Android Camera 系统架构源码分析(2)---->Camera的startPreview和setPreviewCallback

CamerastartPreview流程

上接第一篇，这个过程的主要任务是，如何读取数据的，读取的数据是什么格式，最好能知道是如何去预览的

上层APP调用的是Camera.java的startPreview();，下面列出startPreview的调用流程

//Camera.java

publicnativefinalvoidstartPreview();

//android_hardware_Camera.cpp

staticvoidandroid_hardware_Camera_startPreview(JNIEnv*env,jobjectthiz)

{

//这里的camera变量是，Camera.cpp类

camera->startPreview();

}

//Camera.cpp

status_tCamera::startPreview()

{

//此处的mCamera在CameraService.cpp的connect函数里被设置

//也就是CameraClient类

sp<ICamera>c=mCamera;

returnc->startPreview();

}

CameraClient.cpp里的startPreview函数

status_tCameraClient::startPreview(){

returnstartCameraMode(CAMERA_PREVIEW_MODE);

}

status_tCameraClient::startCameraMode(camera_modemode){

switch(mode){

caseCAMERA_PREVIEW_MODE:

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

LOG1("mSurfaceisnotsetyet.");

//stillabletostartpreviewinthiscase.

}

returnstartPreviewMode();

caseCAMERA_RECORDING_MODE:

//...

}

}

//CameraClient.cpp

status_tCameraClient::startPreviewMode(){

mHardware->previewEnabled();

mHardware->setPreviewWindow(mPreviewWindow);

result=mHardware->startPreview();

}

//CameraHardwareInterface.h

status_tstartPreview(){

//mDevice是Cam1DeviceFactory.cppcreateCam1Device()返回的对象

//既是DefaultCam1Device类

returnmDevice->ops->start_preview(mDevice);

}

上面的mDevice->ops->start_preview()函数对应的是DefaultCam1Device的父类Cam1Device类的操作函数。

Cam1DeviceBase::startPreview()

{

//(1)此函数在其子类DefaultCam1Device中实现

//仅是初始化了CameraAdapter

onStartPreview();

//(2)初始化DisplayClient，重要，稍后研究

enableDisplayClient();

//(3)

mpCamClient->startPreview();

//(4)我们通过(3)和(4)开始研究，再返回去看(1)(2)

mpCamAdapter->startPreview();

enableMsgType(CAMERA_MSG_PREVIEW_METADATA);

//

mIsPreviewEnabled=true;

}

mpCamclient->startPreview()

CamClient::startPreview()

{

mpPreviewClient->startPreview();

}

//PreviewClient.cpp

PreviewClient::startPreview()

{

//获得预览参数，这里参数为800*480，yuv420sp

ms8PrvTgtFmt=mpParamsMgr->getPreviewFormat();

mpParamsMgr->getPreviewSize(&mi4PrvWidth,&mi4PrvHeight);

//初始化预览Buf

initBuffers();

//

returnonStateChanged();

}

PreviewClient::initBuffers()

{

//预览数据的Buf

mpImgBufMgr=ImgBufManager::alloc(ms8PrvTgtFmt,mi4PrvWidth,

mi4PrvHeight,eMAX_PREVIEW_BUFFER_NUM,

"PreviewClientCb",mpCamMsgCbInfo->mRequestMemory,

0,0);

//预览数据的处理类，这里只是保留了一个处理接口

//里面并没有什么东西，可自行填充

mpExtImgProc=ExtImgProc::createInstance();

mpExtImgProc->init();

}

PreviewClient::onStateChanged()

{//发送了一个eID_WAKEUP的消息

postCommand(Command(Command::eID_WAKEUP));

}

//接收eID_WAKEUP消息

PreviewClient::threadLoop()

{

Commandcmd;

if(getCommand(cmd))

{

switch(cmd.eId)

{

caseCommand::eID_WAKEUP:

caseCommand::eID_PREVIEW_FRAME:

caseCommand::eID_POSTVIEW_FRAME:

onClientThreadLoop(cmd);

break;

//

caseCommand::eID_EXIT:

//...

}

}

//开始处理数据Buf

PreviewClient::onClientThreadLoop(Commandconst&rCmd)

{

//(1)Getreferencestopool/queuebeforestarting,sothatnothingwillbefreeduringoperations.

sp<ImgBufManager>pBufMgr=NULL;

sp<IImgBufQueue>pBufQueue=NULL;

{

Mutex::Autolock_l(mModuleMtx);

//

pBufMgr=mpImgBufMgr;

pBufQueue=mpImgBufQueue;

if(pBufMgr==0||pBufQueue==0||!isEnabledState())

}

//(2)stop&clearallbufferssothatwewon'tdequeanyundefinedbuffer.

pBufQueue->stopProcessor();

//(3)PrepareallTODObuffers.准备buf

if(!prepareAllTodoBuffers(pBufQueue,pBufMgr))

//(4)Start这个函数只是发出了一个广播，通知等待者

if(!pBufQueue->startProcessor())

//(5)Dountilallwantedmessagesaredisabled.

while(1)

{

//(.1)阻塞等待通知，并开始处理buf

waitAndHandleReturnBuffers(pBufQueue);

//(.2)breakifdisabled.

