本文均属自己阅读源码的点滴总结，转账请注明出处谢谢。
欢迎和大家交流。qq:1037701636 email:gzzaigcn2009@163.com
Software：系统源码Android5.1
Camera3研读前沿：
当初在研读Camera1.0相关的内容时，主要围绕着CameraClient、CameraHardwareInterface等方面进行工作的开展，无论是数据流还是控制流看起来都很简单、明了，一系列的流程化操作使得整个框架学起来特别的容易。因为没有Camera2.0相关的基础，所以这次直接看3.0相关的源码时，显得十分的吃紧，再加上底层高通HAL3.0实现的过程也是相当的复杂，都给整个研读过程带来了很多的困难。可以说，自身目前对Camera3.0框架的熟悉度也大概只有70%左右，希望通过总结来进一步梳理他的工作原理与整个框架，并进一步熟悉与加深理解。
1.Camera3下的整体架构图。
整个CameraService建立起一个可用操作底层Camera device大致需要经过Camera2Client、Camera3Device以及HAL层的camera3_device_t三个部分。
从上图中可以发现Camera3架构看上去明显比camera1来的复杂，但他更加的模块化。对比起Android4.2.2 Camer系统架构图（HAL和回调处理）一文中描述的单顺序执行流程，Camera3将更多的工作集中在了Framework去完成，将更多的控制权掌握在自己的手里，从而与HAL的交互的数据信息更少，也进一步减轻了一些在旧版本中HAL层所需要做的事情。
2. Camera2Client的建立与初始化过程
在建立好Camera2Client后会进行initialize操作，完成各个处理模块的创建：
....
mStreamingProcessor = new StreamingProcessor(this);//preview和recorder
threadName = String8::format("C2-%d-StreamProc",
mCameraId);
mStreamingProcessor->run(threadName.string());//预览与录像
mFrameProcessor = new FrameProcessor(mDevice, this);// 3A
threadName = String8::format("C2-%d-FrameProc",
mCameraId);
mFrameProcessor->run(threadName.string()); //3A
mCaptureSequencer = new CaptureSequencer(this);
threadName = String8::format("C2-%d-CaptureSeq",
mCameraId);
mCaptureSequencer->run(threadName.string());//录像，拍照
mJpegProcessor = new JpegProcessor(this, mCaptureSequencer);
threadName = String8::format("C2-%d-JpegProc",
mCameraId);
mJpegProcessor->run(threadName.string());
....
mCallbackProcessor = new CallbackProcessor(this);//回调处理
threadName = String8::format("C2-%d-CallbkProc",
mCameraId);
mCallbackProcessor->run(threadName.string());
StreamingProcessor并启动一个他所属的thread，该模块主要负责处理previews与record两种视频流的处理，用于从hal层获取原始的视频数据
FrameProcessor并启动一个thread，该模块专门用于处理回调回来的每一帧的3A等信息，即每一帧视频除去原始视频数据外，还应该有其他附加的数据信息，如3A值。
CaptureSequencer并启动一个thread，该模块需要和其他模块配合使用，主要用于向APP层告知capture到的picture。
JpegProcessor并启动一个thread，该模块和streamprocessor类似，他启动一个拍照流，一般用于从HAL层获取jpeg编码后的图像照片数据。
此外ZslProcessor模块称之为0秒快拍，其本质是直接从原始的Preview流中获取预存着的最近的几帧，直接编码后返回给APP，而不需要再经过take picture去请求获取jpeg数据。0秒快拍技术得意于当下处理器CSI2 MIPI性能的提升以及Sensor支持全像素高帧率的实时输出。一般手机拍照在按下快门后都会有一定的延时，是因为需要切换底层Camera以及ISP等的工作模式，并重新设置参数以及重新对焦等等，都需要花一定时间后才抓取一帧用于编码为jpeg图像。
以上5个模块整合在一起基本上实现了Camera应用开发所需的基本业务功能。
3. 预览Preview下的控制流
研读Camera具体的业务处理功能，一般从视频实时预览Preview入手。一般熟悉Camera架构的人，可以从一个app端的一个api一直连续打通到底层hal的一个控制命令。大致可以如下图所示：
对于preview部分到CameraService的控制流可以参考博文Android4.2.2的preview的数据流和控制流以及最终的预览显示，本文将直接从Camera2Client::startPreview() 作为入口来分析整个Framework层中Preview相关的数据流。
status_t Camera2Client::startPreview() {
ATRACE_CALL();
ALOGV("%s: E", __FUNCTION__);
Mutex::Autolock icl(mBinderSerializationLock);
status_t res;
if ( (res = checkPid(__FUNCTION__) ) != OK) return res;
SharedParameters::Lock l(mParameters);
return startPreviewL(l.mParameters, false);
}status_t Camera2Client::startPreviewL(Parameters ¶ms, bool restart) {//restart == false
ATRACE_CALL();
status_t res;
......
