CAMERA预览数据流程分析(一)-------数据的获取

预览数据流分析（一）  数据的获取

 

mCameraDevice.startPreview();

 

/*

上篇文章已经有知道这个mCameraDevice就是对应的CameraClient的客户端，所以这个的startPreview就是CameraClient::startPreview()

*/

Step 1:

\frameworks\av\services\camera\libcameraservice\api1\CameraClient.cpp

// start preview mode

status_t CameraClient::startPreview() {

   LOG1("startPreview (pid %d)", getCallingPid());

   return startCameraMode(CAMERA_PREVIEW_MODE);

}

 

Step 2:

\frameworks\av\services\camera\libcameraservice\api1\CameraClient.cpp

 

// start preview or recording

status_tCameraClient::startCameraMode(camera_mode mode) {

   LOG1("startCameraMode(%d)", mode);

   Mutex::Autolock lock(mLock);

   status_t result = checkPidAndHardware();

   if (result != NO_ERROR) return result;

 

   switch(mode) {

       case CAMERA_PREVIEW_MODE:

           if (mSurface == 0 && mPreviewWindow == 0) {

                LOG1("mSurface is not setyet.");

               // still able to startpreview in this case.

           }

           return startPreviewMode();

       case CAMERA_RECORDING_MODE:

           if (mSurface == 0 && mPreviewWindow == 0) {

                ALOGE("mSurface ormPreviewWindow must be set before startRecordingMode.");

                return INVALID_OPERATION;

           }

           return startRecordingMode();

       default:

           return UNKNOWN_ERROR;

    }

}

 

Step 3:

\frameworks\av\services\camera\libcameraservice\api1\CameraClient.cpp

 

status_t CameraClient::startPreviewMode() {

   LOG1("startPreviewMode");

   status_t result = NO_ERROR;

 

   // if preview has been enabled, nothing needs to be done

   if (mHardware->previewEnabled()) {

       return NO_ERROR;

    }

 

   if (mPreviewWindow != 0) {

       native_window_set_scaling_mode(mPreviewWindow.get(),

               NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW);

       native_window_set_buffers_transform(mPreviewWindow.get(),

                mOrientation);

    }

    mHardware->setPreviewWindow(mPreviewWindow);

   result = mHardware->startPreview();

 

   return result;

}

 

/*

主要分析这两个接口：

1，  mHardware->setPreviewWindow

2，  mHardware->startPreview();

mHardware前面已经有说明说，对应的就是Cam1Device类，而其具体的实现则是在其父类Cam1DeviceBase中实现的。所以mHardware->setPreviewWindow

对应就是Cam1DeviceBase::

setPreviewWindow(preview_stream_ops*window)

mHardware->startPreview();对应的是status_t

Cam1DeviceBase::

startPreview()

*/

 

Step 4.1.1:

\vendor\mediatek\proprietary\hardware\mtkcam\legacy\v1\device\Cam1DeviceBase.cpp

status_t

Cam1DeviceBase::

setPreviewWindow(preview_stream_ops* window)

{

   CAM_TRACE_CALL();

   MY_LOGI("+ window(%p)", window);

/*

这里主要是初始化了一个DisplayClient的类。具体这个DisplayClient的功能。后面再分析。

DisplayClient创建的时候，生成了一个createDisplayThread的线程，用来处理displayclient发送过来的消息，

createImgBufQueue 则用于存储数据，具体如何运作的待分析。

bool

DisplayClient::

init()

{

    bool ret =false;

    //

   MY_LOGD("+");

    //

    ret =   createDisplayThread()

       &&  createImgBufQueue()

            ;

    //

    MY_LOGD("-ret(%d)", ret);

    return  ret;

}

*/

   status_t status = initDisplayClient(window);

   if  ( OK == status &&previewEnabled() && mpDisplayClient != 0 )

    {

       status = enableDisplayClient();

       if(mbWindowReady)

       {

           waitStartPreviewDone();

       }

    }

   //

   return  status;

}

 

Step 4.1.2:

 

status_t

Cam1DeviceBase::

initDisplayClient(preview_stream_ops*window)

{

   CAM_TRACE_CALL();

#if '1'!=MTKCAM_HAVE_DISPLAY_CLIENT

   #warning "Not Build Display Client"

   MY_LOGD("Not Build Display Client");

   return  OK;

#else

   status_t status = OK;

   Size previewSize;

   //

   MY_LOGD("+ window(%p)", window);

   //

   //

   //  [1] Check to see whether thepassed window is NULL or not.

   if  ( ! window )

    {

       MY_LOGW("NULL window is passed into...");

       mbWindowReady = false;

       //

       if  ( mpDisplayClient != 0 )

       {

           MY_LOGW("destroy the current display client(%p)...",mpDisplayClient.get());

           mpDisplayClient->uninit();

           mpDisplayClient.clear();

       }

       status = OK;

       goto lbExit;

    }

   mbWindowReady = true;

   //

   //

   //  [2] Get preview size.

   if  ( !queryPreviewSize(previewSize.width, previewSize.height) )

    {

       MY_LOGE("queryPreviewSize");

       status = DEAD_OBJECT;

       goto lbExit;

    }

   //

   //

   //  [3] Initialize Display Client.

   if  ( mpDisplayClient != 0 )

    {

       if  ( previewEnabled() )

       {

           MY_LOGW("Do nothing since Display Client(%p) is already createdafter startPreview()", mpDisplayClient.get());

//         This method must be called before startPreview(). The one exception isthat

//         if the preview surface texture is not set (or set to null) beforestartPreview() is called,

//         then this method may be called once with a non-null parameter to set thepreview surface.

           status = OK;

           goto lbExit;

       }

&n