第17讲 初始化VendorTags, Flashlight和PerfClass - Android Camera Native Framework

本讲是Android Camera Native Framework专题的第17讲，我们介绍cameraserver进程启动之初始化VendorTags, Flashlight和PerfClass。

更多资源：

创建VendorTagDescriptorCache

VendorTagDescriptorCache是一个Manager，管理不同Provider里面的Vendor Tag Descriptor，VendorTagDescriptor维护管理所有Vendor Tags的Section、Name、Type，ID之间的关系：

Android 13 代码逻辑：CameraProviderManager::setUpVendorTags()

status_t CameraProviderManager::setUpVendorTags() {
    sp tagCache = new VendorTagDescriptorCache();

    for (auto& provider : mProviders) {
        tagCache->addVendorDescriptor(provider->mProviderTagid, provider->mVendorTagDescriptor);
    }

    VendorTagDescriptorCache::setAsGlobalVendorTagCache(tagCache);

    return OK;
}

Flashlight初始化

CameraServer通过CameraFlashlight来管理各CameraDevice的Flashlight，类图如下：

通过CameraFlashlight::findFlashUnits完成Flashlight的初始化，流程如下：

Android 13代码，CameraFlashlight::findFlashUnits：

status_t CameraFlashlight::findFlashUnits() {
    Mutex::Autolock l(mLock);
    status_t res;

    std::vector cameraIds;
    std::vector ids = mProviderManager->getCameraDeviceIds();
    int numberOfCameras = static_cast(ids.size());
    cameraIds.resize(numberOfCameras);
    // No module, must be provider
    for (size_t i = 0; i < cameraIds.size(); i++) {
        cameraIds[i] = String8(ids[i].c_str());
    }

    mFlashControl.clear();

    for (auto &id : cameraIds) {
        ssize_t index = mHasFlashlightMap.indexOfKey(id);
        if (0 <= index) {
            continue;
        }

        bool hasFlash = false;
        res = createFlashlightControl(id);
        if (res) {
            ALOGE("%s: failed to create flash control for %s", __FUNCTION__,
                    id.string());
        } else {
            res = mFlashControl->hasFlashUnit(id, &hasFlash);
            if (res == -EUSERS || res == -EBUSY) {
                ALOGE("%s: failed to check if camera %s has a flash unit. Some "
                        "camera devices may be opened", __FUNCTION__,
                        id.string());
                return res;
            } else if (res) {
                ALOGE("%s: failed to check if camera %s has a flash unit. %s"
                        " (%d)", __FUNCTION__, id.string(), strerror(-res),
                        res);
            }

            mFlashControl.clear();
        }
        mHasFlashlightMap.add(id, hasFlash);
    }

    mFlashlightMapInitialized = true;
    return OK;
}

为SPerfClass过滤Characteristics

执行条件：

• ro.odm.build.media_performance_class >= 31

执行动作：

• 针对主后置和主前置，过滤掉<1080p的JPEG尺寸

CTS(SPerfClassTest.java)：

• testSPerfClassJpegSizesByCamera

流程：

Android 13代码：

void CameraService::filterSPerfClassCharacteristicsLocked() {
    // To claim to be S Performance primary cameras, the cameras must be
    // backward compatible. So performance class primary camera Ids must be API1
    // compatible.
    bool firstRearCameraSeen = false, firstFrontCameraSeen = false;
    for (const auto& cameraId : mNormalDeviceIdsWithoutSystemCamera) {
        int facing = -1;
        int orientation = 0;
        String8 cameraId8(cameraId.c_str());
        getDeviceVersion(cameraId8, /*out*/&facing, /*out*/&orientation);
        if (facing == -1) {
            ALOGE("%s: Unable to get camera device \"%s\" facing", __FUNCTION__, cameraId.c_str());
            return;
        }

        if ((facing == hardware::CAMERA_FACING_BACK && !firstRearCameraSeen) ||
                (facing == hardware::CAMERA_FACING_FRONT && !firstFrontCameraSeen)) {
            status_t res = mCameraProviderManager->filterSmallJpegSizes(cameraId);
            if (res == OK) {
                mPerfClassPrimaryCameraIds.insert(cameraId);
            } else {
                ALOGE("%s: Failed to filter small JPEG sizes for performance class primary "
                        "camera %s: %s(%d)", __FUNCTION__, cameraId.c_str(), strerror(-res), res);
                break;
            }

            if (facing == hardware::CAMERA_FACING_BACK) {
                firstRearCameraSeen = true;
            }
            if (facing == hardware::CAMERA_FACING_FRONT) {
                firstFrontCameraSeen = true;
            }
        }

        if (firstRearCameraSeen && firstFrontCameraSeen) {
            break;
        }
    }
}