5.3 相机管理功能（camera manager）

5.3.1 基本功能介绍

camera manager功能是OSDK端口功能，与camera emu不一样。camera emu用于集成一个第三方相机负载挂载到M300上，OSDK端口的camera manager是用于对负载端口的相机进行控制。camera manager可以控制M300适配的DJI相机，也支持通过PSDK camera emu接入M300的相机。

camera manager的主要功能支持，拍照/录像、变焦等、可通过API访问并下载相机SD卡中的照片等文件。以主要适配的H20/T机型为例，功能列表如下：

功能（camera manager API）	H20/H20T
设置/获取相机工作模式（DjiCameraManager_SetMode）	√
设置/获取相机对焦模式（DjiCameraManager_SetFocusMode）	√
设置/获取曝光模式（DjiCameraManager_SetExposureMode）	√
设置/获取ISO（DjiCameraManager_SetISO）	√
设置/获取光圈（DjiCameraManager_SetAperture）	√
设置/获取快门（DjiCameraManager_SetShutterSpeed）	√
设置/获取EV（曝光补偿）（DjiCameraManager_SetExposureCompensation）	√
设置/获取分接缩放参数（DjiCameraManager_SetTapZoomMultiplier）	√
设置/获取分接缩放点（DjiCameraManager_TapZoomAtTarget）	√
设置/获取焦点（DjiCameraManager_SetFocusTarget）	√
设置/获取拍摄照片模式（DjiCameraManager_SetShootPhotoMode）	√
拍摄单张照片（DjiCameraManager_StartShootPhoto）	√
设置/获取间隔拍摄参数（DjiCameraManager_SetPhotoTimeIntervalSettings）	√
拍摄间隔照片（DjiCameraManager_StartShootPhoto）	√
设置/获取自动包围曝光拍摄参数（DjiCameraManager_SetPhotoAEBCount）	×
拍摄自动包围曝光照片（DjiCameraManager_StartShootPhoto）	×
设置/获取连拍参数（DjiCameraManager_SetPhotoBurstCount）	×
拍摄连拍照片（DjiCameraManager_StartShootPhoto）	×
录制视频（DjiCameraManager_StartRecordVideo）	√
下载文件列表（DjiCameraManager_DownloadFileList）	√
下载媒体文件（DjiCameraManager_DownloadFileByIndex）	√
删除媒体文件（DjiCameraManager_DeleteFileByIndex）	√

说明：

camera manager主要是对相机负载的控制，主要是通过给相机下发指令，由相机完成相关动作执行。
拍照或录像照片均保存在SD卡中，因为OSDK主要是机载计算机的控制，用户一般不能直接查看，照片或录像文件并不能在机载计算机端预览。
OSDK可通过API对文件列表或文件主动下载或删除。
不支持的API主要与相机功能、API适配有关。

5.3.2 主要代码文件

sample代码文件

~/Payload-SDK-master/samples/sample_c/module_sample

camera_manager/
├── test_camera_manager.c
└── test_camera_manager.h

lib头文件

dji_camera_manager.h

5.3.3 sample代码实现

widget功能入口

widget线程DjiTest_WidgetInteractionTask中通过宏定义：E_DJI_SAMPLE_INDEX_CAMERA_MANAGER进入camera sample：

T_DjiReturnCode DjiTest_CameraManagerRunSample(E_DjiMountPosition mountPosition,
                                               E_DjiTestCameraManagerSampleSelect cameraManagerSampleSelect)

参数：

mountPosition，相机负载挂载云台位置
cameraManagerSampleSelect，选择要测试的相机功能，由枚举E_DjiTestCameraManagerSampleSelect定义

T_DjiReturnCode DjiTest_CameraManagerRunSample(E_DjiMountPosition mountPosition,
                                               E_DjiTestCameraManagerSampleSelect cameraManagerSampleSelect)
{
    T_DjiOsalHandler *osalHandler = DjiPlatform_GetOsalHandler();
    T_DjiReturnCode returnCode;
    E_DjiCameraType cameraType;
    T_DjiCameraManagerFirmwareVersion firmwareVersion;
    T_DjiCameraManagerFocusPosData focusPosData;
    T_DjiCameraManagerTapZoomPosData tapZoomPosData;

