上一次我们详细分析了openCamera启动过程的源码，从CameraServer进程创建了很多对象，比如CameraDeviceClient、Camera3Device、FrameProcessorBase，而真正打开相机还是在驱动层中上电后才完成的，有时候真想把公司的系统组件和芯片组件的源码拷回来，这样就能看到完整的过程了，但是还是不敢，哈哈哈！华为手机是仿照高通，和CameraServer进程交互的是CameraDaemon进程，HAL、算法的代码都是执行在CameraDaemon进程当中的，而这部分每个手机厂商都不一样，因为是手机厂商自定义的代码，所以一般都是在系统源码中vendor目录下的，而且是在芯片组件当中，这里没有代码，这部分也就无法分析了。
之前我们也说过，相机最重要的四个节点就是openCamera、createCaptureSession、preview、capture，我们这节就来看一下createCaptureSession过程。在之前openCamera过程的源码分析中，我们最后说到，当成功打开相机后，会通过CameraDevice.StateCallback回调接口的public abstract void onOpened(@NonNull CameraDevice camera)方法返回一个CameraDevice对象给我们应用层，而这个CameraDevice对象真正是一个CameraDeviceImpl，那么接下来的createCaptureSession就是调用它来实现的，我们就来看一下frameworks\base\core\java\android\hardware\camera2\impl\CameraDeviceImpl.java类的createCaptureSession方法是如何实现的，源码如下：
@Override
public void createCaptureSession(List<Surface> outputs,
CameraCaptureSession.StateCallback callback, Handler handler)
throws CameraAccessException {
List<OutputConfiguration> outConfigurations = new ArrayList<>(outputs.size());
for (Surface surface : outputs) {
outConfigurations.add(new OutputConfiguration(surface));
}
createCaptureSessionInternal(null, outConfigurations, callback, handler,
/*operatingMode*/ICameraDeviceUser.NORMAL_MODE);
}这里我们来看一下该方法的几个参数，第一个参数是一个范型为Surface的List，这里的Surface就是我们用来创建流的，一般如果没有特殊的要求，那我们只需要下两个Surface，一个提供预览，一个提供拍照，预览的Surface就是相机预览区域，buffer轮转时，预览区的buffer就是要从这个预览Surface当中获取的，这个Surface一定要正确，否则就会导致session创建失败，预览区就会黑屏了，我们在平时的工作中经常碰到这样的情况；而至于拍照Surface，我们一般使用ImageReader对象来获取，ImageReader是系统提供的一个类，它的创建过程已经为我们创建好了一个Surface，我们直接使用它来当作拍照Surface，当拍照成功后，我们就可以从ImageReader.OnImageAvailableListener内部类的onImageAvailable回调方法中获取到一个ImageReader对象，再调用getPlanes()获取到Plane数组，一般取第一个Plane，继续调用getBuffer()就可以获取到拍摄的照片的byte数组了，第二个参数callback的类型为frameworks\base\core\java\android\hardware\camera2\CameraCaptureSession.java类的内部类StateCallback，和openCamera一样，当session创建成功后，framework也会通过这个回调接口的public abstract void onConfigured(@NonNull CameraCaptureSession session)方法返回一个CameraCaptureSession对象给我们，而真正的实现是一个CameraCaptureSessionImpl对象，我们可以使用它来作很多的工作，比如断开session连接调用abortCaptures()；拍照调用capture()方法；下预览调用setRepeatingRequest；停预览调用stopRepeating()，这里的设计和openCamera是完全一样的。第三个参数Handler的作用和openCamera也一样，还是为了保证线程不发生切换，我们在应用进程的哪个工作线程中执行createCaptureSession，那么framework回调我们时，也会通过这个handler把回调消息发送到当前handler线程的Looper循环上。好了，参数分析完了，我们继续往下看代码，它实际就是调用createCaptureSessionInternal方法进一步处理的，这里的会把我们传入的surface列表进行一下转换，转换为OutputConfiguration对象，调用createCaptureSessionInternal方法时的第一个参数inputConfig一般为空，我们只关注outputConfig。createCaptureSessionInternal方法的源码如下：
private void createCaptureSessionInternal(InputConfiguration inputConfig,
List<OutputConfiguration> outputConfigurations,
CameraCaptureSession.StateCallback callback, Handler handler,
int operatingMode) throws CameraAccessException {
synchronized (mInterfaceLock) {
if (DEBUG) {
Log.d(TAG, "createCaptureSessionInternal");
}
checkIfCameraClosedOrInError();
boolean isConstrainedHighSpeed =
(operatingMode == ICameraDeviceUser.CONSTRAINED_HIGH_SPEED_MODE);
if (isConstrainedHighSpeed && inputConfig != null) {
throw new IllegalArgumentException("Constrained high speed session doesn't support"
+ " input configuration yet.");
}
// Notify current session that it's going away, before starting camera operations
// After this call completes, the session is not allowed to call into CameraDeviceImpl
if (mCurrentSession != null) {
mCurrentSession.replaceSessionClose();
}
// TODO: dont block for this
boolean configureSuccess = true;
CameraAccessException pendingException = null;
Surface input = null;
try {
// configure streams and then block until IDLE
configureSuccess = configureStreamsChecked(inputConfig, outputConfigurations,
operatingMode);
if (configureSuccess == true && inputConfig != null) {
input = mRemoteDevice.getInputSurface();
}
} catch (CameraAccessException e) {
configureSuccess = false;
pendingException = e;
input = null;
if (DEBUG) {
Log.v(TAG, "createCaptureSession - failed with exception ", e);
}
}
// Fire onConfigured if configureOutputs succeeded, fire onConfigureFailed otherwise.
CameraCaptureSessionCore newSession = null;
if (isConstrainedHighSpeed) {
newSession = new CameraConstrainedHighSpeedCaptureSessionImpl(mNextSessionId++,
callback, handler, this, mDeviceHandler, configureSuccess,
mCharacteristics);
} else {
newSession = new CameraCaptureSessionImpl(mNextSessionId++, input,
callback, handler, this, mDeviceHandler,
configureSuccess);
}
// TODO: wait until current session closes, then create the new session
mCurrentSession = newSession;
if (pendingException != null) {
throw pendingException;
}
mSessionStateCallback = mCurrentSession.getDeviceStateCallback();
}
}这个方法的作用就是配置surface了。该方法中最重要的就是configureSuccess = configureStreamsChecked(inputConfig, outputConfigurations, operatingMode)这句了，它会执行surface配置，如果配置成功，则configureSuccess值为true，否则为false，接下来会创建session的实现类对象，一般是执行else分支，创建CameraCaptureSessionImpl对象，frameworks\base\core\java\android\hardware\camera2\impl\CameraCaptureSessionImpl.java类的构造方法的源码如下：
CameraCaptureSessionImpl(int id, Surface input,
CameraCaptureSession.StateCallback callback, Handler stateHandler,
android.hardware.camera2.impl.CameraDeviceImpl deviceImpl,
Handler deviceStateHandler, boolean configureSuccess) {
if (callback == null) {
throw new IllegalArgumentException("callback must not be null");
}
mId = id;
mIdString = String.format("Session %d: ", mId);
mInput = input;
mStateHandler = checkHandler(stateHandler);
mStateCallback = createUserStateCallbackProxy(mStateHandler, callback);
mDeviceHandler = checkNotNull(deviceStateHandler, "deviceStateHandler must not be null");
mDeviceImpl = checkNotNull(deviceImpl, "deviceImpl must not be null");
/*
* Use the same handler as the device's StateCallback for all the internal coming events
*
* This ensures total ordering between CameraDevice.StateCallback and
* CameraDeviceImpl.CaptureCallback events.
