Android camera2

news2024/11/6 5:48:20

一、序言

为了对阶段性的知识积累、方便以后调查问题，特做此文档！
将以camera app 使用camera2 api进行分析。
(1)、打开相机 openCamera
(2)、创建会话 createCaptureSession
(3)、开始预览 setRepeatingRequest
(4)、停止预览 stopRepeating
(5)、关闭相机 closeCamera

二、打开相机

1、camera app在使用camera2 api的第一步就是调用cameraManager的openCamera接口此接口有三个参数

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2、调用时序

2.1 调用openCamera接口

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2.2 内部调用到openCameraDeviceUserAsync

调用内部方法getCameraCharacteristics查询camera设备的相关属性，这里会通过binder调用到CameraService(c++), 主要是camera 的前后朝向、图像显示角度（0度、90度、180度、270度）

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new CameraDeviceImpl 的时候将一些变量保存在该对象内，这个CameraDeviceImpl会返回一个CameraDeviceCallbacks后面会将这个callback通过CameraService的接口connect()给到CameraDeviceClientBase, 后续不管是预览、录制、拍照存在帧相关的error都会通过CameraDeviceCallbacks --> CaptureCallback
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new CameraDeviceClient -> new Camera2ClientBase -> new CameraDeviceClientBase() -> new BasicClient(), 在Camera2ClientBase的构造函数里面还会new Camera3Device

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等new client结束后就会去调用initialize
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CameraDeviceClient::initialize() -> Camera2ClientBase::initialize() -> Camera2ClientBase::initializeImpl() -> Camera3Device::initialize -> CameraProviderManager::openSession, CameraProviderManager类可以理解为hal camera的代理类

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Camera3Device持有CameraProviderManager对象，而CameraProviderManager可以理解native和hal camera直接的桥梁，它会枚举出camera provider以及这些provider提供的摄像头设备，并提供方法去访问它们.
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这里必须要插播一下CameraProviderManager的实例化和初始化了，如下图在CameraService 被new的时候就会自动走进onFirstRef(), 然后在该方法里面去new CameraProviderManager，紧接着调用mCameraProviderManager的initialize()方法，initialize()第二个参数是默认参数，直接赋值了HardwareServiceInteractionProxy的对象sHardwareServiceInteractionProxy， HardwareServiceInteractionProxy有两个方法，一个是registerForNotifications(), 一个是getService(), 这里getService()会拿到进程android.hardware.camera.provider@2.4-service中CameraProvider类的远端代理，而CameraProvider中的initialize()方法在CameraProvider的结构体中会被调用，在CameraProvider::initialize() 会去通过hw_get_module()方法打开动态库（camera*.so), 然后CameraProvider::
CameraModule中的camera_module_t *mModule 持有这个真正实现操作camera device的so句柄。

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接着看addDevice方法

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好了插播到此结束，接着上面的2.15 deviceInfo3->mInterface->open, mInterface就是CameraDevice，并且持有CameraModule，那么这里就会调用到CameraModule::open，紧接着调用到hal层真正实现者v4l2_camera_hal中的open

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三、创建会话

1、在opencamera成功后，就会返回一个对象CameraDeviceImpl，后面在创建的会话和请求预览的时候都会调用该对象的方法。

2、创建会话会调用CameraDeviceImpl::createCaptureSession，分别有三个参数

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3、创建会话代码流程分析
frameworks/base/core/java/android/hardware/camera2/impl/CameraDeviceImpl.java

    // 当open camera成功之后，就会返回CameraDeviceImpl对象，然后在opened回调里面去创建会话，
    // 需要传进来两个surface，一个用于拍照，一个用于预览
    public void createCaptureSession(List<Surface> outputs,
            CameraCaptureSession.StateCallback callback, Handler handler)
            throws CameraAccessException {
        List<OutputConfiguration> outConfigurations = new ArrayList<>(outputs.size());
        for (Surface surface : outputs) {
            outConfigurations.add(new OutputConfiguration(surface));
        }
        createCaptureSessionInternal(null, outConfigurations, callback,
                checkAndWrapHandler(handler), /*operatingMode*/ICameraDeviceUser.NORMAL_MODE,
                /*sessionParams*/ null);
    }

frameworks/base/core/java/android/hardware/camera2/params/OutputConfiguration.java

    public OutputConfiguration(@NonNull Surface surface) {
        this(SURFACE_GROUP_ID_NONE, surface, ROTATION_0);
    }