//addisProcessorRunningtomakesuretheformerpauseProcessor

//issucessfullyprocessed.

if(!isEnabledState()||!pBufQueue->isProcessorRunning())

{

MY_LOGI("Previewclientdisabled");

break;

}

//(.3)re-prepareallTODObuffers,ifpossible,

//sincesomeDONE/CANCELbuffersreturn.把Buf放回队列里

prepareAllTodoBuffers(pBufQueue,pBufMgr);

}

//(6)stop.

pBufQueue->pauseProcessor();

pBufQueue->flushProcessor();//clear"TODO"

pBufQueue->stopProcessor();//clear"DONE"

//

//(7)Cancelallun-returnedbuffers.

cancelAllUnreturnBuffers();

}

PreviewClient::waitAndHandleReturnBuffers(sp<IImgBufQueue>const&rpBufQueue)

{

Vector<ImgBufQueNode>vQueNode;

//(1)dequebuffersfromprocessor.阻塞等待通知

rpBufQueue->dequeProcessor(vQueNode);

//(2)handlebuffersdequedfromprocessor.

ret=handleReturnBuffers(vQueNode);

}

我们找到了哪里开始处理数据，那问题来了，是如何处理数据，数据又是如何被显示的，而这些数据又是从哪里来的

先来看数据是如何处理的

PreviewClient::handleReturnBuffers(Vector<ImgBufQueNode>const&rvQueNode)

{

//(1)determinetheindexofthelatestDONEbufferforcallback.

int32_tidxToCallback=0;

for(idxToCallback=rvQueNode.size()-1;idxToCallback>=0;idxToCallback--)

{

if(rvQueNode[idxToCallback].isDONE())

break;

}

//ShowTimeduration.

if(0<=idxToCallback)

{

nsecs_tconst_timestamp1=rvQueNode[idxToCallback].getImgBuf()->getTimestamp();

mProfile_buffer_timestamp.pulse(_timestamp1);

nsecs_tconst_msDuration_buffer_timestamp=::ns2ms(mProfile_buffer_timestamp.getDuration());

mProfile_buffer_timestamp.reset(_timestamp1);

//

mProfile_dequeProcessor.pulse();

nsecs_tconst_msDuration_dequeProcessor=::ns2ms(mProfile_dequeProcessor.getDuration());

mProfile_dequeProcessor.reset();

}

//

//(2)RemovefromListandpeformcallback,onebyone.

int32_tconstqueSize=rvQueNode.size();

for(int32_ti=0;i<queSize;i++)

{

ImgBufQueNodeconst&rQueNode=rvQueNode[i];

sp<IImgBuf>const&rpQueImgBuf=rQueNode.getImgBuf();//ImgBufinQueue.

sp<ICameraImgBuf>pListImgBuf=NULL;

ImgBufNodeconstListNode=*mImgBufList.begin();//NodeinList.

pListImgBuf=ListNode.getImgBuf();//ImgBufinList.

//(.4)Performcallback.

if(i==idxToCallback){

//

if(mpExtImgProc!=NULL)

{

if(mpExtImgProc->getImgMask()&ExtImgProc::BufType_PreviewCB)

{

IExtImgProc::ImgInfoimg;

//

img.bufType=ExtImgProc::BufType_PreviewCB;

img.format=rpQueImgBuf->getImgFormat();

img.width=rpQueImgBuf->getImgWidth();

img.height=rpQueImgBuf->getImgHeight();

img.stride[0]=rpQueImgBuf->getImgWidthStride(0);

img.stride[1]=rpQueImgBuf->getImgWidthStride(1);

img.stride[2]=rpQueImgBuf->getImgWidthStride(2);

img.virtAddr=(MUINT32)(rpQueImgBuf->getVirAddr());

img.bufSize=rpQueImgBuf->getBufSize();

//预留的处理函数，现在这里是空

mpExtImgProc->doImgProc(img);

}

}

//对数据进行处理

performPreviewCallback(pListImgBuf,rQueNode.getCookieDE());

}

}

}

PreviewClient::performPreviewCallback(sp<ICameraImgBuf>const&pCameraImgBuf,int32_tconstmsgType)

{

if(pCameraImgBuf!=0)

{

//[2]Callback

sp<CamMsgCbInfo>pCamMsgCbInfo;

{

pCamMsgCbInfo=mpCamMsgCbInfo;

}

//调用处理函数

//这个mDataCb回调函数藏得很深

//在CameraClient.cpp的initialize()函数里

//mHardware->setCallbacks(notifyCallback,dataCallback,dataCallbackTimestamp,(void*)mCameraId);

//这句话其中的dataCallback，设置了mDataCb函数

pCamMsgCbInfo->mDataCb(

0!=msgType?msgType:(int32_t)CAMERA_MSG_PREVIEW_FRAME,

pCameraImgBuf->get_camera_memory(),

pCameraImgBuf->getBufIndex(),

NULL,

pCamMsgCbInfo->mCbCookie

);

}

}

最后调用了mDataCb()回调函数。如果在APP层用了setPreviewCallback()，则会在此时调用回调函数，并把数据传回去给APP。注意，这里的msgType被设置成了CAMERA_MSG_PREVIEW_FRAME。