*/
mSequenceDrainer = new TaskDrainer<>(mDeviceHandler, new SequenceDrainListener(),
/*name*/"seq");
mIdleDrainer = new TaskSingleDrainer(mDeviceHandler, new IdleDrainListener(),
/*name*/"idle");
mAbortDrainer = new TaskSingleDrainer(mDeviceHandler, new AbortDrainListener(),
/*name*/"abort");
// CameraDevice should call configureOutputs and have it finish before constructing us
if (configureSuccess) {
mStateCallback.onConfigured(this);
if (DEBUG) Log.v(TAG, mIdString + "Created session successfully");
mConfigureSuccess = true;
} else {
mStateCallback.onConfigureFailed(this);
mClosed = true; // do not fire any other callbacks, do not allow any other work
Log.e(TAG, mIdString + "Failed to create capture session; configuration failed");
mConfigureSuccess = false;
}
}可以看到，在它的构造方法中，就是通过调用mStateCallback.onConfigured(this)通过应用层，session已经创建成功，同时将当前的impl实现类对象返回给应用层。好了，我们继续看一下configureStreamsChecked方法的实现，来学习一下framework是如何配置surface的。configureStreamsChecked方法的源码如下：
public boolean configureStreamsChecked(InputConfiguration inputConfig,
List<OutputConfiguration> outputs, int operatingMode)
throws CameraAccessException {
// Treat a null input the same an empty list
if (outputs == null) {
outputs = new ArrayList<OutputConfiguration>();
}
if (outputs.size() == 0 && inputConfig != null) {
throw new IllegalArgumentException("cannot configure an input stream without " +
"any output streams");
}
checkInputConfiguration(inputConfig);
boolean success = false;
synchronized (mInterfaceLock) {
checkIfCameraClosedOrInError();
// Streams to create
HashSet<OutputConfiguration> addSet = new HashSet<OutputConfiguration>(outputs);
// Streams to delete
List<Integer> deleteList = new ArrayList<Integer>();
// Determine which streams need to be created, which to be deleted
for (int i = 0; i < mConfiguredOutputs.size(); ++i) {
int streamId = mConfiguredOutputs.keyAt(i);
OutputConfiguration outConfig = mConfiguredOutputs.valueAt(i);
if (!outputs.contains(outConfig) || outConfig.isDeferredConfiguration()) {
// Always delete the deferred output configuration when the session
// is created, as the deferred output configuration doesn't have unique surface
// related identifies.
deleteList.add(streamId);
} else {
addSet.remove(outConfig); // Don't create a stream previously created
}
}
mDeviceHandler.post(mCallOnBusy);
stopRepeating();
try {
waitUntilIdle();
mRemoteDevice.beginConfigure();
// reconfigure the input stream if the input configuration is different.
InputConfiguration currentInputConfig = mConfiguredInput.getValue();
if (inputConfig != currentInputConfig &&
(inputConfig == null || !inputConfig.equals(currentInputConfig))) {
if (currentInputConfig != null) {
mRemoteDevice.deleteStream(mConfiguredInput.getKey());
mConfiguredInput = new SimpleEntry<Integer, InputConfiguration>(
REQUEST_ID_NONE, null);
}
if (inputConfig != null) {
int streamId = mRemoteDevice.createInputStream(inputConfig.getWidth(),
inputConfig.getHeight(), inputConfig.getFormat());
mConfiguredInput = new SimpleEntry<Integer, InputConfiguration>(
streamId, inputConfig);
}
}
// Delete all streams first (to free up HW resources)
for (Integer streamId : deleteList) {
mRemoteDevice.deleteStream(streamId);
mConfiguredOutputs.delete(streamId);
}
// Add all new streams
for (OutputConfiguration outConfig : outputs) {
if (addSet.contains(outConfig)) {
int streamId = mRemoteDevice.createStream(outConfig);
mConfiguredOutputs.put(streamId, outConfig);
}
}
mRemoteDevice.endConfigure(operatingMode);
success = true;
} catch (IllegalArgumentException e) {
// OK. camera service can reject stream config if it's not supported by HAL
// This is only the result of a programmer misusing the camera2 api.
Log.w(TAG, "Stream configuration failed due to: " + e.getMessage());
return false;
} catch (CameraAccessException e) {
if (e.getReason() == CameraAccessException.CAMERA_IN_USE) {
throw new IllegalStateException("The camera is currently busy." +
" You must wait until the previous operation completes.", e);
}
throw e;
} finally {
if (success && outputs.size() > 0) {
mDeviceHandler.post(mCallOnIdle);
} else {
// Always return to the 'unconfigured' state if we didn't hit a fatal error
mDeviceHandler.post(mCallOnUnconfigured);
}
}
}
return success;
}上面调入进来前，我们已经看过，inputConfig为空，首先调用mDeviceHandler.post(mCallOnBusy)往DeviceHandler的Looper循环上发一个CallOnBusy的消息，表示接下来要开始配置surface，处理繁忙状态了，然后调用stopRepeating()停预览。接着调用mRemoteDevice.beginConfigure()通知CameraServer进程中的binder服务端对象，开始配置。这个mRemoteDevice的实现，我们在openCamera中已经分析过了，它实际上就是CameraDeviceClient对象，它的beginConfigure()方法中是空实现，接下来最重要的就是调用for (OutputConfiguration outConfig : outputs)配置surface列表了。配置完成后调用mRemoteDevice.endConfigure(operatingMode)通知CameraDeviceClient结束配置，如果中间有任何异常，则返回false，表示配置失败，那么构造CameraCaptureSessionImpl对象时，也就会执行mStateCallback.onConfigureFailed(this)通知应用层，session创建失败了。for循环中是调用int streamId = mRemoteDevice.createStream(outConfig)来配置surface的，这里需要注意，华为手机的相机应用一般包括三条流，一条预览流，一条拍照流，一条回调流，也就是创建session时对应有三个surface了，所以从这里进去的逻辑相关的日志都会打印三次，每次的streamId递增，大家要注意这个，要区分这三条流，可以通过format格式来判断，CameraServer在配置surface创建流时会打印出每个流的信息，其中的format也会打印出来，比如0x21、0x22、0x23，这几个表示什么意思呢？这就是Android定义的像素格式了，它的源码定义在system\core\libsystem\include\system\graphics-base.h头文件中，该文件的源码如下：
