Android camera HAL四个callback

Android camera HAL四个callback

CameraHardwareInterface.h定义了CameraService和CameraHAL之间的接口，在这个文件中定义了四个回调函数

typedef camera_memory_t* (*camera_request_memory)(int fd, size_t buf_size, unsigned int num_bufs,

void *user); typedef void (*camera_notify_callback)(int32_t msg_type,

int32_t ext1,

int32_t ext2,

void *user);

typedef void (*camera_data_callback)(int32_t msg_type,

const camera_memory_t *data, unsigned int index,

camera_frame_metadata_t *metadata, void *user);

typedef void (*camera_data_timestamp_callback)(int64_t timestamp, int32_t msg_type,

const camera_memory_t *data, unsigned int index,

void *user);

这四个回调函数在

frameworks/av/services/camera/libcameraservice/CameraClient.cpp中实现。camera_request_memory

Camera HAL通知CameraService申请buffer

@buf_size: buf的大小

@num_bufs：buf数目

msg_type的取值范围定义在 android/system/core/include/system/camera.h中

/** msgType in notifyCallback and dataCallback functions */

enum {

CAMERA_MSG_ERROR = 0x0001, // notifyCallback

CAMERA_MSG_SHUTTER = 0x0002, // notifyCallback

CAMERA_MSG_FOCUS = 0x0004, // notifyCallback

CAMERA_MSG_ZOOM = 0x0008, // notifyCallback

CAMERA_MSG_PREVIEW_FRAME = 0x0010, // dataCallback

CAMERA_MSG_VIDEO_FRAME = 0x0020, // data_timestamp_callb ack

CAMERA_MSG_POSTVIEW_FRAME = 0x0040, // dataCallback

CAMERA_MSG_RAW_IMAGE = 0x0080, // dataCallback

CAMERA_MSG_COMPRESSED_IMAGE = 0x0100, // dataCallback

CAMERA_MSG_RAW_IMAGE_NOTIFY = 0x0200, // dataCallback // Preview frame metadata. This can be combined with

// CAMERA_MSG_PREVIEW_FRAME in dataCallback. For example, the apps can

// request FRAME and METADATA. Or the apps can request only F RAME or only

// METADATA.

CAMERA_MSG_PREVIEW_METADATA = 0x0400, // dataCallback // Notify on autofocus start and stop. This is useful in cont inuous

// autofocus -

FOCUS_MODE_CONTINUOUS_VIDEO and FOCUS_MODE_CONTINUOUS_PICTURE. CAMERA_MSG_FOCUS_MOVE = 0x0800, // notifyCallback

CAMERA_MSG_ALL_MSGS = 0xFFFF

};

camera_notify_callback

用来传递一些消息: 如快门消息，自动对焦完成消息，出错消息，拍照编码结束等参数@msg_type可以是：

CAMERA_MSG_ERROR

CAMERA_MSG_SHUTTER

CAMERA_MSG_FOCUS

CAMERA_MSG_ZOOM

CAMERA_MSG_FOCUS_MOVE

camera_data_callback

该函数用于从camera HAL返回数据，

返回的数据可以是：

preview的数据帧，

preview的元数据，

以及压缩为jpeg格式的帧数据

参数@msg_type可以是：

CAMERA_MSG_PREVIEW_FRAME

CAMERA_MSG_PREVIEW_METADATA

CAMERA_MSG_COMPRESSED_IMAGE

CAMERA_MSG_RAW_IMAGE

CAMERA_MSG_RAW_IMAGE_NOTIFY

CAMERA_MSG_POSTVIEW_FRAME

参数@data 用来返回图像数据

参数@metadata 用来返回图像的元数据

camera_data_timestamp_callback

该回调函数用来从Camera HAL返回帧数据以及对应的时间戳，这个callback用于录像的场景。

@timestamp：生成帧数据的时间戳

@msg_type: 取值为CAMERA_MSG_VIDEO_FRAME

@data：用来返回帧数据