Android Camera 数据流
Camera应用部分：
Packages/apps/camera/src/com/android/camera/camera.java
Camera本地框架：
frameworks/base/core/java/android/hardware/camera.java
Camera服务部分：
frameworks/base/services/camera/libcameraservice，这部分需要camera的硬件抽象层来实现上述的本地框架，会被编译成库Libcameraservice.so
Camera硬件接口层
frameworks/base/include/camera/CameraHardwareInterface.h
Camera HAL部分：
Devices/Samsung/proprietary/libcamera/
篇幅主要以take picture为例
点击(此处)折叠或打开
- 首先从上层讲解下来
- Packages/apps/camera/src/com/android/camera/camera.java
- private void capture() {
- mCaptureOnlyData = null;
- // See android.hardware.Camera.Parameters.setRotation for
- mParameters.setRotation(rotation);
- …….
- mCameraDevice.setParameters(mParameters);
- //app 应用注册takepicture回调函数
- mCameraDevice.takePicture(mShutterCallback, mRawPictureCallback,
- mPostViewPictureCallback, new JpegPictureCallback(loc));
- mPreviewing = false;
- }
- 下面是关于四个回调函数的实现
- private final class ShutterCallback
- implements android.hardware.Camera.ShutterCallback {
- public void onShutter() {
- mShutterCallbackTime = System.currentTimeMillis();
- mShutterLag = mShutterCallbackTime - mCaptureStartTime;
- Log.v(TAG, "mShutterLag = " + mShutterLag + "ms");
- clearFocusState();
- }
- }
- private final class RawPictureCallback implements PictureCallback {
- public void onPictureTaken(
- byte [] rawData, android.hardware.Camera camera) {
- mRawPictureCallbackTime = System.currentTimeMillis();
- Log.v(TAG, "mShutterToRawCallbackTime = "
- + (mRawPictureCallbackTime - mShutterCallbackTime) + "ms");
- }
- }
- private final class PostViewPictureCallback implements PictureCallback {
- public void onPictureTaken(
- byte [] data, android.hardware.Camera camera) {
- mPostViewPictureCallbackTime = System.currentTimeMillis();
- Log.v(TAG, "mShutterToPostViewCallbackTime = "
- + (mPostViewPictureCallbackTime - mShutterCallbackTime)
- + "ms");
- }
- }
- private final class JpegPictureCallback implements PictureCallback {
- Location mLocation;
- public void onPictureTaken(
- final byte [] jpegData, final android.hardware.Camera camera) {
- if (mPausing) {
- return;
- }
- mJpegPictureCallbackTime = System.currentTimeMillis();
-
- …………………..
- //这个函数等下做详解
- mImageCapture.storeImage(jpegData, camera, mLocation);
- }
- }
- 2、上层注册好回调函数之后frameworks/base/core/java/android/hardware/camera.java注册回调函数
- public final void takePicture(ShutterCallback shutter, PictureCallback raw,
- PictureCallback postview, PictureCallback jpeg) {
- mShutterCallback = shutter;
- mRawImageCallback = raw;
- mPostviewCallback = postview;
- mJpegCallback = jpeg;
- native_takePicture();
- }
- frameworks/base/services/camera/libcameraservice
- // take a picture - image is returned in callback
- status_t CameraService::Client::takePicture() {
- LOG1("takePicture (pid %d)", getCallingPid());
- Mutex::Autolock lock(mLock);
- status_t result = checkPidAndHardware();
- if (result != NO_ERROR) return result;
- //用于判断指定的msg所对应的callback是否可以回调
- enableMsgType(CAMERA_MSG_SHUTTER |
- CAMERA_MSG_POSTVIEW_FRAME |
- CAMERA_MSG_RAW_IMAGE |
- CAMERA_MSG_COMPRESSED_IMAGE);
- return mHardware->takePicture();//从这里就进入hal实现了，即上层提供操作设备驱动的接口
- }
- 3、HAL层的实现，接口被定义在cameraHardwareInterface.h文件中，所以hal层要做的就是实现其接口
- 其实写到这里，还是有很多不了解，如service中stub的概念，IPC的机制如何实现，功底还是太浅了，有空专门研究下这块
- 下面就仔细看下hal如何实现takepicture操作，同时向上层传递data