#ifndef HIDL_GENERATED_ANDROID_HARDWARE_GRAPHICS_COMMON_V1_0_EXPORTED_CONSTANTS_H_
#define HIDL_GENERATED_ANDROID_HARDWARE_GRAPHICS_COMMON_V1_0_EXPORTED_CONSTANTS_H_
#ifdef __cplusplus
extern "C" {
#endif
typedef enum {
HAL_PIXEL_FORMAT_RGBA_8888 = 1,
HAL_PIXEL_FORMAT_RGBX_8888 = 2,
HAL_PIXEL_FORMAT_RGB_888 = 3,
HAL_PIXEL_FORMAT_RGB_565 = 4,
HAL_PIXEL_FORMAT_BGRA_8888 = 5,
HAL_PIXEL_FORMAT_RGBA_1010102 = 43, // 0x2B
HAL_PIXEL_FORMAT_RGBA_FP16 = 22, // 0x16
HAL_PIXEL_FORMAT_YV12 = 842094169, // 0x32315659
HAL_PIXEL_FORMAT_Y8 = 538982489, // 0x20203859
HAL_PIXEL_FORMAT_Y16 = 540422489, // 0x20363159
HAL_PIXEL_FORMAT_RAW16 = 32, // 0x20
HAL_PIXEL_FORMAT_RAW10 = 37, // 0x25
HAL_PIXEL_FORMAT_RAW12 = 38, // 0x26
HAL_PIXEL_FORMAT_RAW_OPAQUE = 36, // 0x24
HAL_PIXEL_FORMAT_BLOB = 33, // 0x21
HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED = 34, // 0x22
HAL_PIXEL_FORMAT_YCBCR_420_888 = 35, // 0x23
HAL_PIXEL_FORMAT_YCBCR_422_888 = 39, // 0x27
HAL_PIXEL_FORMAT_YCBCR_444_888 = 40, // 0x28
HAL_PIXEL_FORMAT_FLEX_RGB_888 = 41, // 0x29
HAL_PIXEL_FORMAT_FLEX_RGBA_8888 = 42, // 0x2A
HAL_PIXEL_FORMAT_YCBCR_422_SP = 16, // 0x10
HAL_PIXEL_FORMAT_YCRCB_420_SP = 17, // 0x11
HAL_PIXEL_FORMAT_YCBCR_422_I = 20, // 0x14
HAL_PIXEL_FORMAT_JPEG = 256, // 0x100
} android_pixel_format_t;
typedef enum {
HAL_TRANSFORM_FLIP_H = 1, // 0x01
HAL_TRANSFORM_FLIP_V = 2, // 0x02
HAL_TRANSFORM_ROT_90 = 4, // 0x04
HAL_TRANSFORM_ROT_180 = 3, // 0x03
HAL_TRANSFORM_ROT_270 = 7, // 0x07
} android_transform_t;
typedef enum {
HAL_DATASPACE_UNKNOWN = 0, // 0x0
HAL_DATASPACE_ARBITRARY = 1, // 0x1
HAL_DATASPACE_STANDARD_SHIFT = 16,
HAL_DATASPACE_STANDARD_MASK = 4128768, // (63 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_UNSPECIFIED = 0, // (0 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT709 = 65536, // (1 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT601_625 = 131072, // (2 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT601_625_UNADJUSTED = 196608, // (3 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT601_525 = 262144, // (4 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT601_525_UNADJUSTED = 327680, // (5 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT2020 = 393216, // (6 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT2020_CONSTANT_LUMINANCE = 458752, // (7 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_BT470M = 524288, // (8 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_FILM = 589824, // (9 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_DCI_P3 = 655360, // (10 << STANDARD_SHIFT)
HAL_DATASPACE_STANDARD_ADOBE_RGB = 720896, // (11 << STANDARD_SHIFT)
HAL_DATASPACE_TRANSFER_SHIFT = 22,
HAL_DATASPACE_TRANSFER_MASK = 130023424, // (31 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_UNSPECIFIED = 0, // (0 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_LINEAR = 4194304, // (1 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_SRGB = 8388608, // (2 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_SMPTE_170M = 12582912, // (3 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_GAMMA2_2 = 16777216, // (4 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_GAMMA2_6 = 20971520, // (5 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_GAMMA2_8 = 25165824, // (6 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_ST2084 = 29360128, // (7 << TRANSFER_SHIFT)
HAL_DATASPACE_TRANSFER_HLG = 33554432, // (8 << TRANSFER_SHIFT)
HAL_DATASPACE_RANGE_SHIFT = 27,
HAL_DATASPACE_RANGE_MASK = 939524096, // (7 << RANGE_SHIFT)
HAL_DATASPACE_RANGE_UNSPECIFIED = 0, // (0 << RANGE_SHIFT)
HAL_DATASPACE_RANGE_FULL = 134217728, // (1 << RANGE_SHIFT)
HAL_DATASPACE_RANGE_LIMITED = 268435456, // (2 << RANGE_SHIFT)
HAL_DATASPACE_RANGE_EXTENDED = 402653184, // (3 << RANGE_SHIFT)
HAL_DATASPACE_SRGB_LINEAR = 512, // 0x200
HAL_DATASPACE_V0_SRGB_LINEAR = 138477568, // ((STANDARD_BT709 | TRANSFER_LINEAR) | RANGE_FULL)
HAL_DATASPACE_V0_SCRGB_LINEAR = 406913024, // ((STANDARD_BT709 | TRANSFER_LINEAR) | RANGE_EXTENDED)
HAL_DATASPACE_SRGB = 513, // 0x201
HAL_DATASPACE_V0_SRGB = 142671872, // ((STANDARD_BT709 | TRANSFER_SRGB) | RANGE_FULL)
HAL_DATASPACE_V0_SCRGB = 411107328, // ((STANDARD_BT709 | TRANSFER_SRGB) | RANGE_EXTENDED)
HAL_DATASPACE_JFIF = 257, // 0x101
HAL_DATASPACE_V0_JFIF = 146931712, // ((STANDARD_BT601_625 | TRANSFER_SMPTE_170M) | RANGE_FULL)
HAL_DATASPACE_BT601_625 = 258, // 0x102
HAL_DATASPACE_V0_BT601_625 = 281149440, // ((STANDARD_BT601_625 | TRANSFER_SMPTE_170M) | RANGE_LIMITED)
HAL_DATASPACE_BT601_525 = 259, // 0x103
HAL_DATASPACE_V0_BT601_525 = 281280512, // ((STANDARD_BT601_525 | TRANSFER_SMPTE_170M) | RANGE_LIMITED)
