driver-peripherals-camera-des.md

# Camera

## 概述<a name="1"></a>
### 功能简介<a name="2"></a>

OpenHarmony相机驱动框架模型对上实现相机HDI（Hardware Device Interface）接口，对下实现相机Pipeline模型，管理相机各个硬件设备。
该驱动框架模型内部分为三层，依次为HDI实现层、框架层和设备适配层。各层基本概念如下：

+ HDI实现层：实现OHOS（OpenHarmony Operation System）相机标准南向接口。
+ 框架层：对接HDI实现层的控制、流的转发，实现数据通路的搭建，管理相机各个硬件设备等功能。
+ 设备适配层：屏蔽底层芯片和OS（Operation System）差异，支持多平台适配。

### 运作机制<a name="3"></a>

Camera模块主要包含服务、设备的初始化，数据通路的搭建，流的配置、创建、下发、捕获等，具体运作机制参考以下图文解析：

**图 1**  基于HDF驱动框架的Camera驱动模型　

　　　　　　　　![](figures/Camera模块驱动模型.png)

1. 系统启动时创建camera_host进程。进程创建后，首先枚举底层设备，创建（也可以通过配置表创建）管理设备树的DeviceManager类及其内部各个底层设备的对象，创建对应的CameraHost类实例并且将其注册到UHDF服务中，方便相机服务层通过UHDF服务获取底层CameraDeviceHost的服务，从而操作硬件设备。

2. Service通过CameraDeviceHost服务获取CameraHost实例，CameraHost可以获取底层的Camera能力，打开手电筒、调用Open接口打开Camera创建连接、创建DeviceManager（负责底层硬件模块上电）、创建CameraDevice（向上提供设备控制接口）。创建CameraDevice时会实例化PipelineCore的各个子模块，其中StreamPipelineCore负责创建Pipeline，MetaQueueManager负责上报metaData。

3. Service通过CameraDevice模块配置流、创建Stream类。StreamPipelineStrategy模块通过上层下发的模式和查询配置表创建对应流的Node连接方式，StreamPipelineBuilder模块创建Node实例并且连接返回该Pipeline给StreamPipelineDispatcher。StreamPipelineDispatcher提供统一的Pipeline调用管理。

4. Service通过Stream控制整个流的操作，AttachBufferQueue接口将从显示模块申请的BufferQueue下发到底层，由CameraDeviceDriverModel自行管理buffer，当Capture接口下发命令后，底层开始向上传递buffer。Pipeline的IspNode依次从BufferQueue获取指定数量buffer，然后下发到底层ISP（Image Signal Processor，图像信号处理器）硬件，ISP填充完之后将buffer传递给CameraDeviceDriverModel，CameraDeviceDriverModel通过循环线程将buffer填充到已经创建好的Pipeline中，各个Node处理后通过回调传递给上层，同时buffer返回BufferQueue等待下一次下发。

5. Service通过Capture接口下发拍照命令。ChangeToOfflineStream接口查询拍照buffer位置，如果ISP已经出图，并且图像数据已经送到IPP node，可以将普通拍照流转换为离线流，否则直接走关闭流程。ChangeToOfflineStream接口通过传递StreamInfo使离线流获取到普通流的流信息，并且通过配置表确认离线流的具体Node连接方式，创建离线流的Node连接（如果已创建则通过CloseCamera释放非离线流所需的Node），等待buffer从底层Pipeline回传到上层再释放持有的Pipeline相关资源。

6. Service通过CameraDevice的UpdateSettings接口向下发送CaptureSetting参数，CameraDeviceDriverModel通过StreamPipelineDispatcher模块向各个Node转发，StartStreamingCapture和Capture接口携带的CaptureSetting通过StreamPipelineDispatcher模块向该流所属的Node转发。

7. Service通过EnableResult和DisableResult接口控制底层metaData的上报。如果需要底层metaData上报，pipeline会创建CameraDeviceDriverModel内部的一个Bufferqueue用来收集和传递metaData，根据StreamPipelineStrategy模块查询配置表并通过StreamPipelineBuilder创建和连接Node，MetaQueueManager下发buffer至底层，底层相关Node填充数据，MetaQueueManager模块再调用上层回调传递给上层。

8. Service调用CameraDevice的Close接口，CameraDevice调用对应的DeviceManager模块对各个硬件下电；如果此时在Ipp的SubPipeline中存在OfflineStream，则需要保留OfflineStream，直到执行完毕。

9. 动态帧率控制。在StreamOperator中起一个CollectBuffer线程，CollectBuffer线程从每一路stream的BufferQueue中获取buffer，如果某一路流的帧率需要控制（为sensor出帧帧率的1/n），可以根据需求控制每一帧的buffer打包，并决定是否collect此路流的buffer（比如sensor出帧帧率为120fps，预览流的帧率为30fps，CollectBuffer线程collect预览流的buffer时，每隔4fps collect一次）。