    USER_LOG_INFO("Camera manager sample start");
    DjiTest_WidgetLogAppend("Camera manager sample start");

    USER_LOG_INFO("--> Step 1: Init camera manager module");
    DjiTest_WidgetLogAppend("--> Step 1: Init camera manager module");
    returnCode = DjiCameraManager_Init();
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
        USER_LOG_ERROR("Init camera manager failed, error code: 0x%08X\r\n", returnCode);
        goto exitCameraModule;
    }

    USER_LOG_INFO("--> Step 2: Get camera type and version");
    DjiTest_WidgetLogAppend("--> Step 2: Get camera type and version");
    returnCode = DjiCameraManager_GetCameraType(mountPosition, &cameraType);
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
        USER_LOG_ERROR("Get mounted position %d camera's type failed, error code: 0x%08X\r\n",
                       mountPosition, returnCode);
        goto exitCameraModule;
    }
    USER_LOG_INFO("Mounted position %d camera's type is [cameraType:%d, i: %d]:%s",
                  mountPosition,
                  cameraType, DjiTest_CameraManagerGetCameraTypeIndex(cameraType), s_cameraTypeStrList[DjiTest_CameraManagerGetCameraTypeIndex(cameraType)].cameraTypeStr);

    returnCode = DjiCameraManager_GetFirmwareVersion(mountPosition, &firmwareVersion);
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
        USER_LOG_ERROR("Get mounted position %d camera's firmware version failed, error code: 0x%08X\r\n",
                       mountPosition, returnCode);
        goto exitCameraModule;
    }
    USER_LOG_INFO("Mounted position %d camera's firmware is V%d.%d.%d.%d\r\n", mountPosition,
                  firmwareVersion.firmware_version[0], firmwareVersion.firmware_version[1],
                  firmwareVersion.firmware_version[2], firmwareVersion.firmware_version[3]);

    E_DjiLiveViewCameraSource liveViewCameraSource;

    if (cameraType == DJI_CAMERA_TYPE_H20 || cameraType == DJI_CAMERA_TYPE_H20T) {
        USER_LOG_INFO("--> Step 3: Change camera's live view source");
        DjiTest_WidgetLogAppend("--> Step 3: Change camera's live view source");

        USER_LOG_INFO("Init live view.");
        returnCode = DjiLiveview_Init();
        if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
            USER_LOG_ERROR("Init live view failed, error code: 0x%08X\r\n", returnCode);
            goto exitLiveViewModule;
        }

        USER_LOG_INFO("Set mounted position %d camera's live view source to zoom.\r\n",
                      mountPosition);
        liveViewCameraSource = (cameraType == DJI_CAMERA_TYPE_H20) ? DJI_LIVEVIEW_CAMERA_SOURCE_H20_ZOOM :
                               DJI_LIVEVIEW_CAMERA_SOURCE_H20T_ZOOM;
        returnCode = DjiLiveview_StartH264Stream((uint8_t) mountPosition, liveViewCameraSource, NULL);
        if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
            USER_LOG_ERROR("Set mounted position %d camera's live view source failed,"
                           "error code: 0x%08X\r\n", mountPosition, returnCode);
            goto exitLiveViewSource;
        }
    }
    switch (cameraManagerSampleSelect) {
    ...
}

初始化

/**
 * @brief Initialise camera manager module, and user should call this function
 * before using camera manager features.
 * @return Execution result.
 */
T_DjiReturnCode DjiCameraManager_Init(void);

API简介：

初始化camera manager module，使用camera manager功能前需要先调用此API。

读取相机信息

读取相机型号

/**
 * @brief Get camera type of the selected camera mounted position.
 * @param position: camera mounted position
 * @param cameraType: see references of E_DjiCameraType.
 * @return Execution result.
 */
T_DjiReturnCode DjiCameraManager_GetCameraType(E_DjiMountPosition position, E_DjiCameraType *cameraType);

