OpenHarmony 3.2 Beta多媒体系列：视频录制-电子发烧友网

一、简介

媒体子系统为开发者提供了媒体相关的很多功能，本文针对其中的视频录制功能做个详细的介绍。首先，我将通过媒体子系统提供的视频录制Test代码作为切入点，给大家梳理一下整个录制的流程。

二、目录

foundation/multimedia/camera_framework

├── frameworks
│   ├── js
│   │   └── camera_napi                            #napi实现
│   │       └── src
│   │           ├── input                          #Camera输入
│   │           ├── output                         #Camera输出
│   │           └── session                        #会话管理
│   └── native                                     #native实现
│       └── camera
│           ├── BUILD.gn
│           ├── src
│           │   ├── input                          #Camera输入
│           │   ├── output                         #Camera输出
│           │   └── session                        #会话管理
├── interfaces                                     #接口定义
│   ├── inner_api                                  #内部native实现
│   │   └── native
│   │       ├── camera
│   │       │   └── include
│   │       │       ├── input
│   │       │       ├── output
│   │       │       └── session
│   └── kits                                       #napi接口
│       └── js
│           └── camera_napi
│               ├── BUILD.gn
│               ├── include
│               │   ├── input
│               │   ├── output
│               │   └── session
│               └── @ohos.multimedia.camera.d.ts
└── services                                       #服务端
    └── camera_service
        ├── binder
        │   ├── base
        │   ├── client                             #IPC的客户端
        │   │   └── src
        │   └── server                             #IPC的服务端
        │       └── src
        └── src

三、录制的总体流程

四、Native接口使用

在OpenAtom OpenHarmony（以下简称“OpenHarmony”）系统中，多媒体子系统通过N-API接口提供给上层JS调用，N-API相当于是JS和Native之间的桥梁，在OpenHarmony源码中，提供了C++直接调用视频录制功能的例子，foundation/multimedia/camera_framework/interfaces/inner_api/native/test目录中。本文章主要参考了camera_video.cpp文件中的视频录制流程。

首先根据camera_video.cpp的main方法，了解下视频录制的主要流程代码。

int main(int argc, char **argv)
{
    ......


    // 创建CameraManager实例
    sptr camManagerObj = CameraManager::GetInstance();


    // 设置回调
    camManagerObj->SetCallback(std::make_shared(testName));


    // 获取支持的相机设备列表
    std::vector> cameraObjList = camManagerObj->GetSupportedCameras();


    // 创建采集会话
    sptr captureSession = camManagerObj->CreateCaptureSession();


    // 开始配置采集会话
    captureSession->BeginConfig();


    // 创建CameraInput
    sptr captureInput = camManagerObj->CreateCameraInput(cameraObjList[0]);
    sptr cameraInput = (sptr &)captureInput;


    // 开启CameraInput
    cameraInput->Open();


    // 设置CameraInput的Error回调
    cameraInput->SetErrorCallback(std::make_shared(testName));


    // 添加CameraInput实例到采集会话中
    ret = captureSession->AddInput(cameraInput);


    sptr videoSurface = nullptr;
    std::shared_ptr recorder = nullptr;


    // 创建Video的Surface
    videoSurface = Surface::CreateSurfaceAsConsumer();


    sptr videoListener = new SurfaceListener("Video", SurfaceType::VIDEO, g_videoFd, videoSurface);


    // 注册Surface的事件监听
    videoSurface->RegisterConsumerListener((sptr &)videoListener);


    // 视频的配置
    VideoProfile videoprofile = VideoProfile(static_cast(videoFormat), videosize, videoframerates);


    // 创建VideoOutput实例
    sptr videoOutput = camManagerObj->CreateVideoOutput(videoprofile, videoSurface);


    // 设置VideoOutput的回调
    ((sptr &)videoOutput)->SetCallback(std::make_shared(testName));


    // 添加videoOutput到采集会话中
    ret = captureSession->AddOutput(videoOutput);


    // 提交会话配置
    ret = captureSession->CommitConfig();


