t*)handle;
  18.  
  19.   if (p_cb == NULL) {
  20.     BTIF_TRACE_ERROR("%s : Invalid handle", __func__);
  21.     return BT_STATUS_FAIL;
  22.   }
  23.  
  24.   if (p_cb->p_handlers[p_cb->state](event, data) == false)
  25.     return BT_STATUS_UNHANDLED;
  26.  
  27.   return status;
  28. }

这里的state  还是idle 状态， 这里发现 对于这个BTA_AV_ENABLE_EVT 并么有处理，这里就不分析。（和src的分析的流程基本一致）

下面继续看看BTA_AvRegister(BTA_AV_CHNL_AUDIO, BTIF_AVK_SERVICE_NAME, 0,bte_av_sink_media_callback, UUID_SERVCLASS_AUDIO_SINK);的实现：

这里和之前的src的分析不同点在于（Android版本不同）这里的参数个数多了一个，这里会传入了一个参数，标志是src还是sink 进行的注册。

  1. /*******************************************************************************
  2.  *
  3.  * Function         BTA_AvRegister
  4.  *
  5.  * Description      Register the audio or video service to stack. When the
  6.  *                  operation is complete the callback function will be
  7.  *                  called with a BTA_AV_REGISTER_EVT. This function must
  8.  *                  be called before AVDT stream is open.
  9.  *
  10.  *
  11.  * Returns          void
  12.  *
  13.  ******************************************************************************/
  14. void BTA_AvRegister(tBTA_AV_CHNL chnl, const char* p_service_name,
  15.                     uint8_t app_id, tBTA_AV_SINK_DATA_CBACK* p_sink_data_cback,
  16.                     uint16_t service_uuid) {
  17.   tBTA_AV_API_REG* p_buf =
  18.       (tBTA_AV_API_REG*)osi_malloc(sizeof(tBTA_AV_API_REG));
  19.  
  20.   p_buf->hdr.layer_specific = chnl;//BTA_AV_CHNL_AUDIO = 0x40
  21.   p_buf->hdr.event = BTA_AV_API_REGISTER_EVT;
  22.   if (p_service_name)
  23.     strlcpy(p_buf->p_service_name, p_service_name, BTA_SERVICE_NAME_LEN);
  24.   else
  25.     p_buf->p_service_name[] = ;
  26.   p_buf->app_id = app_id;//
  27.   p_buf->p_app_sink_data_cback = p_sink_data_cback;//bte_av_sink_media_callback
  28.   p_buf->service_uuid = service_uuid;//UUID_SERVCLASS_AUDIO_SINK = 0x110B
  29.  
  30.   bta_sys_sendmsg(p_buf);
  31. }

我们继续看这个event 的处理，我们发现bta_av_api_register 这个函数也是 sink 和src 共用的，这也是和Android6.0的实现不同的地方。

