Android之Camera预览

一、命令流程

1.APP

packages/apps/Camera/src/com/android/camera/PhotoModule.java

private void startPreview() {  mCameraDevice.setPreviewDisplayAsync(mCameraSurfaceHolder);  mCameraDevice.startPreviewAsync();}

packages/apps/Camera/src/com/android/camera/CameraManager.java

public void setPreviewDisplayAsync(final SurfaceHolder surfaceHolder) {  mCameraHandler.obtainMessage(SET_PREVIEW_DISPLAY_ASYNC, surfaceHolder).sendToTarget();}public void startPreviewAsync() {  mCameraHandler.sendEmptyMessage(START_PREVIEW_ASYNC);}public void handleMessage(final Message msg) {  switch (msg.what) {    case SET_PREVIEW_DISPLAY_ASYNC:      try {        mCamera.setPreviewDisplay((SurfaceHolder) msg.obj);      } catch(IOException e) {          throw new RuntimeException(e);      }      return;  // no need to call mSig.open()    case START_PREVIEW_ASYNC:      mCamera.startPreview();      return;  // no need to call mSig.open()  }}

2.frameworks

frameworks/base/core/java/android/hardware/Camera.java

public final void setPreviewDisplay(SurfaceHolder holder) throws IOException {  setPreviewDisplay(holder.getSurface());}public native final void startPreview();

frameworks/base/core/jni/android_hardware_Camera.cpp

static void android_hardware_Camera_setPreviewDisplay(JNIEnv *env, jobject thiz, jobject jSurface){  sp<Camera> camera = get_native_camera(env, thiz, NULL);  if (camera->setPreviewDisplay(surface) != NO_ERROR) {    jniThrowException(env, "java/io/IOException", "setPreviewDisplay failed");  }}static void android_hardware_Camera_startPreview(JNIEnv *env, jobject thiz){  sp<Camera> camera = get_native_camera(env, thiz, NULL);  if (camera->startPreview() != NO_ERROR) {    jniThrowRuntimeException(env, "startPreview failed");    return;  }}

frameworks/av/camera/Camera.cpp

status_t Camera::setPreviewDisplay(const sp<Surface>& surface){  sp <ICamera> c = mCamera;  return c->setPreviewDisplay(surface);}status_t Camera::startPreview(){  sp <ICamera> c = mCamera;  return c->startPreview();}

Binder调用

frameworks/av/services/camera/libcameraservice/CameraClient.cpp

status_t CameraClient::setPreviewDisplay(const sp<Surface>& surface) {  return setPreviewWindow(binder, window);}status_t CameraClient::startPreview() {  return startCameraMode(CAMERA_PREVIEW_MODE);}status_t CameraClient::startCameraMode(camera_mode mode) {  switch(mode) {    case CAMERA_PREVIEW_MODE:      return startPreviewMode();  }}status_t CameraClient::startPreviewMode() {  mHardware->setPreviewWindow(mPreviewWindow);  result = mHardware->startPreview();}

frameworks/av/services/camera/libcameraservice/CameraHardwareInterface.h

status_t setPreviewWindow(const sp<ANativeWindow>& buf){  mPreviewWindow = buf;  /*  #define anw(n) __to_anw(((struct camera_preview_window *)n)->user)  static ANativeWindow *__to_anw(void *user){    CameraHardwareInterface *__this =                reinterpret_cast<CameraHardwareInterface *>(user);    return __this->mPreviewWindow.get();  }  */  return mDevice->ops->set_preview_window(mDevice,                    buf.get() ? &mHalPreviewWindow.nw : 0);  /*  void initHalPreviewWindow(){    mHalPreviewWindow.nw.cancel_buffer = __cancel_buffer;    mHalPreviewWindow.nw.lock_buffer = __lock_buffer;    mHalPreviewWindow.nw.dequeue_buffer = __dequeue_buffer;    mHalPreviewWindow.nw.enqueue_buffer = __enqueue_buffer;    mHalPreviewWindow.nw.set_buffer_count = __set_buffer_count;    mHalPreviewWindow.nw.set_buffers_geometry = __set_buffers_geometry;    mHalPreviewWindow.nw.set_crop = __set_crop;    mHalPreviewWindow.nw.set_timestamp = __set_timestamp;    mHalPreviewWindow.nw.set_usage = __set_usage;    mHalPreviewWindow.nw.set_swap_interval = __set_swap_interval;    mHalPreviewWindow.nw.get_min_undequeued_buffer_count =                __get_min_undequeued_buffer_count;  }  */}status_t startPreview(){  return mDevice->ops->start_preview(mDevice);}