HAL_DATASPACE_BT709 = 260, // 0x104
HAL_DATASPACE_V0_BT709 = 281083904, // ((STANDARD_BT709 | TRANSFER_SMPTE_170M) | RANGE_LIMITED)
HAL_DATASPACE_DCI_P3_LINEAR = 139067392, // ((STANDARD_DCI_P3 | TRANSFER_LINEAR) | RANGE_FULL)
HAL_DATASPACE_DCI_P3 = 155844608, // ((STANDARD_DCI_P3 | TRANSFER_GAMMA2_6) | RANGE_FULL)
HAL_DATASPACE_DISPLAY_P3_LINEAR = 139067392, // ((STANDARD_DCI_P3 | TRANSFER_LINEAR) | RANGE_FULL)
HAL_DATASPACE_DISPLAY_P3 = 143261696, // ((STANDARD_DCI_P3 | TRANSFER_SRGB) | RANGE_FULL)
HAL_DATASPACE_ADOBE_RGB = 151715840, // ((STANDARD_ADOBE_RGB | TRANSFER_GAMMA2_2) | RANGE_FULL)
HAL_DATASPACE_BT2020_LINEAR = 138805248, // ((STANDARD_BT2020 | TRANSFER_LINEAR) | RANGE_FULL)
HAL_DATASPACE_BT2020 = 147193856, // ((STANDARD_BT2020 | TRANSFER_SMPTE_170M) | RANGE_FULL)
HAL_DATASPACE_BT2020_PQ = 163971072, // ((STANDARD_BT2020 | TRANSFER_ST2084) | RANGE_FULL)
HAL_DATASPACE_DEPTH = 4096, // 0x1000
HAL_DATASPACE_SENSOR = 4097, // 0x1001
} android_dataspace_t;
typedef enum {
HAL_COLOR_MODE_NATIVE = 0,
HAL_COLOR_MODE_STANDARD_BT601_625 = 1,
HAL_COLOR_MODE_STANDARD_BT601_625_UNADJUSTED = 2,
HAL_COLOR_MODE_STANDARD_BT601_525 = 3,
HAL_COLOR_MODE_STANDARD_BT601_525_UNADJUSTED = 4,
HAL_COLOR_MODE_STANDARD_BT709 = 5,
HAL_COLOR_MODE_DCI_P3 = 6,
HAL_COLOR_MODE_SRGB = 7,
HAL_COLOR_MODE_ADOBE_RGB = 8,
HAL_COLOR_MODE_DISPLAY_P3 = 9,
} android_color_mode_t;
typedef enum {
HAL_COLOR_TRANSFORM_IDENTITY = 0,
HAL_COLOR_TRANSFORM_ARBITRARY_MATRIX = 1,
HAL_COLOR_TRANSFORM_VALUE_INVERSE = 2,
HAL_COLOR_TRANSFORM_GRAYSCALE = 3,
HAL_COLOR_TRANSFORM_CORRECT_PROTANOPIA = 4,
HAL_COLOR_TRANSFORM_CORRECT_DEUTERANOPIA = 5,
HAL_COLOR_TRANSFORM_CORRECT_TRITANOPIA = 6,
} android_color_transform_t;
typedef enum {
HAL_HDR_DOLBY_VISION = 1,
HAL_HDR_HDR10 = 2,
HAL_HDR_HLG = 3,
} android_hdr_t;
我们可以换算一下，0x21也就是33，对应HAL_PIXEL_FORMAT_BLOB，从它的命名也可以看出，是用来存储BLOB数据的，所以对应的就是拍照流，0x22是34，对应HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED，它对应预览流，该format一般是预览surface的格式，而预览surface是显示系统给我们的，它不像拍照流定义一个ImageReader就可以了，它涉及到界面显示，是一个真正的View，在实际的问题分析当中，这块的日志对我们也很有用，大家一定要注意。好了，明白了format之后，我们继续往下看代码，int streamId = mRemoteDevice.createStream(outConfig)逻辑中，mRemoteDevice就是运行在CameraServer进程当中的CameraDeviceClient对象，所以我们就接着看一下frameworks\av\services\camera\libcameraservice\api2\CameraDeviceClient.cpp类的createStream方法的实现，源码如下：
binder::Status CameraDeviceClient::createStream(
const hardware::camera2::params::OutputConfiguration &outputConfiguration,
/*out*/
int32_t* newStreamId) {
ATRACE_CALL();
binder::Status res;
if (!(res = checkPidStatus(__FUNCTION__)).isOk()) return res;
Mutex::Autolock icl(mBinderSerializationLock);
const std::vector<sp<IGraphicBufferProducer>>& bufferProducers =
outputConfiguration.getGraphicBufferProducers();
size_t numBufferProducers = bufferProducers.size();
bool deferredConsumer = outputConfiguration.isDeferred();
bool isShared = outputConfiguration.isShared();
if (numBufferProducers > MAX_SURFACES_PER_STREAM) {
ALOGE("%s: GraphicBufferProducer count %zu for stream exceeds limit of %d",
__FUNCTION__, bufferProducers.size(), MAX_SURFACES_PER_STREAM);
return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT, "Surface count is too high");
}
bool deferredConsumerOnly = deferredConsumer && numBufferProducers == 0;
int surfaceType = outputConfiguration.getSurfaceType();
bool validSurfaceType = ((surfaceType == OutputConfiguration::SURFACE_TYPE_SURFACE_VIEW) ||
(surfaceType == OutputConfiguration::SURFACE_TYPE_SURFACE_TEXTURE));
if (deferredConsumer && !validSurfaceType) {
ALOGE("%s: Target surface is invalid: bufferProducer = %p, surfaceType = %d.",
__FUNCTION__, bufferProducers[0].get(), surfaceType);
return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT, "Target Surface is invalid");
}
if (!mDevice.get()) {
return STATUS_ERROR(CameraService::ERROR_DISCONNECTED, "Camera device no longer alive");
}
std::vector<sp<Surface>> surfaces;
std::vector<sp<IBinder>> binders;
status_t err;
// Create stream for deferred surface case.
if (deferredConsumerOnly) {
return createDeferredSurfaceStreamLocked(outputConfiguration, isShared, newStreamId);
}
OutputStreamInfo streamInfo;
bool isStreamInfoValid = false;
for (auto& bufferProducer : bufferProducers) {
// Don't create multiple streams for the same target surface
sp<IBinder> binder = IInterface::asBinder(bufferProducer);
ssize_t index = mStreamMap.indexOfKey(binder);
if (index != NAME_NOT_FOUND) {
String8 msg = String8::format("Camera %s: Surface already has a stream created for it "
"(ID %zd)", mCameraIdStr.string(), index);
ALOGW("%s: %s", __FUNCTION__, msg.string());
return STATUS_ERROR(CameraService::ERROR_ALREADY_EXISTS, msg.string());
}
sp<Surface> surface;
res = createSurfaceFromGbp(streamInfo, isStreamInfoValid, surface, bufferProducer);
if (!res.isOk())
return res;
if (!isStreamInfoValid) {
// Streaming sharing is only supported for IMPLEMENTATION_DEFINED
// formats.