   

## 开发指导<a name="4"></a>


### 场景介绍<a name="5"></a>

Camera模块主要用以相机预览、拍照、视频流等场景下对相机操作封装，使开发者更易操作相机硬件，提高开发效率。

### 接口说明<a name="6"></a>

- icamera_device.h

  | 功能描述                     | 接口名称                                                     |
  | ---------------------------- | ------------------------------------------------------------ |
  | 获取流控制器                 | CamRetCode GetStreamOperator(const OHOS::sptr<IStreamOperatorCallback> &callback, OHOS::sptr<IStreamOperator> &streamOperator) |
  | 更新设备控制参数             | CamRetCode UpdateSettings(const std::shared_ptr<CameraSetting> &settingss) |
  | 设置Result回调模式和回调函数 | CamRetCode SetResultMode(const ResultCallbackMode &mode)     |
  | 获取使能的ResultMeta         | CamRetCode GetEnabledResults(std::vector<MetaType> &results) |
  | 使能具体的ResultMeta         | CamRetCode EnableResult(const std::vector<MetaType> &results) |
  | 禁止具体的ResultMeta         | CamRetCode DisableResult(const std::vector<MetaType> &results) |
  | 关闭Camera设备               | void Close()                                                 |

- icamera_device_callback.h

  | 功能描述                                                   | 接口名称                                                     |
  | ---------------------------------------------------------- | ------------------------------------------------------------ |
  | 设备发生错误时调用，由调用者实现，用于返回错误信息给调用者 | void OnError(ErrorType type, int32_t errorCode)              |
  | 上报camera设备相关的metadata的回调                         | void OnResult(uint64_t timestamp, const std::shared_ptr<CameraMetadata> &result) |


- icamera_host.h

  | 功能描述                       | 接口名称                                                     |
  | ------------------------------ | ------------------------------------------------------------ |
  | 设置ICameraHost回调接口        | CamRetCode SetCallback(const OHOS::sptr<ICameraHostCallback> &callback) |
  | 获取当前可用的Camera设备ID列表 | CamRetCode GetCameraIds(std::vector\<std::string\> &cameraIds) |
  | 获取Camera设备能力集合         | CamRetCode GetCameraAbility(const std::string &cameraId, std::shared_ptr<CameraAbility> &ability) |
  | 打开Camera设备                 | CamRetCode OpenCamera(const std::string &cameraId, const OHOS::sptr<ICameraDeviceCallback> &callback, OHOS::sptr<ICameraDevice> &device) |
  | 打开或关闭闪光灯               | CamRetCode SetFlashlight(const std::string &cameraId, bool &isEnable) |

- icamera_host_callback.h

  | 功能描述               | 接口名称                                                     |
  | ---------------------- | ------------------------------------------------------------ |
  | Camera设备状态变化上报 | void OnCameraStatus(const std::string &cameraId, CameraStatus status) |
  | 闪光灯状态变化回调     | void OnFlashlightStatus(const std::string &cameraId, FlashlightStatus status) |

- ioffline_stream_operator.h

  | 功能描述       | 接口名称                                                     |
  | -------------- | ------------------------------------------------------------ |
  | 取消捕获请求   | CamRetCode CancelCapture(int captureId)                      |
  | 释放流         | CamRetCode ReleaseStreams(const std::vector<int> &streamIds) |
  | 释放所有离线流 | CamRetCode Release()                                         |

- istream_operator.h

  | 功能描述                         | 接口名称                                                     |
  | -------------------------------- | ------------------------------------------------------------ |
  | 查询是否支持添加参数对应的流     | CamRetCode IsStreamsSupported(OperationMode mode, const std::shared_ptr\<Camera::CameraMetadata\> &modeSetting, const std::vector&ltstd::shared_ptr&ltStreamInfo&gt> &info, StreamSupportType &type) |
  | 创建流                           | CamRetCode CreateStreams(const std::vector<std::shared_ptr<StreamInfo>> &streamInfos) |
  | 释放流                           | CamRetCode ReleaseStreams(const std::vector<int> &streamIds) |
  | 配置流                           | CamRetCode CommitStreams(OperationMode mode, const std::shared_ptr<CameraMetadata> &modeSetting) |
  | 获取流的属性                     | CamRetCode GetStreamAttributes(std::vector<std::shared_ptr<StreamAttribute>> &attributes) |
  | 绑定生产者句柄和指定流           | CamRetCode AttachBufferQueue(int streamId, const OHOS::sptr\<OHOS::IBufferProducer\> &producer) |
  | 解除生产者句柄和指定流的绑定关系 | CamRetCode DetachBufferQueue(int streamId)                   |
  | 捕获图像                         | CamRetCode Capture(int captureId, const std::shared_ptr<CaptureInfo> &info, bool isStreaming) |
  | 取消捕获                         | CamRetCode CancelCapture(int captureId)                      |
  | 将指定流转换成离线流             | CamRetCode ChangeToOfflineStream(const std::vector<int> &streamIds, OHOS::sptr<IStreamOperatorCallback> &callback, OHOS::sptr<IOfflineStreamOperator> &offlineOperator) |

