Android Camera 系统架构源码分析(3)---->Camera的显示流程

Preview的显示流程

这次我们要从最开始startPreview的时候开始，在starPreview之间就setPreviewWindow()。

//CameraClient.cpp

status_tCameraClient::startPreviewMode(){

mHardware->previewEnabled();

mHardware->setPreviewWindow(mPreviewWindow);

result=mHardware->startPreview();

}

最后会调用到Cam1DeviceBase的setPreviewWindow()，其中的调用过程和startPreview()的一样，不再赘述

Cam1DeviceBase::setPreviewWindow(preview_stream_ops*window)

{

//(1)初始化显示

status_tstatus=initDisplayClient(window);

//(2)开始显示

status=enableDisplayClient();

}

initDisplayClient();在之前说的Cam1DeviceBase::startPreview()的(2)也调用了initDisplayClient();

Cam1DeviceBase::initDisplayClient(preview_stream_ops*window)

{

SizepreviewSize;

//[1]ChecktoseewhetherthepassedwindowisNULLornot.

//...

//[2]Getpreviewsize.获得预览参数

queryPreviewSize(previewSize.width,previewSize.height);

//[3]InitializeDisplayClient.

//[3.1]createaDisplayClient.仅是初始化变量

mpDisplayClient=IDisplayClient::createInstance();

//[3.2]initializethenewly-createdDisplayClient.

mpDisplayClient->init();

//[3.3]setpreview_stream_ops&relatedwindowinfo.

mpDisplayClient->setWindow(window,previewSize.width,previewSize.height,queryDisplayBufCount());

//[3.4]setImageBufferProviderClientifitexist.

mpCamAdapter!=0&&!mpDisplayClient->setImgBufProviderClient(mpCamAdapter);

}

下面是initDisplayClient();的细节分析

DisplayClient::init()

{

/**

构造DisplayThread并让它run起来，注意构造时传入的handle参数为dispalyClient

构造ImgBufQueue,它的id为eID_DISPLAY

在previewClientinit()时，也创建了一个ImgBufQueue，而ID是eID_PRV_CB

**/

ret=createDisplayThread()&&createImgBufQueue();

}

DisplayClient::setWindow(preview_stream_ops*constwindow,int32_tconstwndWidth,

int32_tconstwndHeight,int32_tconsti4MaxImgBufCount)

{returnset_preview_stream_ops(window,wndWidth,wndHeight,i4MaxImgBufCount);

}

DisplayClient::set_preview_stream_ops(preview_stream_ops*constwindow,int32_tconstwndWidth,

int32_tconstwndHeight,int32_tconsti4MaxImgBufCount)

{

int32_tmin_undequeued_buf_count=0;

//

//(2)Check

//....

//(3)Savainfo.

mpStreamImgInfo.clear();

mpStreamImgInfo=newImgInfo(wndWidth,wndHeight,CAMERA_DISPLAY_FORMAT,CAMERA_DISPLAY_FORMAT_HAL,"Camera@Display");

mpStreamOps=window;

mi4MaxImgBufCount=i4MaxImgBufCount;

//(4.1)Setgrallocusagebitsforwindow.

err=mpStreamOps->set_usage(mpStreamOps,CAMERA_GRALLOC_USAGE);

//(4.2)Getminimumundequeuebuffercount

err=mpStreamOps->get_min_undequeued_buffer_count(mpStreamOps,&min_undequeued_buf_count);

//(4.3)Setthenumberofbuffersneededfordisplay.

err=mpStreamOps->set_buffer_count(mpStreamOps,mi4MaxImgBufCount+min_undequeued_buf_count);

//(4.4)Setwindowgeometry

err=mpStreamOps->set_buffers_geometry(mpStreamOps,mpStreamImgInfo->mu4ImgWidth,

mpStreamImgInfo->mu4ImgHeight,mpStreamImgInfo->mi4ImgFormat);

}

DisplayClient::setImgBufProviderClient(sp<IImgBufProviderClient>const&rpClient)

{

rpClient->onImgBufProviderCreated(mpImgBufQueue);

mpImgBufPvdrClient=rpClient;

}

//BaseCamAdapter.cpp

BaseCamAdapter::onImgBufProviderCreated(sp<IImgBufProvider>const&rpProvider)

{

int32_tconsti4ProviderId=rpProvider->getProviderId();

mpImgBufProvidersMgr->setProvider(i4ProviderId,rpProvider);

}

DispalyClient的初始化就这么完成了，从但是我们并不知道上面已经初始化的参数有什么作用，又是如何开始刷显示的呢？我们返回到enableDisplayClient()继续跟踪