其实可以仿照AndroidO的代码去修改AndroidM的代码，以此将sink 和src 分开。

  1.     /*******************************************************************************
  2.  *
  3.  * Function         bta_av_api_register
  4.  *
  5.  * Description      allocate stream control block,
  6.  *                  register the service to stack
  7.  *                  create SDP record
  8.  *
  9.  * Returns          void
  10.  *
  11.  ******************************************************************************/
  12. static void bta_av_api_register(tBTA_AV_DATA* p_data) {
  13.   tBTA_AV_REGISTER registr;
  14.   tBTA_AV_SCB* p_scb; /* stream control block */
  15.   tAVDT_REG reg;
  16.   tAVDT_CS cs;
  17.   char* p_service_name;
  18.   tBTA_UTL_COD cod;
  19.  
  20.   memset(&cs, , sizeof(tAVDT_CS));//初始化cs，该项最终拷贝到p_scb->cfg，并且AVDT_CreateStream 会使用到
  21.  
  22.   registr.status = BTA_AV_FAIL_RESOURCES;//register 记录注册的信息，回调的时候会上报
  23.   registr.app_id = p_data->api_reg.app_id;//
  24.   registr.chnl = (tBTA_AV_CHNL)p_data->hdr.layer_specific;//layer_specific = 0x40
  25.  
  26.   uint16_t profile_initialized = p_data->api_reg.service_uuid;//sink
  27.   if (profile_initialized == UUID_SERVCLASS_AUDIO_SINK) {
  28.     p_bta_av_cfg = (tBTA_AV_CFG*)&bta_avk_cfg;
  29.   } else if (profile_initialized == UUID_SERVCLASS_AUDIO_SOURCE) {
  30.     p_bta_av_cfg = (tBTA_AV_CFG*)&bta_av_cfg;
  31.   }
  32.  
  33.   do {
  34.     p_scb = bta_av_alloc_scb(registr.chnl);//分配了一个 stream control block  ：bta_av_cb.p_scb[xx] = p_scb
  35.  
  36.     registr.hndl = p_scb->hndl;//0x41 or 0x42  --- hndl = (tBTA_AV_HNDL)((xx + 1) | chnl);
  37.     p_scb->app_id = registr.app_id;
  38.  
  39.     /* initialize the stream control block */
  40.     registr.status = BTA_AV_SUCCESS;
  41.  
  42.     if ((bta_av_cb.reg_audio + bta_av_cb.reg_video) == ) {
  43.       /* the first channel registered. register to AVDTP */
  44.       reg.ctrl_mtu = p_bta_av_cfg->sig_mtu;
  45.       reg.ret_tout = BTA_AV_RET_TOUT;
  46.       reg.sig_tout = BTA_AV_SIG_TOUT;
  47.       reg.idle_tout = BTA_AV_IDLE_TOUT;
  48.       reg.sec_mask = bta_av_cb.sec_mask;
  49.  
  50.       bta_ar_reg_avdt(&reg, bta_av_conn_cback, BTA_ID_AV);//注册到AVDT
  51.  
  52.       bta_sys_role_chg_register(&bta_av_sys_rs_cback);
  53.  
  54.       /* create remote control TG service if required */
  55.       if (bta_av_cb.features & (BTA_AV_FEAT_RCTG)) {
  56. /* register with no authorization; let AVDTP use authorization instead */
  57.         bta_ar_reg_avct(p_bta_av_cfg->avrc_mtu, p_bta_av_cfg->avrc_br_mtu,
  58.                         (uint8_t)(bta_av_cb.sec_mask & (~BTA_SEC_AUTHORIZE)),
  59.                         BTA_ID_AV);
  60.  
  61.         /* For the Audio Sink role we support additional TG 1.3 to support
  62.          * absolute volume.
  63.          */
  64.         uint16_t profile_version = AVRC_REV_1_0;
  65.  
  66.         if (profile_initialized == UUID_SERVCLASS_AUDIO_SOURCE) {
  67. ...
  68.         } else if (profile_initialized == UUID_SERVCLASS_AUDIO_SINK) {
  69.           // Initialize AVRCP1.4 to provide Absolute Volume control.
  70.           profile_version = AVRC_REV_1_4;
  71.         }
  72.  
  73.         bta_ar_reg_avrc(
  74.             UUID_SERVCLASS_AV_REM_CTRL_TARGET, "AV Remote Control Target", NULL,
  75.             p_bta_av_cfg->avrc_tg_cat, BTA_ID_AV,
  76.             (bta_av_cb.features & BTA_AV_FEAT_BROWSE), profile_version);
  77. #endif
  78.       }
  79.  
  80.       /* Set the Capturing service class bit */
  81.       if (profile_initialized == UUID_SERVCLASS_AUDIO_SOURCE)
  82.         cod.service = BTM_COD_SERVICE_CAPTURING;
  83.       else if (profile_initialized == UUID_SERVCLASS_AUDIO_SINK)
  84.         cod.service = BTM_COD_SERVICE_RENDERING;
  85.       utl_set_device_class(&cod, BTA_UTL_SET_COD_SERVICE_CLASS);
  86.     } /* if 1st channel */
  87.  
  88.     /* get stream configuration and create stream */
  89.     cs.cfg.num_codec = ;
  90.     cs.nsc_mask =
  91.         AVDT_NSC_RECONFIG |
  92.         ((bta_av_cb.features & BTA_AV_FEAT_PROTECT) ?  : AVDT_NSC_SECURITY);
  93.     APPL_TRACE_DEBUG("nsc_mask: 0x%x", cs.nsc_mask);
  94.  
  95.     if (p_data->api_reg.p_service_name[] == ) {
  96.       p_service_name = NULL;
  97.     } else {
  98.       p_service_name = p_data->api_reg.p_service_name;//用于后面创建SDP record
  99.     }
  100.  
  101.     p_scb->suspend_sup = true;
  102.     p_scb->recfg_sup = true;
  103.     p_scb->skip_sdp = false;
  104.  
  105.     cs.p_ctrl_cback = bta_av_dt_cback[p_scb->hdi];
  106.     if (registr.chnl == BTA_AV_CHNL_AUDIO) {//填充p_scb
  107.       /* set up the audio stream control block */