if (isShared && streamInfo.format != HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED) {
String8 msg = String8::format("Camera %s: Stream sharing is only supported for "
"IMPLEMENTATION_DEFINED format", mCameraIdStr.string());
ALOGW("%s: %s", __FUNCTION__, msg.string());
return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT, msg.string());
}
isStreamInfoValid = true;
}
binders.push_back(IInterface::asBinder(bufferProducer));
surfaces.push_back(surface);
}
int streamId = camera3::CAMERA3_STREAM_ID_INVALID;
err = mDevice->createStream(surfaces, deferredConsumer, streamInfo.width,
streamInfo.height, streamInfo.format, streamInfo.dataSpace,
static_cast<camera3_stream_rotation_t>(outputConfiguration.getRotation()),
&streamId, outputConfiguration.getSurfaceSetID(), isShared);
if (err != OK) {
res = STATUS_ERROR_FMT(CameraService::ERROR_INVALID_OPERATION,
"Camera %s: Error creating output stream (%d x %d, fmt %x, dataSpace %x): %s (%d)",
mCameraIdStr.string(), streamInfo.width, streamInfo.height, streamInfo.format,
streamInfo.dataSpace, strerror(-err), err);
} else {
int i = 0;
for (auto& binder : binders) {
ALOGV("%s: mStreamMap add binder %p streamId %d, surfaceId %d",
__FUNCTION__, binder.get(), streamId, i);
mStreamMap.add(binder, StreamSurfaceId(streamId, i++));
}
mStreamInfoMap[streamId] = streamInfo;
ALOGV("%s: Camera %s: Successfully created a new stream ID %d for output surface"
" (%d x %d) with format 0x%x.",
__FUNCTION__, mCameraIdStr.string(), streamId, streamInfo.width,
streamInfo.height, streamInfo.format);
// Set transform flags to ensure preview to be rotated correctly.
res = setStreamTransformLocked(streamId);
*newStreamId = streamId;
}
return res;
}该方法的第二个参数是输出参数，也就是我们配置完成的streamId，我们忽略掉其它无关的逻辑，该方法中主要就是for (auto& bufferProducer : bufferProducers)、mDevice->createStream这两句逻辑了，for循环中使用outputConfiguration.getGraphicBufferProducers()得到的GraphicBufferProducers创建出对应的surface，同时会对这些surface对象进行判断，检查它们的合法性，合法的话就会将它们加入到surfaces集合中，然后调用mDevice->createStream进一步执行流的创建。
这里就要说一说Android显示系统的一些知识了，大家要清楚，Android上最终绘制在屏幕上的buffer都是在显存中分配的，而除了这部分外，其他都是在内存中分配的，buffer管理的模块有两个，一个是framebuffer，一个是gralloc，framebuffer用来将渲染好的buffer显示到屏幕上，而gralloc用于分配buffer，我们相机预览的buffer轮转也不例外，它所申请的buffer根上也是由gralloc来分配的，在native层的描述是一个private_handle_t指针，而中间会经过多层的封装，这些buffer都是共享的，只不过它的生命周期中的某个时刻只能属于一个所有者，而这些所有者的角色在不断的变换，这也就是Android中最经典的生产者–消费者的循环模型了，生产者就是BufferProducer，消费者就是BufferConsumer，每一个buffer在它的生命周期过程中转换时都会被锁住，这样它的所有者角色发生变化，而其他对象想要修改它就不可能了，这样就保证了buffer同步。
好了，for循环中的逻辑我们就不分析了，继续看一下mDevice->createStream，在openCamera分析过程，我们已经看到，mDevice的类型为Camera3Device，那我们就来看一下frameworks\av\services\camera\libcameraservice\device3\Camera3Device.cpp类的createStream方法的实现，源码如下：
status_t Camera3Device::createStream(sp<Surface> consumer,
uint32_t width, uint32_t height, int format,
android_dataspace dataSpace, camera3_stream_rotation_t rotation, int *id,
int streamSetId, bool isShared, uint32_t consumerUsage) {
ATRACE_CALL();
if (consumer == nullptr) {
ALOGE("%s: consumer must not be null", __FUNCTION__);
return BAD_VALUE;
}
std::vector<sp<Surface>> consumers;
consumers.push_back(consumer);
return createStream(consumers, /*hasDeferredConsumer*/ false, width, height,
format, dataSpace, rotation, id, streamSetId, isShared, consumerUsage);
}
status_t Camera3Device::createStream(const std::vector<sp<Surface>>& consumers,
bool hasDeferredConsumer, uint32_t width, uint32_t height, int format,
android_dataspace dataSpace, camera3_stream_rotation_t rotation, int *id,
int streamSetId, bool isShared, uint32_t consumerUsage) {
ATRACE_CALL();
Mutex::Autolock il(mInterfaceLock);
Mutex::Autolock l(mLock);
ALOGV("Camera %s: Creating new stream %d: %d x %d, format %d, dataspace %d rotation %d"
" consumer usage 0x%x, isShared %d", mId.string(), mNextStreamId, width, height, format,
dataSpace, rotation, consumerUsage, isShared);
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 (consumers.size() == 0 && !hasDeferredConsumer) {
ALOGE("%s: Number of consumers cannot be smaller than 1", __FUNCTION__);
return BAD_VALUE;
}
if (hasDeferredConsumer && format != HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED) {
ALOGE("Deferred consumer stream creation only support IMPLEMENTATION_DEFINED format");
return BAD_VALUE;
}
if (format == HAL_PIXEL_FORMAT_BLOB) {
ssize_t blobBufferSize;
if (dataSpace != HAL_DATASPACE_DEPTH) {
blobBufferSize = getJpegBufferSize(width, height);
if (blobBufferSize <= 0) {
SET_ERR_L("Invalid jpeg buffer size %zd", blobBufferSize);
return BAD_VALUE;
}
} else {
blobBufferSize = getPointCloudBufferSize();
if (blobBufferSize <= 0) {
SET_ERR_L("Invalid point cloud buffer size %zd", blobBufferSize);
return BAD_VALUE;
}
}
newStream = new Camera3OutputStream(mNextStreamId, consumers[0],
width, height, blobBufferSize, format, dataSpace, rotation,
mTimestampOffset, streamSetId);
} else if (format == HAL_PIXEL_FORMAT_RAW_OPAQUE) {
ssize_t rawOpaqueBufferSize = getRawOpaqueBufferSize(width, height);
if (rawOpaqueBufferSize <= 0) {
SET_ERR_L("Invalid RAW opaque buffer size %zd", rawOpaqueBufferSize);
return BAD_VALUE;
}
newStream = new Camera3OutputStream(mNextStreamId, consumers[0],
width, height, rawOpaqueBufferSize, format, dataSpace, rotation,
mTimestampOffset, streamSetId);
} else if (isShared) {
newStream = new Camera3SharedOutputStream(mNextStreamId, consumers,
width, height, format, consumerUsage, dataSpace, rotation,
