Android(安卓)Camera2 Hal3(二)startPreview预览过程
16lz
2021-01-26
引言
上一节分析了Camera2 Hal3的初始化过程。这一节来分析写预览过程，预览过程我将以Camera2Client::startPreview为入口分析这个过程。
时序图
类图
创建流，启动流
startPreview过程会先调用mStreamingProcessor->updatePreviewStream来创建Camera3OutputStream
status_t Camera2Client::startPreview() {...SharedParameters::Lock l(mParameters);//上一节的分析我们知道了l.mParameters.initialize实际上就是调用Parameters::initialize，只不过给它加了一把Mutex而已//所以这里l.mParameters的调用也是返回Parameters对象，同时给它加了一把Mutex锁return startPreviewL(l.mParameters, false);}status_t Camera2Client::startPreviewL(Parameters ¶ms, bool restart) {...res = mStreamingProcessor->updatePreviewStream(params);....}status_t StreamingProcessor::updatePreviewStream(const Parameters ¶ms) {sp<CameraDeviceBase> device = mDevice.promote();//上一节的分析我们知道了mDevice就是指向Camera3Deviceif (mPreviewStreamId == NO_STREAM) { res = device->createStream(mPreviewWindow, params.previewWidth, params.previewHeight, CAMERA2_HAL_PIXEL_FORMAT_OPAQUE, &mPreviewStreamId);}}status_t Camera3Device::createStream(sp<ANativeWindow> consumer, uint32_t width, uint32_t height, int format, int *id) { newStream = new Camera3OutputStream(mNextStreamId, consumer,width, height, format); mOutputStreams.add(mNextStreamId, newStream);}Camera3OutputStream::Camera3OutputStream(int id, sp<ANativeWindow> consumer,uint32_t width, uint32_t height, int format) : Camera3IOStreamBase(id, CAMERA3_STREAM_OUTPUT, width, height, /*maxSize*/0, format), mConsumer(consumer), mTransform(0), mTraceFirstBuffer(true) { ......}在创建Camera3OutputStream的过程中有一个变量要注意一下mPreviewWindow，来看看mPreviewWindow是什么东西。
在初始化camera的时候会调用Camera2Client::setPreviewTarget把绘图相关接口IGraphicBufferProducer传递过来，创建Surface，我们知道Surface相当于一块画布，不同画布的绘图最终会通过SurfaceFlinger去指导合成，最后输出在屏幕上面。
status_t Camera2Client::setPreviewTarget( const sp<IGraphicBufferProducer>& bufferProducer) { sp<IBinder> binder; sp<ANativeWindow> window; if (bufferProducer != 0) { binder = bufferProducer->asBinder(); // Using controlledByApp flag to ensure that the buffer queue remains in // async mode for the old camera API, where many applications depend // on that behavior. window = new Surface(bufferProducer, /*controlledByApp*/ true); } return setPreviewWindowL(binder, window);}status_t Camera2Client::setPreviewWindowL(const sp<IBinder>& binder,sp<ANativeWindow> window) {...res = mStreamingProcessor->setPreviewWindow(window);}status_t StreamingProcessor::setPreviewWindow(sp<ANativeWindow> window) {... mPreviewWindow = window;}可以看出mPreviewWindow就是相当于刚才创建的Surface。
继续分析startPreviewL
status_t Camera2Client::startPreviewL(Parameters ¶ms, bool restart) {...res = mStreamingProcessor->updatePreviewStream(params);...outputStreams.push(getPreviewStreamId());//一个Camera3OutputStream对应一个idres = mStreamingProcessor->updatePreviewRequest(params);...res = mStreamingProcessor->startStream(StreamingProcessor::PREVIEW, outputStreams);}status_t StreamingProcessor::updatePreviewRequest(const Parameters ¶ms) {sp<CameraDeviceBase> device = mDevice.promote();res = device->createDefaultRequest(CAMERA3_TEMPLATE_PREVIEW,&mPreviewRequest);res = mPreviewRequest.update(ANDROID_REQUEST_ID,&mPreviewRequestId, 1);//这个mPreviewRequest下面就会用到}status_t Camera3Device::createDefaultRequest(int templateId,CameraMetadata *request) { const camera_metadata_t *rawRequest; rawRequest = mHal3Device->ops->construct_default_request_settings(mHal3Device, templateId);//hal层去填充默认设置 *request = rawRequest;//上一节分析以及指导CameraMetadata维护的就是camera_metadata_t }继续分析startPreviewL调用的mStreamingProcessor->startStream