- istream_operator_callback.h

  | 功能描述                                 | 接口名称                                                     |
  | ---------------------------------------- | ------------------------------------------------------------ |
  | 捕获开始回调，在捕获开始时调用           | void OnCaptureStarted(int32_t captureId, const std::vector<int32_t> &streamIds) |
  | 捕获结束回调，在捕获结束时调用           | void OnCaptureEnded(int32_t captureId, const std::vector<std::shared_ptr<CaptureEndedInfo>> &infos) |
  | 捕获错误回调，在捕获过程中发生错误时调用 | void OnCaptureError(int32_t captureId, const std::vector<std::shared_ptr<CaptureErrorInfo>> &infos) |
  | 帧捕获回调                               | void OnFrameShutter(int32_t captureId, const std::vector<int32_t> &streamIds, uint64_t timestamp) |

### 开发步骤<a name="7"></a>
Camera驱动的开发过程主要包含以下步骤：

1. 注册CameraHost

    定义Camera的HdfDriverEntry结构体，该结构体中定义了CameraHost初始化的方法。
    ```
   struct HdfDriverEntry g_cameraHostDriverEntry = {
       .moduleVersion = 1,
       .moduleName = "camera_service",
       .Bind = HdfCameraHostDriverBind,
       .Init = HdfCameraHostDriverInit,
       .Release = HdfCameraHostDriverRelease,
   };
   HDF_INIT(g_cameraHostDriverEntry); // 将Camera的HdfDriverEntry结构体注册到HDF上
   ```

2. 初始化Host服务

    步骤1中提到的HdfCameraHostDriverBind接口提供了CameraServiceDispatch和CameraHostStubInstance的注册。这两个接口一个是远端调用CameraHost的方法，如OpenCamera()，SetFlashlight()等，另外一个是Camera设备的初始化，在开机时被调用。

   ```
   int HdfCameraHostDriverBind(HdfDeviceObject *deviceObject)
   {
       HDF_LOGI("HdfCameraHostDriverBind enter!");
       if (deviceObject == nullptr) {
           HDF_LOGE("HdfCameraHostDriverBind: HdfDeviceObject is NULL!");
           return HDF_FAILURE;
       }
       HdfCameraService *hdfCameraService = reinterpret_cast<HdfCameraService *>(OsalMemAlloc(sizeof(HdfCameraService)));
       if (hdfCameraService == nullptr) {
           HDF_LOGE("HdfCameraHostDriverBind OsalMemAlloc HdfCameraService failed!");
           return HDF_FAILURE;
       }
       hdfCameraService->ioservice.Dispatch = CameraServiceDispatch; // 提供远端CameraHost调用方法
       hdfCameraService->ioservice.Open = nullptr;
       hdfCameraService->ioservice.Release = nullptr;
       hdfCameraService->instance = CameraHostStubInstance(); // 初始化Camera设备
       deviceObject->service = &hdfCameraService->ioservice;
       return HDF_SUCCESS;
   }
   ```

   下面的函数是远端CameraHost调用的方法：

   ```
   int32_t CameraHostStub::CameraHostServiceStubOnRemoteRequest(int cmdId, MessageParcel &data,
       MessageParcel &reply, MessageOption &option)
   {
       switch(cmdId) {
           case CMD_CAMERA_HOST_SET_CALLBACK: {
               return CameraHostStubSetCallback(data, reply, option);
           }
           case CMD_CAMERA_HOST_GET_CAMERAID: {
               return CameraHostStubGetCameraIds(data, reply, option);
           }
           case CMD_CAMERA_HOST_GET_CAMERA_ABILITY: {
               return CameraHostStubGetCameraAbility(data, reply, option);
           }
           case CMD_CAMERA_HOST_OPEN_CAMERA: {
               return CameraHostStubOpenCamera(data, reply, option);
           }
           case CMD_CAMERA_HOST_SET_FLASH_LIGHT: {
               return CameraHostStubSetFlashlight(data, reply, option);
           }
           default: {
               HDF_LOGE("%s: not support cmd %d", __func__, cmdId);
               return HDF_ERR_INVALID_PARAM;
           }
       }
       return HDF_SUCCESS;
   }
   ```

   CameraHostStubInstance()接口最终调用CameraHostImpl::Init()方法，该方法会获取物理Camera，并对DeviceManager和PipelineCore进行初始化。

