Android Camera HAL3中預覽preview模式下的控制流
本文均屬自己閱讀原始碼的點滴總結，轉賬請註明出處謝謝。
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Software：系統原始碼Android5.1
Camera3研讀前沿：
當初在研讀Camera1.0相關的內容時，主要圍繞著CameraClient、CameraHardwareInterface等方面進行工作的開展，無論是資料流還是控制流看起來都很簡單、明瞭，一系列的流程化操作使得整個框架學起來特別的容易。因為沒有Camera2.0相關的基礎，所以這次直接看3.0相關的原始碼時，顯得十分的吃緊，再加上底層高通HAL3.0實現的過程也是相當的複雜，都給整個研讀過程帶來了很多的困難。可以說，自身目前對Camera3.0框架的熟悉度也大概只有70%左右，希望通過總結來進一步梳理他的工作原理與整個框架，並進一步熟悉與加深理解
1.Camera3下的整體架構圖。
整個CameraService建立起一個可用操作底層Camera device大致需要經過Camera2Client、Camera3Device以及HAL層的camera3_device_t三個部分。
從上圖中可以發現Camera3架構看上去明顯比camera1來的複雜，但他更加的模組化。對比起Android4.2.2 Camer系統架構圖（HAL和回撥處理）一文中描述的單順序執行流程，Camera3將更多的工作集中在了Framework去完成，將更多的控制權掌握在自己的手裡，從而與HAL的互動的資料資訊更少，也進一步減輕了一些在舊版本中HAL層所需要做的事情。
2. Camera2Client的建立與初始化過程
在建立好Camera2Client後會進行initialize操作，完成各個處理模組的建立：
依次分別建立了：.... mStreamingProcessor = new StreamingProcessor(this);//preview和recorder threadName = String8::format("C2-%d-StreamProc", mCameraId); mStreamingProcessor->run(threadName.string());//預覽與錄影 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());//錄影，拍照 mJpegProcessor = new JpegProcessor(this, mCaptureSequencer); threadName = String8::format("C2-%d-JpegProc", mCameraId); mJpegProcessor->run(threadName.string()); .... mCallbackProcessor = new CallbackProcessor(this);//回撥處理 threadName = String8::format("C2-%d-CallbkProc", mCameraId); mCallbackProcessor->run(threadName.string());
StreamingProcessor並啟動一個他所屬的thread，該模組主要負責處理previews與record兩種視訊流的處理，用於從hal層獲取原始的視訊資料
FrameProcessor並啟動一個thread，該模組專門用於處理回調回來的每一幀的3A等資訊，即每一幀視訊除去原始視訊資料外，還應該有其他附加的資料資訊，如3A值。
CaptureSequencer並啟動一個thread，該模組需要和其他模組配合使用，主要用於向APP層告知capture到的picture。
JpegProcessor並啟動一個thread，該模組和streamprocessor類似，他啟動一個拍照流，一般用於從HAL層獲取jpeg編碼後的影象照片資料。
此外ZslProcessor模組稱之為0秒快拍，其本質是直接從原始的Preview流中獲取預存著的最近的幾幀，直接編碼後返回給APP，而不需要再經過take picture去請求獲取jpeg資料。0秒快拍技術得意於當下處理器CSI2 MIPI效能的提升以及Sensor支援全畫素高幀率的實時輸出。一般手機拍照在按下快門後都會有一定的延時，是因為需要切換底層Camera以及ISP等的工作模式，並重新設定引數以及重新對焦等等，都需要花一定時間後才抓取一幀用於編碼為jpeg影象。
以上5個模組整合在一起基本上實現了Camera應用開發所需的基本業務功能。
3. 預覽Preview下的控制流
研讀Camera具體的業務處理功能，一般從視訊實時預覽Preview入手。一般熟悉Camera架構的人，可以從一個app端的一個api一直連續打通到底層hal的一個控制命令。大致可以如下圖所示：
對於preview部分到CameraService的控制流可以參考博文Android4.2.2的preview的資料流和控制流以及最終的預覽顯示，本文將直接從Camera2Client::startPreview() 作為入口來分析整個Framework層中Preview相關的資料流。
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();//獲取上一層Preview stream id
res = mStreamingProcessor->updatePreviewStream(params);//建立camera3device stream， Camera3OutputStream
.....
int lastJpegStreamId = mJpegProcessor->getStreamId();
res = updateProcessorStream(mJpegProcessor, params);//預覽啟動時就建立一個jpeg的outstream
.....
res = mCallbackProcessor->updateStream(params);//回撥處理建立一個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());//預覽stream
......
