1. CameraService模块启动流程

CameraService是NativeService，所以随着init启动并加入到Native ServiceManager中。

2. 相机startPreview流程图

- Camera的请求和响应处理流程

Camera FW和HAL3的请求和响应，还有数据交互都是基于Stream的（Camera3InputStream，Camera3OutputStream）

请求分为三大类：

Preview（预览)
Capture（拍照）
Recording（录像）

流程：

Camera2Client 发起预览/拍照/录像请求；
创建(Preview/Capture/Recording)OutputStream(mSurface), 返回对应的streamId，并记录在对应的Processor中；
创建(Preview/Capture/Recording)Request;
将需要请求数据的outputstream添加到request中;
初始化Request, 并最终加入到Request列表中;
在Camera3Device的threadLoop中处理所有的Request请求;
处理请求前, 从每个ouputstream中保存的surfaceProducer各自申请一块buffer(dequeueBuffer);
将buffer携带到request中, 然后发送携带了请求包含的所有outputstreams和每个stream对应的buffer到HAL3;
HAL3收到并处理请求, 然后会填充camera获取的图象数据到携带的buffer, 并填充结果信息,并返回给Camera FW.
Camera FW收到返回的内容之后, 获取到填充了图像信息的buffer和outputstream;
遍历所有outputStreams（请求时带给HAL的outputstreams），获取到每个outputstream中的surfaceProducer, 通过surfaceProducer将获取的buffer queueBuffer到图形队列BufferQueue中, 交给Consumer来处理;

- repeating原理：

Camera3Device::RequestThread::waitForNextRequestBatch()

void Camera3Device::RequestThread::waitForNextRequestBatch() {    ATRACE_CALL();    // 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);    assert(mNextRequests.empty());    NextRequest nextRequest;    //获取下一个请求（先只获取一个）    nextRequest.captureRequest = waitForNextRequestLocked();    if (nextRequest.captureRequest == nullptr) {    //请求队列和repeating类型的请求都没有        return;    }    nextRequest.halRequest = camera3_capture_request_t();    nextRequest.submitted = false;    mNextRequests.add(nextRequest);    // Wait for additional requests    //当前要是支持批量请求的发送方式，则继续获取下一个请求    //（注意：repeatingRequest最多只会获取一个，当队列不为空时， 将不会再获取    //repeating请求，所以上面已经有一个请求(不管是不是repeating请求)，这类都不会再获    //取repeating请求， 二十从队列中获取其他类型的请求， 比如capture）    const size_t batchSize = nextRequest.captureRequest->mBatchSize;//获取到camera HAL设备支持的最大批量数量的请求。    for (size_t i = 1; i < batchSize; i++) {        NextRequest additionalRequest;        additionalRequest.captureRequest = waitForNextRequestLocked();        if (additionalRequest.captureRequest == nullptr) {            break;        }        additionalRequest.halRequest = camera3_capture_request_t();        additionalRequest.submitted = false;        mNextRequests.add(additionalRequest);    }    if (mNextRequests.size() < batchSize) {        ALOGE("RequestThread: only get %zu out of %zu requests. Skipping requests.",                mNextRequests.size(), batchSize);        cleanUpFailedRequests(/*sendRequestError*/true);    }    return;}sp<Camera3Device::CaptureRequest>        Camera3Device::RequestThread::waitForNextRequestLocked() {    status_t res;    sp<CaptureRequest> nextRequest;//注意 这里当队列为空的时候，才回去尝试获取repeating请求，获取不到说明//当前没有任何请求可以获取，则阻塞等待；    while (mRequestQueue.empty()) {        if (!mRepeatingRequests.empty()) {        //请求队列为空，但是mRepeatingRequests不为空，尝试获取repeating request；            // 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();//获取一个repeating request；            nextRequest = *firstRequest;            //插入到请求队列中            mRequestQueue.insert(mRequestQueue.end(),                    ++firstRequest,                    requests.end());            // No need to wait any longer            mRepeatingLastFrameNumber = mFrameNumber + requests.size() - 1;            //获取到请求之后， 跳出            break;        }//没有获取到任何请求， 阻塞等待新的请求到来；        res = mRequestSignal.waitRelative(mRequestLock, kRequestTimeout);        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) {    //没有获取到repeating请求        // Don't have a repeating request already in hand, so queue        // must have an entry now.        //从请求队列中获取新的请求        RequestList::iterator firstRequest =                mRequestQueue.begin();        nextRequest = *firstRequest;        mRequestQueue.erase(firstRequest);        if (mRequestQueue.empty() && !nextRequest->mRepeating) {            sp<NotificationListener> listener = mListener.promote();            if (listener != NULL) {                listener->notifyRequestQueueEmpty();            }        }    }    // 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++;        nextRequest->mResultExtras.afTriggerId = mCurrentAfTriggerId;        nextRequest->mResultExtras.precaptureTriggerId = mCurrentPreCaptureTriggerId;        // Since RequestThread::clear() removes buffers from the input stream,        // get the right buffer here before unlocking mRequestLock        if (nextRequest->mInputStream != NULL) {            res = nextRequest->mInputStream->getInputBuffer(&nextRequest->mInputBuffer);            if (res != OK) {                // Can't get input buffer from gralloc queue - this could be due to                // disconnected queue or other producer misbehavior, so not a fatal                // error                ALOGE("%s: Can't get input buffer, skipping request:"                        " %s (%d)", __FUNCTION__, strerror(-res), res);                sp<NotificationListener> listener = mListener.promote();                if (listener != NULL) {                    listener->notifyError(                            hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_REQUEST,                            nextRequest->mResultExtras);                }                return NULL;            }        }    }    return nextRequest; //最后返回获取到的请求}

- 注意

CallbackProcessor和JpegProcessor 的Consumer是CpuConsumer, 注册的FrameAvailableListener是自己, 所以queueBuffer之后, 回调响应是自己的onFrameAvailable函数。
CpuConsumer的lockNextBuffer(&buffer)可以获取到来自produser queue的buffer.
- JpegProcessor 收到的图象buffer最终在CaptureSequencer中处理.
- CaptureSequencer是一个状态机模型, 每个状态函数的返回值代表了要转移的状态.
最终完成拍照数据获取,是在CaptureSequencer::manageDone函数.

3. Camera2 录像流程图

Camera2 的录像使用的是Camera2 API_1 的接口

4. Camera2 API_2 从CameraActivity初始化到Camera preview的流程

Camera2 preview流程使用的是Camera2 API_2 的接口
开始预览流程

5. Camera2 takePicture代码流程

Android(安卓)9.0 Camera学习笔记

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