3. 获取Host服务

   调用Get()接口从远端CameraService中获取CameraHost对象。get()方法如下：

   ```
   sptr<ICameraHost> ICameraHost::Get(const char *serviceName)
   {
       do {
           using namespace OHOS::HDI::ServiceManager::V1_0;
           auto servMgr = IServiceManager::Get();
           if (servMgr == nullptr) {
               HDF_LOGE("%s: IServiceManager failed!", __func__);
               break;
           }
           auto remote = servMgr->GetService(serviceName);  // 根据serviceName名称获取CameraHost
           if (remote != nullptr) {
               sptr<CameraHostProxy> hostSptr = iface_cast<CameraHostProxy>(remote); // 将CameraHostProxy对象返回给调用者，该对象中包含OpenCamera()等方法。
               return hostSptr;
           }
           HDF_LOGE("%s: GetService failed! serviceName = %s", __func__, serviceName);
       } while(false);
       HDF_LOGE("%s: get %s failed!", __func__, serviceName);
       return nullptr;
   }
   ```

4. 打开设备

   CameraHostProxy对象中有五个方法，分别是SetCallback、GetCameraIds、GetCameraAbility、OpenCamera和SetFlashlight。下面着重描述OpenCamera接口。
   CameraHostProxy的OpenCamera()接口通过CMD_CAMERA_HOST_OPEN_CAMERA调用远端CameraHostStubOpenCamera()接口并获取ICameraDevice对象。

   ```
   CamRetCode CameraHostProxy::OpenCamera(const std::string &cameraId, const OHOS::sptr<ICameraDeviceCallback> &callback, OHOS::sptr<ICameraDevice> &pDevice)
   {
       int32_t ret = Remote()->SendRequest(CMD_CAMERA_HOST_REMOTE_OPEN_CAMERA, data, reply, option);
       if (ret != HDF_SUCCESS) {
           HDF_LOGE("%{public}s: SendRequest failed, error code is %{public}d", __func__, ret);
           return INVALID_ARGUMENT;
       }
       CamRetCode retCode = static_cast<CamRetCode>(reply.ReadInt32());
       bool flag = reply.ReadBool();
       if (flag) {
           sptr<IRemoteObject> remoteCameraDevice = reply.ReadRemoteObject();
           if (remoteCameraDevice == nullptr) {
               HDF_LOGE("%{public}s: CameraHostProxy remoteCameraDevice is null", __func__);
           }
           pDevice = OHOS::iface_cast<ICameraDevice>(remoteCameraDevice);
       }
       return retCode;
   }
   ```

   Remote()->SendRequest调用上文提到的CameraHostServiceStubOnRemoteRequest()，根据cmdId进入CameraHostStubOpenCamera()接口，最终调用CameraHostImpl::OpenCamera()，该接口获取了CameraDevice并对硬件进行上电等操作。

   ```
   CamRetCode CameraHostImpl::OpenCamera(const std::string &cameraId, const OHOS::sptr<ICameraDeviceCallback> &callback, OHOS::sptr<ICameraDevice> &device)
   {
       std::shared_ptr<CameraDeviceImpl> cameraDevice = std::static_pointer_cast<CameraDeviceImpl>(itr->second);
       if (cameraDevice == nullptr) {
           CAMERA_LOGE("camera device is null.");
           return INSUFFICIENT_RESOURCES;
       }
       CamRetCode ret = cameraDevice->SetCallback(callback);
       if (ret != NO_ERROR) {
           CAMERA_LOGW("set camera device callback failed.");
           return ret;
       }
       CameraHostConfig *config = CameraHostConfig::GetInstance();
       if (config == nullptr) {
           return INVALID_ARGUMENT;
       }
       std::vector<std::string> phyCameraIds;
       RetCode rc = config->GetPhysicCameraIds(cameraId, phyCameraIds);
       if (rc != RC_OK) {
           CAMERA_LOGE("get physic cameraId failed.");
           return DEVICE_ERROR;
       }
       if (CameraPowerUp(cameraId, phyCameraIds) != RC_OK) { // 对Camera硬件上电
           CAMERA_LOGE("camera powerup failed.");
           CameraPowerDown(phyCameraIds);
           return DEVICE_ERROR;
       }
   