    
    @SystemApi
    public OutputConfiguration(int surfaceGroupId, @NonNull Surface surface, int rotation) {
        checkNotNull(surface, "Surface must not be null");
        checkArgumentInRange(rotation, ROTATION_0, ROTATION_270, "Rotation constant");
        mSurfaceGroupId = surfaceGroupId;
        mSurfaceType = SURFACE_TYPE_UNKNOWN;
        mSurfaces = new ArrayList<Surface>(); // 有效值其实只有surface
        mSurfaces.add(surface);
        mRotation = rotation;
        mConfiguredSize = SurfaceUtils.getSurfaceSize(surface);
        mConfiguredFormat = SurfaceUtils.getSurfaceFormat(surface);
        mConfiguredDataspace = SurfaceUtils.getSurfaceDataspace(surface);
        mConfiguredGenerationId = surface.getGenerationId();
        mIsDeferredConfig = false;
        mIsShared = false;
        mPhysicalCameraId = null;
        mIsMultiResolution = false;
        mSensorPixelModesUsed = new ArrayList<Integer>();
    }

frameworks/base/core/java/android/hardware/camera2/impl/CameraDeviceImpl.java
紧接着上面的createCaptureSessionInternal

private void createCaptureSessionInternal(InputConfiguration inputConfig,
            List<OutputConfiguration> outputConfigurations,
            CameraCaptureSession.StateCallback callback, Executor executor,
            int operatingMode, CaptureRequest sessionParams) throws CameraAccessException {
            .......
            try {
                // configure streams and then block until IDLE
                // 这里开始创建streams
                configureSuccess = configureStreamsChecked(inputConfig, outputConfigurations,
                        operatingMode, sessionParams, createSessionStartTime);
                if (configureSuccess == true && inputConfig != null) {
                    input = mRemoteDevice.getInputSurface();
                }
            } catch (CameraAccessException e) {
                configureSuccess = false;
                pendingException = e;
                input = null;
                if (DEBUG) {
                    Log.v(TAG, "createCaptureSession - failed with exception ", e);
                }
            }

            // Fire onConfigured if configureOutputs succeeded, fire onConfigureFailed otherwise.
            CameraCaptureSessionCore newSession = null;
            if (isConstrainedHighSpeed) {
                ArrayList<Surface> surfaces = new ArrayList<>(outputConfigurations.size());
                for (OutputConfiguration outConfig : outputConfigurations) {
                    surfaces.add(outConfig.getSurface());
                }
                StreamConfigurationMap config =
                    getCharacteristics().get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
                SurfaceUtils.checkConstrainedHighSpeedSurfaces(surfaces, /*fpsRange*/null, config);

                newSession = new CameraConstrainedHighSpeedCaptureSessionImpl(mNextSessionId++,
                        callback, executor, this, mDeviceExecutor, configureSuccess,
                        mCharacteristics);
            } else {
                // 上面创建了stream之后就会去创建session, 后面又用session对象去请求预览camera
                // 创建session就是直接一个java的对象
                newSession = new CamerraCaptureSessionImpl(mNextSessionId++, input,
                        callback, executor, this, mDeviceExecutor, configureSuccess);
            }

            // TODO: wait until current session closes, then create the new session
            mCurrentSession = newSession;

            if (pendingException != null) {
                throw pendingException;
            }

            mSessionStateCallback = mCurrentSession.getDeviceStateCallback();
        }
    }

构建Streams

 public boolean configureStreamsChecked(InputConfiguration inputConfig,
            List<OutputConfiguration> outputs, int operatingMode, CaptureRequest sessionParams,
            long createSessionStartTime)
                    throws CameraAccessException {
        // Treat a null input the same an empty list
        if (outputs == null) {
            outputs = new ArrayList<OutputConfiguration>();
        }
        if (outputs.size() == 0 && inputConfig != null) {
            throw new IllegalArgumentException("cannot configure an input stream without " +
                    "any output streams");
        }
        
        // 传进来的inputConfig就是 null
        checkInputConfiguration(inputConfig);

        boolean success = false;

        synchronized(mInterfaceLock) {
            checkIfCameraClosedOrInError();
            // Streams to create
            HashSet<OutputConfiguration> addSet = new HashSet<OutputConfiguration>(outputs);
            // Streams to delete
            List<Integer> deleteList = new ArrayList<Integer>();

            // Determine which streams need to be created, which to be deleted
            // 这里新创建的CameraDeviceImpl 对象 mConfiguredOutputs.size() 都是0
            for (int i = 0; i < mConfiguredOutputs.size(); ++i) {
                int streamId = mConfiguredOutputs.keyAt(i);
                OutputConfiguration outConfig = mConfiguredOutputs.valueAt(i);

                if (!outputs.contains(outConfig) || outConfig.isDeferredConfiguration()) {
                    // Always delete the deferred output configuration when the session
                    // is created, as the deferred output configuration doesn't have unique surface
                    // related identifies.
                    deleteList.add(streamId);
                } else {
                    addSet.remove(outConfig);  // Don't create a stream previously created
                }
            }

            mDeviceExecutor.execute(mCallOnBusy);
            // 这里新创建的CameraDeviceImpl 对象, mRepeatingRequestId == REQUEST_ID_NONE , 
            // stopRepeating()等于什么都没有做
            stopRepeating();

            try {
                waitUntilIdle();
                // 调到 CameraDeviceClient::beginConfigure 中这里是个空实现，什么都没有做
                mRemoteDevice.beginConfigure();

                ......
                // Delete all streams first (to free up HW resources)
                for (Integer streamId : deleteList) {
                    mRemoteDevice.deleteStream(streamId);
                    mConfiguredOutputs.delete(streamId);
                }