int lastPreviewStreamId = mStreamingProcessor->getPreviewStreamId();//获取上一层Preview stream id
res = mStreamingProcessor->updatePreviewStream(params);//创建camera3device stream， Camera3OutputStream
.....
int lastJpegStreamId = mJpegProcessor->getStreamId();
res = updateProcessorStream(mJpegProcessor, params);//预览启动时就建立一个jpeg的outstream
.....
res = mCallbackProcessor->updateStream(params);//回调处理建立一个Camera3outputstream
if (res != OK) {
ALOGE("%s: Camera %d: Unable to update callback stream: %s (%d)",
__FUNCTION__, mCameraId, strerror(-res), res);
return res;
}
outputStreams.push(getCallbackStreamId());
......
outputStreams.push(getPreviewStreamId());//预览stream
......
if (!params.recordingHint) {
if (!restart) {
res = mStreamingProcessor->updatePreviewRequest(params);//request处理,更新了mPreviewrequest
if (res != OK) {
ALOGE("%s: Camera %d: Can't set up preview request: "
"%s (%d)", __FUNCTION__, mCameraId,
strerror(-res), res);
return res;
}
}
res = mStreamingProcessor->startStream(StreamingProcessor::PREVIEW,
outputStreams);//启动stream，传入outputStreams即stream 的id
} else {
if (!restart) {
res = mStreamingProcessor->updateRecordingRequest(params);
if (res != OK) {
ALOGE("%s: Camera %d: Can't set up preview request with "
"record hint: %s (%d)", __FUNCTION__, mCameraId,
strerror(-res), res);
return res;
}
}
res = mStreamingProcessor->startStream(StreamingProcessor::RECORD,
outputStreams);
}
......
}
(1). mStreamingProcessor->updatePreviewStream()
由预览与录像处理模块更新一个预览流，其实现过程如下：
status_t StreamingProcessor::updatePreviewStream(const Parameters ¶ms) {
ATRACE_CALL();
Mutex::Autolock m(mMutex);
status_t res;
sp<CameraDeviceBase> device = mDevice.promote();//Camera3Device
if (device == 0) {
ALOGE("%s: Camera %d: Device does not exist", __FUNCTION__, mId);
return INVALID_OPERATION;
}
if (mPreviewStreamId != NO_STREAM) {
// Check if stream parameters have to change
uint32_t currentWidth, currentHeight;
res = device->getStreamInfo(mPreviewStreamId,
¤tWidth, ¤tHeight, 0);
if (res != OK) {
ALOGE("%s: Camera %d: Error querying preview stream info: "
"%s (%d)", __FUNCTION__, mId, strerror(-res), res);
return res;
}
if (currentWidth != (uint32_t)params.previewWidth ||
currentHeight != (uint32_t)params.previewHeight) {
ALOGV("%s: Camera %d: Preview size switch: %d x %d -> %d x %d",
__FUNCTION__, mId, currentWidth, currentHeight,
params.previewWidth, params.previewHeight);
res = device->waitUntilDrained();
if (res != OK) {
ALOGE("%s: Camera %d: Error waiting for preview to drain: "
"%s (%d)", __FUNCTION__, mId, strerror(-res), res);
return res;
}
res = device->deleteStream(mPreviewStreamId);
if (res != OK) {
ALOGE("%s: Camera %d: Unable to delete old output stream "
"for preview: %s (%d)", __FUNCTION__, mId,
strerror(-res), res);
return res;
}
mPreviewStreamId = NO_STREAM;
}
}
if (mPreviewStreamId == NO_STREAM) {//首次create stream
res = device->createStream(mPreviewWindow,
params.previewWidth, params.previewHeight,
CAMERA2_HAL_PIXEL_FORMAT_OPAQUE, &mPreviewStreamId);//创建一个Camera3OutputStream
if (res != OK) {
ALOGE("%s: Camera %d: Unable to create preview stream: %s (%d)",
__FUNCTION__, mId, strerror(-res), res);
return res;
}
}
res = device->setStreamTransform(mPreviewStreamId,
params.previewTransform);
if (res != OK) {
ALOGE("%s: Camera %d: Unable to set preview stream transform: "
"%s (%d)", __FUNCTION__, mId, strerror(-res), res);
return res;
}
return OK;
}
注意：在Camera2Client中，Stream大行其道，5大模块的数据交互均以stream作为基础。
下面我们来重点关注Camera3Device的接口createStream，他是5个模块创建stream的基础：
status_t Camera3Device::createStream(sp<ANativeWindow> consumer,
uint32_t width, uint32_t height, int format, int *id) {
ATRACE_CALL();
Mutex::Autolock il(mInterfaceLock);
Mutex::Autolock l(mLock);
ALOGV("Camera %d: Creating new stream %d: %d x %d, format %d",
mId, mNextStreamId, width, height, format);
status_t res;
bool wasActive = false;
switch (mStatus) {
case STATUS_ERROR:
CLOGE("Device has encountered a serious error");
return INVALID_OPERATION;
case STATUS_UNINITIALIZED:
CLOGE("Device not initialized");
return INVALID_OPERATION;
case STATUS_UNCONFIGURED:
case STATUS_CONFIGURED:
// OK
break;
case STATUS_ACTIVE:
ALOGV("%s: Stopping activity to reconfigure streams", __FUNCTION__);
res = internalPauseAndWaitLocked();
if (res != OK) {
SET_ERR_L("Can't pause captures to reconfigure streams!");
return res;
}
wasActive = true;
break;
default:
SET_ERR_L("Unexpected status: %d", mStatus);
return INVALID_OPERATION;
}
assert(mStatus != STATUS_ACTIVE);
sp<Camera3OutputStream> newStream;
if (format == HAL_PIXEL_FORMAT_BLOB) {//图片
ssize_t jpegBufferSize = getJpegBufferSize(width, height);
if (jpegBufferSize <= 0) {
SET_ERR_L("Invalid jpeg buffer size %zd", jpegBufferSize);
return BAD_VALUE;
}
newStream = new Camera3OutputStream(mNextStreamId, consumer,
width, height, jpegBufferSize, format);//jpeg 缓存的大小
} else {
newStream = new Camera3OutputStream(mNextStreamId, consumer,
width, height, format);//Camera3OutputStream
}
newStream->setStatusTracker(mStatusTracker);
res = mOutputStreams.add(mNextStreamId, newStream);//一个streamid与Camera3OutputStream绑定
if (res < 0) {
SET_ERR_L("Can't add new stream to set: %s (%d)", strerror(-res), res);
return res;
}
*id = mNextStreamId++;//至少一个previewstream 一般还有CallbackStream
mNeedConfig = true;
// Continue captures if active at start
if (wasActive) {
ALOGV("%s: Restarting activity to reconfigure streams", __FUNCTION__);
res = configureStreamsLocked();
if (res != OK) {
CLOGE("Can't reconfigure device for new stream %d: %s (%d)",
mNextStreamId, strerror(-res), res);
return res;
}
internalResumeLocked();
}
ALOGV("Camera %d: Created new stream", mId);
return OK;
}每当创建一个OutPutStream后，相关的stream信息被push维护在一个mOutputStreams的KeyedVector<int, sp<camera3::Camera3OutputStreamInterface> >表中，分别是该stream在Camera3Device中创建时的ID以及Camera3OutputStream的sp值。同时对mNextStreamId记录下一个Stream的ID号。
上述过程完成StreamingProcessor模块中一个PreviewStream的创建，其中Camera3OutputStream创建时的ID值被返回记录作为mPreviewStreamId的值，此外每个Stream都会有一个对应的ANativeWindow，这里称之为Consumer。
（2）mCallbackProcessor->updateStream(params)
对比StreamingProcessor模块创建previewstream的过程，很容易定位到Callback模块是需要建立一个callback流，同样需要创建一个Camera3OutputStream来接收HAL返回的每一帧帧数据，是否需要callback可以通过callbackenable来控制。一般但预览阶段可能不需要回调每一帧的数据到APP，但涉及到相应的其他业务如视频处理时，就需要进行callback的enable。
status_t CallbackProcessor::updateStream(const Parameters ¶ms) {
ATRACE_CALL();
status_t res;
Mutex::Autolock l(mInputMutex);
sp<CameraDeviceBase> device = mDevice.promote();
if (device == 0) {
ALOGE("%s: Camera %d: Device does not exist", __FUNCTION__, mId);
return INVALID_OPERATION;
}
// If possible, use the flexible YUV format
int32_t callbackFormat = params.previewFormat;
if (mCallbackToApp) {
// TODO: etalvala: This should use the flexible YUV format as well, but
// need to reconcile HAL2/HAL3 requirements.
callbackFormat = HAL_PIXEL_FORMAT_YV12;
} else if(params.fastInfo.useFlexibleYuv &&
(params.previewFormat == HAL_PIXEL_FORMAT_YCrCb_420_SP ||
params.previewFormat == HAL_PIXEL_FORMAT_YV12) ) {
callbackFormat = HAL_PIXEL_FORMAT_YCbCr_420_888;
}
if (!mCallbackToApp && mCallbackConsumer == 0) {
// Create CPU buffer queue endpoint, since app hasn't given us one
// Make it async to avoid disconnect deadlocks
sp<IGraphicBufferProducer> producer;
sp<IGraphicBufferConsumer> consumer;
BufferQueue::createBufferQueue(&producer, &consumer);//BufferQueueProducer与BufferQueueConsumer
mCallbackConsumer = new CpuConsumer(consumer, kCallbackHeapCount);
mCallbackConsumer->setFrameAvailableListener(this);//当前CallbackProcessor继承于CpuConsumer::FrameAvailableListener
mCallbackConsumer->setName(String8("Camera2Client::CallbackConsumer"));
mCallbackWindow = new Surface(producer);//用于queue操作，这里直接进行本地的buffer操作
}
if (mCallbackStreamId != NO_STREAM) {
// Check if stream parameters have to change
uint32_t currentWidth, currentHeight, currentFormat;
res = device->getStreamInfo(mCallbackStreamId,
¤tWidth, ¤tHeight, ¤tFormat);
if (res != OK) {
ALOGE("%s: Camera %d: Error querying callback output stream info: "
"%s (%d)", __FUNCTION__, mId,
strerror(-res), res);
return res;
}
if (currentWidth != (uint32_t)params.previewWidth ||
currentHeight != (uint32_t)params.previewHeight ||
currentFormat != (uint32_t)callbackFormat) {
// Since size should only change while preview is not running,
// assuming that all existing use of old callback stream is
// completed.