    // 开始录制
    ret = ((sptr &)videoOutput)->Start();




    sleep(videoPauseDuration);
    MEDIA_DEBUG_LOG("Resume video recording");
    // 暂停录制
    ret = ((sptr &)videoOutput)->Resume();


    MEDIA_DEBUG_LOG("Wait for 5 seconds before stop");
    sleep(videoCaptureDuration);
    MEDIA_DEBUG_LOG("Stop video recording");
    // 停止录制
    ret = ((sptr &)videoOutput)->Stop();


    MEDIA_DEBUG_LOG("Closing the session");
    // 停止采集会话
    ret = captureSession->Stop();


    MEDIA_DEBUG_LOG("Releasing the session");
    // 释放会话采集
    captureSession->Release();


    // Close video file
    TestUtils::SaveVideoFile(nullptr, 0, VideoSaveMode::CLOSE, g_videoFd);
    cameraInput->Release();
    camManagerObj->SetCallback(nullptr);
    return 0;
}

以上是视频录制的整体流程，其过程主要通过Camera模块支持的能力来实现，其中涉及几个重要的类：CaptureSession、CameraInput、VideoOutput。CaptureSession是整个过程的控制者，CameraInput和VideoOutput相当于是设备的输入和输出。

五、调用流程

后续主要针对上面的调用流程，梳理具体的调用流程，方便我们对了解视频录制的整理架构有一个更加深入的了解。

创建CameraManager实例

通过CameraManager::GetInstance()获取CameraManager的实例，后续的一些接口都是通过该实例进行调用的。GetInstance使用了单例模式，在OpenHarmony代码中这种方式很常见。

sptr &CameraManager::GetInstance()
{
    if (CameraManager::cameraManager_ == nullptr) {
        MEDIA_INFO_LOG("Initializing camera manager for first time!");
        CameraManager::cameraManager_ = new(std::nothrow) CameraManager();
        if (CameraManager::cameraManager_ == nullptr) {
            MEDIA_ERR_LOG("CameraManager::GetInstance failed to new CameraManager");
        }
    }
    return CameraManager::cameraManager_;
}

获取支持的相机设备列表

通过调用CameraManager的GetSupportedCameras()接口，获取设备支持的CameraDevice列表。跟踪代码可以发现serviceProxy_->GetCameras最终会调用到Camera服务端的对应接口。

std::vector> CameraManager::GetSupportedCameras()
{
    CAMERA_SYNC_TRACE;


    std::lock_guard lock(mutex_);
    std::vector cameraIds;
    std::vector> cameraAbilityList;
    int32_t retCode = -1;
    sptr cameraObj = nullptr;
    int32_t index = 0;


    if (cameraObjList.size() > 0) {
        cameraObjList.clear();
    }
    if (serviceProxy_ == nullptr) {
        MEDIA_ERR_LOG("CameraManager::GetCameras serviceProxy_ is null, returning empty list!");
        return cameraObjList;
    }
    std::vector> supportedCameras;
    retCode = serviceProxy_->GetCameras(cameraIds, cameraAbilityList);
    if (retCode == CAMERA_OK) {
        for (auto& it : cameraIds) {
            cameraObj = new(std::nothrow) CameraDevice(it, cameraAbilityList[index++]);
            if (cameraObj == nullptr) {
                MEDIA_ERR_LOG("CameraManager::GetCameras new CameraDevice failed for id={public}%s", it.c_str());
                continue;
            }
            supportedCameras.emplace_back(cameraObj);
        }
    } else {
        MEDIA_ERR_LOG("CameraManager::GetCameras failed!, retCode: %{public}d", retCode);
    }