Cam1DeviceBase的setCallbacks()设置了很多回调函数，这些回调函数应该是挺有用的，有空了解一下。类似于startPreview()提供给Frameworks层调用。在Frameworks的CameraClient::initialize被调用

//设置Camera的各种回调函数

Cam1DeviceBase::setCallbacks(

camera_notify_callbacknotify_cb,

camera_data_callbackdata_cb,

camera_data_timestamp_callbackdata_cb_timestamp,

camera_request_memoryget_memory,

void*user

)

{

mpCamMsgCbInfo->mCbCookie=user;

mpCamMsgCbInfo->mNotifyCb=notify_cb;

mpCamMsgCbInfo->mDataCb=data_cb;

mpCamMsgCbInfo->mDataCbTimestamp=data_cb_timestamp;

mpCamMsgCbInfo->mRequestMemory=get_memory;

//

if(mpCamClient!=0)

{

mpCamClient->setCallbacks(mpCamMsgCbInfo);

}

//

if(mpCamAdapter!=0)

{

mpCamAdapter->setCallbacks(mpCamMsgCbInfo);

}

}

Frameworks:

status_tCameraClient::initialize(camera_module_t*module){

mHardware=newCameraHardwareInterface(camera_device_name);

res=mHardware->initialize(&module->common);

//Cam1DeviceBase的setCallbacks()

mHardware->setCallbacks(notifyCallback,

dataCallback,

dataCallbackTimestamp,

(void*)mCameraId);

}

dataCallback是个回调函数，也在CameraClient中。此函数中，接收了多种的msgType。这就表示数据回调中可以有多种的数据类型，有RAW的，有COMPRESSD的，等

voidCameraClient::dataCallback(int32_tmsgType,

constsp<IMemory>&dataPtr,camera_frame_metadata_t*metadata,void*user){

switch(msgType&~CAMERA_MSG_PREVIEW_METADATA){

//!++

#if1//defined(MTK_CAMERA_BSP_SUPPORT)

caseMTK_CAMERA_MSG_EXT_DATA:

client->handleMtkExtData(dataPtr,metadata);

break;

#endif

//!--

caseCAMERA_MSG_PREVIEW_FRAME:

client->handlePreviewData(msgType,dataPtr,metadata);

break;

caseCAMERA_MSG_POSTVIEW_FRAME:

client->handlePostview(dataPtr);

break;

caseCAMERA_MSG_RAW_IMAGE:

client->handleRawPicture(dataPtr);

break;

caseCAMERA_MSG_COMPRESSED_IMAGE:

client->handleCompressedPicture(dataPtr);

break;

default:

client->handleGenericData(msgType,dataPtr,metadata);

break;

}

}

我们的msgType是CAMERA_MSG_PREVIEW_FRAME。调用了handlePreviewData函数

voidCameraClient::handlePreviewData(int32_tmsgType,

constsp<IMemory>&mem,

camera_frame_metadata_t*metadata){

//获取mem

sp<IMemoryHeap>heap=mem->getMemory(&offset,&size);

//iscallbackenabled?判断

if(!(flags&CAMERA_FRAME_CALLBACK_FLAG_ENABLE_MASK)){

//Iftheenablebitisoff,thecopy-outandone-shotbitsareignored

LOG2("framecallbackisdisabled");

return;

}

//holdastrongpointertotheclient

sp<ICameraClient>c=mRemoteCallback;

//clearcallbackflagsifnoclientorone-shotmode判断

if(c==0||(mPreviewCallbackFlag&CAMERA_FRAME_CALLBACK_FLAG_ONE_SHOT_MASK)){

LOG2("Disablepreviewcallback");

}

//有两种方式把mem发送出去，一种是copy一种是直接把地址发送出去

if(c!=0){

//Isthereceivedframecopiedoutornot?

if(flags&CAMERA_FRAME_CALLBACK_FLAG_COPY_OUT_MASK){

LOG2("frameiscopied");

copyFrameAndPostCopiedFrame(msgType,c,heap,offset,size,metadata);

}else{

LOG2("frameisforwarded");

c->dataCallback(msgType,mem,metadata);

}

}

}

最后是通过sp<ICameraClient>c=mRemoteCallback;mRemoteCallback->dataCallback发送出去的。mRemoteCallback是ICameraClient类型和CameraClient两者都有dataCallback两者又是什么关系，如果有关系，这里此不是会死循环。mRemoteCallback搜一下，是在CameraClient::connect()被里初始化的，于是乎在这里找，找了大半天也没找到在哪里被初始化的。被坑了半天，原来在CameraClient的构造函数里。

我们返回到Camera.cpp的connect函数里。发现，还是挺好玩的。再从Camera.cpp的connect()细跟一下

sp<Camera>Camera::connect(intcameraId,constString16&clientPackageName,

intclientUid)

{

returnCameraBaseT::connect(cameraId,clientPackageName,clientUid);

}

//CameraBaseT在CameraBase被定义成typedefCameraBase<TCam>CameraBaseT;

//CameraBase在Camera被初始化为CameraBase<Camera>，所以上面就相应于调用了CameraBase<Camera>::connect()

template<typenameTCam,typenameTCamTraits>

sp<TCam>CameraBase<TCam,TCamTraits>::connect(intcameraId,

constString16&clientPackageName,intclientUid)