Cam1DeviceBase::enableDisplayClient()

{

SizepreviewSize;

//[1]Getpreviewsize.获取预览参数

queryPreviewSize(previewSize.width,previewSize.height);

//[2]Enable

mpDisplayClient->enableDisplay(previewSize.width,previewSize.height,queryDisplayBufCount(),mpCamAdapter);

}

Cam1DeviceBase::enableDisplayClient()

{

SizepreviewSize;

//[1]Getpreviewsize.获取预览参数

queryPreviewSize(previewSize.width,previewSize.height);

//[2]Enable

mpDisplayClient->enableDisplay(previewSize.width,previewSize.height,queryDisplayBufCount(),mpCamAdapter);

}

DisplayClient::enableDisplay(int32_tconsti4Width,int32_tconsti4Height,

int32_tconsti4BufCount,sp<IImgBufProviderClient>const&rpClient)

{

//Enable.

enableDisplay();

}

DisplayClient::enableDisplay()

{

//Postacommandtowakeupthethread.向DisplayThread发送消息

mpDisplayThread->postCommand(Command(Command::eID_WAKEUP));

}

DisplayThread::threadLoop()

{

Commandcmd;

if(getCommand(cmd))

{

switch(cmd.eId)

{

caseCommand::eID_EXIT:

//....

caseCommand::eID_WAKEUP:

default:

//调用的是handler的onThreadloop

//在前面已知DisplayThread的handler被设置成了DisplayClient

mpThreadHandler->onThreadLoop(cmd);

break;

}

}

}

DisplayClient的onThreadLoop()在DisplayClient.BufOps.cpp里，仔细观察下面的函数是不会有似曾相识的感觉，原来下面函数的结构和Preview的onClientThreadLoop的函数结构一模一样，边里面使用的函数名都一样，虽然不是同一个函数

DisplayClient::onThreadLoop(Commandconst&rCmd)

{

//(0)lockProcessor.

sp<IImgBufQueue>pImgBufQueue;

//(1)PrepareallTODObuffers.准备buf，把buf放入队列里

if(!prepareAllTodoBuffers(pImgBufQueue))

{

returntrue;

}

//(2)Start通知开始处理

pImgBufQueue->startProcessor();

//(3)Dountildisabled.

while(1)

{

//(.1)阻塞等待通知，并开始处理buf

waitAndHandleReturnBuffers(pImgBufQueue);

//(.2)breakifdisabled.

if(!isDisplayEnabled())

{

MY_LOGI("Displaydisabled");

break;

}

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

//sincesomeDONE/CANCELbuffersreturn.准备buf，把buf放入队列里

prepareAllTodoBuffers(pImgBufQueue);

}

//

//(4)Stop

pImgBufQueue->pauseProcessor();

pImgBufQueue->flushProcessor();

pImgBufQueue->stopProcessor();

//

//(5)Cancelallun-returnedbuffers.

cancelAllUnreturnBuffers();

//

{

Mutex::Autolock_l(mStateMutex);

mState=eState_Suspend;

mStateCond.broadcast();

}

}

根据之前的经验很直觉地找到了waitAndHandleReturnBuffers()函数，正是里面处理了数据，但是又怎么样把数据显示出来的呢？继续看

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

{

Vector<ImgBufQueNode>vQueNode;

//(1)dequebuffersfromprocessor.阻塞等待通知读取Buf

rpBufQueue->dequeProcessor(vQueNode);

//(2)handlebuffersdequedfromprocessor.

ret=handleReturnBuffers(vQueNode);

}

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

{

/*

*Notes:

*For30fps,wejustenque(display)thelatestframe,

*andcanceltheothers.

*Forframerate>30fps,weshouldjudgethetimestamphereorsource.

*/

//

//(3)RemovefromListandenquePrvOps/cancelPrvOps,onebyone.

int32_tconstqueSize=rvQueNode.size();

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

{

sp<IImgBuf>const&rpQueImgBuf=rvQueNode[i].getImgBuf();//ImgBufinQueue.

sp<StreamImgBuf>constpStreamImgBuf=*mStreamBufList.begin();//ImgBufinList.