       auto sptrDevice = deviceBackup_.find(cameraId);
       if (sptrDevice == deviceBackup_.end()) {
           deviceBackup_[cameraId] = cameraDevice.get();
       }
       device = deviceBackup_[cameraId];
       cameraDevice->SetStatus(true);
       return NO_ERROR;
   }
   ```

5. 获取流

   CameraDeviceImpl定义了GetStreamOperator、UpdateSettings、SetResultMode和GetEnabledResult等方法，获取流操作方法如下：

   ```
   CamRetCode CameraDeviceImpl::GetStreamOperator(const OHOS::sptr<IStreamOperatorCallback> &callback,
    OHOS::sptr<IStreamOperator> &streamOperator)
   {
       if (callback == nullptr) {
           CAMERA_LOGW("input callback is null.");
           return INVALID_ARGUMENT;
       }
       spCameraDeviceCallback_ = callback;
       if (spStreamOperator_ == nullptr) {
           // 这里新建一个spStreamOperator对象传递给调用者，以便对stream进行各种操作。
           spStreamOperator_ = new(std::nothrow) StreamOperatorImpl(spCameraDeviceCallback_, shared_from_this());
           if (spStreamOperator_ == nullptr) {
               CAMERA_LOGW("create stream operator failed.");
               return DEVICE_ERROR;
           }
           ismOperator_ = spStreamOperator_;
       }
       streamOperator = ismOperator_;
   
       spStreamOperator_->SetRequestCallback([this](){
           spCameraDeviceCallback_->OnError(REQUEST_TIMEOUT, 0);
       });
   }
   ```

6. 创建流

   调用CreateStreams创建流前需要填充StreamInfo结构体，具体内容如下：

   ```
   using StreamInfo = struct _StreamInfo {
       int streamId_; 
       int width_;  // 数据流宽
       int height_; // 数据流高
       int format_; // 数据流格式，如PIXEL_FMT_YCRCB_420_SP
       int dataSpace_; 
       StreamIntent intent_; // StreamIntent 如PREVIEW
       bool tunneledMode_;
       OHOS::sptr<OHOS::IBufferProducer> bufferQueue_; // 数据流bufferQueue可用streamCustomer->CreateProducer()接口创建
       int minFrameDuration_;
       EncodeType encodeType_;
   };
   ```

   CreateStreams()接口是StreamOperatorImpl类中的方法，该接口的主要作用是创建一个StreamBase对象，通过StreamBase的Init方法初始化CreateBufferPool等操作。

   ```
   RetCode StreamOperatorImpl::CreateStream(const std::shared_ptr<StreamInfo>& streamInfo)
   {
       static std::map<StreamIntent, std::string> typeMap = {
           {PREVIEW, "PREVIEW"},
           {VIDEO, "VIDEO"},
           {STILL_CAPTURE, "STILL_CAPTURE"},
           {POST_VIEW, "POST_VIEW"}, {ANALYZE, "ANALYZE"},
           {CUSTOM, "CUSTOM"}
       };
   
       auto itr = typeMap.find(streamInfo->intent_);
       if (itr == typeMap.end()) {
           CAMERA_LOGE("do not support stream type. [type = %{public}d]", streamInfo->intent_);
           return RC_ERROR;
       }
       std::shared_ptr<StreamBase> stream = StreamFactory::Instance().CreateShared(itr->second); // 创建StreamBase实例
       RetCode rc = stream->Init(streamInfo); 
       return RC_OK;
   }
   ```

7. **配置流**

   CommitStreams()是配置流的接口，必须在创建流之后调用，其主要作用是初始化Pipeline和创建Pipeline。

   ```
   CamRetCode StreamOperatorImpl::CommitStreams(OperationMode mode, const std::shared_ptr<Camera::CameraMetadata>& modeSetting)
   {
       auto cameraDevice = cameraDevice_.lock();
       if (cameraDevice == nullptr) {
           CAMERA_LOGE("camera device closed.");
           return CAMERA_CLOSED;
       }
       std::shared_ptr<IPipelineCore> PipelineCore =
           std::static_pointer_cast<CameraDeviceImpl>(cameraDevice)->GetPipelineCore();
       if (PipelineCore == nullptr) {
           CAMERA_LOGE("get pipeline core failed.");
           return CAMERA_CLOSED;
       }
   
       streamPipeCore_ = PipelineCore->GetStreamPipelineCore();
       if (streamPipeCore_ == nullptr) {
           CAMERA_LOGE("get stream pipeline core failed.");
           return DEVICE_ERROR;
       }
   