if (!params.recordingHint) {
if (!restart) {
res = mStreamingProcessor->updatePreviewRequest(params);//request處理,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);//啟動stream，傳入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()
由預覽與錄影處理模組更新一個預覽流，其實現過程如下：
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);//建立一個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大模組的資料互動均以stream作為基礎。
下面我們來重點關注Camera3Device的介面createStream，他是5個模組建立stream的基礎：
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) {//圖片
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 快取的大小
} else {
newStream = new Camera3OutputStream(mNextStreamId, consumer,
width, height, format);//Camera3OutputStream
}
newStream->setStatusTracker(mStatusTracker);
res = mOutputStreams.add(mNextStreamId, newStream);//一個streamid與Camera3OutputStream繫結
if (res < 0) {
SET_ERR_L("Can't add new stream to set: %s (%d)", strerror(-res), res);
return res;
}
*id = mNextStreamId++;//至少一個previewstream 一般還有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;
}兩種stream，前者主要作為HAL的輸出，是請求HAL填充資料的OutPutStream，後者是由Framework將Stream進行填充。無論是Preview、record還是capture均是從HAL層獲取資料，故都會以OutPutStream的形式存在，是我們關注的重點，後面在描述Preview的資料流時還會進一步的闡述。
每當建立一個OutPutStream後，相關的stream資訊被push維護在一個mOutputStreams的KeyedVector<int, sp<camera3::Camera3OutputStreamInterface> >表中，分別是該stream在Camera3Device中建立時的ID以及Camera3OutputStream的sp值。同時對mNextStreamId記錄下一個Stream的ID號。
上述過程完成StreamingProcessor模組中一個PreviewStream的建立，其中Camera3OutputStream建立時的ID值被返回記錄作為mPreviewStreamId的值，此外每個Stream都會有一個對應的ANativeWindow，這裡稱之為Consumer。
（2）mCallbackProcessor->updateStream(params)
對比StreamingProcessor模組建立previewstream的過程，很容易定位到Callback模組是需要建立一個callback流，同樣需要建立一個Camera3OutputStream來接收HAL返回的每一幀幀資料，是否需要callback可以通過callbackenable來控制。一般但預覽階段可能不需要回調每一幀的資料到APP，但涉及到相應的其他業務如視訊處理時，就需要進行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與BufferQueueConsumer
mCallbackConsumer = new CpuConsumer(consumer, kCallbackHeapCount);
mCallbackConsumer->setFrameAvailableListener(this);//當前CallbackProcessor繼承於CpuConsumer::FrameAvailableListener
mCallbackConsumer->setName(String8("Camera2Client::CallbackConsumer"));
mCallbackWindow = new Surface(producer);//用於queue操作，這裡直接進行本地的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;
}通過這個對比，也需要重點關注到，對於每個Camera3OutPutStream來說，每一個stream都被一個Consumer，而在此處都是Surface(ANativeWindow)所擁有，這個Consumer和HAL相匹配來說是消費者，但對於真正的處理Buffer的Consumer來說如CPUConsumer，Surface卻又是以一個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);
.......
}此外需要說明一點：
在preview模式下，就去建立一個jpeg處理的stream，目的在於啟動takepicture時，可以更快的進行capture操作。是通過犧牲記憶體空間來提升效率。
（4）整合startPreviewL中所有的stream 到Vector<int32_t> outputStreams
outputStreams.push(getPreviewStreamId());//預覽stream
outputStreams.push(getCallbackStreamId())//Callback stream
目前一次Preview構建的stream數目至少為兩個。
（5）mStreamingProcessor->updatePreviewRequest()
在建立好多路stream後，由StreamingProcessor模組來將所有的stream資訊交由Camera3Device去打包成Request請求。
注意：
Camera HAL2/3的特點是：將所有stream的請求都轉化為幾個典型的Request請求，而這些Request需要由HAL去解析，進而處理所需的業務。這也是Camera3資料處理複雜化的原因所在。
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);//建立一個Preview相關的request，由底層的hal來完成default建立
}
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);//根據引數來更新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是一個CameraMetadata型別資料，用於封裝當前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)
將當前的PreviewRequest相應的ID儲存到camera metadata。
（6）mStreamingProcessor->startStream啟動整個預覽的stream流
該函式的處理過程較為複雜，可以說是整個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中新增outputStreams
res = device->setStreamingRequest(request);//向hal傳送request
.....