3.HAL

hardware/amlogic/camera/CameraHal_Module.cpp

int camera_set_preview_window(struct camera_device * device,        struct preview_stream_ops *window){  rv = gCameraHals[aml_dev->cameraid]->setPreviewWindow(window);}int camera_start_preview(struct camera_device * device){  rv = gCameraHals[aml_dev->cameraid]->startPreview();}

hardware/amlogic/camera/CameraHal.cpp

status_t CameraHal::setPreviewWindow(struct preview_stream_ops *window){  mDisplayAdapter = new ANativeWindowDisplayAdapter();  mDisplayAdapter->setFrameProvider(mCameraAdapter); //将frameCallbackRelay设置为BaseCameraAdapter的回调函数  mDisplayAdapter->setErrorHandler(mAppCallbackNotifier.get()); //设置BaseCameraAdapter错误处理函数  ret  = mDisplayAdapter->setPreviewWindow(window);//设置post的Surface  /*  hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp  int ANativeWindowDisplayAdapter::setPreviewWindow(preview_stream_ops_t* window){    mANativeWindow = window;  }  */}status_t CameraHal::startPreview(){  //hardware/amlogic/camera/inc/V4LCameraAdapter/V4LCameraAdapter.h  //#define DEFAULT_PREVIEW_PIXEL_FORMAT        V4L2_PIX_FMT_NV21  ret = allocPreviewBufs(mPreviewWidth, mPreviewHeight, mParameters.getPreviewFormat(), required_buffer_count, max_queueble_buffers);  /*  status_t CameraHal::allocPreviewBufs(int width, int height, const char* previewFormat,                                        unsigned int buffercount, unsigned int &max_queueable){    mPreviewBufs = (int32_t *) mDisplayAdapter->allocateBuffer(width, height,                                                                    previewFormat,                                                                    mPreviewLength,                                                                    buffercount);  }  hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp  void* ANativeWindowDisplayAdapter::allocateBuffer(int width, int height, const char* format, int &bytes, int numBufs){    err = mANativeWindow->set_buffers_geometry(            mANativeWindow,            width,            height,            mNativeWindowPixelFormat); //NV21  }  frameworks/av/services/camera/libcameraservice/CameraHardwareInterface.h  static int __set_buffers_geometry(struct preview_stream_ops* w,                       int width, int height, int format){    ANativeWindow *a = anw(w);    //#define anw(n) __to_anw(((struct camera_preview_window *)n)->user)    //__this->mPreviewWindow.get();    return native_window_set_buffers_geometry(a,                           width, height, format);  }  */}

二、数据流程

hardware/amlogic/camera/V4LCameraAdapter/V4LCameraAdapter.cpp

int V4LCameraAdapter::previewThread(){  yuyv422_to_nv21(src,dest,width,height);  frame.mFrameMask |= CameraFrame::PREVIEW_FRAME_SYNC;  frame.mPixelFmt = mPixelFormat;  ret = sendFrameToSubscribers(&frame);}

hardware/amlogic/camera/BaseCameraAdapter.cpp

status_t BaseCameraAdapter::sendFrameToSubscribers(CameraFrame *frame){  ret = __sendFrameToSubscribers(frame, &mFrameSubscribers, CameraFrame::PREVIEW_FRAME_SYNC);}status_t BaseCameraAdapter::__sendFrameToSubscribers(CameraFrame* frame,                                                     KeyedVector<int, frame_callback> *subscribers,                                                     CameraFrame::FrameType frameType){  callback = (frame_callback) subscribers->valueAt(k);  callback(frame);}

hardware/amlogic/camera/ANativeWindowDisplayAdapter.cpp

void ANativeWindowDisplayAdapter::frameCallbackRelay(CameraFrame* caFrame){  ANativeWindowDisplayAdapter *da = (ANativeWindowDisplayAdapter*) caFrame->mCookie;  da->frameCallback(caFrame);}void ANativeWindowDisplayAdapter::frameCallback(CameraFrame* caFrame){  PostFrame(df);}status_t ANativeWindowDisplayAdapter::PostFrame(ANativeWindowDisplayAdapter::DisplayFrame &dispFrame){  mANativeWindow->set_crop(mANativeWindow, xOff/bytesPerPixel, yOff,                                     (xOff/bytesPerPixel)+mPreviewWidth, yOff+mPreviewHeight);  ret = mANativeWindow->enqueue_buffer(mANativeWindow, mBufferHandleMap[i]);}

frameworks/av/services/camera/libcameraservice/CameraHardwareInterface.h

static int __set_crop(struct preview_stream_ops *w,                       int left, int top, int right, int bottom){  ANativeWindow *a = anw(w);  return native_window_set_crop(a, &crop);}static int __enqueue_buffer(struct preview_stream_ops* w,                       buffer_handle_t* buffer){  ANativeWindow *a = anw(w);  return a->queueBuffer(a,                   container_of(buffer, ANativeWindowBuffer, handle), -1);}

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