       RetCode rc = streamPipeCore_->Init(); // 对pipelinecore的初始化
       if (rc != RC_OK) {
           CAMERA_LOGE("stream pipeline core init failed.");
           return DEVICE_ERROR;
       }
       rc = streamPipeCore_->CreatePipeline(mode); // 创建一个pipeline
       if (rc != RC_OK) {
           CAMERA_LOGE("create pipeline failed.");
           return INVALID_ARGUMENT;
       }
       return NO_ERROR;
   }
   ```

8. **捕获图像**

   在调用Capture()接口前需要先填充CaptureInfo结构体，具体内容如下：

   ```
   using CaptureInfo = struct _CaptureInfo {
         std::vector<int> streamIds_; //需要Capture的streamIds
         std::shared_ptr<Camera::CameraMetadata> captureSetting_; // 这里填充camera ability 可通过CameraHost 的GetCameraAbility()接口获取
        bool enableShutterCallback_;
   };
   ```

   StreamOperatorImpl中的Capture方法主要调用CreateCapture()接口去捕获数据流：

   ```
   CamRetCode StreamOperatorImpl::Capture(int captureId, const std::shared_ptr<CaptureInfo>& captureInfo, bool isStreaming)
   {
        if (!ValidCaptureInfo(captureId, captureInfo)) {
           CAMERA_LOGE("capture streamIds is empty. [captureId = %d]", captureId);
           return INVALID_ARGUMENT;
       }
       std::shared_ptr<CameraCapture> cameraCapture = nullptr;
       RetCode rc = CreateCapture(captureId, captureInfo, isStreaming, cameraCapture);
       if (rc != RC_OK) {
           CAMERA_LOGE("create capture is failed.");
           return DEVICE_ERROR;
       }
   
       {
           std::unique_lock<std::mutex> lock(captureMutex_);
           camerCaptureMap_.insert(std::make_pair(captureId, cameraCapture));
       }
   
       rc = StartThread();
       if (rc != RC_OK) {
           CAMERA_LOGE("preview start failed.");
           return DEVICE_ERROR;
       }
       return NO_ERROR;
   }  
   ```

9. 取消捕获和释放离线流

   StreamOperatorImpl类中的CancelCapture()接口的主要作用是根据captureId取消数据流的捕获。

   ```
   CamRetCode StreamOperatorImpl::CancelCapture(int captureId)
   {
         auto itr = camerCaptureMap_.find(captureId); // 根据captureId 在Map中查找对应的CameraCapture对象
         RetCode rc = itr->second->Cancel(); // 调用CameraCapture中Cancel方法结束数据捕获
         std::unique_lock<std::mutex> lock(captureMutex_);
         camerCaptureMap_.erase(itr); // 擦除该CameraCapture对象
         return NO_ERROR;
   }
   ```

   StreamOperatorImpl类中的ReleaseStreams接口的主要作用是释放之前通过CreateStream()和CommitStreams()接口创建的流，并销毁Pipeline。

   ```
   CamRetCode StreamOperatorImpl::ReleaseStreams(const std::vector<int>& streamIds)
   {
       RetCode rc = DestroyStreamPipeline(streamIds); // 销毁该streamIds 的pipeline
       rc = DestroyHostStreamMgr(streamIds);
       rc = DestroyStreams(streamIds); // 销毁该streamIds 的 Stream
       return NO_ERROR;
   }
   ```

10. 关闭Camera设备
    
    调用CameraDeviceImpl中的Close()来关闭CameraDevice，该接口调用deviceManager中的PowerDown()来给设备下电。     

### 开发实例<a name = "8"></a>

在/drivers/peripheral/camera/hal/init目录下有一个关于Camera的demo，开机后会在/vendor/bin下生成可执行文件ohos_camera_demo，该demo可以完成Ｃamera的预览，拍照等基础功能。下面我们就以此demo为例讲述怎样用HDI接口去编写预览PreviewOn()和拍照CaptureON()的用例，可参考[ohos_camera_demo](https://gitee.com/openharmony/drivers_peripheral/tree/master/camera/hal/init)。

1. 在main函数中构造一个CameraDemo 对象，该对象中有对Ｃamera初始化、启停流、释放等控制的方法。下面mainDemo->InitSensors()函数为初始化CameraHost，mainDemo->InitCameraDevice()函数为初始化CameraDevice。

   ```
   int main(int argc, char** argv)
   {
       RetCode rc = RC_OK;
       auto mainDemo = std::make_shared<CameraDemo>();
       rc = mainDemo->InitSensors(); // 初始化CameraHost
       if (rc == RC_ERROR) {
           CAMERA_LOGE("main test: mainDemo->InitSensors() error\n");
           return -1;
       }
   
       rc = mainDemo->InitCameraDevice(); // 初始化CameraDevice
       if (rc == RC_ERROR) {
           CAMERA_LOGE("main test: mainDemo->InitCameraDevice() error\n");
           return -1;
       }
   
       rc = PreviewOn(0, mainDemo); // 配流和启流
       if (rc != RC_OK) {
           CAMERA_LOGE("main test: PreviewOn() error demo exit");
           return -1;
       }
   