                // Add all new streams
                // 根据新的OutputConfiguration创建stream
                for (OutputConfiguration outConfig : outputs) {`
                    if (addSet.contains(outConfig)) {
                       // 这里创建了Camera3OutputStream
                        int streamId = mRemoteDevice.createStream(outConfig);
                        mConfiguredOutputs.put(streamId, outConfig);
                    }
                }

                int offlineStreamIds[];
                if (sessionParams != null) {
                    // 这里将stream的一些配置给到hal层，最终会调用到V4L2Camera::setupStreams
                    offlineStreamIds = mRemoteDevice.endConfigure(operatingMode,
                            sessionParams.getNativeCopy(), createSessionStartTime);
                } else {
                    offlineStreamIds = mRemoteDevice.endConfigure(operatingMode, null,
                            createSessionStartTime);
                }
                ......
                success = true;
            } catch (IllegalArgumentException e) {
                // OK. camera service can reject stream config if it's not supported by HAL
                // This is only the result of a programmer misusing the camera2 api.
                Log.w(TAG, "Stream configuration failed due to: " + e.getMessage());
                return false;
            } catch (CameraAccessException e) {
                if (e.getReason() == CameraAccessException.CAMERA_IN_USE) {
                    throw new IllegalStateException("The camera is currently busy." +
                            " You must wait until the previous operation completes.", e);
                }
                throw e;
            } finally {
                if (success && outputs.size() > 0) {
                    mDeviceExecutor.execute(mCallOnIdle);
                } else {
                    // Always return to the 'unconfigured' state if we didn't hit a fatal error
                    mDeviceExecutor.execute(mCallOnUnconfigured);
                }
            }
        }

        return success;
    }

frameworks/av/services/camera/libcameraservice/api2/CameraDeviceClient
根据outputConfiguration去创建stream


binder::Status CameraDeviceClient::createStream(
        const hardware::camera2::params::OutputConfiguration &outputConfiguration,
        /*out*/
        int32_t* newStreamId) {
    ATRACE_CALL();

    binder::Status res;
    if (!(res = checkPidStatus(__FUNCTION__)).isOk()) return res;

    Mutex::Autolock icl(mBinderSerializationLock);

    // outputConfiguration是持有surface, surface中持有graphicBufferProducer,这个producer就是
    // 给到camera hal去填充camera数据的
    const std::vector<sp<IGraphicBufferProducer>>& bufferProducers =
            outputConfiguration.getGraphicBufferProducers();
    size_t numBufferProducers = bufferProducers.size();
    bool deferredConsumer = outputConfiguration.isDeferred();
    bool isShared = outputConfiguration.isShared();
    String8 physicalCameraId = String8(outputConfiguration.getPhysicalCameraId());
    bool deferredConsumerOnly = deferredConsumer && numBufferProducers == 0;
    bool isMultiResolution = outputConfiguration.isMultiResolution();
    ..........
    std::vector<sp<Surface>> surfaces;
    std::vector<sp<IBinder>> binders;
    ..........
    OutputStreamInfo streamInfo;
    bool isStreamInfoValid = false;
    const std::vector<int32_t> &sensorPixelModesUsed =
            outputConfiguration.getSensorPixelModesUsed();
    for (auto& bufferProducer : bufferProducers) {
        // Don't create multiple streams for the same target surface
        // 一个stream 可以对应多个surface，但是一个surface只能对应一个stream
        sp<IBinder> binder = IInterface::asBinder(bufferProducer);
        ssize_t index = mStreamMap.indexOfKey(binder);
        // if 走进去说明这个surface 已经对应了 stream，之前已经保存在了mStreamMap中
        if (index != NAME_NOT_FOUND) {
            String8 msg = String8::format("Camera %s: Surface already has a stream created for it "
                    "(ID %zd)", mCameraIdStr.string(), index);
            ALOGW("%s: %s", __FUNCTION__, msg.string());
            return STATUS_ERROR(CameraService::ERROR_ALREADY_EXISTS, msg.string());
        }

        // 根据前面app申请的surface，获取其中的bufferProducer，然后去创建streamInfo和 c++ surface,
        // 并返回
        sp<Surface> surface;
        res = SessionConfigurationUtils::createSurfaceFromGbp(streamInfo,
                isStreamInfoValid, surface, bufferProducer, mCameraIdStr,
                mDevice->infoPhysical(physicalCameraId), sensorPixelModesUsed);
        .......
        binders.push_back(IInterface::asBinder(bufferProducer));
        surfaces.push_back(surface);
    }

    // If mOverrideForPerfClass is true, do not fail createStream() for small
    // JPEG sizes because existing createSurfaceFromGbp() logic will find the
    // closest possible supported size.