mTimestampOffset, streamSetId);
} else if (consumers.size() == 0 && hasDeferredConsumer) {
newStream = new Camera3OutputStream(mNextStreamId,
width, height, format, consumerUsage, dataSpace, rotation,
mTimestampOffset, streamSetId);
} else {
newStream = new Camera3OutputStream(mNextStreamId, consumers[0],
width, height, format, dataSpace, rotation,
mTimestampOffset, streamSetId);
}
newStream->setStatusTracker(mStatusTracker);
newStream->setBufferManager(mBufferManager);
res = mOutputStreams.add(mNextStreamId, newStream);
if (res < 0) {
SET_ERR_L("Can't add new stream to set: %s (%d)", strerror(-res), res);
return res;
}
*id = mNextStreamId++;
mNeedConfig = true;
// Continue captures if active at start
if (wasActive) {
ALOGV("%s: Restarting activity to reconfigure streams", __FUNCTION__);
// Reuse current operating mode for new stream config
res = configureStreamsLocked(mOperatingMode);
if (res != OK) {
CLOGE("Can't reconfigure device for new stream %d: %s (%d)",
mNextStreamId, strerror(-res), res);
return res;
}
internalResumeLocked();
}
ALOGV("Camera %s: Created new stream", mId.string());
return OK;
}首先将上一步传入的surface，也就是以后的consumer加入到队列中，然后调用重载的createStream方法进一步处理。这里的参数width就表示我们要配置的surface的宽度，height表示高度，format表示格式，我们前面已经说过，dataSpace的类型为android_dataspace，它表示我们buffer轮转时，buffer的大小，接下来定义一个Camera3OutputStream局部变量，这个也就是我们说的配置流了，接下来的if/else判断会根据我们的意图，创建不同的流对象，比如我们要配置拍照流，它的format格式为HAL_PIXEL_FORMAT_BLOB，所以就执行第一个if分支，创建一个Camera3OutputStream，创建完成后，执行*id = mNextStreamId++，给id指针赋值，这也就是当前流的id了，所以它是递增的。一般情况下，mStatus的状态在initializeCommonLocked()初始化通过调用internalUpdateStatusLocked方法被赋值为STATUS_UNCONFIGURED状态，所以这里的switch/case分支中就进入case STATUS_UNCONFIGURED，然后直接break跳出了，所以局部变量wasActive的值为false，最后直接返回OK。
到这里，createStream的逻辑就执行完成了，还是要提醒大家，createStream的逻辑是在framework中的for循环里执行的，我们的创建相当于只配置了一个surface，如果有多个surface的话，这里会执行多次，相应的Camera3OutputStream流的日志也会打印多次，这对于大家定位问题也非常有帮助。
流创建完成后，for循环执行完成，在CameraDeviceImpl类的configureStreamsChecked方法中最后调用mRemoteDevice.endConfigure(operatingMode)结束配置，它的实现在CameraDeviceClient中，源码如下：
binder::Status CameraDeviceClient::endConfigure(int operatingMode) {
ALOGV("%s: ending configure (%d input stream, %zu output surfaces)",
__FUNCTION__, mInputStream.configured ? 1 : 0,
mStreamMap.size());
binder::Status res;
if (!(res = checkPidStatus(__FUNCTION__)).isOk()) return res;
Mutex::Autolock icl(mBinderSerializationLock);
if (!mDevice.get()) {
return STATUS_ERROR(CameraService::ERROR_DISCONNECTED, "Camera device no longer alive");
}
if (operatingMode < 0) {
String8 msg = String8::format(
"Camera %s: Invalid operating mode %d requested", mCameraIdStr.string(), operatingMode);
ALOGE("%s: %s", __FUNCTION__, msg.string());
return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
msg.string());
}
// Sanitize the high speed session against necessary capability bit.
bool isConstrainedHighSpeed = (operatingMode == ICameraDeviceUser::CONSTRAINED_HIGH_SPEED_MODE);
if (isConstrainedHighSpeed) {
CameraMetadata staticInfo = mDevice->info();
camera_metadata_entry_t entry = staticInfo.find(ANDROID_REQUEST_AVAILABLE_CAPABILITIES);
bool isConstrainedHighSpeedSupported = false;
for(size_t i = 0; i < entry.count; ++i) {
uint8_t capability = entry.data.u8[i];
if (capability == ANDROID_REQUEST_AVAILABLE_CAPABILITIES_CONSTRAINED_HIGH_SPEED_VIDEO) {
isConstrainedHighSpeedSupported = true;
break;
}
}
if (!isConstrainedHighSpeedSupported) {
String8 msg = String8::format(
"Camera %s: Try to create a constrained high speed configuration on a device"
" that doesn't support it.", mCameraIdStr.string());
ALOGE("%s: %s", __FUNCTION__, msg.string());
return STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT,
msg.string());
}
}
status_t err = mDevice->configureStreams(operatingMode);
if (err == BAD_VALUE) {
String8 msg = String8::format("Camera %s: Unsupported set of inputs/outputs provided",
mCameraIdStr.string());
ALOGE("%s: %s", __FUNCTION__, msg.string());
res = STATUS_ERROR(CameraService::ERROR_ILLEGAL_ARGUMENT, msg.string());
} else if (err != OK) {
String8 msg = String8::format("Camera %s: Error configuring streams: %s (%d)",
mCameraIdStr.string(), strerror(-err), err);
ALOGE("%s: %s", __FUNCTION__, msg.string());
res = STATUS_ERROR(CameraService::ERROR_INVALID_OPERATION, msg.string());
}
return res;
}该方法中就是调用mDevice->configureStreams(operatingMode)进一步处理，mDevice的类型为Camera3Device，configureStreams方法的源码如下：
status_t Camera3Device::configureStreams(int operatingMode) {
ATRACE_CALL();
ALOGV("%s: E", __FUNCTION__);
Mutex::Autolock il(mInterfaceLock);
Mutex::Autolock l(mLock);
return configureStreamsLocked(operatingMode);
}这里就是调用configureStreamsLocked进一步处理，源码如下：
status_t Camera3Device::configureStreamsLocked(int operatingMode) {
ATRACE_CALL();
status_t res;
if (mStatus != STATUS_UNCONFIGURED && mStatus != STATUS_CONFIGURED) {
CLOGE("Not idle");
return INVALID_OPERATION;
}
if (operatingMode < 0) {
CLOGE("Invalid operating mode: %d", operatingMode);
return BAD_VALUE;
}
bool isConstrainedHighSpeed =
static_cast<int>(StreamConfigurationMode::CONSTRAINED_HIGH_SPEED_MODE) ==
operatingMode;
if (mOperatingMode != operatingMode) {
mNeedConfig = true;
mIsConstrainedHighSpeedConfiguration = isConstrainedHighSpeed;
mOperatingMode = operatingMode;
}
if (!mNeedConfig) {
ALOGV("%s: Skipping config, no stream changes", __FUNCTION__);
return OK;
}
// Workaround for device HALv3.2 or older spec bug - zero streams requires
// adding a dummy stream instead.