       ManuList(mainDemo, argc, argv); // 打印菜单到控制台
   
       return RC_OK;
   }
   ```

   初始化CameraHost函数实现如下，这里调用了HDI接口ICameraHost::Get()去获取demoCameraHost，并对其设置回调函数。

   ```
   RetCode CameraDemo::InitSensors()
   {
       demoCameraHost_ = ICameraHost::Get(DEMO_SERVICE_NAME);
       if (demoCameraHost_ == nullptr) {
           CAMERA_LOGE("demo test: ICameraHost::Get error");
           return RC_ERROR;
       }
   
       hostCallback_ = new CameraHostCallback();
       rc = demoCameraHost_->SetCallback(hostCallback_);
       return RC_OK;
   }
   ```

   初始化CameraDevice函数实现如下，这里调用了GetCameraIds(cameraIds_)，GetCameraAbility(cameraId, ability_)，OpenCamera(cameraIds_.front(), callback, demoCameraDevice_)等接口实现了demoCameraHost的获取。

   ```
   RetCode CameraDemo::InitCameraDevice()
   {
       (void)demoCameraHost_->GetCameraIds(cameraIds_);
       const std::string cameraId = cameraIds_.front();
       demoCameraHost_->GetCameraAbility(cameraId, ability_);
   
       sptr<CameraDeviceCallback> callback = new CameraDeviceCallback();
       rc = demoCameraHost_->OpenCamera(cameraIds_.front(), callback, demoCameraDevice_);
       return RC_OK;
   }   
   ```

2. PreviewOn()接口包含配置流、开启预览流和启动Capture动作。该接口执行完成后Camera预览通路已经开始运转并开启了两路流，一路流是preview，另外一路流是capture或者video，两路流中仅对preview流进行capture动作。

   ```
   static RetCode PreviewOn(int mode, const std::shared_ptr<CameraDemo>& mainDemo)
   {
        rc = mainDemo->StartPreviewStream(); // 配置preview流
        if (mode == 0) {
           rc = mainDemo->StartCaptureStream(); // 配置capture流
         } else {
           rc = mainDemo->StartVideoStream(); // 配置video流
         }
   
       rc = mainDemo->CaptureON(STREAM_ID_PREVIEW, CAPTURE_ID_PREVIEW, CAPTURE_PREVIEW); // 将preview流capture
       return RC_OK;
   }           
   ```

   StartCaptureStream()、StartVideoStream()和StartPreviewStream()接口都会调用CreateStream()接口，只是传入的参数不同。

   ```
   RetCode CameraDemo::StartVideoStream()
   {
       RetCode rc = RC_OK;
       if (isVideoOn_ == 0) {
           isVideoOn_ = 1;
           rc = CreateStream(STREAM_ID_VIDEO, streamCustomerVideo_, VIDEO); // 如需启preview或者capture流更改该接口参数即可。
       }
       return RC_OK;
   }
   ```

   CreateStream()方法调用HDI接口去配置和创建流，首先调用HDI接口去获取StreamOperation对象，然后创建一个StreamInfo。调用CreateStreams()和CommitStreams()实际创建流并配置流。

   ```
   RetCode CameraDemo::CreateStreams(const int streamIdSecond, StreamIntent intent)
   {
       std::vector<std::shared_ptr<StreamInfo>> streamInfos;
       std::vector<std::shared_ptr<StreamInfo>>().swap(streamInfos);
       GetStreamOpt(); // 获取StreamOperator对象
       std::shared_ptr<StreamInfo> previewStreamInfo = std::make_shared<StreamInfo>();
       SetStreamInfo(previewStreamInfo, streamCustomerPreview_, STREAM_ID_PREVIEW, PREVIEW); // 填充StreamInfo
       if (previewStreamInfo->bufferQueue_ == nullptr) {
           CAMERA_LOGE("demo test: CreateStream CreateProducer(); is nullptr\n");
           return RC_ERROR;
       }
       streamInfos.push_back(previewStreamInfo);
   
       std::shared_ptr<StreamInfo> secondStreamInfo = std::make_shared<StreamInfo>();
       if (streamIdSecond == STREAM_ID_CAPTURE) {
           SetStreamInfo(secondStreamInfo, streamCustomerCapture_, STREAM_ID_CAPTURE, intent);
       } else {
           SetStreamInfo(secondStreamInfo, streamCustomerVideo_, STREAM_ID_VIDEO, intent);
       }
   
       if (secondStreamInfo->bufferQueue_ == nullptr) {
           CAMERA_LOGE("demo test: CreateStreams CreateProducer() secondStreamInfo is nullptr\n");
           return RC_ERROR;
       }
       streamInfos.push_back(secondStreamInfo);
   
       rc = streamOperator_->CreateStreams(streamInfos); // 创建流
       if (rc != Camera::NO_ERROR) {
           CAMERA_LOGE("demo test: CreateStream CreateStreams error\n");
           return RC_ERROR;
       }
   