{

//把所有的TCam替换成Camera,就是刚才Camera.cpp里的camera在这里被构造

sp<TCam>c=newTCam(cameraId);

//TCamCallbacks在Camera.h里被定义为ICameraClient，被赋值为Camera。Camera继承ICameraClient

sp<TCamCallbacks>cl=c;

constsp<ICameraService>&cs=getCameraService();

//fnConnectService在Camera被初始化为ICameraService::connect()

TCamConnectServicefnConnectService=TCamTraits::fnConnectService;

//下面调用了CameraService::connect()c和cl是同一个值，做为两个不同的参数传进了CameraService::connect()

status=(cs.get()->*fnConnectService)(cl,cameraId,clientPackageName,clientUid,/*out*/c->mCamera);

}

//CameraService::connec()构造了一个CameraClient(),又是一个CameraClient，

//但是和上面的ICameraClient没有半毛线关系。只是名字相似,真的是一万个++泥马在奔腾。

status_tCameraService::connect(constsp<ICameraClient>&cameraClient,intcameraId,

constString16&clientPackageName,intclientUid,/*out*/sp<ICamera>&device){

//CameraService::connec()就做了两件事情，初始化Camera里的mCamera和把Camera传给CameraClient

//CameraClient的构造函数会传到他的父类构造函数Client()里，Client却是在CameraService。Camera类就是mRemoteCallback

client=newCameraClient(this,cameraClient,clientPackageName,cameraId,

facing,callingPid,clientUid,getpid());

device=client;

returnOK;}

所以，上面的c->dataCallback。调用的是Camera的dataCallback()

//callbackfromcameraservicewhenframeorimageisready

voidCamera::dataCallback(int32_tmsgType,constsp<IMemory>&dataPtr,

camera_frame_metadata_t*metadata)

{

sp<CameraListener>listener;

listener=mListener;

listener->postData(msgType,dataPtr,metadata);

}

这里的mListener是在android_hardware_Camera_native_setup()里被设置的类型是MtkJNICameraContext。所以listener->postData()调用的是MtkJNICameraContext的postData()。

voidMtkJNICameraContext::postData(int32_tmsgType,constsp<IMemory>&dataPtr,

camera_frame_metadata_t*metadata)

{

JNICameraContext::postData(msgType,dataPtr,metadata);

}

voidJNICameraContext::postData(int32_tmsgType,constsp<IMemory>&dataPtr,

camera_frame_metadata_t*metadata)

{

switch(dataMsgType){

caseCAMERA_MSG_VIDEO_FRAME:

//...

caseCAMERA_MSG_RAW_IMAGE:

//Thereisnodata.

case0:

break;

default:

ALOGV("dataCallback(%d,%p)",dataMsgType,dataPtr.get());

copyAndPost(env,dataPtr,dataMsgType);

break;

}

//postframemetadatatoJava

if(metadata&&(msgType&CAMERA_MSG_PREVIEW_METADATA)){

postMetadata(env,CAMERA_MSG_PREVIEW_METADATA,metadata);

}

}

voidJNICameraContext::copyAndPost(JNIEnv*env,constsp<IMemory>&dataPtr,intmsgType)

{

jbyteArrayobj=NULL;

//allocateJavabytearrayandcopydata

if(dataPtr!=NULL){

sp<IMemoryHeap>heap=dataPtr->getMemory(&offset,&size);

uint8_t*heapBase=(uint8_t*)heap->base();

constjbyte*data=reinterpret_cast<constjbyte*>(heapBase+offset);

if(msgType==CAMERA_MSG_RAW_IMAGE){

obj=getCallbackBuffer(env,&mRawImageCallbackBuffers,size);

}elseif(msgType==CAMERA_MSG_PREVIEW_FRAME&&mManualBufferMode){

//再次构造一个Buffer，并发送出去

obj=getCallbackBuffer(env,&mCallbackBuffers,size);

}else{

ALOGD("Allocatingcallbackbuffer");

obj=env->NewByteArray(size);

}

if(obj==NULL){

ALOGE("Couldn'tallocatebytearrayforJPEGdata");

env->ExceptionClear();

}else{

env->SetByteArrayRegion(obj,0,size,data);

}

}else{

ALOGE("imageheapisNULL");

}

}

//postimagedatatoJava

//主要是这句话，调用了一个Java函数，函数名为fields.post_event，post_event被初始化为postEventFromNative()

env->CallStaticVoidMethod(mCameraJClass,fields.post_event,

mCameraJObjectWeak,msgType,0,0,obj);

if(obj){

env->DeleteLocalRef(obj);

}

}

//终于加到Java了

privatestaticvoidpostEventFromNative(Objectcamera_ref,

intwhat,intarg1,intarg2,Objectobj)

{

//就是发送了一个msg，what为CAMERA_MSG_PREVIEW_FRAME。剩下的就不深究了

Messagem=c.mEventHandler.obtainMessage(what,arg1,arg2,obj);

c.mEventHandler.sendMessage(m);

}

不过看到这里，我们好像并没有看出个所有然来，最后的回调仅仅是调用上层的回调函数，把数据往上丢，却不显示也不处理。接下来我们还有两个问题，数据从哪里来？然后这些数据又是怎么显示的。请看下一篇