- status_t CameraHardwareSec::takePicture()
- {
- stopPreview();
- Mutex::Autolock lock(mStateLock);
- if (mCaptureInProgress) {
- LOGE("%s : capture already in progress", __func__);
- return INVALID_OPERATION;
- }
- //启动PictureThread线程
- if (mPictureThread->run("CameraPictureThread", PRIORITY_DEFAULT) != NO_ERROR) {
- LOGE("%s : couldn't run picture thread", __func__);
- return INVALID_OPERATION;
- }
- mCaptureInProgress = true;
- return NO_ERROR;
- }
- int CameraHardwareSec::pictureThread()
- {
- mRawHeap = new MemoryHeapBase(picture_size);
- if (mRawHeap->getHeapID() < 0) {
- LOGE("ERR(%s): Raw heap creation fail", __func__);
- mRawHeap.clear();
- return UNKNOWN_ERROR;
- }
- sp<MemoryHeapBase> JpegHeap;
- sp<MemoryHeapBase> PostviewHeap;
- sp<MemoryHeapBase> ThumbnailHeap;
- sp<MemoryBase> buffer = new MemoryBase(mRawHeap, 0, picture_size + 8);
- //主要是将raw data照片原始数据通过encode成jpeg的格式
- if ((mMsgEnabled & CAMERA_MSG_RAW_IMAGE)&&(mSecCamera->getJpegStreamPossible() != true)) {
- LOG_TIME_DEFINE(1)
- LOG_TIME_START(1)
- JpegHeap = new MemoryHeapBase(jpeg_heap_size);
- PostviewHeap = new MemoryHeapBase(picture_size);
- ThumbnailHeap = new MemoryHeapBase(thumb_size);
- // Modified the shutter sound timing for Jpeg capture
- mSecCamera->startSnapshot();
- if (mMsgEnabled & CAMERA_MSG_SHUTTER) {
- //回调shuttcallback的接口
- mNotifyCb(CAMERA_MSG_SHUTTER, 0, 0, mCallbackCookie);
- }
- if(mSecCamera->getJpegStreamPossible() != true){
- if (mSecCamera->getSnapshotAndJpeg((unsigned char*)PostviewHeap->base(),
- (unsigned char*)JpegHeap->base(), &jpeg_size) < 0) {
- LOGE("ERR(%s):Fail on SecCamera->getSnapshotAndJpeg()", __func__);
- mStateLock.lock();
- mCaptureInProgress = false;
- mStateLock.unlock();
- return UNKNOWN_ERROR;
- }
- }
- }
- int JpegImageSize = 10000, JpegExifSize;
- bool isLSISensor = false;
- JpegImageSize = static_cast<int>(jpeg_size);
- CropScaleYUY2((char *)PostviewHeap->base(), picture_width, picture_height, 0, 0,
- (char *)ThumbnailHeap->base(), thumb_width, thumb_height);
- memcpy(mRawHeap->base(),PostviewHeap->base(), picture_size);
- }
- memcpy(static_cast<unsigned char*>(mPreviewHeap->base()) + offset + (previewWidth*previewHeight * 3 / 2),
- overlay_header, mSizeOfADDRS);
- ret = mOverlay->queueBuffer((void*)(static_cast<unsigned char *>(mPreviewHeap->base()) + offset +
- (previewWidth * previewHeight * 3 / 2)));
- if ((mMsgEnabled & CAMERA_MSG_COMPRESSED_IMAGE) &&(mSecCamera->getJpegStreamPossible() != true)) {
- sp<MemoryHeapBase> ExifHeap = new MemoryHeapBase(EXIF_FILE_SIZE + picture_size);
- if (mMsgEnabled & CAMERA_MSG_RAW_IMAGE)
- mDataCb(CAMERA_MSG_RAW_IMAGE, buffer, mCallbackCookie);
- JpegExifSize = mSecCamera->getExif((unsigned char *)ExifHeap->base(),
- (unsigned char *)ThumbnailHeap->base());
- LOGW("JpegExifSize=%d", JpegExifSize);
- unsigned char *ExifStart = (unsigned char *)JpegHeap->base() + 2;
- unsigned char *ImageStart = ExifStart + JpegExifSize;
- memmove(ImageStart, ExifStart, JpegImageSize - 2);
- memcpy(ExifStart, ExifHeap->base(), JpegExifSize);
- sp<MemoryBase> mem = new MemoryBase(JpegHeap, 0, JpegImageSize + JpegExifSize);
- //压缩格式照片消息
- mDataCb(CAMERA_MSG_COMPRESSED_IMAGE, mem, mCallbackCookie);
- }
- }
- 现在我们来看下在hal定义的三个回调函数
- typedef void (*notify_callback)(int32_t msgType, //用于处理一些通知的消息，如快门