       rc = streamOperator_->CommitStreams(Camera::NORMAL, ability_);
       if (rc != Camera::NO_ERROR) {
           CAMERA_LOGE("demo test: CreateStream CommitStreams error\n");
           std::vector<int> streamIds = {STREAM_ID_PREVIEW, streamIdSecond};
           streamOperator_->ReleaseStreams(streamIds);
           return RC_ERROR;
       }
       return RC_OK;
   }
   ```

   CaptureON()接口调用streamOperator的Capture()方法获取Ｃamera数据并轮转buffer，拉起一个线程接收相应类型的数据。

   ```
   RetCode CameraDemo::CaptureON(const int streamId, const int captureId, CaptureMode mode)
   {
       std::shared_ptr<Camera::CaptureInfo> captureInfo = std::make_shared<Camera::CaptureInfo>(); // 创建并填充CaptureInfo
       captureInfo->streamIds_ = {streamId};
       captureInfo->captureSetting_ = ability_;
       captureInfo->enableShutterCallback_ = false;
   
       int rc = streamOperator_->Capture(captureId, captureInfo, true); // 实际capture开始，buffer轮转开始
       if (mode == CAPTURE_PREVIEW) {
           streamCustomerPreview_->ReceiveFrameOn(nullptr); // 创建预览线程接收递上来的buffer
       } else if (mode == CAPTURE_SNAPSHOT) {
           streamCustomerCapture_->ReceiveFrameOn([this](void* addr, const uint32_t size) { // 创建capture线程通过StoreImage回调接收递上来的buffer
               StoreImage(addr, size);
           });
       } else if (mode == CAPTURE_VIDEO) {
           OpenVideoFile();
           streamCustomerVideo_->ReceiveFrameOn([this](void* addr, const uint32_t size) {// 创建Video线程通过StoreVideo回调接收递上来的buffer
               StoreVideo(addr, size);
           });
       }
       return RC_OK;
   }
   ```

3. ManuList()函数从控制台通过fgets()接口获取字符，不同字符所对应demo支持的功能不同，并打印出该demo所支持功能的菜单。

   ```
   static void ManuList(const std::shared_ptr<CameraDemo>& mainDemo,
       const int argc, char** argv)
   {
       int idx, c;
       int awb = 1;
       constexpr char shortOptions[] = "h:cwvaqof:";
       c = getopt_long(argc, argv, shortOptions, longOptions, &idx);
       while(1) {
           switch (c) {
               case 'h':
                   c = PutMenuAndGetChr(); // 打印菜单
                   break;
                   
                   case 'f':
                   FlashLightTest(mainDemo); // 手电筒功能测试
                   c = PutMenuAndGetChr();
                   break;
               case 'o':
                   OfflineTest(mainDemo); // Offline功能测试
                   c = PutMenuAndGetChr();
                   break;
               case 'c':
                   CaptureTest(mainDemo); // Capture功能测试
                   c = PutMenuAndGetChr();
                   break;
               case 'w': // AWB功能测试
                   if (awb) {
                       mainDemo->SetAwbMode(OHOS_CAMERA_AWB_MODE_INCANDESCENT);
                   } else {
                       mainDemo->SetAwbMode(OHOS_CAMERA_AWB_MODE_OFF);
                   }
                   awb = !awb;
                   c = PutMenuAndGetChr();
                   break;
               case 'a': // AE功能测试
                   mainDemo->SetAeExpo();
                   c = PutMenuAndGetChr();
                   break;
               case 'v': // Video功能测试
                   VideoTest(mainDemo);
                   c = PutMenuAndGetChr();
                   break;
               case 'q': // 退出demo
                   PreviewOff(mainDemo);
                   mainDemo->QuitDemo();
                   exit(EXIT_SUCCESS);
   
               default:
                   CAMERA_LOGE("main test: command error please retry input command");
                   c = PutMenuAndGetChr();
                   break;
           }
       }
   }
   ```

   PutMenuAndGetChr()接口打印了demo程序的菜单，并调用fgets()等待从控制台输入命令，内容如下：

   ``` 
   static int PutMenuAndGetChr(void)
   {
       constexpr uint32_t inputCount = 50;
       int c = 0;
       char strs[inputCount];
       Usage(stdout);
       CAMERA_LOGD("pls input command(input -q exit this app)\n");
       fgets(strs, inputCount, stdin);
   
       for (int i = 0; i < inputCount; i++) {
           if (strs[i] != '-') {
               c = strs[i];
               break;
           }
       }
       return c;
   }
   ```

   控制台输出菜单详情如下：

   ```
   "Options:\n"
   "-h | --help          Print this message\n"
   "-o | --offline       stream offline test\n"
   "-c | --capture       capture one picture\n"
   "-w | --set WB        Set white balance Cloudy\n"
   "-v | --video         capture Viedeo of 10s\n"
   "-a | --Set AE        Set Auto exposure\n"
   "-f | --Set Flashlight        Set flashlight ON 5s OFF\n"
   "-q | --quit          stop preview and quit this app\n");
   ```