    ChooseDeFaultCameras(supportedCameras);
    return cameraObjList;
}

创建采集会话

下面是比较重要的环节，通过调用CameraManager的CreateCaptureSession接口创建采集会话。CameraManager创建采集会话，是通过serviceProxy_->CreateCaptureSession方式进行调用，这里涉及到了OpenHarmony中的IPC的调用，serviceProxy_是远端服务在本地的代理，通过这个代理可以调用到具体的服务端，这里是HCameraService。

sptr CameraManager::CreateCaptureSession()
{
    CAMERA_SYNC_TRACE;
    sptr captureSession = nullptr;
    sptr result = nullptr;
    int32_t retCode = CAMERA_OK;


    if (serviceProxy_ == nullptr) {
        MEDIA_ERR_LOG("CameraManager::CreateCaptureSession serviceProxy_ is null");
        return nullptr;
    }
    retCode = serviceProxy_->CreateCaptureSession(captureSession);
    if (retCode == CAMERA_OK && captureSession != nullptr) {
        result = new(std::nothrow) CaptureSession(captureSession);
        if (result == nullptr) {
            MEDIA_ERR_LOG("Failed to new CaptureSession");
        }
    } else {
        MEDIA_ERR_LOG("Failed to get capture session object from hcamera service!, %{public}d", retCode);
    }
    return result;
}

代码最终来到HCameraService::CreateCaptureSession中，该方法中new了一个HCaptureSession对象，并且将该对象传递给了参数session，所以前面的captureSession对象就是这里new出来的HCaptureSession，前面的CameraManager的CreateCaptureSession()方法中将captureSession封装成CaptureSession对象返回给应用层使用。

int32_t HCameraService::CreateCaptureSession(sptr &session)
{
    CAMERA_SYNC_TRACE;
    sptr captureSession;
    if (streamOperatorCallback_ == nullptr) {
        streamOperatorCallback_ = new(std::nothrow) StreamOperatorCallback();
        if (streamOperatorCallback_ == nullptr) {
            MEDIA_ERR_LOG("HCameraService::CreateCaptureSession streamOperatorCallback_ allocation failed");
            return CAMERA_ALLOC_ERROR;
        }
    }


    std::lock_guard lock(mutex_);
    OHOS::AccessTokenID callerToken = IPCSkeleton::GetCallingTokenID();
    captureSession = new(std::nothrow) HCaptureSession(cameraHostManager_, streamOperatorCallback_, callerToken);
    if (captureSession == nullptr) {
        MEDIA_ERR_LOG("HCameraService::CreateCaptureSession HCaptureSession allocation failed");
        return CAMERA_ALLOC_ERROR;
    }
    session = captureSession;
    return CAMERA_OK;
}

开始配置采集会话

调用CaptureSession的BeginConfig进行采集会话的配置工作。这个工作最终调用到被封装的HCaptureSession中。

int32_t HCaptureSession::BeginConfig()
{
    CAMERA_SYNC_TRACE;
    if (curState_ == CaptureSessionState::SESSION_CONFIG_INPROGRESS) {
        MEDIA_ERR_LOG("HCaptureSession::BeginConfig Already in config inprogress state!");
        return CAMERA_INVALID_STATE;
    }
    std::lock_guard lock(sessionLock_);
    prevState_ = curState_;
    curState_ = CaptureSessionState::SESSION_CONFIG_INPROGRESS;
    tempCameraDevices_.clear();
    tempStreams_.clear();
    deletedStreamIds_.clear();
    return CAMERA_OK;
}

创建CameraInput

应用层通过camManagerObj->CreateCameraInput(cameraObjList[0])的方式进行CameraInput的创建，cameraObjList[0]就是前面获取支持设备的第一个。根据CameraDevice创建对应的CameraInput对象。

sptr CameraManager::CreateCameraInput(sptr &camera)
{
    CAMERA_SYNC_TRACE;
    sptr cameraInput = nullptr;
    sptr deviceObj = nullptr;


    if (camera != nullptr) {
        deviceObj = CreateCameraDevice(camera->GetID());
        if (deviceObj != nullptr) {
            cameraInput = new(std::nothrow) CameraInput(deviceObj, camera);
            if (cameraInput == nullptr) {
                MEDIA_ERR_LOG("failed to new CameraInput Returning null in CreateCameraInput");
                return cameraInput;
            }
        } else {
            MEDIA_ERR_LOG("Returning null in CreateCameraInput");
        }
    } else {
        MEDIA_ERR_LOG("CameraManager: Camera object is null");
    }
    return cameraInput;
}