    int streamId = camera3::CAMERA3_STREAM_ID_INVALID;
    std::vector<int> surfaceIds;
      ......
    } else {
       // 这里走到Camera3Device中，注意这里的streamId、surfaceIds是要在createStream进行赋值的，而surfaces给到Camera3OutputStream
       // 中，createStream 创建一个Camera3OutputStream 就会streamId++
        err = mDevice->createStream(surfaces, deferredConsumer, streamInfo.width,
                streamInfo.height, streamInfo.format, streamInfo.dataSpace,
                static_cast<camera_stream_rotation_t>(outputConfiguration.getRotation()),
                &streamId, physicalCameraId, streamInfo.sensorPixelModesUsed, &surfaceIds,
                outputConfiguration.getSurfaceSetID(), isShared, isMultiResolution);
    }

    if (err != OK) {
       ......
    } else {
        int i = 0;
        // binders 中对应的是每个surface的bufferProducer，即可以理解binder中存在的就是surface
        for (auto& binder : binders) {
            ALOGV("%s: mStreamMap add binder %p streamId %d, surfaceId %d",
                    __FUNCTION__, binder.get(), streamId, i);
            // streamMap 一个surface的bufferProducer, 对应一个StreamSurfaceId对象，
            // 该对象又存一个streamId和对应的surfaceIds[i], 这个streamId就是创建第几个
            // Camera3OutputStream，surfaceIds[i] 存在的都是0；
            mStreamMap.add(binder, StreamSurfaceId(streamId, surfaceIds[i]));
            i++;
        }
        
        // 一个streamId对应一个outputConfiguration
        mConfiguredOutputs.add(streamId, outputConfiguration);
        // 每个Camera3OutputStream 和 streamInfo对应关系
        mStreamInfoMap[streamId] = streamInfo;

        ALOGV("%s: Camera %s: Successfully created a new stream ID %d for output surface"
                    " (%d x %d) with format 0x%x.",
                  __FUNCTION__, mCameraIdStr.string(), streamId, streamInfo.width,
                  streamInfo.height, streamInfo.format);

        // Set transform flags to ensure preview to be rotated correctly.
        res = setStreamTransformLocked(streamId);

        // Fill in mHighResolutionCameraIdToStreamIdSet map
        const String8 &cameraIdUsed =
                physicalCameraId.size() != 0 ? physicalCameraId : mCameraIdStr;
        const char *cameraIdUsedCStr = cameraIdUsed.string();
        // Only needed for high resolution sensors
        if (mHighResolutionSensors.find(cameraIdUsedCStr) !=
                mHighResolutionSensors.end()) {
            mHighResolutionCameraIdToStreamIdSet[cameraIdUsedCStr].insert(streamId);
        }

        // 这个返回给app
        *newStreamId = streamId;
    }

    return res;
}

frameworks/av/services/camera/libcameraservice/utils/SessionConfigurationUtils.cpp

// 构建OutputStreamInfo，从app 申请的surface 获取wdith、height、fromat等信息 
binder::Status SessionConfigurationUtils::createSurfaceFromGbp(
        OutputStreamInfo& streamInfo, bool isStreamInfoValid,
        sp<Surface>& surface, const sp<IGraphicBufferProducer>& gbp,
        const String8 &logicalCameraId, const CameraMetadata &physicalCameraMetadata,
        const std::vector<int32_t> &sensorPixelModesUsed){
    .......
    // 其实前面的surface 中的gbp，new 一个c++ 层的Surface对象，C++ Surface 继承自ANativeWindow
    surface = new Surface(gbp, useAsync);
    ANativeWindow *anw = surface.get();

    int width, height, format;
    android_dataspace dataSpace;
    
    
    // 从ANativeWindow 中获取surface的width、height、format等，
    if ((err = anw->query(anw, NATIVE_WINDOW_WIDTH, &width)) != OK) {
        String8 msg = String8::format("Camera %s: Failed to query Surface width: %s (%d)",
                 logicalCameraId.string(), strerror(-err), err);
        ALOGE("%s: %s", __FUNCTION__, msg.string());
        return STATUS_ERROR(CameraService::ERROR_INVALID_OPERATION, msg.string());
    }
    if ((err = anw->query(anw, NATIVE_WINDOW_HEIGHT, &height)) != OK) {
        String8 msg = String8::format("Camera %s: Failed to query Surface height: %s (%d)",
                logicalCameraId.string(), strerror(-err), err);
        ALOGE("%s: %s", __FUNCTION__, msg.string());
        return STATUS_ERROR(CameraService::ERROR_INVALID_OPERATION, msg.string());
    }
    if ((err = anw->query(anw, NATIVE_WINDOW_FORMAT, &format)) != OK) {
        String8 msg = String8::format("Camera %s: Failed to query Surface format: %s (%d)",
                logicalCameraId.string(), strerror(-err), err);
        ALOGE("%s: %s", __FUNCTION__, msg.string());
        return STATUS_ERROR(CameraService::ERROR_INVALID_OPERATION, msg.string());
    }
    if ((err = anw->query(anw, NATIVE_WINDOW_DEFAULT_DATASPACE,
            reinterpret_cast<int*>(&dataSpace))) != OK) {
        String8 msg = String8::format("Camera %s: Failed to query Surface dataspace: %s (%d)",
                logicalCameraId.string(), strerror(-err), err);
        ALOGE("%s: %s", __FUNCTION__, msg.string());
        return STATUS_ERROR(CameraService::ERROR_INVALID_OPERATION, msg.string());
    }
    ......
    // isStreamInfoValid 传进来就是false，然后将上面的信息给到streaminfo
    if (!isStreamInfoValid) {
        streamInfo.width = width;
        streamInfo.height = height;
        streamInfo.format = format;
        streamInfo.dataSpace = dataSpace;
        streamInfo.consumerUsage = consumerUsage;
        streamInfo.sensorPixelModesUsed = overriddenSensorPixelModes;
        return binder::Status::ok();
    }
    ......
    }
    return binder::Status::ok();
}