//(.1)CheckvalidpointerstoimagebuffersinQueue&List

if(rpQueImgBuf==0||pStreamImgBuf==0)

{

MY_LOGW("BadImgBuf:(Que[%d],List.begin)=(%p,%p)",i,rpQueImgBuf.get(),pStreamImgBuf.get());

continue;

}

//(.2)ChecktheequalityofimagebuffersbetweenQueue&List.

if(rpQueImgBuf->getVirAddr()!=pStreamImgBuf->getVirAddr())

{

MY_LOGW("BadaddressinImgBuf:(Que[%d],List.begin)=(%p,%p)",i,rpQueImgBuf->getVirAddr(),pStreamImgBuf->getVirAddr());

continue;

}

//(.3)Everycheckisok.Nowremovethenodefromthelist.

mStreamBufList.erase(mStreamBufList.begin());

//

//(.4)enquePrvOps/cancelPrvOps

if(i==idxToDisp){

//

if(mpExtImgProc!=NULL)

{

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

{

IExtImgProc::ImgInfoimg;

//

img.bufType=ExtImgProc::BufType_Display;

img.format=pStreamImgBuf->getImgFormat();

img.width=pStreamImgBuf->getImgWidth();

img.height=pStreamImgBuf->getImgHeight();

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

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

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

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

img.bufSize=pStreamImgBuf->getBufSize();

//预留的处理接口，用户可自行填充

mpExtImgProc->doImgProc(img);

}

}

//处理将要显示的Buf

enquePrvOps(pStreamImgBuf);

}

else{

//处理被忽略的buf

cancelPrvOps(pStreamImgBuf);

}

}

}

DisplayClient::enquePrvOps(sp<StreamImgBuf>const&rpImgBuf)

{

//[1]unlockbufferbeforesendingtodisplay

GraphicBufferMapper::get().unlock(rpImgBuf->getBufHndl());

//[2]Dumpimageifwanted.

dumpImgBuf_If(rpImgBuf);

//[3]settimestamp.

err=mpStreamOps->set_timestamp(mpStreamOps,rpImgBuf->getTimestamp());

//[4]setgrallocbuffertype&dirty设置buf的参数

::gralloc_extra_setBufParameter(rpImgBuf->getBufHndl(),

GRALLOC_EXTRA_MASK_TYPE|GRALLOC_EXTRA_MASK_DIRTY,GRALLOC_EXTRA_BIT_TYPE_CAMERA|GRALLOC_EXTRA_BIT_DIRTY);

//[5]unlocksandpostthebuffertodisplay.

//此处我们的mpStreamOps在之前的set_preview_stream_ops()被初始化为window，即setWindow()传下来的window参数。

//所以我们得往上找，这个window是什么东西。

err=mpStreamOps->enqueue_buffer(mpStreamOps,rpImgBuf->getBufHndlPtr());

}

再往回找，可以看到这个mpStramOps变量，即window变量是一个Surface。

//setthebufferconsumerthatthepreviewwilluse

status_tCameraClient::setPreviewTarget(

constsp<IGraphicBufferProducer>&bufferProducer){

sp<IBinder>binder;

sp<ANativeWindow>window;

if(bufferProducer!=0){

binder=bufferProducer->asBinder();

//UsingcontrolledByAppflagtoensurethatthebufferqueueremainsin

//asyncmodefortheoldcameraAPI,wheremanyapplicationsdepend

//onthatbehavior.

window=newSurface(bufferProducer,/*controlledByApp*/true);

}

returnsetPreviewWindow(binder,window);

}

写过APP的都知道，这个Surface是Android上层用于显示的一个辅助类。而Camera的预览也相当于调用了Surface的操作函数。那问题又来了，调用这些Surface是如何去显示的呢？......我就到此为止了，完成了我做知识储备的目的，日后要是工作有需要深入再深入了，有兴趣的朋友可以自行..........深入。我们还是再继续看，这些数据是如何来的呢？

现在回头看看现在涉及到的几个大类做一下总结。

Cam1DeviceBase（包括其子类和父类）包含了所有的Camera的操作函数，如Open，显示，拍照，录像，自动对焦的操作，以及这些Camera操作和Camera硬件涉及到的参数，可以说，Cam1Device对Frameworks及App层来说就是一个Camera了。

在Cam1DeviceBase里包含了ParamsManager，顾名思义就是Camera的参数管理，我们之前也没去理会他，就让它飘会吧。Cam1DeviceBase还包含了几个Client，用于负责所有的功能操作。DisplayClient用来负责显示，CamClient则是一个大统一，把Camera的操作都归集于此。CamClient又把自己的功能分成几个
Client去负责，其中PreviewClient负责显示，RecordClient负责录制，在拍照的功能里FDClient，OTClient，PreviewClient都参了一脚，具体有什么用，有空再研究。但还有一个CameraAdapter，这也非常重要的