API说明：

获取指定位置挂载相机的型号。

参数：

position，相机负载挂载的位置.
cameraType，读到position位置的相机类型

位置参数是输入参数，对应枚举定义

typedef enum {
    DJI_MOUNT_POSITION_UNKNOWN = 0,
    DJI_MOUNT_POSITION_PAYLOAD_PORT_NO1 = 1,
    DJI_MOUNT_POSITION_PAYLOAD_PORT_NO2 = 2,
    DJI_MOUNT_POSITION_PAYLOAD_PORT_NO3 = 3,
    DJI_MOUNT_POSITION_EXTENSION_PORT = 4
} E_DjiMountPosition;

DJI_MOUNT_POSITION_PAYLOAD_PORT_NO1: 主云台接口，飞机（M300）朝向左侧，挂单云台时，通常也是这个位置
DJI_MOUNT_POSITION_PAYLOAD_PORT_NO2：副云台接口，飞机（M300）朝向右侧
DJI_MOUNT_POSITION_PAYLOAD_PORT_NO3：上云台接口
DJI_MOUNT_POSITION_EXTENSION_PORT: OSDK设备挂载位置，此地方用不到

相机类型枚举定义：

/**
 * @brief Camera type.
 */
typedef enum {
    DJI_CAMERA_TYPE_UNKNOWN = 0, /*!< Camera type is unknown. */
    DJI_CAMERA_TYPE_Z30 = 20, /*!< Camera type is Z30. */
    DJI_CAMERA_TYPE_XT2 = 26, /*!< Camera type is XT2. */
    DJI_CAMERA_TYPE_PSDK = 31, /*!< Camera type is third party camera based on Payload SDK. */
    DJI_CAMERA_TYPE_XTS = 41, /*!< Camera type is XT S. */
    DJI_CAMERA_TYPE_H20 = 42, /*!< Camera type is H20. */
    DJI_CAMERA_TYPE_H20T = 43, /*!< Camera type is H20T. */
    DJI_CAMERA_TYPE_P1 = 50, /*!< Camera type is P1. */
    DJI_CAMERA_TYPE_L1, /*!< Camera type is L1. */
} E_DjiCameraType;

说明：

DJI_CAMERA_TYPE_PSDK为使用PSDK开发的第三方负载，其他见注释说明。

读取相机固件版本

/**
 * @brief Get camera firmware version of the selected camera mounted position.
 * @param position: camera mounted position
 * @param firmwareVersion: see references of T_DjiCameraManagerFirmwareVersion.
 * @return Execution result.
 */
T_DjiReturnCode DjiCameraManager_GetFirmwareVersion(E_DjiMountPosition position,
                                                    T_DjiCameraManagerFirmwareVersion *firmwareVersion);

API说明：

获取指定位置挂载相机的固件版本。

参数：

position，相机负载挂载的位置。
firmwareVersion，读到position位置的相机固件版本。

定义在dji_camera_manager.h
```
typedef struct {
    uint8_t firmware_version[4];
} T_DjiCameraManagerFirmwareVersion;
```
版本号由4byte组成，存放数组结构，输出时按照V[0].[1].[2].[3]即可对应官方发布的版本号。

切换变焦镜头

切换镜头不是必要的动作，因为H20/T是多镜头相机。部分相机功能与相机特定相关，sample中有用到变焦功能测试，所以此处需要将镜头切换至变焦镜头。

主要API：

/**
 * @brief Start the FPV or Camera H264 Stream by selected position.
 * @param position: point out which camera to output the H264 stream
 * @param source: point out which sub camera to output the H264 stream
 * @param callback: callback function that is called in a callback thread when a new h264 frame is received
 * @return Execution result.
 */
T_DjiReturnCode DjiLiveview_StartH264Stream(E_DjiLiveViewCameraPosition position, E_DjiLiveViewCameraSource source,
                                            DjiLiveview_H264Callback callback);

API说明：

打开指定位置相机的视频流。

参数：

position，指定相机挂载位置
source，指定相机源（镜头）
callback，读取视频流回调

可以发现此API并不是相机功能模块中API，是liveview模块。我们在初始化步骤仅初始化了相机模块，所以在调用此API前需要先初始化实时视频流模块。

/**
 * @brief Deinitialize the liveview module.
 * @return Execution result.
 */
T_DjiReturnCode DjiLiveview_Init(void);