status_t StreamingProcessor::startStream(StreamType type, const Vector<int32_t> &outputStreams) { CameraMetadata &request = (type == PREVIEW) ?//这里type是PREVIEW所以会使用刚才赋值的mPreviewRequest mPreviewRequest : mRecordingRequest; res = request.update( ANDROID_REQUEST_OUTPUT_STREAMS, outputStreams);//把刚才创建Camera3OutputStream对应的id保存到这个request里面 ... res = device->setStreamingRequest(request);}status_t Camera3Device::setStreamingRequest(const CameraMetadata &request,int64_t* /*lastFrameNumber*/) { List<const CameraMetadata> requests; requests.push_back(request); return setStreamingRequestList(requests, /*lastFrameNumber*/NULL);}status_t Camera3Device::setStreamingRequestList(const List<const CameraMetadata> &requests,int64_t *lastFrameNumber) { return submitRequestsHelper(requests, /*repeating*/true, lastFrameNumber);}status_t Camera3Device::submitRequestsHelper( const List<const CameraMetadata> &requests, bool repeating, /*out*/ int64_t *lastFrameNumber) { RequestList requestList; res = convertMetadataListToRequestListLocked(requests, /*out*/&requestList);//利用CameraMetadata创建CaptureRequest if (repeating) {//第二个参数是true res = mRequestThread->setRepeatingRequests(requestList, lastFrameNumber); } }status_t Camera3Device::convertMetadataListToRequestListLocked(...){for (List<const CameraMetadata>::const_iterator it = metadataList.begin();it != metadataList.end(); ++it){sp<CaptureRequest> newRequest = setUpRequestLocked(*it);}}sp<Camera3Device::CaptureRequest> Camera3Device::setUpRequestLocked(...){sp<CaptureRequest> newRequest = createCaptureRequest(request);}sp<Camera3Device::CaptureRequest> Camera3Device::createCaptureRequest(...){camera_metadata_entry_t streams = //获取到刚才保存的id newRequest->mSettings.find(ANDROID_REQUEST_OUTPUT_STREAMS);for (size_t i = 0; i < streams.count; i++) {int idx = mOutputStreams.indexOfKey(streams.data.i32[i]);sp<Camera3OutputStreamInterface> stream =mOutputStreams.editValueAt(idx);newRequest->mOutputStreams.push(stream);//得到outputstream的对象，保存到CaptureRequest中}}status_t Camera3Device::RequestThread::setRepeatingRequests(const RequestList &requests,/*out*/ int64_t *lastFrameNumber) { mRepeatingRequests.clear(); mRepeatingRequests.insert(mRepeatingRequests.begin(),requests.begin(), requests.end()); ....}到了这里，mRepeatingRequests会被插入一个RequestList，mRepeatingRequests如果不为空的话，RequestThread会不断的触发预览事件。
threadLoop和帧数据回调
Camera3Device::RequestThread::threadLoop是一个处理Request的线程，得到request后它会去调用hal接口获取到图像数据，然后hal层会回调Camera3Device::processCaptureResult接口，通过层层调用把图像数据送给显示系统显示图像。
sp<Camera3Device::CaptureRequest> Camera3Device::RequestThread::waitForNextRequest() { while (mRequestQueue.empty()) { if (!mRepeatingRequests.empty()) {//从上面知道这里不是空的，mRepeatingRequests也没有擦除，所以一直进来这里 const RequestList &requests = mRepeatingRequests; RequestList::const_iterator firstRequest =requests.begin(); nextRequest = *firstRequest; mRequestQueue.insert(mRequestQueue.end(), ++firstRequest, requests.end()); break;//直接退出循环了，无需等待 } res = mRequestSignal.waitRelative(mRequestLock, kRequestTimeout); ...... } ...... return nextRequest;}bool Camera3Device::RequestThread::threadLoop() {sp<CaptureRequest> nextRequest = waitForNextRequest();camera3_capture_request_t request = camera3_capture_request_t();//构建一个camera3_capture_request_t ....outputBuffers.insertAt(camera3_stream_buffer_t(), 0, nextRequest->mOutputStreams.size());//先插入一个camera3_stream_buffer_t request.output_buffers = outputBuffers.array();//保存到request中 for (size_t i = 0; i < nextRequest->mOutputStreams.size(); i++) { res = nextRequest->mOutputStreams.editItemAt(i)->//前面已经知道了这里获取到的item是Camera3OutputStream getBuffer(&outputBuffers.editItemAt(i));//调用Camera3Stream::returnBuffer去填充camera3_stream_buffer } .... res = mHal3Device->ops->process_capture_request(mHal3Device, &request);//调用hal去获取一帧数据}status_t Camera3Stream::getBuffer(camera3_stream_buffer *buffer) { res = getBufferLocked(buffer);}status_t Camera3OutputStream::getBufferLocked(camera3_stream_buffer *buffer) {ANativeWindowBuffer* anb;sp<ANativeWindow> currentConsumer = mConsumer;//前面创建的surfaceres = currentConsumer->dequeueBuffer(currentConsumer.get(), &anb, &fenceFd);//出队buffer handoutBufferLocked(*buffer, &(anb->handle), /*acquireFence*/fenceFd, //填充camera3_stream_buffer /*releaseFence*/-1, CAMERA3_BUFFER_STATUS_OK, /*output*/true);}void Camera3IOStreamBase::handoutBufferLocked(camera3_stream_buffer &buffer,buffer_handle_t *handle,int acquireFence, int releaseFence, camera3_buffer_status_t status,bool output) { buffer.stream = this;//设置回调 buffer.buffer = handle; buffer.acquire_fence = acquireFence; buffer.release_fence = releaseFence; buffer.status = status; ...