// TODO: Bug: 17321404 for fixing the HAL spec and removing this workaround.
if (mOutputStreams.size() == 0) {
addDummyStreamLocked();
} else {
tryRemoveDummyStreamLocked();
}
// Start configuring the streams
ALOGV("%s: Camera %s: Starting stream configuration", __FUNCTION__, mId.string());
camera3_stream_configuration config;
config.operation_mode = mOperatingMode;
config.num_streams = (mInputStream != NULL) + mOutputStreams.size();
Vector<camera3_stream_t*> streams;
streams.setCapacity(config.num_streams);
if (mInputStream != NULL) {
camera3_stream_t *inputStream;
inputStream = mInputStream->startConfiguration();
if (inputStream == NULL) {
CLOGE("Can't start input stream configuration");
cancelStreamsConfigurationLocked();
return INVALID_OPERATION;
}
streams.add(inputStream);
}
for (size_t i = 0; i < mOutputStreams.size(); i++) {
// Don't configure bidi streams twice, nor add them twice to the list
if (mOutputStreams[i].get() ==
static_cast<Camera3StreamInterface*>(mInputStream.get())) {
config.num_streams--;
continue;
}
camera3_stream_t *outputStream;
outputStream = mOutputStreams.editValueAt(i)->startConfiguration();
if (outputStream == NULL) {
CLOGE("Can't start output stream configuration");
cancelStreamsConfigurationLocked();
return INVALID_OPERATION;
}
streams.add(outputStream);
}
config.streams = streams.editArray();
// Do the HAL configuration; will potentially touch stream
// max_buffers, usage, priv fields.
res = mInterface->configureStreams(&config);
if (res == BAD_VALUE) {
// HAL rejected this set of streams as unsupported, clean up config
// attempt and return to unconfigured state
CLOGE("Set of requested inputs/outputs not supported by HAL");
cancelStreamsConfigurationLocked();
return BAD_VALUE;
} else if (res != OK) {
// Some other kind of error from configure_streams - this is not
// expected
SET_ERR_L("Unable to configure streams with HAL: %s (%d)",
strerror(-res), res);
return res;
}
// Finish all stream configuration immediately.
// TODO: Try to relax this later back to lazy completion, which should be
// faster
if (mInputStream != NULL && mInputStream->isConfiguring()) {
res = mInputStream->finishConfiguration();
if (res != OK) {
CLOGE("Can't finish configuring input stream %d: %s (%d)",
mInputStream->getId(), strerror(-res), res);
cancelStreamsConfigurationLocked();
return BAD_VALUE;
}
}
for (size_t i = 0; i < mOutputStreams.size(); i++) {
sp<Camera3OutputStreamInterface> outputStream =
mOutputStreams.editValueAt(i);
if (outputStream->isConfiguring() && !outputStream->isConsumerConfigurationDeferred()) {
res = outputStream->finishConfiguration();
if (res != OK) {
CLOGE("Can't finish configuring output stream %d: %s (%d)",
outputStream->getId(), strerror(-res), res);
cancelStreamsConfigurationLocked();
return BAD_VALUE;
}
}
}
// Request thread needs to know to avoid using repeat-last-settings protocol
// across configure_streams() calls
mRequestThread->configurationComplete(mIsConstrainedHighSpeedConfiguration);
char value[PROPERTY_VALUE_MAX];
property_get("camera.fifo.disable", value, "0");
int32_t disableFifo = atoi(value);
if (disableFifo != 1) {
// Boost priority of request thread to SCHED_FIFO.
pid_t requestThreadTid = mRequestThread->getTid();
res = requestPriority(getpid(), requestThreadTid,
kRequestThreadPriority, /*isForApp*/ false, /*asynchronous*/ false);
if (res != OK) {
ALOGW("Can't set realtime priority for request processing thread: %s (%d)",
strerror(-res), res);
} else {
ALOGD("Set real time priority for request queue thread (tid %d)", requestThreadTid);
}
}
// Update device state
mNeedConfig = false;
internalUpdateStatusLocked((mDummyStreamId == NO_STREAM) ?
STATUS_CONFIGURED : STATUS_UNCONFIGURED);
ALOGV("%s: Camera %s: Stream configuration complete", __FUNCTION__, mId.string());
// tear down the deleted streams after configure streams.
mDeletedStreams.clear();
return OK;
}
该方法中会调用res = mInterface->configureStreams(&config)提供给HAL层去执行配置，因为HAL层的逻辑每个厂商都不一样，我们就不进入去分析了，大家可以自己看一下。配置完成后，在保证正确的情况下，调用outputStream->finishConfiguration()结束配置，finishConfiguration方法的实现在父类frameworks\av\services\camera\libcameraservice\device3\Camera3Stream.cpp当中，源码如下：
status_t Camera3Stream::finishConfiguration() {
ATRACE_CALL();
Mutex::Autolock l(mLock);
switch (mState) {
case STATE_ERROR:
ALOGE("%s: In error state", __FUNCTION__);
return INVALID_OPERATION;
case STATE_IN_CONFIG:
case STATE_IN_RECONFIG:
// OK
break;
case STATE_CONSTRUCTED:
case STATE_CONFIGURED:
ALOGE("%s: Cannot finish configuration that hasn't been started",
__FUNCTION__);
return INVALID_OPERATION;
default:
ALOGE("%s: Unknown state", __FUNCTION__);
return INVALID_OPERATION;
}
// Register for idle tracking
sp<StatusTracker> statusTracker = mStatusTracker.promote();
if (statusTracker != 0) {
mStatusId = statusTracker->addComponent();
}
// Check if the stream configuration is unchanged, and skip reallocation if
// so. As documented in hardware/camera3.h:configure_streams().
if (mState == STATE_IN_RECONFIG &&
mOldUsage == camera3_stream::usage &&
mOldMaxBuffers == camera3_stream::max_buffers) {
mState = STATE_CONFIGURED;
return OK;
}
// Reset prepared state, since buffer config has changed, and existing
// allocations are no longer valid
mPrepared = false;
mStreamUnpreparable = false;
status_t res;
res = configureQueueLocked();
if (res != OK) {
ALOGE("%s: Unable to configure stream %d queue: %s (%d)",
__FUNCTION__, mId, strerror(-res), res);
mState = STATE_ERROR;
return res;
}
mState = STATE_CONFIGURED;
return res;
}这里又会调用configureQueueLocked回到子类中去处理，我们看一下frameworks\av\services\camera\libcameraservice\device3\Camera3OutputStream.cpp类的configureQueueLocked方法，源码如下：
status_t Camera3OutputStream::configureQueueLocked() {
status_t res;
mTraceFirstBuffer = true;
if ((res = Camera3IOStreamBase::configureQueueLocked()) != OK) {
return res;
}
if ((res = configureConsumerQueueLocked()) != OK) {
return res;
}
// Set dequeueBuffer/attachBuffer timeout if the consumer is not hw composer or hw texture.