CamerastartPreview流程

上接第一篇，这个过程的主要任务是，如何读取数据的，读取的数据是什么格式，最好能知道是如何去预览的

上层APP调用的是Camera.java的startPreview();，下面列出startPreview的调用流程

//Camera.java

publicnativefinalvoidstartPreview();

//android_hardware_Camera.cpp

staticvoidandroid_hardware_Camera_startPreview(JNIEnv*env,jobjectthiz)

{

//这里的camera变量是，Camera.cpp类

camera->startPreview();

}

//Camera.cpp

status_tCamera::startPreview()

{

//此处的mCamera在CameraService.cpp的connect函数里被设置

//也就是CameraClient类

sp<ICamera>c=mCamera;

returnc->startPreview();

}

CameraClient.cpp里的startPreview函数

status_tCameraClient::startPreview(){

returnstartCameraMode(CAMERA_PREVIEW_MODE);

}

status_tCameraClient::startCameraMode(camera_modemode){

switch(mode){

caseCAMERA_PREVIEW_MODE:

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

LOG1("mSurfaceisnotsetyet.");

//stillabletostartpreviewinthiscase.

}

returnstartPreviewMode();

caseCAMERA_RECORDING_MODE:

//...

}

}

//CameraClient.cpp

status_tCameraClient::startPreviewMode(){

mHardware->previewEnabled();

mHardware->setPreviewWindow(mPreviewWindow);

result=mHardware->startPreview();

}

//CameraHardwareInterface.h

status_tstartPreview(){

//mDevice是Cam1DeviceFactory.cppcreateCam1Device()返回的对象

//既是DefaultCam1Device类

returnmDevice->ops->start_preview(mDevice);

}

上面的mDevice->ops->start_preview()函数对应的是DefaultCam1Device的父类Cam1Device类的操作函数。

Cam1DeviceBase::startPreview()

{

//(1)此函数在其子类DefaultCam1Device中实现

//仅是初始化了CameraAdapter

onStartPreview();

//(2)初始化DisplayClient，重要，稍后研究

enableDisplayClient();

//(3)

mpCamClient->startPreview();

//(4)我们通过(3)和(4)开始研究，再返回去看(1)(2)

mpCamAdapter->startPreview();

enableMsgType(CAMERA_MSG_PREVIEW_METADATA);

//

mIsPreviewEnabled=true;

}

mpCamclient->startPreview()

CamClient::startPreview()

{

mpPreviewClient->startPreview();

}

//PreviewClient.cpp

PreviewClient::startPreview()

{

//获得预览参数，这里参数为800*480，yuv420sp

ms8PrvTgtFmt=mpParamsMgr->getPreviewFormat();

mpParamsMgr->getPreviewSize(&mi4PrvWidth,&mi4PrvHeight);

//初始化预览Buf

initBuffers();

//

returnonStateChanged();

}

PreviewClient::initBuffers()

{

//预览数据的Buf

mpImgBufMgr=ImgBufManager::alloc(ms8PrvTgtFmt,mi4PrvWidth,

mi4PrvHeight,eMAX_PREVIEW_BUFFER_NUM,

"PreviewClientCb",mpCamMsgCbInfo->mRequestMemory,

0,0);

//预览数据的处理类，这里只是保留了一个处理接口

//里面并没有什么东西，可自行填充

mpExtImgProc=ExtImgProc::createInstance();

mpExtImgProc->init();

}

PreviewClient::onStateChanged()

{//发送了一个eID_WAKEUP的消息

postCommand(Command(Command::eID_WAKEUP));

}

//接收eID_WAKEUP消息

PreviewClient::threadLoop()

{

Commandcmd;

if(getCommand(cmd))

{

switch(cmd.eId)

{

caseCommand::eID_WAKEUP:

caseCommand::eID_PREVIEW_FRAME:

caseCommand::eID_POSTVIEW_FRAME:

onClientThreadLoop(cmd);

break;

//

caseCommand::eID_EXIT:

//...

}

}

//开始处理数据Buf

PreviewClient::onClientThreadLoop(Commandconst&rCmd)

{

//(1)Getreferencestopool/queuebeforestarting,sothatnothingwillbefreeduringoperations.

sp<ImgBufManager>pBufMgr=NULL;

sp<IImgBufQueue>pBufQueue=NULL;

{

Mutex::Autolock_l(mModuleMtx);

//

pBufMgr=mpImgBufMgr;

pBufQueue=mpImgBufQueue;

if(pBufMgr==0||pBufQueue==0||!isEnabledState())

}

//(2)stop&clearallbufferssothatwewon'tdequeanyundefinedbuffer.

pBufQueue->stopProcessor();

//(3)PrepareallTODObuffers.准备buf

if(!prepareAllTodoBuffers(pBufQueue,pBufMgr))

//(4)Start这个函数只是发出了一个广播，通知等待者

if(!pBufQueue->startProcessor())

//(5)Dountilallwantedmessagesaredisabled.

while(1)

{

//(.1)阻塞等待通知，并开始处理buf

waitAndHandleReturnBuffers(pBufQueue);

//(.2)breakifdisabled.