ALOGV("%s: Camera %d: Deleting stream %d since the buffer "
"parameters changed", __FUNCTION__, mId, mCallbackStreamId);
res = device->deleteStream(mCallbackStreamId);
if (res != OK) {
ALOGE("%s: Camera %d: Unable to delete old output stream "
"for callbacks: %s (%d)", __FUNCTION__,
mId, strerror(-res), res);
return res;
}
mCallbackStreamId = NO_STREAM;
}
}
if (mCallbackStreamId == NO_STREAM) {
ALOGV("Creating callback stream: %d x %d, format 0x%x, API format 0x%x",
params.previewWidth, params.previewHeight,
callbackFormat, params.previewFormat);
res = device->createStream(mCallbackWindow,
params.previewWidth, params.previewHeight,
callbackFormat, &mCallbackStreamId);//Creating callback stream
if (res != OK) {
ALOGE("%s: Camera %d: Can't create output stream for callbacks: "
"%s (%d)", __FUNCTION__, mId,
strerror(-res), res);
return res;
}
}
return OK;
}通过这个对比，也需要重点关注到，对于每个Camera3OutPutStream来说，每一个stream都被一个Consumer，而在此处都是Surface(ANativeWindow)所拥有，这个Consumer和HAL相匹配来说是消费者，但对于真正的处理Buffer的Consumer来说如CPUConsumer，Surface却又是以一个Product的角色存在的。
（3）updateProcessorStream(mJpegProcessor, params)
status_t Camera2Client::updateProcessorStream(sp<ProcessorT> processor,
camera2::Parameters params) {
// No default template arguments until C++11, so we need this overload
return updateProcessorStream<ProcessorT, &ProcessorT::updateStream>(
processor, params);
}
template <typename ProcessorT,
status_t (ProcessorT::*updateStreamF)(const Parameters &)>
status_t Camera2Client::updateProcessorStream(sp<ProcessorT> processor,
Parameters params) {
status_t res;
// Get raw pointer since sp<T> doesn't have operator->*
ProcessorT *processorPtr = processor.get();
res = (processorPtr->*updateStreamF)(params);
.......
}此外需要说明一点：
在preview模式下，就去创建一个jpeg处理的stream，目的在于启动takepicture时，可以更快的进行capture操作。是通过牺牲内存空间来提升效率。
（4）整合startPreviewL中所有的stream 到Vector<int32_t> outputStreams
outputStreams.push(getPreviewStreamId());//预览stream
outputStreams.push(getCallbackStreamId())//Callback stream
目前一次Preview构建的stream数目至少为两个。
（5）mStreamingProcessor->updatePreviewRequest()
在创建好多路stream后，由StreamingProcessor模块来将所有的stream信息交由Camera3Device去打包成Request请求。
注意：
Camera HAL2/3的特点是：将所有stream的请求都转化为几个典型的Request请求，而这些Request需要由HAL去解析，进而处理所需的业务。这也是Camera3数据处理复杂化的原因所在。
status_t StreamingProcessor::updatePreviewRequest(const Parameters ¶ms) {
ATRACE_CALL();
status_t res;
sp<CameraDeviceBase> device = mDevice.promote();
if (device == 0) {
ALOGE("%s: Camera %d: Device does not exist", __FUNCTION__, mId);
return INVALID_OPERATION;
}
Mutex::Autolock m(mMutex);
if (mPreviewRequest.entryCount() == 0) {
sp<Camera2Client> client = mClient.promote();
if (client == 0) {
ALOGE("%s: Camera %d: Client does not exist", __FUNCTION__, mId);
return INVALID_OPERATION;
}
// Use CAMERA3_TEMPLATE_ZERO_SHUTTER_LAG for ZSL streaming case.