frameworks/av/services/camera/libcameraservice/device3/Camera3Device.cpp

        bool hasDeferredConsumer, uint32_t width, uint32_t height, int format,
        android_dataspace dataSpace, camera_stream_rotation_t rotation, int *id,
        const String8& physicalCameraId, const std::unordered_set<int32_t> &sensorPixelModesUsed,
        std::vector<int> *surfaceIds, int streamSetId, bool isShared, bool isMultiResolution,
        uint64_t consumerUsage) {
    ......
    sp<Camera3OutputStream> newStream;
    ......
    if (format == HAL_PIXEL_FORMAT_BLOB) {
     ......
    } else {
        // new 一个 Camera3OutputStream
        newStream = new Camera3OutputStream(mNextStreamId, consumers[0],
                width, height, format, dataSpace, rotation,
                mTimestampOffset, physicalCameraId, sensorPixelModesUsed, streamSetId,
                isMultiResolution);
    }

    size_t consumerCount = consumers.size();
    for (size_t i = 0; i < consumerCount; i++) {
        // 这里Camera3OutputStream::getSurfaceId 的实现就是返回0；
        int id = newStream->getSurfaceId(consumers[i]);
        if (id < 0) {
            SET_ERR_L("Invalid surface id");
            return BAD_VALUE;
        }
        // 这里将前面传进来的surface其中的Id都存到surfaceIds中 
        if (surfaceIds != nullptr) {
            surfaceIds->push_back(id);
        }
    }

    newStream->setStatusTracker(mStatusTracker);

    newStream->setBufferManager(mBufferManager);

    newStream->setImageDumpMask(mImageDumpMask);

    res = mOutputStreams.add(mNextStreamId, newStream);
    if (res < 0) {
        SET_ERR_L("Can't add new stream to set: %s (%d)", strerror(-res), res);
        return res;
    }

    mSessionStatsBuilder.addStream(mNextStreamId);

    *id = mNextStreamId++;
    mNeedConfig = true;

    // Continue captures if active at start
    if (wasActive) {
        ALOGV("%s: Restarting activity to reconfigure streams", __FUNCTION__);
        // Reuse current operating mode and session parameters for new stream config
        res = configureStreamsLocked(mOperatingMode, mSessionParams);
        if (res != OK) {
            CLOGE("Can't reconfigure device for new stream %d: %s (%d)",
                    mNextStreamId, strerror(-res), res);
            return res;
        }
        internalResumeLocked();
    }
    ALOGV("Camera %s: Created new stream", mId.string());
    return OK;
}

frameworks/av/services/camera/libcameraservice/device3/Camera3OutputStream.cpp

Camera3OutputStream::Camera3OutputStream(int id,
        sp<Surface> consumer,
        uint32_t width, uint32_t height, int format,
        android_dataspace dataSpace, camera_stream_rotation_t rotation,
        nsecs_t timestampOffset, const String8& physicalCameraId,
        const std::unordered_set<int32_t> &sensorPixelModesUsed,
        int setId, bool isMultiResolution) :
        Camera3IOStreamBase(id, CAMERA_STREAM_OUTPUT, width, height,
                            /*maxSize*/0, format, dataSpace, rotation,
                            physicalCameraId, sensorPixelModesUsed, setId, isMultiResolution),
        mConsumer(consumer),
        mTransform(0),
        mTraceFirstBuffer(true),
        mUseBufferManager(false),
        mTimestampOffset(timestampOffset),
        mConsumerUsage(0),
        mDropBuffers(false),
        mDequeueBufferLatency(kDequeueLatencyBinSize) {

    if (mConsumer == NULL) {
        ALOGE("%s: Consumer is NULL!", __FUNCTION__);
        mState = STATE_ERROR;
    }

    bool needsReleaseNotify = setId > CAMERA3_STREAM_SET_ID_INVALID;
    mBufferProducerListener = new BufferProducerListener(this, needsReleaseNotify);
}

时序图如下：
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四、开始预览

1、从CameraManger -> openCamera() 获取CameraDeviceImpl ，然后调用CameraDeviceImpl的createCaptureSession的去创建会话，获取CameraCaptureSessionImpl对象，接着调用CameraCaptureSessionImpl的setRepeatingRequest去预览。

frameworks/base/core/java/android/hardware/camera2/impl/CameraCaptureSessionImpl.java

  public int setRepeatingRequest(CaptureRequest request, CaptureCallback callback,
            Handler handler) throws CameraAccessException {
        checkRepeatingRequest(request);

        synchronized (mDeviceImpl.mInterfaceLock) {
            checkNotClosed();

            handler = checkHandler(handler, callback);

            if (DEBUG) {
                Log.v(TAG, mIdString + "setRepeatingRequest - request " + request + ", callback " +
                        callback + " handler" + " " + handler);
            }

            return addPendingSequence(mDeviceImpl.setRepeatingRequest(request,
                    createCaptureCallbackProxy(handler, callback), mDeviceExecutor));
        }
    }

frameworks/base/core/java/android/hardware/camera2/impl/CameraDeviceImpl.java

            Executor executor) throws CameraAccessException {
        List<CaptureRequest> requestList = new ArrayList<CaptureRequest>();
        requestList.add(request);
        return submitCaptureRequest(requestList, callback, executor, /*streaming*/true);
    }

 private int submitCaptureRequest(List<CaptureRequest> requestList, CaptureCallback callback,
            Executor executor, boolean repeating) throws CameraAccessException {