开启CameraInput

调用了CameraInput的Open方法，进行输入设备的启动打开。

void CameraInput::Open()
{
    int32_t retCode = deviceObj_->Open();
    if (retCode != CAMERA_OK) {
        MEDIA_ERR_LOG("Failed to open Camera Input, retCode: %{public}d", retCode);
    }
}

添加CameraInput实例到采集会话中

通过调用captureSession的AddInput方法，将创建的CameraInput对象添加到采集会话的输入中，这样采集会话就知道采集输入的设备。

int32_t CaptureSession::AddInput(sptr &input)
{
    CAMERA_SYNC_TRACE;
    if (input == nullptr) {
        MEDIA_ERR_LOG("CaptureSession::AddInput input is null");
        return CAMERA_INVALID_ARG;
    }
    input->SetSession(this);
    inputDevice_ = input;
    return captureSession_->AddInput(((sptr &)input)->GetCameraDevice());
}

最终调用到HCaptureSession的AddInput方法，该方法中核心的代码是tempCameraDevices_.emplace_back(localCameraDevice)，将需要添加的CameraDevice插入到tempCameraDevices_容器中。

int32_t HCaptureSession::AddInput(sptr cameraDevice)
{
    CAMERA_SYNC_TRACE;
    sptr localCameraDevice = nullptr;


    if (cameraDevice == nullptr) {
        MEDIA_ERR_LOG("HCaptureSession::AddInput cameraDevice is null");
        return CAMERA_INVALID_ARG;
    }
    if (curState_ != CaptureSessionState::SESSION_CONFIG_INPROGRESS) {
        MEDIA_ERR_LOG("HCaptureSession::AddInput Need to call BeginConfig before adding input");
        return CAMERA_INVALID_STATE;
    }
    if (!tempCameraDevices_.empty() || (cameraDevice_ != nullptr && !cameraDevice_->IsReleaseCameraDevice())) {
        MEDIA_ERR_LOG("HCaptureSession::AddInput Only one input is supported");
        return CAMERA_INVALID_SESSION_CFG;
    }
    localCameraDevice = static_cast(cameraDevice.GetRefPtr());
    if (cameraDevice_ == localCameraDevice) {
        cameraDevice_->SetReleaseCameraDevice(false);
    } else {
        tempCameraDevices_.emplace_back(localCameraDevice);
        CAMERA_SYSEVENT_STATISTIC(CreateMsg("CaptureSession::AddInput"));
    }


    sptr streamOperator;
    int32_t rc = localCameraDevice->GetStreamOperator(streamOperatorCallback_, streamOperator);
    if (rc != CAMERA_OK) {
        MEDIA_ERR_LOG("HCaptureSession::GetCameraDevice GetStreamOperator returned %{public}d", rc);
        localCameraDevice->Close();
        return rc;
    }
    return CAMERA_OK;
}

创建Video的Surface

通过Surface::CreateSurfaceAsConsumer创建Surface。

sptr Surface::string name, bool isShared)
{
    sptr surf = new ConsumerSurface(name, isShared);
    GSError ret = surf->Init();
    if (ret != GSERROR_OK) {
        BLOGE("Failure, Reason: consumer surf init failed");
        return nullptr;
    }
    return surf;
}

创建VideoOutput实例

通过调用CameraManager的CreateVideoOutput来创建VideoOutput实例。

sptr CameraManager::CreateVideoOutput(VideoProfile &profile, sptr &surface)
{
    CAMERA_SYNC_TRACE;
    sptr streamRepeat = nullptr;
    sptr result = nullptr;
    int32_t retCode = CAMERA_OK;
    camera_format_t metaFormat;


    metaFormat = GetCameraMetadataFormat(profile.GetCameraFormat());
    retCode = serviceProxy_->CreateVideoOutput(surface->GetProducer(), metaFormat,
                                               profile.GetSize().width, profile.GetSize().height, streamRepeat);
    if (retCode == CAMERA_OK) {
        result = new(std::nothrow) VideoOutput(streamRepeat);
        if (result == nullptr) {
            MEDIA_ERR_LOG("Failed to new VideoOutput");
        } else {
            std::vector videoFrameRates = profile.GetFrameRates();
            if (videoFrameRates.size() >= 2) { // vaild frame rate range length is 2
                result->SetFrameRateRange(videoFrameRates[0], videoFrameRates[1]);
            }
            POWERMGR_SYSEVENT_CAMERA_CONFIG(VIDEO,
                                            profile.GetSize().width,
                                            profile.GetSize().height);
        }
    } else {
        MEDIA_ERR_LOG("VideoOutpout: Failed to get stream repeat object from hcamera service! %{public}d", retCode);
    }
    return result;
}