if (client->getCameraDeviceVersion() >= CAMERA_DEVICE_API_VERSION_3_0) {
if (params.zslMode && !params.recordingHint) {
res = device->createDefaultRequest(CAMERA3_TEMPLATE_ZERO_SHUTTER_LAG,
&mPreviewRequest);
} else {
res = device->createDefaultRequest(CAMERA3_TEMPLATE_PREVIEW,
&mPreviewRequest);
}
} else {
res = device->createDefaultRequest(CAMERA2_TEMPLATE_PREVIEW,
&mPreviewRequest);//创建一个Preview相关的request，由底层的hal来完成default创建
}
if (res != OK) {
ALOGE("%s: Camera %d: Unable to create default preview request: "
"%s (%d)", __FUNCTION__, mId, strerror(-res), res);
return res;
}
}
res = params.updateRequest(&mPreviewRequest);//根据参数来更新CameraMetadata request
if (res != OK) {
ALOGE("%s: Camera %d: Unable to update common entries of preview "
"request: %s (%d)", __FUNCTION__, mId,
strerror(-res), res);
return res;
}
res = mPreviewRequest.update(ANDROID_REQUEST_ID,
&mPreviewRequestId, 1);//mPreviewRequest的ANDROID_REQUEST_ID
if (res != OK) {
ALOGE("%s: Camera %d: Unable to update request id for preview: %s (%d)",
__FUNCTION__, mId, strerror(-res), res);
return res;
}
return OK;
}
a mPreviewRequest是一个CameraMetadata类型数据，用于封装当前previewRequest。
b device->createDefaultRequest(CAMERA3_TEMPLATE_PREVIEW, &mPreviewRequest)
const camera_metadata_t *rawRequest;
ATRACE_BEGIN("camera3->construct_default_request_settings");
rawRequest = mHal3Device->ops->construct_default_request_settings(
mHal3Device, templateId);
ATRACE_END();
if (rawRequest == NULL) {
SET_ERR_L("HAL is unable to construct default settings for template %d",
templateId);
return DEAD_OBJECT;
}
*request = rawRequest;
mRequestTemplateCache[templateId] = rawRequest;
struct camera_metadata {
metadata_size_t size;
uint32_t version;
uint32_t flags;
metadata_size_t entry_count;
metadata_size_t entry_capacity;
metadata_uptrdiff_t entries_start; // Offset from camera_metadata
metadata_size_t data_count;
metadata_size_t data_capacity;
metadata_uptrdiff_t data_start; // Offset from camera_metadata
uint8_t reserved[];
};c mPreviewRequest.update(ANDROID_REQUEST_ID,&mPreviewRequestId, 1)
将当前的PreviewRequest相应的ID保存到camera metadata。
（6）mStreamingProcessor->startStream启动整个预览的stream流
该函数的处理过程较为复杂，可以说是整个Preview正常工作的核心控制
status_t StreamingProcessor::startStream(StreamType type,
const Vector<int32_t> &outputStreams) {
.....
CameraMetadata &request = (type == PREVIEW) ?
mPreviewRequest : mRecordingRequest;//取preview的CameraMetadata request
....res = request.update(
ANDROID_REQUEST_OUTPUT_STREAMS,
outputStreams);//CameraMetadata中添加outputStreams
res = device->setStreamingRequest(request);//向hal发送request
.....
}该函数首先是根据当前工作模式来确定StreamingProcessor需要处理的Request，该模块负责Preview和Record两个Request。
以PreviewRequest就是之前createDefaultRequest构建的，这里先是将这个Request所需要操作的Outputstream打包到一个tag叫ANDROID_REQUEST_OUTPUT_STREAMS的entry当中。
a:setStreamingRequest
真正的请求Camera3Device去处理这个带有多路stream的PreviewRequest。
status_t Camera3Device::setStreamingRequest(const CameraMetadata &request,
int64_t* /*lastFrameNumber*/) {
ATRACE_CALL();
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) {
ATRACE_CALL();
return submitRequestsHelper(requests, /*repeating*/true, lastFrameNumber);
}
status_t Camera3Device::submitRequestsHelper(
const List<const CameraMetadata> &requests, bool repeating,
/*out*/
int64_t *lastFrameNumber) {//repeating = 1;lastFrameNumber = NULL
ATRACE_CALL();
Mutex::Autolock il(mInterfaceLock);
Mutex::Autolock l(mLock);
status_t res = checkStatusOkToCaptureLocked();
if (res != OK) {
// error logged by previous call
return res;
}
RequestList requestList;
res = convertMetadataListToRequestListLocked(requests, /*out*/&requestList);//返回的是CaptureRequest RequestList
if (res != OK) {
// error logged by previous call
return res;
}
if (repeating) {
res = mRequestThread->setRepeatingRequests(requestList, lastFrameNumber);//重复的request存入到RequestThread
} else {
res = mRequestThread->queueRequestList(requestList, lastFrameNumber);//capture模式，拍照单词