- int32_t ext1,
- int32_t ext2,
- void* user);
- typedef void (*data_callback)(int32_t msgType, // 返回通过camera得到的raw data
- const sp<IMemory>& dataPtr,
- void* user);
- // 返回通过camera得到的raw data并且携带时间戳
- typedef void (*data_callback_timestamp)(nsecs_t timestamp,
- int32_t msgType,
- const sp<IMemory>& dataPtr,
- void* user);
- 接口如下：
- /** Set the notification and data callbacks */
- virtual void setCallbacks(notify_callback notify_cb,
- data_callback data_cb,
- data_callback_timestamp data_cb_timestamp,
- void* user) = 0;
- 现在又返回到cameraService是如何处理hal发过来的消息
- void CameraService::Client::notifyCallback(int32_t msgType, int32_t ext1,
- int32_t ext2, void* user) {
- LOG2("notifyCallback(%d)", msgType);
- sp<Client> client = getClientFromCookie(user);
- if (client == 0) return;
- if (!client->lockIfMessageWanted(msgType)) return;
- switch (msgType) {//接收到的Hal层消息
- case CAMERA_MSG_SHUTTER:
- // ext1 is the dimension of the yuv picture.
- client->handleShutter((image_rect_type *)ext1);
- break;
- default:
- client->handleGenericNotify(msgType, ext1, ext2);
- break;
- }
- }
- void CameraService::Client::dataCallback(int32_t msgType,
- const sp<IMemory>& dataPtr, void* user) {
- LOG2("dataCallback(%d)", msgType);
- sp<Client> client = getClientFromCookie(user);
- if (client == 0) return;
- if (!client->lockIfMessageWanted(msgType)) return;
- if (dataPtr == 0) {
- LOGE("Null data returned in data callback");
- client->handleGenericNotify(CAMERA_MSG_ERROR, UNKNOWN_ERROR, 0);
- return;
- }
- switch (msgType) {
- case CAMERA_MSG_PREVIEW_FRAME:
- client->handlePreviewData(dataPtr);
- break;
- case CAMERA_MSG_POSTVIEW_FRAME:
- client->handlePostview(dataPtr);
- break;
- case CAMERA_MSG_RAW_IMAGE:
- client->handleRawPicture(dataPtr);
- break;
- case CAMERA_MSG_COMPRESSED_IMAGE:
- client->handleCompressedPicture(dataPtr);
- break;
- default:
- client->handleGenericData(msgType, dataPtr);
- break;
- }
- }
- // picture callback - compressed picture ready
- void CameraService::Client::handleCompressedPicture(const sp<IMemory>& mem) {
- disableMsgType(CAMERA_MSG_COMPRESSED_IMAGE);
- sp<ICameraClient> c = mCameraClient;
- mLock.unlock();
- if (c != 0) {
- //回调函数
- c->dataCallback(CAMERA_MSG_COMPRESSED_IMAGE, mem);
- }
- }
- 回到frameworks/base/core/java/android/hardware/camera.java 处理消息
- @Override
- public void handleMessage(Message msg) {
- switch(msg.what) {
- case CAMERA_MSG_SHUTTER:
- if (mShutterCallback != null) {
- mShutterCallback.onShutter();
- }
- return;
- ………………
- case CAMERA_MSG_COMPRESSED_IMAGE:
- if (mJpegCallback != null) {
- //现在总算回到app时候注册的几个回调函数了
- mJpegCallback.onPictureTaken((byte[])msg.obj, mCamera);
- }
- return;
- default:
- Log.e(TAG, "Unknown message type " + msg.what);
- return;
- }
- }
- //这里就是存储数据的地方了，这里采用file的形式
- private int storeImage(byte[] data, Location loc) {
- try {
- long dateTaken = System.currentTimeMillis();
- String title = createName(dateTaken);
- String filename = title + ".jpg";
- int[] degree = new int[1];
- mLastContentUri = ImageManager.addImage(
- mContentResolver,
- title,
- dateTaken,
- loc, // location from gps/network
- ImageManager.CAMERA_IMAGE_BUCKET_NAME, filename,
- null, data,
- degree);
- return degree[0];
- } catch (Exception ex) {
- Log.e(TAG, "Exception while compressing image.", ex);
- return 0;
- }
- }