继续回到切换镜头，实际上这个API有耦合，此处仅需关注第二个参数即可。callback回调用于读取实时视频流，将在liveview模块中详解。

source枚举定义

/**
 * @brief Liveview camera stream source.
 */
typedef enum {
    DJI_LIVEVIEW_CAMERA_SOURCE_DEFAULT = 0,        
    DJI_LIVEVIEW_CAMERA_SOURCE_H20_WIDE = 1,   //H20广角镜头
    DJI_LIVEVIEW_CAMERA_SOURCE_H20T_WIDE = 1,  //H20T广角镜头
    DJI_LIVEVIEW_CAMERA_SOURCE_H20_ZOOM = 2,   //H20变焦镜头
    DJI_LIVEVIEW_CAMERA_SOURCE_H20T_ZOOM = 2,  //H20变焦镜头
    DJI_LIVEVIEW_CAMERA_SOURCE_H20T_IR = 3     //H20T红外镜头
} E_DjiLiveViewCameraSource;

说明：

H20T比H20多一个红外镜头，具体可以参考H20系列相机产品手册。

功能测试

sample结合widget选择列表，定义了一系列的功能枚举，然后通过switch进入到特定的功能运行，也就是调用5.3.1功能部分介绍对应的API，不同功能使用基本一致，即调用API给相机发送指令即可。以第一个设置快门速度举例

功能枚举定义

typedef enum {
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_SHUTTER_SPEED,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_APERTURE,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_EV,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_ISO,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_FOCUS_POINT,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_TAP_ZOOM_POINT,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_ZOOM_PARAM,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SHOOT_SINGLE_PHOTO,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SHOOT_AEB_PHOTO,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SHOOT_BURST_PHOTO,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SHOOT_INTERVAL_PHOTO,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_RECORD_VIDEO,
    E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_DOWNLOAD_AND_DELETE_MEDIA_FILE,
} E_DjiTestCameraManagerSampleSelect;

设置快门速度（E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_SHUTTER_SPEED）代码实现：

 case E_DJI_TEST_CAMERA_MANAGER_SAMPLE_SELECT_SET_CAMERA_SHUTTER_SPEED: {
            USER_LOG_INFO("--> Function a: Set camera shutter speed to 1/100 s");
            DjiTest_WidgetLogAppend("--> Function a: Set camera shutter speed to 1/100 s");
            if (cameraType == DJI_CAMERA_TYPE_H20 || cameraType == DJI_CAMERA_TYPE_H20T) {
                USER_LOG_INFO("Set mounted position %d camera's exposure mode to manual mode.",
                              mountPosition);
                returnCode = DjiTest_CameraManagerSetExposureMode(mountPosition,
                                                                  DJI_CAMERA_MANAGER_EXPOSURE_MODE_EXPOSURE_MANUAL);
                if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
                    USER_LOG_ERROR("Set mounted position %d camera's exposure mode failed,"
                                   "error code: 0x%08X\r\n", mountPosition, returnCode);
                    goto exitLiveViewSource;
                }
            } else {
                USER_LOG_INFO("Set mounted position %d camera's exposure mode to shutter priority mode.",
                              mountPosition);
                returnCode = DjiTest_CameraManagerSetExposureMode(mountPosition,
                                                                  DJI_CAMERA_MANAGER_EXPOSURE_MODE_SHUTTER_PRIORITY);
                if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
                    USER_LOG_ERROR("Set mounted position %d camera's exposure mode failed,"
                                   "error code: 0x%08X\r\n", mountPosition, returnCode);
                    goto exitLiveViewSource;
                }
            }

            USER_LOG_INFO("Set mounted position %d camera's shutter speed to 1/100 s.",
                          mountPosition);
            returnCode = DjiTest_CameraManagerSetShutterSpeed(mountPosition,
                                                              DJI_CAMERA_MANAGER_SHUTTER_SPEED_1_100);
            if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS) {
                USER_LOG_ERROR("Set mounted position %d camera's shutter speed failed,"
                               "error code: 0x%08X\r\n", mountPosition, returnCode);
                goto exitLiveViewSource;
            }
            break;
        }

