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一、簡(jiǎn)介

媒體子系統(tǒng)為開(kāi)發(fā)者提供了媒體相關(guān)的很多功能，本文針對(duì)其中的視頻錄制功能做個(gè)詳細(xì)的介紹。首先，我將通過(guò)媒體子系統(tǒng)提供的視頻錄制Test代碼作為切入點(diǎn)，給大家梳理一下整個(gè)錄制的流程。

二、目錄

foundation/multimedia/camera_framework

├── frameworks
│   ├── js
│   │   └── camera_napi                            #napi實(shí)現(xiàn)
│   │       └── src
│   │           ├── input                          #Camera輸入
│   │           ├── output                         #Camera輸出
│   │           └── session                        #會(huì)話管理
│   └── native                                     #native實(shí)現(xiàn)
│       └── camera
│           ├── BUILD.gn
│           ├── src
│           │   ├── input                          #Camera輸入
│           │   ├── output                         #Camera輸出
│           │   └── session                        #會(huì)話管理
├── interfaces                                     #接口定義
│   ├── inner_api                                  #內(nèi)部native實(shí)現(xiàn)
│   │   └── 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                                       #服務(wù)端
    └── camera_service
        ├── binder
        │   ├── base
        │   ├── client                             #IPC的客戶端
        │   │   └── src
        │   └── server                             #IPC的服務(wù)端
        │       └── src
        └── src

三、錄制的總體流程

四、Native接口使用

在OpenAtom OpenHarmony（以下簡(jiǎn)稱“OpenHarmony”）系統(tǒng)中，多媒體子系統(tǒng)通過(guò)N-API接口提供給上層JS調(diào)用，N-API相當(dāng)于是JS和Native之間的橋梁，在OpenHarmony源碼中，提供了C++直接調(diào)用視頻錄制功能的例子，foundation/multimedia/camera_framework/interfaces/inner_api/native/test目錄中。本文章主要參考了camera_video.cpp文件中的視頻錄制流程。

首先根據(jù)camera_video.cpp的main方法，了解下視頻錄制的主要流程代碼。

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


    // 創(chuàng)建CameraManager實(shí)例
    sptr camManagerObj = CameraManager::GetInstance();


    // 設(shè)置回調(diào)
    camManagerObj->SetCallback(std::make_shared(testName));


    // 獲取支持的相機(jī)設(shè)備列表
    std::vector> cameraObjList = camManagerObj->GetSupportedCameras();


    // 創(chuàng)建采集會(huì)話
    sptr captureSession = camManagerObj->CreateCaptureSession();


    // 開(kāi)始配置采集會(huì)話
    captureSession->BeginConfig();


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


    // 開(kāi)啟CameraInput
    cameraInput->Open();


    // 設(shè)置CameraInput的Error回調(diào)
    cameraInput->SetErrorCallback(std::make_shared(testName));


    // 添加CameraInput實(shí)例到采集會(huì)話中
    ret = captureSession->AddInput(cameraInput);


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


    // 創(chuàng)建Video的Surface
    videoSurface = Surface::CreateSurfaceAsConsumer();


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


    // 注冊(cè)Surface的事件監(jiān)聽(tīng)
    videoSurface->RegisterConsumerListener((sptr &)videoListener);


    // 視頻的配置
    VideoProfile videoprofile = VideoProfile(static_cast(videoFormat), videosize, videoframerates);


    // 創(chuàng)建VideoOutput實(shí)例
    sptr videoOutput = camManagerObj->CreateVideoOutput(videoprofile, videoSurface);


    // 設(shè)置VideoOutput的回調(diào)
    ((sptr &)videoOutput)->SetCallback(std::make_shared(testName));


    // 添加videoOutput到采集會(huì)話中
    ret = captureSession->AddOutput(videoOutput);


    // 提交會(huì)話配置
    ret = captureSession->CommitConfig();


    // 開(kāi)始錄制
    ret = ((sptr &)videoOutput)->Start();




    sleep(videoPauseDuration);
    MEDIA_DEBUG_LOG("Resume video recording");
    // 暫停錄制
    ret = ((sptr &)videoOutput)->Resume();


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


    MEDIA_DEBUG_LOG("Closing the session");
    // 停止采集會(huì)話
    ret = captureSession->Stop();


    MEDIA_DEBUG_LOG("Releasing the session");
    // 釋放會(huì)話采集
    captureSession->Release();


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

以上是視頻錄制的整體流程，其過(guò)程主要通過(guò)Camera模塊支持的能力來(lái)實(shí)現(xiàn)，其中涉及幾個(gè)重要的類：CaptureSession、CameraInput、VideoOutput。CaptureSession是整個(gè)過(guò)程的控制者，CameraInput和VideoOutput相當(dāng)于是設(shè)備的輸入和輸出。

五、調(diào)用流程

后續(xù)主要針對(duì)上面的調(diào)用流程，梳理具體的調(diào)用流程，方便我們對(duì)了解視頻錄制的整理架構(gòu)有一個(gè)更加深入的了解。