}該函式首先是根據當前工作模式來確定StreamingProcessor需要處理的Request，該模組負責Preview和Record兩個Request。
以PreviewRequest就是之前createDefaultRequest構建的，這裡先是將這個Request所需要操作的Outputstream打包到一個tag叫ANDROID_REQUEST_OUTPUT_STREAMS的entry當中。
a:setStreamingRequest
真正的請求Camera3Device去處理這個帶有多路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);//重複的request存入到RequestThread
} else {
res = mRequestThread->queueRequestList(requestList, lastFrameNumber);//capture模式，拍照單詞
}
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;
}
這個函式是需要將Requestlist中儲存的CameraMetadata資料轉換為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轉化而來
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];//設定該request對應的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 重點來關注setUpRequestLocked複雜的處理過程
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轉為CaptureRequest，包含mOutputStreams
return newRequest;
}configureStreamsLocked函式主要是將Camera3Device側建立的所有Stream包括Output與InPut格式的交由HAL3層的Device去實現處理的核心介面是configure_streams與register_stream_buffer。該部分內容會涉及到更多的資料流，詳細的處理過程會放在下一博文中進行分析。
createCaptureRequest函式是將一個CameraMetadata格式的資料如PreviewRequest轉換為一個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);//讀取儲存在CameraMetadata的stream id資訊
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新增到CaptureRequest的mOutputStreams
}
newRequest->mSettings.erase(ANDROID_REQUEST_OUTPUT_STREAMS);
return newRequest;
}在構建這個PreviewRequest時，已經將ANDROID_REQUEST_OUTPUT_STREAMS這個Tag進行了初始化，相應的內容為Vector<int32_t> &outputStreams，包含著屬於PreviewRequest這個Request所需要的輸出stream的ID值，通過這個ID index值，可以遍歷到Camera3Device下所createstream創造的Camera3OutputStream，即說明不同型別的Request在Camera3Device端存在多個Stream，而每次不同業務下所需要Request的對應的Stream又僅是其中的個別而已。
idx = mOutputStreams.indexOfKey(streams.data.i32[i])是通過屬於PreviewRequest中包含的一個stream的ID值來查詢到mOutputStreams這個KeyedVector中對應的標定值index。注意：兩個索引值不一定是一致的。
mOutputStreams.editValueAt(idx)是獲取一個與該ID值(如Previewstream ID、Callback Stream ID等等)相對應的Camera3OutputStream。
在找到了當前Request中所有的Camera3OutputStream後，將其維護在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，現在已經完成了一個CameraMetadata Request的處理，生產的是一個CaptureRequest。我們將這個ANDROID_REQUEST_ID的ID值，保留在
newRequest->mResultExtras.requestId = it->find(ANDROID_REQUEST_ID).data.i32[0]。
這個值在整個Camera3的架構中，僅存在3大種Request型別，說明了整個和HAL層互動的Request型別是不多的：
預覽Request mPreviewRequest： mPreviewRequestId(Camera2Client::kPreviewRequestIdStart),
拍照Request mCaptureRequest：mCaptureId(Camera2Client::kCaptureRequestIdStart),
錄影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)
對於Preview來說，一次Preview後底層硬體就該可以連續的工作，而不需要進行過多的切換，故Framework每次向HAL傳送的Request均是一種repeat的操作模式，故呼叫了一個重複的RequestQueue來迴圈處理每次的Request。
status_t Camera3Device::RequestThread::setRepeatingRequests(
const RequestList &requests,
/*out*/
int64_t *lastFrameNumber) {
Mutex::Autolock l(mRequestLock);
if (lastFrameNumber != NULL) {//第一次進來為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 請求處理執行緒
RequestThread::threadLoop()函式主要用於響應並處理新加入到Request佇列中的請求。
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轉為給HAL3.0的camera3_capture_request_t
request.frame_number = nextRequest->mResultExtras.frameNumber;//當前幀號
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];//獲取requestid,這裡是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);//呼叫底層的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());//把當前的mRepeatingRequests插入到mRequestQueue
// No need to wait any longer
mRepeatingLastFrameNumber = mFrameNumber + requests.size() - 1;
break;
}
res = mRequestSignal.waitRelative(mRequestLock, kRequestTimeout);//等待下一個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，來自於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++;//對每一個非空的request需要幀號++
nextRequest->mResultExtras.afTriggerId = mCurrentAfTriggerId;
nextRequest->mResultExtras.precaptureTriggerId = mCurrentPreCaptureTriggerId;
}
return nextRequest;
}通過nextRequest->mResultExtras.frameNumber = mFrameNumber++表示當前CaptureRequest在處理的一幀影象號。
對於mRepeatingRequests而言，只有其非空，在執行完一次queue操作後，在迴圈進入執行時，會自動對mRequestQueue進行erase操作，是的mRequestQueue變為empty後再次重新載入mRepeatingRequests中的內容，從而形成一個隊repeatRequest的重複響應過程。
(7.2) camera_metadata_entry_t requestIdEntry = nextRequest->mSettings.find(ANDROID_REQUEST_ID);提取該CaptureRequest對應的Request 型別值
(7.3) getBuffer操作
涉及到比較複雜的資料流操作過程的內容見下一博文
(7.4) mHal3Device->ops->process_capture_request(mHal3Device, &request)
這裡的request是已經由一個CaptureRequest轉換為和HAL3.0互動的camera3_capture_request_t結構。
8 小結
至此已經完成了一次向HAL3.0 Device傳送一次完整的Request的請求。從最初Preview啟動建立多個OutPutStream，再是將這些Stream打包成一個mPreviewRequest來啟動stream，隨後將這個Request又轉變為一個CaptureRequest，直到轉為Capture list後交由RequestThread來處理這些請求。每一次的Request簡單可以說是Camera3Device向HAL3.0請求一幀資料，當然每一次Request也可以包含各種控制操作，如AutoFocus等內容，會在後續補充。
到這裡從StartPreview的入口開始，直到相應的Request下發到HAL3.0，基本描述了一次完成的控制流的處理。對於較為複雜的資料流本質也是一併合併在這個控制操作中的，但作為Buffer視訊快取流的管理維護將在下一博文進行描述與總結。