设置曝光模式

对PSDK lib API再进行了一次封装，功能：先读取当前曝光模式，如果与预期模式一致，无需再设置。如不一致，再调用设置模式API去设置。

T_DjiReturnCode DjiTest_CameraManagerSetExposureMode(E_DjiMountPosition position,
                                                     E_DjiCameraManagerExposureMode exposureMode)
{
    T_DjiReturnCode returnCode;
    E_DjiCameraManagerExposureMode exposureModeTemp;

    returnCode = DjiCameraManager_GetExposureMode(position, &exposureModeTemp);
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS &&
        returnCode != DJI_ERROR_CAMERA_MANAGER_MODULE_CODE_UNSUPPORTED_COMMAND) {
        USER_LOG_ERROR("Get mounted position %d exposure mode failed, error code: 0x%08X",
                       position, returnCode);
        return returnCode;
    }

    if (exposureModeTemp == exposureMode) {
        USER_LOG_INFO("The mounted position %d camera's exposure mode is already what you expected.",
                      position);
        return DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS;
    }

    returnCode = DjiCameraManager_SetExposureMode(position, exposureMode);
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS &&
        returnCode != DJI_ERROR_CAMERA_MANAGER_MODULE_CODE_UNSUPPORTED_COMMAND) {
        USER_LOG_ERROR("Set mounted position %d camera's exposure mode %d failed, current exposure is %d,"
                       " error code: 0x%08X", position, exposureMode, exposureModeTemp, returnCode);
    }

    return returnCode;
}

API 举例（set）：

/**
 * @brief Set camera's exposure mode of the selected camera mounted position.
 * @note  The different exposure modes define whether aperture, shutter speed,
 * ISO can be set automatically or manually. Exposure compensation can be
 * changed in all modes except manual mode where it is not settable.
 * @param position: camera mounted position
 * @param mode: see reference of E_DjiCameraManagerExposureMode.
 * @return Execution result.
 */
T_DjiReturnCode DjiCameraManager_SetExposureMode(E_DjiMountPosition position,
                                                 E_DjiCameraManagerExposureMode mode);

API简介：

设置指定挂载位置相机的曝光模式，如果是录像模式，H20/H20T 变焦镜头曝光模式仅支持程序自动曝光，手动曝光，设置快门速度要先设置成手动曝光模式。

参数说明：

position，相机挂载位置
mode，预期设置的曝光模式

曝光模式枚举定义

/*! @brief the photo action of INTERVAL shooting photo mode
 */
typedef enum {
    DJI_CAMERA_MANAGER_EXPOSURE_MODE_PROGRAM_AUTO = 1,       /*!< Program mode */
    DJI_CAMERA_MANAGER_EXPOSURE_MODE_SHUTTER_PRIORITY = 2,   /*!< Shutter priority mode */
    DJI_CAMERA_MANAGER_EXPOSURE_MODE_APERTURE_PRIORITY = 3,  /*!< Aperture priority mode */
    DJI_CAMERA_MANAGER_EXPOSURE_MODE_EXPOSURE_MANUAL = 4,    /*!< Manual mode */
    DJI_CAMERA_MANAGER_EXPOSURE_MODE_EXPOSURE_UNKNOWN = 0xFF /*!< The camera exposure mode is unknown. */
} E_DjiCameraManagerExposureMode;