//addisProcessorRunningtomakesuretheformerpauseProcessor

//issucessfullyprocessed.

if(!isEnabledState()||!pBufQueue->isProcessorRunning())

{

MY_LOGI("Previewclientdisabled");

break;

}

//(.3)re-prepareallTODObuffers,ifpossible,

//sincesomeDONE/CANCELbuffersreturn.把Buf放回队列里

prepareAllTodoBuffers(pBufQueue,pBufMgr);

}

//(6)stop.

pBufQueue->pauseProcessor();

pBufQueue->flushProcessor();//clear"TODO"

pBufQueue->stopProcessor();//clear"DONE"

//

//(7)Cancelallun-returnedbuffers.

cancelAllUnreturnBuffers();

}

PreviewClient::waitAndHandleReturnBuffers(sp<IImgBufQueue>const&rpBufQueue)

{

Vector<ImgBufQueNode>vQueNode;

//(1)dequebuffersfromprocessor.阻塞等待通知

rpBufQueue->dequeProcessor(vQueNode);

//(2)handlebuffersdequedfromprocessor.

ret=handleReturnBuffers(vQueNode);

}

我们找到了哪里开始处理数据，那问题来了，是如何处理数据，数据又是如何被显示的，而这些数据又是从哪里来的

先来看数据是如何处理的

PreviewClient::handleReturnBuffers(Vector<ImgBufQueNode>const&rvQueNode)

{

//(1)determinetheindexofthelatestDONEbufferforcallback.

int32_tidxToCallback=0;

for(idxToCallback=rvQueNode.size()-1;idxToCallback>=0;idxToCallback--)

{

if(rvQueNode[idxToCallback].isDONE())

break;

}

//ShowTimeduration.

if(0<=idxToCallback)

{

nsecs_tconst_timestamp1=rvQueNode[idxToCallback].getImgBuf()->getTimestamp();

mProfile_buffer_timestamp.pulse(_timestamp1);

nsecs_tconst_msDuration_buffer_timestamp=::ns2ms(mProfile_buffer_timestamp.getDuration());

mProfile_buffer_timestamp.reset(_timestamp1);

//

mProfile_dequeProcessor.pulse();

nsecs_tconst_msDuration_dequeProcessor=::ns2ms(mProfile_dequeProcessor.getDuration());

mProfile_dequeProcessor.reset();

}

//

//(2)RemovefromListandpeformcallback,onebyone.

int32_tconstqueSize=rvQueNode.size();

for(int32_ti=0;i<queSize;i++)

{

ImgBufQueNodeconst&rQueNode=rvQueNode[i];

sp<IImgBuf>const&rpQueImgBuf=rQueNode.getImgBuf();//ImgBufinQueue.

sp<ICameraImgBuf>pListImgBuf=NULL;

ImgBufNodeconstListNode=*mImgBufList.begin();//NodeinList.

pListImgBuf=ListNode.getImgBuf();//ImgBufinList.

//(.4)Performcallback.

if(i==idxToCallback){

//

if(mpExtImgProc!=NULL)

{

if(mpExtImgProc->getImgMask()&ExtImgProc::BufType_PreviewCB)

{

IExtImgProc::ImgInfoimg;

//

img.bufType=ExtImgProc::BufType_PreviewCB;

img.format=rpQueImgBuf->getImgFormat();

img.width=rpQueImgBuf->getImgWidth();

img.height=rpQueImgBuf->getImgHeight();

img.stride[0]=rpQueImgBuf->getImgWidthStride(0);

img.stride[1]=rpQueImgBuf->getImgWidthStride(1);

img.stride[2]=rpQueImgBuf->getImgWidthStride(2);

img.virtAddr=(MUINT32)(rpQueImgBuf->getVirAddr());

img.bufSize=rpQueImgBuf->getBufSize();

//预留的处理函数，现在这里是空

mpExtImgProc->doImgProc(img);

}

}

//对数据进行处理

performPreviewCallback(pListImgBuf,rQueNode.getCookieDE());

}

}

}

PreviewClient::performPreviewCallback(sp<ICameraImgBuf>const&pCameraImgBuf,int32_tconstmsgType)

{

if(pCameraImgBuf!=0)

{

//[2]Callback

sp<CamMsgCbInfo>pCamMsgCbInfo;

{

pCamMsgCbInfo=mpCamMsgCbInfo;

}

//调用处理函数

//这个mDataCb回调函数藏得很深

//在CameraClient.cpp的initialize()函数里

//mHardware->setCallbacks(notifyCallback,dataCallback,dataCallbackTimestamp,(void*)mCameraId);

//这句话其中的dataCallback，设置了mDataCb函数

pCamMsgCbInfo->mDataCb(

0!=msgType?msgType:(int32_t)CAMERA_MSG_PREVIEW_FRAME,

pCameraImgBuf->get_camera_memory(),

pCameraImgBuf->getBufIndex(),

NULL,

pCamMsgCbInfo->mCbCookie

);

}

}

最后调用了mDataCb()回调函数。如果在APP层用了setPreviewCallback()，则会在此时调用回调函数，并把数据传回去给APP。注意，这里的msgType被设置成了CAMERA_MSG_PREVIEW_FRAME。