創(chuàng)建CameraManager實(shí)例

通過(guò)CameraManager::GetInstance()獲取CameraManager的實(shí)例，后續(xù)的一些接口都是通過(guò)該實(shí)例進(jìn)行調(diào)用的。GetInstance使用了單例模式，在OpenHarmony代碼中這種方式很常見(jiàn)。

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_;
}

獲取支持的相機(jī)設(shè)備列表

通過(guò)調(diào)用CameraManager的GetSupportedCameras()接口，獲取設(shè)備支持的CameraDevice列表。跟蹤代碼可以發(fā)現(xiàn)serviceProxy_->GetCameras最終會(huì)調(diào)用到Camera服務(wù)端的對(duì)應(yīng)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;
}

創(chuàng)建采集會(huì)話

下面是比較重要的環(huán)節(jié)，通過(guò)調(diào)用CameraManager的CreateCaptureSession接口創(chuàng)建采集會(huì)話。CameraManager創(chuàng)建采集會(huì)話，是通過(guò)serviceProxy_->CreateCaptureSession方式進(jìn)行調(diào)用，這里涉及到了OpenHarmony中的IPC的調(diào)用，serviceProxy_是遠(yuǎn)端服務(wù)在本地的代理，通過(guò)這個(gè)代理可以調(diào)用到具體的服務(wù)端，這里是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;
}

代碼最終來(lái)到HCameraService::CreateCaptureSession中，該方法中new了一個(gè)HCaptureSession對(duì)象，并且將該對(duì)象傳遞給了參數(shù)session，所以前面的captureSession對(duì)象就是這里new出來(lái)的HCaptureSession，前面的CameraManager的CreateCaptureSession()方法中將captureSession封裝成CaptureSession對(duì)象返回給應(yīng)用層使用。

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;
}

開(kāi)始配置采集會(huì)話

調(diào)用CaptureSession的BeginConfig進(jìn)行采集會(huì)話的配置工作。這個(gè)工作最終調(diào)用到被封裝的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;
}

創(chuàng)建CameraInput

應(yīng)用層通過(guò)camManagerObj->CreateCameraInput(cameraObjList[0])的方式進(jìn)行CameraInput的創(chuàng)建，cameraObjList[0]就是前面獲取支持設(shè)備的第一個(gè)。根據(jù)CameraDevice創(chuàng)建對(duì)應(yīng)的CameraInput對(duì)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;
}

開(kāi)啟CameraInput

調(diào)用了CameraInput的Open方法，進(jìn)行輸入設(shè)備的啟動(dòng)打開(kāi)。

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實(shí)例到采集會(huì)話中

通過(guò)調(diào)用captureSession的AddInput方法，將創(chuàng)建的CameraInput對(duì)象添加到采集會(huì)話的輸入中，這樣采集會(huì)話就知道采集輸入的設(shè)備。

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());
}

最終調(diào)用到HCaptureSession的AddInput方法，該方法中核心的代碼是tempCameraDevices_.emplace_back(localCameraDevice)，將需要添加的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;
}

創(chuàng)建Video的Surface

通過(guò)Surface::CreateSurfaceAsConsumer創(chuàng)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;
}

創(chuàng)建VideoOutput實(shí)例

通過(guò)調(diào)用CameraManager的CreateVideoOutput來(lái)創(chuàng)建VideoOutput實(shí)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;
}

該方法中通過(guò)IPC的調(diào)用最終調(diào)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?jiǎng)?chuàng)建了HStreamRepeat，并且通過(guò)參數(shù)傳遞給前面的CameraManager使用，CameraManager通過(guò)傳遞的HStreamRepeat對(duì)象，進(jìn)行封裝，創(chuàng)建出VideoOutput對(duì)象。

添加videoOutput到采集會(huì)話中，并且提交采集會(huì)話

該步驟類似添加CameraInput到采集會(huì)話的過(guò)程，可以參考前面的流程。

開(kāi)始錄制

通過(guò)調(diào)用VideoOutput的Start進(jìn)行錄制的操作。

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

該方法中會(huì)調(diào)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;
}

核心的代碼是streamOperator_->Capture，其中最后一個(gè)參數(shù)true，表示采集連續(xù)數(shù)據(jù)。

錄制結(jié)束，保存錄制文件

六、總結(jié)

本文主要對(duì)OpenHarmony 3.2 Beta多媒體子系統(tǒng)的視頻錄制進(jìn)行介紹，首先梳理了整體的錄制流程，然后對(duì)錄制過(guò)程中的主要步驟進(jìn)行了詳細(xì)地分析。視頻錄制主要分為以下幾個(gè)步驟：

（1）獲取CameraManager實(shí)例。

（2）創(chuàng)建采集會(huì)話CaptureSession。

（3）創(chuàng)建CameraInput實(shí)例，并且將輸入設(shè)備添加到CaptureSession中。

（4）創(chuàng)建Video錄制需要的Surface。

（5）創(chuàng)建VideoOutput實(shí)例，并且將輸出添加到CaptureSession中。

（6）提交采集會(huì)話的配置。

（7）調(diào)用VideoOutput的Start方法，進(jìn)行視頻的錄制。

（8）錄制結(jié)束，保存錄制的文件。

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原文標(biāo)題：OpenHarmony 3.2 Beta多媒體系列：視頻錄制

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