设置光圈速度

同样也是对Lib API进行了一次封装，先读取当前快门速度值与预期设置值比对，若不一致才调用API设置。

T_DjiReturnCode DjiTest_CameraManagerSetShutterSpeed(E_DjiMountPosition position,
                                                     E_DjiCameraManagerShutterSpeed shutterSpeed)
{
    T_DjiReturnCode returnCode;
    E_DjiCameraManagerShutterSpeed shutterSpeedTemp;

    returnCode = DjiCameraManager_GetShutterSpeed(position, &shutterSpeedTemp);
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS &&
        returnCode != DJI_ERROR_CAMERA_MANAGER_MODULE_CODE_UNSUPPORTED_COMMAND) {
        USER_LOG_ERROR("Get mounted position %d camera's shutter speed failed, "
                       "error code: 0x%08X.", position, returnCode);
        return returnCode;
    }

    if (shutterSpeedTemp == shutterSpeed) {
        USER_LOG_INFO("The mounted position %d camera's shutter speed is already what you expected.",
                      position);
        return DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS;
    }

    returnCode = DjiCameraManager_SetShutterSpeed(position, shutterSpeed);
    if (returnCode != DJI_ERROR_SYSTEM_MODULE_CODE_SUCCESS &&
        returnCode != DJI_ERROR_CAMERA_MANAGER_MODULE_CODE_UNSUPPORTED_COMMAND) {
        USER_LOG_ERROR("Set mounted position %d camera's shutter speed %d failed, "
                       "error code: 0x%08X.", position, shutterSpeed, returnCode);
    }

    return returnCode;
}

API举例：

/**
 * @brief Set camera's shutter value of the selected camera mounted position.
 * @note Set the camera shutter speed. The shutter speed should not be set
 * slower than the video frame rate when the camera's mode is RECORD_VIDEO.
 * For example, if the video frame rate is 30fps, the shutterSpeed must be <=
 * 1/30. Precondition: The shutter speed can be set only when the camera
 * exposure mode is DJI_CAMERA_MANAGER_EXPOSURE_MODE_EXPOSURE_MANUAL mode or
 * DJI_CAMERA_MANAGER_EXPOSURE_MODE_SHUTTER_PRIORITY
 * @param position: camera mounted position
 * @param shutterSpeed: see reference of E_DjiCameraManagerShutterSpeed.
 * @return Execution result.
 */
T_DjiReturnCode DjiCameraManager_SetShutterSpeed(E_DjiMountPosition position,
                                                 E_DjiCameraManagerShutterSpeed shutterSpeed);

API简介：

设置第指定位置的相机的快门速度

参数说明：

position，指定相机挂载位置
shutterSpeed，预设定快门值，枚举E_DjiCameraManagerShutterSpeed指定。

设置的快门值应该小于相机出帧速率（单帧图像时间），如果相机视频流帧率为30fps,，那么设置的值需要小于等于 1/30。另外设置shutter speed需要先设置曝光模式为DJI_CAMERA_MANAGER_EXPOSURE_MODE_EXPOSURE_MANUAL 或DJI_CAMERA_MANAGER_EXPOSURE_MODE_SHUTTER_PRIORITY

5.3.4 开发注意事项

上述仅通过举例来阅读代码，sample中包含的其他功能API使用也建议阅读。阅读sample代码后，我们将相关信息提取出来。

DjiCameraManager_StartShootPhoto是拍照的通用接口，不同的拍照模式通过参数区分。设置模式后，要先对该模式的参数进行设置。比如间隔时间拍照，在调用DjiCameraManager_StartShootPhoto前，除先设置拍照模式，还需要设置间隔时间。
PSDK 3.0与M300，camera manager是通过USB通信，所以使用此功能，必须连接双A USB使用。
相机功能与相机支持强相关，功能是否支持以及特定功能需要先设定对应的模式，比如工作模式、拍照模式、曝光模式等。还需要确保镜头支持对应的功能，比如变焦镜头、红外镜头等。
不同的功能切换时，可能会涉及模式的转换。模式切换时，需要注意切换频率。如果频率太高，可能会导致相机处理不过来，功能触发失败。
每个功能API都有一个position参数用于输入挂载位置，即camera manager是用于对指定相机的操作。
下载照片文件是OSDK端主动访问相机SD卡并下载，相机照片不能直接保存在机载计算机上。而且OSDK访问相机SD卡时，涉及文件保护，不同使用APP和OSDK同时访问SD卡。
录像同拍照一样，也是发送指令给相机开始/停止录像，文件保存在相机中。

此组别内的文章

5.3 相机管理功能（camera manager）