该方法中通过IPC的调用最终调用到了HCameraService的CreateVideoOutput(surface->GetProducer(), format, streamRepeat)。

sptr CameraManager::CreateVideoOutput(VideoProfile &profile, sptr &surface)
{
    CAMERA_SYNC_TRACE;
    sptr streamRepeat = nullptr;
    sptr result = nullptr;
    int32_t retCode = CAMERA_OK;
    camera_format_t metaFormat;


    metaFormat = GetCameraMetadataFormat(profile.GetCameraFormat());
    retCode = serviceProxy_->CreateVideoOutput(surface->GetProducer(), metaFormat,
                                               profile.GetSize().width, profile.GetSize().height, streamRepeat);
    if (retCode == CAMERA_OK) {
        result = new(std::nothrow) VideoOutput(streamRepeat);
        if (result == nullptr) {
            MEDIA_ERR_LOG("Failed to new VideoOutput");
        } else {
            std::vector videoFrameRates = profile.GetFrameRates();
            if (videoFrameRates.size() >= 2) { // vaild frame rate range length is 2
                result->SetFrameRateRange(videoFrameRates[0], videoFrameRates[1]);
            }
            POWERMGR_SYSEVENT_CAMERA_CONFIG(VIDEO,
                                            profile.GetSize().width,
                                            profile.GetSize().height);
        }
    } else {
        MEDIA_ERR_LOG("VideoOutpout: Failed to get stream repeat object from hcamera service! %{public}d", retCode);
    }
    return result;
}

HCameraService的CreateVideoOutput方法中主要创建了HStreamRepeat，并且通过参数传递给前面的CameraManager使用，CameraManager通过传递的HStreamRepeat对象，进行封装，创建出VideoOutput对象。

添加videoOutput到采集会话中，并且提交采集会话

该步骤类似添加CameraInput到采集会话的过程，可以参考前面的流程。

开始录制

通过调用VideoOutput的Start进行录制的操作。

int32_t VideoOutput::Start()
{
    return static_cast(GetStream().GetRefPtr())->Start();
}

该方法中会调用到HStreamRepeat的Start方法。

int32_t HStreamRepeat::Start()
{
    CAMERA_SYNC_TRACE;


if (streamOperator_ == nullptr) {
return CAMERA_INVALID_STATE;
    }
if (curCaptureID_ != 0) {
        MEDIA_ERR_LOG("HStreamRepeat::Start, Already started with captureID: %{public}d", curCaptureID_);
return CAMERA_INVALID_STATE;
    }
int32_t ret = AllocateCaptureId(curCaptureID_);
if (ret != CAMERA_OK) {
        MEDIA_ERR_LOG("HStreamRepeat::Start Failed to allocate a captureId");
return ret;
    }
std::vector ability;
    OHOS::ConvertMetadataToVec(cameraAbility_, ability);
    CaptureInfo captureInfo;
    captureInfo.streamIds_ = {streamId_};
    captureInfo.captureSetting_ = ability;
    captureInfo.enableShutterCallback_ = false;
    MEDIA_INFO_LOG("HStreamRepeat::Start Starting with capture ID: %{public}d", curCaptureID_);
    CamRetCode rc = (CamRetCode)(streamOperator_->Capture(curCaptureID_, captureInfo, true));
if (rc != HDI::NO_ERROR) {
        ReleaseCaptureId(curCaptureID_);
        curCaptureID_ = 0;
        MEDIA_ERR_LOG("HStreamRepeat::Start Failed with error Code:%{public}d", rc);
        ret = HdiToServiceError(rc);
    }
return ret;
}