}
if (res == OK) {
waitUntilStateThenRelock(/*active*/true, kActiveTimeout);
if (res != OK) {
SET_ERR_L("Can't transition to active in %f seconds!",
kActiveTimeout/1e9);
}
ALOGV("Camera %d: Capture request %" PRId32 " enqueued", mId,
(*(requestList.begin()))->mResultExtras.requestId);
} else {
CLOGE("Cannot queue request. Impossible.");
return BAD_VALUE;
}
return res;
}
这个函数是需要将Requestlist中保存的CameraMetadata数据转换为List<sp<CaptureRequest> >
status_t Camera3Device::convertMetadataListToRequestListLocked(
const List<const CameraMetadata> &metadataList, RequestList *requestList) {
if (requestList == NULL) {
CLOGE("requestList cannot be NULL.");
return BAD_VALUE;
}
int32_t burstId = 0;
for (List<const CameraMetadata>::const_iterator it = metadataList.begin();//CameraMetadata, mPreviewRequest
it != metadataList.end(); ++it) {
sp<CaptureRequest> newRequest = setUpRequestLocked(*it);//新建CaptureRequest由CameraMetadata转化而来
if (newRequest == 0) {
CLOGE("Can't create capture request");
return BAD_VALUE;
}
// Setup burst Id and request Id
newRequest->mResultExtras.burstId = burstId++;
if (it->exists(ANDROID_REQUEST_ID)) {
if (it->find(ANDROID_REQUEST_ID).count == 0) {
CLOGE("RequestID entry exists; but must not be empty in metadata");
return BAD_VALUE;
}
newRequest->mResultExtras.requestId = it->find(ANDROID_REQUEST_ID).data.i32[0];//设置该request对应的id
} else {
CLOGE("RequestID does not exist in metadata");
return BAD_VALUE;
}
requestList->push_back(newRequest);
ALOGV("%s: requestId = %" PRId32, __FUNCTION__, newRequest->mResultExtras.requestId);
}
return OK;
}
c 重点来关注setUpRequestLocked复杂的处理过程
sp<Camera3Device::CaptureRequest> Camera3Device::setUpRequestLocked(
const CameraMetadata &request) {//mPreviewRequest
status_t res;
if (mStatus == STATUS_UNCONFIGURED || mNeedConfig) {
res = configureStreamsLocked();
......
sp<CaptureRequest> newRequest = createCaptureRequest(request);//CameraMetadata转为CaptureRequest，包含mOutputStreams
return newRequest;
}configureStreamsLocked函数主要是将Camera3Device侧建立的所有Stream包括Output与InPut格式的交由HAL3层的Device去实现处理的核心接口是configure_streams与register_stream_buffer。该部分内容会涉及到更多的数据流，详细的处理过程会放在下一博文中进行分析。
createCaptureRequest函数是将一个CameraMetadata格式的数据如PreviewRequest转换为一个CaptureRequest：
sp<Camera3Device::CaptureRequest> Camera3Device::createCaptureRequest(
const CameraMetadata &request) {//mPreviewRequest
ATRACE_CALL();
status_t res;
sp<CaptureRequest> newRequest = new CaptureRequest;
newRequest->mSettings = request;//CameraMetadata
camera_metadata_entry_t inputStreams =
newRequest->mSettings.find(ANDROID_REQUEST_INPUT_STREAMS);
if (inputStreams.count > 0) {
if (mInputStream == NULL ||
mInputStream->getId() != inputStreams.data.i32[0]) {
CLOGE("Request references unknown input stream %d",
inputStreams.data.u8[0]);
return NULL;
}
// Lazy completion of stream configuration (allocation/registration)
// on first use
if (mInputStream->isConfiguring()) {
res = mInputStream->finishConfiguration(mHal3Device);
if (res != OK) {
SET_ERR_L("Unable to finish configuring input stream %d:"
" %s (%d)",
mInputStream->getId(), strerror(-res), res);
return NULL;
}
}
newRequest->mInputStream = mInputStream;
newRequest->mSettings.erase(ANDROID_REQUEST_INPUT_STREAMS);
}
camera_metadata_entry_t streams =
newRequest->mSettings.find(ANDROID_REQUEST_OUTPUT_STREAMS);//读取存储在CameraMetadata的stream id信息
if (streams.count == 0) {
CLOGE("Zero output streams specified!");
return NULL;
}
for (size_t i = 0; i < streams.count; i++) {
int idx = mOutputStreams.indexOfKey(streams.data.i32[i]);//Camera3OutputStream的id在mOutputStreams中
if (idx == NAME_NOT_FOUND) {
CLOGE("Request references unknown stream %d",
streams.data.u8[i]);
return NULL;
}
sp<Camera3OutputStreamInterface> stream =
mOutputStreams.editValueAt(idx);//返回的是Camera3OutputStream，preview/callback等stream
// Lazy completion of stream configuration (allocation/registration)