            ......
            // 如果打开过了就先停掉，然后再打开
            if (repeating) {
                stopRepeating();
            }

            SubmitInfo requestInfo;

            CaptureRequest[] requestArray = requestList.toArray(new CaptureRequest[requestList.size()]);
            // Convert Surface to streamIdx and surfaceIdx
            for (CaptureRequest request : requestArray) {
                request.convertSurfaceToStreamId(mConfiguredOutputs);
            }
            
            // 调到CameraDeviceClient的submitRequestList
            requestInfo = mRemoteDevice.submitRequestList(requestArray, repeating);
            if (DEBUG) {
                Log.v(TAG, "last frame number " + requestInfo.getLastFrameNumber());
            }

             ......

            if (repeating) {
                if (mRepeatingRequestId != REQUEST_ID_NONE) {
                    checkEarlyTriggerSequenceCompleteLocked(mRepeatingRequestId,
                            requestInfo.getLastFrameNumber(),
                            mRepeatingRequestTypes);
                }
                mRepeatingRequestId = requestInfo.getRequestId();
                mRepeatingRequestTypes = getRequestTypes(requestArray);
            } else {
                mRequestLastFrameNumbersList.add(
                    new RequestLastFrameNumbersHolder(requestList, requestInfo));
            }

            if (mIdle) {
                mDeviceExecutor.execute(mCallOnActive);
            }
            mIdle = false;

            return requestInfo.getRequestId();
        }
    }

frameworks/av/services/camera/libcameraservice/api2/CameraDeviceClient.cpp

binder::Status CameraDeviceClient::submitRequestList(
        const std::vector<hardware::camera2::CaptureRequest>& requests,
        bool streaming,
        /*out*/
        hardware::camera2::utils::SubmitInfo *submitInfo) {
      
    ......
    List<const CameraDeviceBase::PhysicalCameraSettingsList> metadataRequestList;
    std::list<const SurfaceMap> surfaceMapList;
    submitInfo->mRequestId = mRequestIdCounter;
    uint32_t loopCounter = 0;

    // 
    for (auto&& request: requests) {
        if (request.mIsReprocess) {
            if (!mInputStream.configured) {
                ALOGE("%s: Camera %s: no input stream is configured.", __FUNCTION__,
                        mCameraIdStr.string());
                return STATUS_ERROR_FMT(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "No input configured for camera %s but request is for reprocessing",
                        mCameraIdStr.string());
            } else if (streaming) {
                ALOGE("%s: Camera %s: streaming reprocess requests not supported.", __FUNCTION__,
                        mCameraIdStr.string());
                return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Repeating reprocess requests not supported");
            } else if (request.mPhysicalCameraSettings.size() > 1) {
                ALOGE("%s: Camera %s: reprocess requests not supported for "
                        "multiple physical cameras.", __FUNCTION__,
                        mCameraIdStr.string());
                return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Reprocess requests not supported for multiple cameras");
            }
        }

        if (request.mPhysicalCameraSettings.empty()) {
            ALOGE("%s: Camera %s: request doesn't contain any settings.", __FUNCTION__,
                    mCameraIdStr.string());
            return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                    "Request doesn't contain any settings");
        }

        //The first capture settings should always match the logical camera id
        String8 logicalId(request.mPhysicalCameraSettings.begin()->id.c_str());
        if (mDevice->getId() != logicalId) {
            ALOGE("%s: Camera %s: Invalid camera request settings.", __FUNCTION__,
                    mCameraIdStr.string());
            return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                    "Invalid camera request settings");
        }

        if (request.mSurfaceList.isEmpty() && request.mStreamIdxList.size() == 0) {
            ALOGE("%s: Camera %s: Requests must have at least one surface target. "
                    "Rejecting request.", __FUNCTION__, mCameraIdStr.string());
            return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                    "Request has no output targets");
        }

        /**
         * Write in the output stream IDs and map from stream ID to surface ID
         * which we calculate from the capture request's list of surface target
         */
        SurfaceMap surfaceMap;
        Vector<int32_t> outputStreamIds;
        std::vector<std::string> requestedPhysicalIds;
        if (request.mSurfaceList.size() > 0) {
            for (const sp<Surface>& surface : request.mSurfaceList) {
                if (surface == 0) continue;

                int32_t streamId;
                sp<IGraphicBufferProducer> gbp = surface->getIGraphicBufferProducer();
                res = insertGbpLocked(gbp, &surfaceMap, &outputStreamIds, &streamId);
                if (!res.isOk()) {
                    return res;
                }