Cam1DeviceBase的setCallbacks()设置了很多回调函数，这些回调函数应该是挺有用的，有空了解一下。类似于startPreview()提供给Frameworks层调用。在Frameworks的CameraClient::initialize被调用

//设置Camera的各种回调函数

Cam1DeviceBase::setCallbacks(

camera_notify_callbacknotify_cb,

camera_data_callbackdata_cb,

camera_data_timestamp_callbackdata_cb_timestamp,

camera_request_memoryget_memory,

void*user

)

{

mpCamMsgCbInfo->mCbCookie=user;

mpCamMsgCbInfo->mNotifyCb=notify_cb;

mpCamMsgCbInfo->mDataCb=data_cb;

mpCamMsgCbInfo->mDataCbTimestamp=data_cb_timestamp;

mpCamMsgCbInfo->mRequestMemory=get_memory;

//

if(mpCamClient!=0)

{

mpCamClient->setCallbacks(mpCamMsgCbInfo);

}

//

if(mpCamAdapter!=0)

{

mpCamAdapter->setCallbacks(mpCamMsgCbInfo);

}

}

Frameworks:

status_tCameraClient::initialize(camera_module_t*module){

mHardware=newCameraHardwareInterface(camera_device_name);

res=mHardware->initialize(&module->common);

//Cam1DeviceBase的setCallbacks()

mHardware->setCallbacks(notifyCallback,

dataCallback,

dataCallbackTimestamp,

(void*)mCameraId);

}

dataCallback是个回调函数，也在CameraClient中。此函数中，接收了多种的msgType。这就表示数据回调中可以有多种的数据类型，有RAW的，有COMPRESSD的，等

voidCameraClient::dataCallback(int32_tmsgType,

constsp<IMemory>&dataPtr,camera_frame_metadata_t*metadata,void*user){

switch(msgType&~CAMERA_MSG_PREVIEW_METADATA){

//!++

#if1//defined(MTK_CAMERA_BSP_SUPPORT)

caseMTK_CAMERA_MSG_EXT_DATA:

client->handleMtkExtData(dataPtr,metadata);

break;

#endif

//!--

caseCAMERA_MSG_PREVIEW_FRAME:

client->handlePreviewData(msgType,dataPtr,metadata);

break;

caseCAMERA_MSG_POSTVIEW_FRAME:

client->handlePostview(dataPtr);

break;

caseCAMERA_MSG_RAW_IMAGE:

client->handleRawPicture(dataPtr);

break;

caseCAMERA_MSG_COMPRESSED_IMAGE:

client->handleCompressedPicture(dataPtr);

break;

default:

client->handleGenericData(msgType,dataPtr,metadata);

break;

}

}

我们的msgType是CAMERA_MSG_PREVIEW_FRAME。调用了handlePreviewData函数

voidCameraClient::handlePreviewData(int32_tmsgType,

constsp<IMemory>&mem,

camera_frame_metadata_t*metadata){

//获取mem

sp<IMemoryHeap>heap=mem->getMemory(&offset,&size);

//iscallbackenabled?判断

if(!(flags&CAMERA_FRAME_CALLBACK_FLAG_ENABLE_MASK)){

//Iftheenablebitisoff,thecopy-outandone-shotbitsareignored

LOG2("framecallbackisdisabled");

return;

}

//holdastrongpointertotheclient

sp<ICameraClient>c=mRemoteCallback;

//clearcallbackflagsifnoclientorone-shotmode判断

if(c==0||(mPreviewCallbackFlag&CAMERA_FRAME_CALLBACK_FLAG_ONE_SHOT_MASK)){

LOG2("Disablepreviewcallback");

}

//有两种方式把mem发送出去，一种是copy一种是直接把地址发送出去

if(c!=0){

//Isthereceivedframecopiedoutornot?

if(flags&CAMERA_FRAME_CALLBACK_FLAG_COPY_OUT_MASK){

LOG2("frameiscopied");

copyFrameAndPostCopiedFrame(msgType,c,heap,offset,size,metadata);

}else{

LOG2("frameisforwarded");

c->dataCallback(msgType,mem,metadata);

}

}

}

最后是通过sp<ICameraClient>c=mRemoteCallback;mRemoteCallback->dataCallback发送出去的。mRemoteCallback是ICameraClient类型和CameraClient两者都有dataCallback两者又是什么关系，如果有关系，这里此不是会死循环。mRemoteCallback搜一下，是在CameraClient::connect()被里初始化的，于是乎在这里找，找了大半天也没找到在哪里被初始化的。被坑了半天，原来在CameraClient的构造函数里。

我们返回到Camera.cpp的connect函数里。发现，还是挺好玩的。再从Camera.cpp的connect()细跟一下

sp<Camera>Camera::connect(intcameraId,constString16&clientPackageName,

intclientUid)

{

returnCameraBaseT::connect(cameraId,clientPackageName,clientUid);

}

//CameraBaseT在CameraBase被定义成typedefCameraBase<TCam>CameraBaseT;

//CameraBase在Camera被初始化为CameraBase<Camera>，所以上面就相应于调用了CameraBase<Camera>::connect()

template<typenameTCam,typenameTCamTraits>

sp<TCam>CameraBase<TCam,TCamTraits>::connect(intcameraId,

constString16&clientPackageName,intclientUid)