// on first use
if (stream->isConfiguring()) {//STATE_IN_CONFIG或者STATE_IN_RECONFIG
res = stream->finishConfiguration(mHal3Device);//register_stream_buffer， STATE_CONFIGURED
if (res != OK) {
SET_ERR_L("Unable to finish configuring stream %d: %s (%d)",
stream->getId(), strerror(-res), res);
return NULL;
}
}
newRequest->mOutputStreams.push(stream);//Camera3OutputStream添加到CaptureRequest的mOutputStreams
}
newRequest->mSettings.erase(ANDROID_REQUEST_OUTPUT_STREAMS);
return newRequest;
}在构建这个PreviewRequest时，已经将ANDROID_REQUEST_OUTPUT_STREAMS这个Tag进行了初始化，相应的内容为Vector<int32_t> &outputStreams，包含着属于PreviewRequest这个Request所需要的输出stream的ID值，通过这个ID index值，可以遍历到Camera3Device下所createstream创造的Camera3OutputStream，即说明不同类型的Request在Camera3Device端存在多个Stream，而每次不同业务下所需要Request的对应的Stream又仅是其中的个别而已。
idx = mOutputStreams.indexOfKey(streams.data.i32[i])是通过属于PreviewRequest中包含的一个stream的ID值来查找到mOutputStreams这个KeyedVector中对应的标定值index。注意：两个索引值不一定是一致的。
mOutputStreams.editValueAt(idx)是获取一个与该ID值(如Previewstream ID、Callback Stream ID等等)相对应的Camera3OutputStream。
在找到了当前Request中所有的Camera3OutputStream后，将其维护在CaptureRequest中
class CaptureRequest : public LightRefBase<CaptureRequest> {
public:
CameraMetadata mSettings;
sp<camera3::Camera3Stream> mInputStream;
Vector<sp<camera3::Camera3OutputStreamInterface> >
mOutputStreams;
CaptureResultExtras mResultExtras;
};返回到convertMetadataListToRequestListLocked中，现在已经完成了一个CameraMetadata Request的处理，生产的是一个CaptureRequest。我们将这个ANDROID_REQUEST_ID的ID值，保留在
newRequest->mResultExtras.requestId = it->find(ANDROID_REQUEST_ID).data.i32[0]。
这个值在整个Camera3的架构中，仅存在3大种Request类型，说明了整个和HAL层交互的Request类型是不多的：
预览Request mPreviewRequest： mPreviewRequestId(Camera2Client::kPreviewRequestIdStart),
拍照Request mCaptureRequest：mCaptureId(Camera2Client::kCaptureRequestIdStart),
录像Request mRecordingRequest： mRecordingRequestId(Camera2Client::kRecordingRequestIdStart),
static const int32_t kPreviewRequestIdStart = 10000000;
static const int32_t kPreviewRequestIdEnd = 20000000;
static const int32_t kRecordingRequestIdStart = 20000000;
static const int32_t kRecordingRequestIdEnd = 30000000;
static const int32_t kCaptureRequestIdStart = 30000000;
static const int32_t kCaptureRequestIdEnd = 40000000;d mRequestThread->setRepeatingRequests(requestList)
对于Preview来说，一次Preview后底层硬件就该可以连续的工作，而不需要进行过多的切换，故Framework每次向HAL发送的Request均是一种repeat的操作模式，故调用了一个重复的RequestQueue来循环处理每次的Request。
status_t Camera3Device::RequestThread::setRepeatingRequests(
const RequestList &requests,
/*out*/
int64_t *lastFrameNumber) {
Mutex::Autolock l(mRequestLock);
if (lastFrameNumber != NULL) {//第一次进来为null
*lastFrameNumber = mRepeatingLastFrameNumber;
}
mRepeatingRequests.clear();
mRepeatingRequests.insert(mRepeatingRequests.begin(),
requests.begin(), requests.end());
unpauseForNewRequests();//signal request_thread in waitfornextrequest
mRepeatingLastFrameNumber = NO_IN_FLIGHT_REPEATING_FRAMES;
return OK;
}
(7) RequestThread 请求处理线程
RequestThread::threadLoop()函数主要用于响应并处理新加入到Request队列中的请求。
bool Camera3Device::RequestThread::threadLoop() {
....
sp<CaptureRequest> nextRequest = waitForNextRequest();//返回的是mRepeatingRequests，mPreviewRequest
if (nextRequest == NULL) {
return true;
}
// Create request to HAL
camera3_capture_request_t request = camera3_capture_request_t();//CaptureRequest转为给HAL3.0的camera3_capture_request_t
request.frame_number = nextRequest->mResultExtras.frameNumber;//当前帧号
Vector<camera3_stream_buffer_t> outputBuffers;
// Get the request ID, if any
int requestId;
camera_metadata_entry_t requestIdEntry =
nextRequest->mSettings.find(ANDROID_REQUEST_ID);
if (requestIdEntry.count > 0) {
requestId = requestIdEntry.data.i32[0];//获取requestid,这里是mPreviewRequest的id
} else {
ALOGW("%s: Did not have android.request.id set in the request",
__FUNCTION__);
requestId = NAME_NOT_FOUND;
}
.....
camera3_stream_buffer_t inputBuffer;
uint32_t totalNumBuffers = 0;
.....