                ssize_t index = mConfiguredOutputs.indexOfKey(streamId);
                if (index >= 0) {
                    String8 requestedPhysicalId(
                            mConfiguredOutputs.valueAt(index).getPhysicalCameraId());
                    requestedPhysicalIds.push_back(requestedPhysicalId.string());
                } else {
                    ALOGW("%s: Output stream Id not found among configured outputs!", __FUNCTION__);
                }
            }
        } else {
            for (size_t i = 0; i < request.mStreamIdxList.size(); i++) {
                int streamId = request.mStreamIdxList.itemAt(i);
                int surfaceIdx = request.mSurfaceIdxList.itemAt(i);

                ssize_t index = mConfiguredOutputs.indexOfKey(streamId);
                if (index < 0) {
                    ALOGE("%s: Camera %s: Tried to submit a request with a surface that"
                            " we have not called createStream on: stream %d",
                            __FUNCTION__, mCameraIdStr.string(), streamId);
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                            "Request targets Surface that is not part of current capture session");
                }

                const auto& gbps = mConfiguredOutputs.valueAt(index).getGraphicBufferProducers();
                if ((size_t)surfaceIdx >= gbps.size()) {
                    ALOGE("%s: Camera %s: Tried to submit a request with a surface that"
                            " we have not called createStream on: stream %d, surfaceIdx %d",
                            __FUNCTION__, mCameraIdStr.string(), streamId, surfaceIdx);
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                            "Request targets Surface has invalid surface index");
                }

                res = insertGbpLocked(gbps[surfaceIdx], &surfaceMap, &outputStreamIds, nullptr);
                if (!res.isOk()) {
                    return res;
                }

                String8 requestedPhysicalId(
                        mConfiguredOutputs.valueAt(index).getPhysicalCameraId());
                requestedPhysicalIds.push_back(requestedPhysicalId.string());
            }
        }

        CameraDeviceBase::PhysicalCameraSettingsList physicalSettingsList;
        for (const auto& it : request.mPhysicalCameraSettings) {
            if (it.settings.isEmpty()) {
                ALOGE("%s: Camera %s: Sent empty metadata packet. Rejecting request.",
                        __FUNCTION__, mCameraIdStr.string());
                return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Request settings are empty");
            }

            // Check whether the physical / logical stream has settings
            // consistent with the sensor pixel mode(s) it was configured with.
            // mCameraIdToStreamSet will only have ids that are high resolution
            const auto streamIdSetIt = mHighResolutionCameraIdToStreamIdSet.find(it.id);
            if (streamIdSetIt != mHighResolutionCameraIdToStreamIdSet.end()) {
                std::list<int> streamIdsUsedInRequest = getIntersection(streamIdSetIt->second,
                        outputStreamIds);
                if (!request.mIsReprocess &&
                        !isSensorPixelModeConsistent(streamIdsUsedInRequest, it.settings)) {
                     ALOGE("%s: Camera %s: Request settings CONTROL_SENSOR_PIXEL_MODE not "
                            "consistent with configured streams. Rejecting request.",
                            __FUNCTION__, it.id.c_str());
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                        "Request settings CONTROL_SENSOR_PIXEL_MODE are not consistent with "
                        "streams configured");
                }
            }

            String8 physicalId(it.id.c_str());
            bool hasTestPatternModePhysicalKey = std::find(mSupportedPhysicalRequestKeys.begin(),
                    mSupportedPhysicalRequestKeys.end(), ANDROID_SENSOR_TEST_PATTERN_MODE) !=
                    mSupportedPhysicalRequestKeys.end();
            bool hasTestPatternDataPhysicalKey = std::find(mSupportedPhysicalRequestKeys.begin(),
                    mSupportedPhysicalRequestKeys.end(), ANDROID_SENSOR_TEST_PATTERN_DATA) !=
                    mSupportedPhysicalRequestKeys.end();
            if (physicalId != mDevice->getId()) {
                auto found = std::find(requestedPhysicalIds.begin(), requestedPhysicalIds.end(),
                        it.id);
                if (found == requestedPhysicalIds.end()) {
                    ALOGE("%s: Camera %s: Physical camera id: %s not part of attached outputs.",
                            __FUNCTION__, mCameraIdStr.string(), physicalId.string());
                    return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
                            "Invalid physical camera id");
                }

                if (!mSupportedPhysicalRequestKeys.empty()) {
                    // Filter out any unsupported physical request keys.
                    CameraMetadata filteredParams(mSupportedPhysicalRequestKeys.size());
                    camera_metadata_t *meta = const_cast<camera_metadata_t *>(
                            filteredParams.getAndLock());
                    set_camera_metadata_vendor_id(meta, mDevice->getVendorTagId());
                    filteredParams.unlock(meta);

                    for (const auto& keyIt : mSupportedPhysicalRequestKeys) {
                        camera_metadata_ro_entry entry = it.settings.find(keyIt);
                        if (entry.count > 0) {
                            filteredParams.update(entry);
                        }
                    }

                    physicalSettingsList.push_back({it.id, filteredParams,
                            hasTestPatternModePhysicalKey, hasTestPatternDataPhysicalKey});
                }
            } else {
                physicalSettingsList.push_back({it.id, it.settings});
            }
        }

        if (!enforceRequestPermissions(physicalSettingsList.begin()->metadata)) {
            // Callee logs
            return STATUS_ERROR(CameraService::ERROR_PERMISSION_DENIED,
                    "Caller does not have permission to change restricted controls");
        }