// We need skip these cases as timeout will disable the non-blocking (async) mode.
if (!(isConsumedByHWComposer() || isConsumedByHWTexture())) {
mConsumer->setDequeueTimeout(kDequeueBufferTimeout);
}
return OK;
}这里又调用configureConsumerQueueLocked进一步处理，该方法源码如下：
status_t Camera3OutputStream::configureConsumerQueueLocked() {
status_t res;
mTraceFirstBuffer = true;
ALOG_ASSERT(mConsumer != 0, "mConsumer should never be NULL");
// Configure consumer-side ANativeWindow interface. The listener may be used
// to notify buffer manager (if it is used) of the returned buffers.
res = mConsumer->connect(NATIVE_WINDOW_API_CAMERA,
/*listener*/mBufferReleasedListener,
/*reportBufferRemoval*/true);
if (res != OK) {
ALOGE("%s: Unable to connect to native window for stream %d",
__FUNCTION__, mId);
return res;
}
mConsumerName = mConsumer->getConsumerName();
res = native_window_set_usage(mConsumer.get(), camera3_stream::usage);
if (res != OK) {
ALOGE("%s: Unable to configure usage %08x for stream %d",
__FUNCTION__, camera3_stream::usage, mId);
return res;
}
res = native_window_set_scaling_mode(mConsumer.get(),
NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW);
if (res != OK) {
ALOGE("%s: Unable to configure stream scaling: %s (%d)",
__FUNCTION__, strerror(-res), res);
return res;
}
if (mMaxSize == 0) {
// For buffers of known size
res = native_window_set_buffers_dimensions(mConsumer.get(),
camera3_stream::width, camera3_stream::height);
} else {
// For buffers with bounded size
res = native_window_set_buffers_dimensions(mConsumer.get(),
mMaxSize, 1);
}
if (res != OK) {
ALOGE("%s: Unable to configure stream buffer dimensions"
" %d x %d (maxSize %zu) for stream %d",
__FUNCTION__, camera3_stream::width, camera3_stream::height,
mMaxSize, mId);
return res;
}
res = native_window_set_buffers_format(mConsumer.get(),
camera3_stream::format);
if (res != OK) {
ALOGE("%s: Unable to configure stream buffer format %#x for stream %d",
__FUNCTION__, camera3_stream::format, mId);
return res;
}
res = native_window_set_buffers_data_space(mConsumer.get(),
camera3_stream::data_space);
if (res != OK) {
ALOGE("%s: Unable to configure stream dataspace %#x for stream %d",
__FUNCTION__, camera3_stream::data_space, mId);
return res;
}
int maxConsumerBuffers;
res = static_cast<ANativeWindow*>(mConsumer.get())->query(
mConsumer.get(),
NATIVE_WINDOW_MIN_UNDEQUEUED_BUFFERS, &maxConsumerBuffers);
if (res != OK) {
ALOGE("%s: Unable to query consumer undequeued"
" buffer count for stream %d", __FUNCTION__, mId);
return res;
}
ALOGV("%s: Consumer wants %d buffers, HAL wants %d", __FUNCTION__,
maxConsumerBuffers, camera3_stream::max_buffers);
if (camera3_stream::max_buffers == 0) {
ALOGE("%s: Camera HAL requested max_buffer count: %d, requires at least 1",
__FUNCTION__, camera3_stream::max_buffers);
return INVALID_OPERATION;
}
mTotalBufferCount = maxConsumerBuffers + camera3_stream::max_buffers;
mHandoutTotalBufferCount = 0;
mFrameCount = 0;
mLastTimestamp = 0;
mUseMonoTimestamp = (isConsumedByHWComposer() | isVideoStream());
res = native_window_set_buffer_count(mConsumer.get(),
mTotalBufferCount);
if (res != OK) {
ALOGE("%s: Unable to set buffer count for stream %d",
__FUNCTION__, mId);
return res;
}
res = native_window_set_buffers_transform(mConsumer.get(),
mTransform);
if (res != OK) {
ALOGE("%s: Unable to configure stream transform to %x: %s (%d)",
__FUNCTION__, mTransform, strerror(-res), res);
return res;
}
/**
* Camera3 Buffer manager is only supported by HAL3.3 onwards, as the older HALs requires
* buffers to be statically allocated for internal static buffer registration, while the
* buffers provided by buffer manager are really dynamically allocated. Camera3Device only
* sets the mBufferManager if device version is > HAL3.2, which guarantees that the buffer
* manager setup is skipped in below code. Note that HAL3.2 is also excluded here, as some
* HAL3.2 devices may not support the dynamic buffer registeration.
*/
if (mBufferManager != 0 && mSetId > CAMERA3_STREAM_SET_ID_INVALID) {
uint32_t consumerUsage = 0;
getEndpointUsage(&consumerUsage);
StreamInfo streamInfo(
getId(), getStreamSetId(), getWidth(), getHeight(), getFormat(), getDataSpace(),
camera3_stream::usage | consumerUsage, mTotalBufferCount,
/*isConfigured*/true);
wp<Camera3OutputStream> weakThis(this);
res = mBufferManager->registerStream(weakThis,
streamInfo);
if (res == OK) {
// Disable buffer allocation for this BufferQueue, buffer manager will take over
// the buffer allocation responsibility.
mConsumer->getIGraphicBufferProducer()->allowAllocation(false);
mUseBufferManager = true;
} else {
ALOGE("%s: Unable to register stream %d to camera3 buffer manager, "
"(error %d %s), fall back to BufferQueue for buffer management!",
__FUNCTION__, mId, res, strerror(-res));
}
}
return OK;
}这里有一句比较重要，就是res = mConsumer->connect(NATIVE_WINDOW_API_CAMERA, /*listener*/mBufferReleasedListener, /*reportBufferRemoval*/true)，mConsumer就是我们配置流时创建的surface，这里会执行连接，如果我们当前surface的GraphicBufferProducer生产者有被其他连接，那么配置也会失败，这里一定要注意，配置失败的话，也会有日志输出，可以帮助我们定位问题。ANativeWindow是OpenGL定义的窗口类型了，在Android设备上，该类型一般有两类，一类就是Surface，一类就是SurfaceFlinger了。
好，到这里，createCaptureSession的过程就分析完了，它是我们相机预览最重要的条件，一般session创建成功，那么我们的预览就会正常，session创建失败，则预览一定黑屏，大家如果有碰到相机黑屏的问题，最大的疑点就是这里，session创建完成后，framework会通过CameraCaptureSession.StateCallback类的public abstract void onConfigured(@NonNull CameraCaptureSession session)回调到应用层，通知我们session创建成功了，那么我们就可以使用回调方法中的CameraCaptureSession参数，调用它的setRepeatingRequest方法来下预览了，该逻辑执行完成后，我们相机的预览就起来了。
还有一点需要说一下，Android 8.0的源码中在CameraCaptureSession类中提供的finalizeOutputConfigurations方法非常巧妙，它可以缩短相机的启动时间，它的实现思路是这样的，原本创建session时，要求我们必须提供预览surface，而该接口可以先不提供预览surface，而只以预览的size构造一个OutputConfiguration对象，将它下到CameraServer进程当中，然后等到预览surface准备就绪以后，再调用该接口去对接，这样也可以保证预览的正常，中间就可以节省出预览surface准备的部分时间，也就达到了缩短相机启动时长的目的了。
关于session创建这块的逻辑，HAL层还有很大一段，在公司的芯片组件的源码中有分析过一部分，家里没有条件，只能先放下了。大家如果有看过Android相机的源码，就可以感觉到，camera部分的逻辑真是太复杂了，framework中（包括Java层和native层的CameraServer进程）还是比较简单的一部分，往下的CameraDaemon进程中还有运行算法、ISP的逻辑，再到内核、驱动，还有很大一部分，想要完全搞通，还是要费很大气力的。
好了，今天就到这里，晚安！！