// Submit request and block until ready for next one
ATRACE_ASYNC_BEGIN("frame capture", request.frame_number);
ATRACE_BEGIN("camera3->process_capture_request");
res = mHal3Device->ops->process_capture_request(mHal3Device, &request);//调用底层的process_capture_request
ATRACE_END();
.......
}(7.1) waitForNextRequest()
Camera3Device::RequestThread::waitForNextRequest() {
status_t res;
sp<CaptureRequest> nextRequest;
// Optimized a bit for the simple steady-state case (single repeating
// request), to avoid putting that request in the queue temporarily.
Mutex::Autolock l(mRequestLock);
while (mRequestQueue.empty()) {
if (!mRepeatingRequests.empty()) {
// Always atomically enqueue all requests in a repeating request
// list. Guarantees a complete in-sequence set of captures to
// application.
const RequestList &requests = mRepeatingRequests;
RequestList::const_iterator firstRequest =
requests.begin();
nextRequest = *firstRequest;//取
mRequestQueue.insert(mRequestQueue.end(),
++firstRequest,
requests.end());//把当前的mRepeatingRequests插入到mRequestQueue
// No need to wait any longer
mRepeatingLastFrameNumber = mFrameNumber + requests.size() - 1;
break;
}
res = mRequestSignal.waitRelative(mRequestLock, kRequestTimeout);//等待下一个request
if ((mRequestQueue.empty() && mRepeatingRequests.empty()) ||
exitPending()) {
Mutex::Autolock pl(mPauseLock);
if (mPaused == false) {
ALOGV("%s: RequestThread: Going idle", __FUNCTION__);
mPaused = true;
// Let the tracker know
sp<StatusTracker> statusTracker = mStatusTracker.promote();
if (statusTracker != 0) {
statusTracker->markComponentIdle(mStatusId, Fence::NO_FENCE);
}
}
// Stop waiting for now and let thread management happen
return NULL;
}
}
if (nextRequest == NULL) {
// Don't have a repeating request already in hand, so queue
// must have an entry now.
RequestList::iterator firstRequest =
mRequestQueue.begin();
nextRequest = *firstRequest;
mRequestQueue.erase(firstRequest);//取一根mRequestQueue中的CaptureRequest，来自于mRepeatingRequests的next
}
// In case we've been unpaused by setPaused clearing mDoPause, need to
// update internal pause state (capture/setRepeatingRequest unpause
// directly).
Mutex::Autolock pl(mPauseLock);
if (mPaused) {
ALOGV("%s: RequestThread: Unpaused", __FUNCTION__);
sp<StatusTracker> statusTracker = mStatusTracker.promote();
if (statusTracker != 0) {
statusTracker->markComponentActive(mStatusId);
}
}
mPaused = false;
// Check if we've reconfigured since last time, and reset the preview
// request if so. Can't use 'NULL request == repeat' across configure calls.
if (mReconfigured) {
mPrevRequest.clear();
mReconfigured = false;
}
if (nextRequest != NULL) {
nextRequest->mResultExtras.frameNumber = mFrameNumber++;//对每一个非空的request需要帧号++
nextRequest->mResultExtras.afTriggerId = mCurrentAfTriggerId;
nextRequest->mResultExtras.precaptureTriggerId = mCurrentPreCaptureTriggerId;
}
return nextRequest;
}通过nextRequest->mResultExtras.frameNumber = mFrameNumber++表示当前CaptureRequest在处理的一帧图像号。
对于mRepeatingRequests而言，只有其非空，在执行完一次queue操作后，在循环进入执行时，会自动对mRequestQueue进行erase操作，是的mRequestQueue变为empty后再次重新加载mRepeatingRequests中的内容，从而形成一个队repeatRequest的重复响应过程。
(7.2) camera_metadata_entry_t requestIdEntry = nextRequest->mSettings.find(ANDROID_REQUEST_ID);提取该CaptureRequest对应的Request 类型值
(7.3) getBuffer操作
涉及到比较复杂的数据流操作过程的内容见下一博文
(7.4) mHal3Device->ops->process_capture_request(mHal3Device, &request)
这里的request是已经由一个CaptureRequest转换为和HAL3.0交互的camera3_capture_request_t结构。
8 小结
至此已经完成了一次向HAL3.0 Device发送一次完整的Request的请求。从最初Preview启动建立多个OutPutStream，再是将这些Stream打包成一个mPreviewRequest来启动stream，随后将这个Request又转变为一个CaptureRequest，直到转为Capture list后交由RequestThread来处理这些请求。每一次的Request简单可以说是Camera3Device向HAL3.0请求一帧数据，当然每一次Request也可以包含各种控制操作，如AutoFocus等内容，会在后续补充。
到这里从StartPreview的入口开始，直到相应的Request下发到HAL3.0，基本描述了一次完成的控制流的处理。对于较为复杂的数据流本质也是一并合并在这个控制操作中的，但作为Buffer视频缓存流的管理维护将在下一博文进行描述与总结。