        physicalSettingsList.begin()->metadata.update(ANDROID_REQUEST_OUTPUT_STREAMS,
                &outputStreamIds[0], outputStreamIds.size());

        if (request.mIsReprocess) {
            physicalSettingsList.begin()->metadata.update(ANDROID_REQUEST_INPUT_STREAMS,
                    &mInputStream.id, 1);
        }

        physicalSettingsList.begin()->metadata.update(ANDROID_REQUEST_ID,
                &(submitInfo->mRequestId), /*size*/1);
        loopCounter++; // loopCounter starts from 1
        ALOGV("%s: Camera %s: Creating request with ID %d (%d of %zu)",
                __FUNCTION__, mCameraIdStr.string(), submitInfo->mRequestId,
                loopCounter, requests.size());

        metadataRequestList.push_back(physicalSettingsList);
        surfaceMapList.push_back(surfaceMap);
    }
    mRequestIdCounter++;

    if (streaming) {
        // 预览走这里
        err = mDevice->setStreamingRequestList(metadataRequestList, surfaceMapList,
                &(submitInfo->mLastFrameNumber));
    } else {
        // 拍照走这里
        err = mDevice->captureList(metadataRequestList, surfaceMapList,
                &(submitInfo->mLastFrameNumber));
    }

    ALOGV("%s: Camera %s: End of function", __FUNCTION__, mCameraIdStr.string());
    return res;
}

status_t Camera3Device::setStreamingRequestList(
        const List<const PhysicalCameraSettingsList> &requestsList,
        const std::list<const SurfaceMap> &surfaceMaps, int64_t *lastFrameNumber) {
    ATRACE_CALL();
    
    return submitRequestsHelper(requestsList, surfaceMaps, /*repeating*/true, lastFrameNumber);
}


status_t Camera3Device::submitRequestsHelper(
        const List<const PhysicalCameraSettingsList> &requests,
        const std::list<const SurfaceMap> &surfaceMaps,
        bool repeating,
        /*out*/
        int64_t *lastFrameNumber) {
    // 预览走这里
    if (repeating) {
        res = mRequestThread->setRepeatingRequests(requestList, lastFrameNumber);
    } else {
        res = mRequestThread->queueRequestList(requestList, lastFrameNumber);
    }

    ......
    return res;
}


status_t Camera3Device::RequestThread::setRepeatingRequests(
        const RequestList &requests,
        /*out*/
        int64_t *lastFrameNumber) {
    ATRACE_CALL();
    Mutex::Autolock l(mRequestLock);
    if (lastFrameNumber != NULL) {
        *lastFrameNumber = mRepeatingLastFrameNumber;
    }
    mRepeatingRequests.clear();
    mFirstRepeating = true;
    // 将requests请求都给到mRepeatingRequests里面
    mRepeatingRequests.insert(mRepeatingRequests.begin(),
            requests.begin(), requests.end());

    unpauseForNewRequests();

    mRepeatingLastFrameNumber = hardware::camera2::ICameraDeviceUser::NO_IN_FLIGHT_REPEATING_FRAMES;
    return OK;
}

void Camera3Device::RequestThread::unpauseForNewRequests() {
    ATRACE_CALL();
    // With work to do, mark thread as unpaused.
    // If paused by request (setPaused), don't resume, to avoid
    // extra signaling/waiting overhead to waitUntilPaused
    // 主要是这里的signal然后，唤醒一个线程去进行发送请求给hal
    mRequestSignal.signal();
    Mutex::Autolock p(mPauseLock);
    if (!mDoPause) {
        ALOGV("%s: RequestThread: Going active", __FUNCTION__);
        if (mPaused) {
            sp<StatusTracker> statusTracker = mStatusTracker.promote();
            if (statusTracker != 0) {
                statusTracker->markComponentActive(mStatusId);
            }
        }
        mPaused = false;
    }
}

mRequestSignal.signal()要去唤醒之前跑起来阻塞住的线程

在这里插入图片描述
下发请求
在这里插入图片描述
Threadloop 开始工作
在这里插入图片描述
等待的线程被打断开始获取buffer，通过processBatchCaptureRequests下发请求到camera hal
在这里插入图片描述
通过onResultAvailable 通知app camera data准备好了

五、关闭预览

停止预览app会调用接口CameraDeviceImpl的stopRepeating接口，通过trace可以看到如下调用在这里插入图片描述
CameraDeviceImpl::stopRepeating -> CameraDeviceClient::cancelRequest -> Camera3Device::clearStreamingRequest -> Camera3Device::RequestThread::clearRepeatingRequests->
Camera3Device::RequestThread::clearRepeatingRequestsLocked
会在clearRepeatingRequestsLocked中clear mRepeatingRequests List, 然后mRepeatingRequests为0后
Camera3Device 的threadloop 就会走到
在这里插入图片描述
然后停止获取buffer向camera hal发送

六、关闭相机

在这里插入图片描述
app调用close接口关闭camera，调用时序如上，在cameraserver中会退出相关的threadloop线程，在camera hal会正式做camera ioctrl close 销毁ais client 对应的camera context

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