  108.       p_scb->p_act_tbl = (const tBTA_AV_ACT*)bta_av_a2dp_action;
  109.       p_scb->p_cos = &bta_av_a2dp_cos;
  110.       p_scb->media_type = AVDT_MEDIA_TYPE_AUDIO;
  111.       cs.cfg.psc_mask = AVDT_PSC_TRANS;
  112.       cs.media_type = AVDT_MEDIA_TYPE_AUDIO;
  113.       cs.mtu = p_bta_av_cfg->audio_mtu;
  114.       cs.flush_to = L2CAP_DEFAULT_FLUSH_TO;
  115.       btav_a2dp_codec_index_t codec_index_min =
  116.           BTAV_A2DP_CODEC_INDEX_SOURCE_MIN;
  117.       btav_a2dp_codec_index_t codec_index_max =
  118.           BTAV_A2DP_CODEC_INDEX_SOURCE_MAX;
  119.  
  120.       if (profile_initialized == UUID_SERVCLASS_AUDIO_SOURCE) {
  121. ...
  122.       } else if (profile_initialized == UUID_SERVCLASS_AUDIO_SINK) {
  123.         cs.tsep = AVDT_TSEP_SNK;
  124.         cs.p_sink_data_cback = bta_av_sink_data_cback;
  125.         codec_index_min = BTAV_A2DP_CODEC_INDEX_SINK_MIN;
  126.         codec_index_max = BTAV_A2DP_CODEC_INDEX_SINK_MAX;
  127.       }
  128.  
  129.       /* Initialize handles to zero */
  130.       for (int xx = ; xx < BTAV_A2DP_CODEC_INDEX_MAX; xx++) {
  131.         p_scb->seps[xx].av_handle = ;
  132.       }
  133.  
  134.       /* keep the configuration in the stream control block */
  135.       memcpy(&p_scb->cfg, &cs.cfg, sizeof(tAVDT_CFG));
  136.       for (int i = codec_index_min; i < codec_index_max; i++) {
  137.         btav_a2dp_codec_index_t codec_index =
  138.             static_cast<btav_a2dp_codec_index_t>(i);
  139.         if (!(*bta_av_a2dp_cos.init)(codec_index, &cs.cfg)) {
  140.           continue;
  141.         }
  142.         if (AVDT_CreateStream(&p_scb->seps[codec_index].av_handle, &cs) !=
  143.             AVDT_SUCCESS) {
  144.           continue;
  145.         }
  146.         /* Save a copy of the codec */
  147.         memcpy(p_scb->seps[codec_index].codec_info, cs.cfg.codec_info,
  148.                AVDT_CODEC_SIZE);
  149.         p_scb->seps[codec_index].tsep = cs.tsep;
  150.         if (cs.tsep == AVDT_TSEP_SNK) {
  151.           p_scb->seps[codec_index].p_app_sink_data_cback =
  152.               p_data->api_reg.p_app_sink_data_cback;
  153.         } else {
  154.           /* In case of A2DP SOURCE we don't need a callback to
  155.            * handle media packets.
  156.            */
  157.           p_scb->seps[codec_index].p_app_sink_data_cback = NULL;
  158.         }
  159.       }
  160.  
  161.       if (!bta_av_cb.reg_audio) {
  162.         bta_av_cb.sdp_a2dp_handle = ;
  163.         bta_av_cb.sdp_a2dp_snk_handle = ;
  164.         if (profile_initialized == UUID_SERVCLASS_AUDIO_SOURCE) {
  165. ...
  166.         } else if (profile_initialized == UUID_SERVCLASS_AUDIO_SINK) {
  167. #if (BTA_AV_SINK_INCLUDED == TRUE)
  168.           bta_av_cb.sdp_a2dp_snk_handle = SDP_CreateRecord();
  169.           A2DP_AddRecord(UUID_SERVCLASS_AUDIO_SINK, p_service_name, NULL,
  170.                          A2DP_SUPF_PLAYER, bta_av_cb.sdp_a2dp_snk_handle);
  171.           bta_sys_add_uuid(UUID_SERVCLASS_AUDIO_SINK);
  172. #endif
  173.         }
  174.         /* start listening when A2DP is registered */
  175.         if (bta_av_cb.features & BTA_AV_FEAT_RCTG)
  176.           bta_av_rc_create(&bta_av_cb, AVCT_ACP, , BTA_AV_NUM_LINKS + );
  177.  
  178.         /* if the AV and AVK are both supported, it cannot support the CT role
  179.          */
  180.         if (bta_av_cb.features & (BTA_AV_FEAT_RCCT)) {
  181.  
  182.           /* create an SDP record as AVRC CT. We create 1.3 for SOURCE
  183.            * because we rely on feature bits being scanned by external
  184.            * devices more than the profile version itself.
  185.            *
  186.            * We create 1.4 for SINK since we support browsing.
  187.            */
  188.           if (profile_initialized == UUID_SERVCLASS_AUDIO_SOURCE) {
  189. ...
  190.           } else if (profile_initialized == UUID_SERVCLASS_AUDIO_SINK) {
  191.             bta_ar_reg_avrc(UUID_SERVCLASS_AV_REMOTE_CONTROL, NULL, NULL,
  192.                             p_bta_av_cfg->avrc_ct_cat, BTA_ID_AV,
  193.                             (bta_av_cb.features & BTA_AV_FEAT_BROWSE),
  194.                             AVRC_REV_1_6);
  195.           }
  196.  
  197.         }
  198.       }
  199.       bta_av_cb.reg_audio |= BTA_AV_HNDL_TO_MSK(p_scb->hdi);
  200.       APPL_TRACE_DEBUG("reg_audio: 0x%x", bta_av_cb.reg_audio);
  201.         }
  202.   } while ();
  203.  
  204.   /* call callback with register event */
  205.   (*bta_av_cb.p_cback)(BTA_AV_REGISTER_EVT, (tBTA_AV*)&registr);
  206. }

上面注册的内容和 a2dp 初始化的流程基本相同，不作具体分析。

关于a2dp sink的初始化的流程，就分析到这里了。

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