相機和系統配置的更改

擴展視圖系統 (EVS) 1.1 中也更新了攝像頭和系統配置管理和使用。由於 EVS 1.0 不提供查詢相機設備信息和系統配置的方法，因此應用程序開發人員必須自己獲取這些信息。例如，如果客戶端實現了一些計算機視覺應用程序，它必須有相機校準數據。

為了緩解這種情況，EVS 1.1 使用相機元數據擴展了相機設備描述符，並提供了多種方法使客戶端能夠獲取相機設備和系統配置信息。

import android.frameworks.cameraservice.device@2.0::CameraMetadata;
import android.frameworks.cameraservice.common@2.0::CameraMetadataType;

/**
 * Structure describing the basic properties of an EVS camera, extended
 * from its v1.0 declaration.
 *
 * The HAL is responsible for filling out this structure for each
 * EVS camera in the system.
 */
struct CameraDesc {
    @1.0::CameraDesc v1;
    /**
     * Store camera metadata such as lens characteristics.
     */
    CameraMetadata metadata;
};

CameraDesc擴展為具有相機設備元數據，並且此類型是從android.frameworks.cameraservice.device@2.0導入的。這種設計選擇允許供應商在其實現中使用camera_metadata_t並利用在camera_metadata.h中定義的 API。此外，供應商不能使用他們自己的元數據類型來傳遞Android 中未定義的其他信息，如camera_vendor_tags.h中所述。

打開具有所需流配置的相機設備

import android.hardware.camera.device@3.2::Stream;

/**
 * Get the IEvsCamera associated with a cameraId from a CameraDesc
 *
 * Given a camera's unique cameraId from CameraDesc, returns the
 * IEvsCamera interface associated with the specified camera. When
 * done using the camera, the caller may release it by calling closeCamera().
 *
 * @param  cameraId  A unique identifier of the camera.
 * @param  streamCfg A stream configuration the client wants to use.
 * @return evsCamera EvsCamera object associated with a given cameraId.
 */
openCamera_1_1(string cameraId, Stream streamCfg) generates (IEvsCamera evsCamera);

Android 定義的元數據字段之一是ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS 。 EVS 驅動程序可以使用此類型來識別每個攝像頭模塊支持的流配置。例如，下面提供的參考實現列出了每個支持的流配置的信息：

• 流 ID
• 寬度
• 高度
• 方向（輸入或輸出）
• 幀率

單個相機硬件實例上的多個客戶端

如果客戶端請求打開一個已經處於活動狀態的相機設備，EVS 管理器會將請求的流配置與活動配置進行比較。如果它們不同，EVS 管理器將返回一個空的 IEvsCamera 對象。客戶端必須正確處理這種可能的故障。

參考配置文件

EVS 1.1 中包含的參考配置文件是用 XML 編寫的，供應商可以使用包含的 DTD 文件（如下所示）來驗證（修改過的）示例配置文件，或者如果他們想使用相同的格式，也可以使用他們自己的文件。 DTD 文件還提供了每個元素和屬性的詳細描述。

<?xml version='1.0' encoding='utf-8'?>
<!-- Copyright (C) 2019 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
-->


<!-- Author : changyeon@google.com
     Version: 1.0
-->

<!ELEMENT configuration (system,camera,display)>

<!-- System Configuration that contains below informations:
     - The dimension of the vehicle.
     - Number of cameras available to EVS.
     - List of predefined use cases.
-->
<!ELEMENT system (dimension,num_cameras,supported_use_case*)>
    <!-- The x, y, and z dimension of the vehicle in the unit of centimeters. Axes are defined at
         https://source.android.com/devices/sensors/sensor-types#auto_axes
    -->
    <!ELEMENT dimension EMPTY>
    <!ATTLIST dimension
        x CDATA '0'
        y CDATA '0'
        z CDATA '0'
    >

    <!-- The number of cameras that are available to EVS on the vehicle.
         This must be equal to the number of camera elements of the device element.
    -->
    <!ELEMENT num_cameras EMPTY>
    <!ATTLIST num_cameras
        value CDATA #REQUIRED
    >