}（参考类图）camera3_stream_buffer的stream类型是camera3_stream_t *，所以buffer.stream = this让camera3_stream_buffer的stream指向了Camera3OutputStream的父类camera3_stream，通过类图可以知道camera3_stream_buffer是camera3_capture_request的成员，所以camera3_capture_request可以通过camera3_stream_buffer的stream成员拿到camera3_stream的地址，而camera3_stream又是Camera3OutputStream的父类，所以camera3_capture_request可以访问到刚才创建的Camera3OutputStream。这一点非常重要，因为下面的帧数据回调就是以这个为基础的。
填充完一个camera3_capture_request后，threadLoop回调用hal接口mHal3Device->ops->process_capture_request(mHal3Device, &request)去hal层取图像。我这里是取一帧图像。
//hal层camera3_device_ops_t Camera::sOps = {....configure_streams = Camera::configureStreams, .process_capture_request = Camera::processCaptureRequest, ...}int Camera::processCaptureRequest(camera3_capture_request_t *request) { const V4l2Device::VBuffer *frame = NULL; Vector<camera3_stream_buffer> buffers; if(request->input_buffer) {//我这里不关心输入buffer，所以我这里直接设置release_fence为-1 request->input_buffer->release_fence = -1; } BENCHMARK_SECTION("Lock/Read") { frame = mDev->readLock();//其实就是调用ioctl(mFd, VIDIOC_DQBUF, &bufInfo)取出一片buffer } for(size_t i = 0; i < request->num_output_buffers; ++i) {//我这里只有一个buffer const camera3_stream_buffer &srcBuf = request->output_buffers[i];//取出刚才所说的那个camera3_stream_buffer sp<Fence> acquireFence = new Fence(srcBuf.acquire_fence);//创建一个Fence，Fence是显示系统的一种同步机制 e = acquireFence->wait(1000); /* FIXME: magic number */ //等待一下，返回的时候说明刚才调用dequeueBuffer出队的buffer真正可用了 if(e == NO_ERROR) { const Rect rect((int)srcBuf.stream->width, (int)srcBuf.stream->height); e = GraphicBufferMapper::get().lock(*srcBuf.buffer, GRALLOC_USAGE_SW_WRITE_OFTEN, rect, (void **)&buf);//锁住buffer switch(srcBuf.stream->format) {//这个是在configure_streams的时候指定的 case HAL_PIXEL_FORMAT_RGB_565:{//我这边指定的是rgb565 //把一帧图像数据保存到buf里面 } } }for(size_t i = 0; i < request->num_output_buffers; ++i) {//只有一个output bufferconst camera3_stream_buffer &srcBuf = request->output_buffers[i];GraphicBufferMapper::get().unlock(*srcBuf.buffer);//解锁bufferbuffers.push_back(srcBuf);//保存到Vector这里的process_capture_result在Camera3Device的构造函数中指定好了，camera3_callback_ops::process_capture_result = &sProcessCaptureResult，所以这里会回调Camera3Device的sProcessCaptureResult函数，进而调用Camera3Device::processCaptureResult函数。
void Camera3Device::processCaptureResult(const camera3_capture_result *result) {for (size_t i = 0; i < result->num_output_buffers; i++){//咦，这个result->output_buffers[i].stream)不就是前面指定为Camera3IOStreamBase了吗//所以这个把Camera3IOStreamBase指针强转成它的父类指针Camera3StreamCamera3Stream *stream =Camera3Stream::cast(result->output_buffers[i].stream);res = stream->returnBuffer(result->output_buffers[i], timestamp);....}}status_t Camera3Stream::returnBuffer(const camera3_stream_buffer &buffer,nsecs_t timestamp) { status_t res = returnBufferLocked(buffer, timestamp);}status_t Camera3OutputStream::returnBufferLocked( const camera3_stream_buffer &buffer,nsecs_t timestamp) { status_t res = returnAnyBufferLocked(buffer, timestamp, /*output*/true);}status_t Camera3IOStreamBase::returnAnyBufferLocked(const camera3_stream_buffer &buffer,nsecs_t timestamp,bool output) { sp<Fence> releaseFence; res = returnBufferCheckedLocked(buffer, timestamp, output, &releaseFence);}status_t Camera3OutputStream::returnBufferCheckedLocked( const camera3_stream_buffer &buffer, nsecs_t timestamp, bool output, /*out*/ sp<Fence> *releaseFenceOut) { ..... res = currentConsumer->queueBuffer(currentConsumer.get(),//送帧图像给显示系统，然后会显示在屏幕上面 container_of(buffer.buffer, ANativeWindowBuffer, handle), anwReleaseFence);}更多相关文章
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