{

//把所有的TCam替换成Camera,就是刚才Camera.cpp里的camera在这里被构造

sp<TCam>c=newTCam(cameraId);

//TCamCallbacks在Camera.h里被定义为ICameraClient，被赋值为Camera。Camera继承ICameraClient

sp<TCamCallbacks>cl=c;

constsp<ICameraService>&cs=getCameraService();

//fnConnectService在Camera被初始化为ICameraService::connect()

TCamConnectServicefnConnectService=TCamTraits::fnConnectService;

//下面调用了CameraService::connect()c和cl是同一个值，做为两个不同的参数传进了CameraService::connect()

status=(cs.get()->*fnConnectService)(cl,cameraId,clientPackageName,clientUid,/*out*/c->mCamera);

}

//CameraService::connec()构造了一个CameraClient(),又是一个CameraClient，

//但是和上面的ICameraClient没有半毛线关系。只是名字相似,真的是一万个++泥马在奔腾。

status_tCameraService::connect(constsp<ICameraClient>&cameraClient,intcameraId,

constString16&clientPackageName,intclientUid,/*out*/sp<ICamera>&device){

//CameraService::connec()就做了两件事情，初始化Camera里的mCamera和把Camera传给CameraClient

//CameraClient的构造函数会传到他的父类构造函数Client()里，Client却是在CameraService。Camera类就是mRemoteCallback

client=newCameraClient(this,cameraClient,clientPackageName,cameraId,

facing,callingPid,clientUid,getpid());

device=client;

returnOK;}

所以，上面的c->dataCallback。调用的是Camera的dataCallback()

//callbackfromcameraservicewhenframeorimageisready

voidCamera::dataCallback(int32_tmsgType,constsp<IMemory>&dataPtr,

camera_frame_metadata_t*metadata)

{

sp<CameraListener>listener;

listener=mListener;

listener->postData(msgType,dataPtr,metadata);

}

这里的mListener是在android_hardware_Camera_native_setup()里被设置的类型是MtkJNICameraContext。所以listener->postData()调用的是MtkJNICameraContext的postData()。

voidMtkJNICameraContext::postData(int32_tmsgType,constsp<IMemory>&dataPtr,

camera_frame_metadata_t*metadata)

{

JNICameraContext::postData(msgType,dataPtr,metadata);

}

voidJNICameraContext::postData(int32_tmsgType,constsp<IMemory>&dataPtr,

camera_frame_metadata_t*metadata)

{

switch(dataMsgType){

caseCAMERA_MSG_VIDEO_FRAME:

//...

caseCAMERA_MSG_RAW_IMAGE:

//Thereisnodata.

case0:

break;

default:

ALOGV("dataCallback(%d,%p)",dataMsgType,dataPtr.get());

copyAndPost(env,dataPtr,dataMsgType);

break;

}

//postframemetadatatoJava

if(metadata&&(msgType&CAMERA_MSG_PREVIEW_METADATA)){

postMetadata(env,CAMERA_MSG_PREVIEW_METADATA,metadata);

}

}

voidJNICameraContext::copyAndPost(JNIEnv*env,constsp<IMemory>&dataPtr,intmsgType)

{

jbyteArrayobj=NULL;

//allocateJavabytearrayandcopydata

if(dataPtr!=NULL){

sp<IMemoryHeap>heap=dataPtr->getMemory(&offset,&size);

uint8_t*heapBase=(uint8_t*)heap->base();

constjbyte*data=reinterpret_cast<constjbyte*>(heapBase+offset);

if(msgType==CAMERA_MSG_RAW_IMAGE){

obj=getCallbackBuffer(env,&mRawImageCallbackBuffers,size);

}elseif(msgType==CAMERA_MSG_PREVIEW_FRAME&&mManualBufferMode){

//再次构造一个Buffer，并发送出去

obj=getCallbackBuffer(env,&mCallbackBuffers,size);

}else{

ALOGD("Allocatingcallbackbuffer");

obj=env->NewByteArray(size);

}

if(obj==NULL){

ALOGE("Couldn'tallocatebytearrayforJPEGdata");

env->ExceptionClear();

}else{

env->SetByteArrayRegion(obj,0,size,data);

}

}else{

ALOGE("imageheapisNULL");

}

}

//postimagedatatoJava

//主要是这句话，调用了一个Java函数，函数名为fields.post_event，post_event被初始化为postEventFromNative()

env->CallStaticVoidMethod(mCameraJClass,fields.post_event,

mCameraJObjectWeak,msgType,0,0,obj);

if(obj){

env->DeleteLocalRef(obj);

}

}

//终于加到Java了

privatestaticvoidpostEventFromNative(Objectcamera_ref,

intwhat,intarg1,intarg2,Objectobj)

{

//就是发送了一个msg，what为CAMERA_MSG_PREVIEW_FRAME。剩下的就不深究了

Messagem=c.mEventHandler.obtainMessage(what,arg1,arg2,obj);

c.mEventHandler.sendMessage(m);

}

不过看到这里，我们好像并没有看出个所有然来，最后的回调仅仅是调用上层的回调函数，把数据往上丢，却不显示也不处理。接下来我们还有两个问题，数据从哪里来？然后这些数据又是怎么显示的。请看下一篇