    <!-- List of predefined use cases -->
    <!ELEMENT supported_use_case (use_case)*>
        <!-- Predefined configurations for each of listed use cases.
             @attr  id       : Unique string identifier of this use case.
             @attr  camera   : ID of either a single camera device or a camera group.
             @attr  stream_id: Preferred stream configuration of camera device/group
                               that is set by camera attribute.
        -->
        <!ELEMENT use_case EMPTY>
        <!ATTLIST use_case
            id        CDATA #REQUIRED
            camera    CDATA #REQUIRED
            stream_id CDATA #REQUIRED
        >

<!-- Device descriptions -->
<!ELEMENT camera (group|device)*>
    <!-- Camera group descriptor
         @attr group_id    : Unique logical camera group identifier. Camera device use this to be
                             a member of the group.
         @attr device_id   : Comma-separated list of unique camera identifiers of member camera
                             devices.
         @attr synchronized: Boolean field that tells whether or not this camera is synchronized
                             with other cameras in the same group. This will be ineffective if
                             there is a single camera in the group or a group is invalid.
    -->
    <!ELEMENT group (caps)>
    <!ATTLIST group
        group_id        CDATA #REQUIRED
        device_id       CDATA #REQUIRED
        synchronized    CDATA #REQUIRED
    >
    <!-- Please note that a camera may have stream configurations. If it has, all stream
         configurations must be supported by each camera device in the group.
    -->

    <!-- Camera device descriptor
         @attr id          : Unique camera identifier.
         @attr position    : Must be one of front, rear, left, or right.
    -->
    <!ELEMENT device (caps,characteristics*)>
    <!ATTLIST device
        id              CDATA #REQUIRED
        position        CDATA #REQUIRED
    >
        <!-- Camera metadata that contains:
             - A list of supported controls.
             - A list of supported stream configurations.
        -->
        <!ELEMENT caps (supported_controls|stream)*>
            <!-- A list of supported controls.
                 This must be a subset of android.hardware.automotive.evs@1.1::CameraParam.
            -->
            <!ELEMENT supported_controls EMPTY>
            <!ATTLIST supported_controls
                value CDATA #REQUIRED
            >

            <!-- A list of supported output sizes. -->
            <!ELEMENT stream EMPTY>
            <!ATTLIST stream
                id     CDATA #REQUIRED
                width  CDATA #REQUIRED
                height CDATA #REQUIRED
                format CDATA #REQUIRED
            >

        <!-- Camera module characteristics including its optics and imaging sensor. -->
        <!ELEMENT characteristics (parameter)*>
                <!ELEMENT parameter EMPTY>
                <!-- A name of camera characteristic. This must be a subset of
                     android.hardware.automotive.evs@1.1::CameraCharacteristics.
                -->
                <!ATTLIST parameter
                    name  CDATA #REQUIRED
                    type  CDATA #REQUIRED
                    size  CDATA #REQUIRED
                    value CDATA #REQUIRED
                >

<!-- Available display devices -->
<!ELEMENT display (display_device)*>
    <!-- Display device descriptor
     @attr id      : Unique display identifier.
     @attr position: Display mount location.
    -->
    <!ELEMENT display_device (supported_formats)*>
    <!ATTLIST display_device
        id        CDATA #REQUIRED
        position  CDATA #REQUIRED
    >
        <!-- A list of supported input data formats.
             @attr value: A comma separated list of input data formats
        -->
        <!ELEMENT supported_formats EMPTY>
        <!ATTLIST supported_formats
            value CDATA #REQUIRED
        >

示例配置文件如下所示（示例包含虛擬數字數據）。

<?xml version='1.0' encoding='utf-8'?>
<!-- Copyright (C) 2019 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0
     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
-->

<!-- Extended View System Example Configuration

     Android Automotive axes are used to define coordinates.
     See https://source.android.com/devices/sensors/sensor-types#auto_axes

     Use evs_configuration.dtd with xmllint tool, to validate XML configuration file
-->

<configuration>
    <!-- system configuration -->
    <system>
        <!-- reference dimension of the vehicle in the unit of centimeters -->
        <dimension x='200' y='400' z='100' />

        <!-- number of cameras available to EVS -->
        <num_cameras value='2'/>

        <!-- list of supported use cases -->
        <supported_use_case>
            <!-- use case configuration -->
            <use_case
                id='rear_view'
                camera='/dev/video1'
                stream_id='1'
            />

            <!-- use case configuration -->
            <use_case
                id='surround_view'
                camera='group1'
                stream_id='0'
            />
        </supported_use_case>
    </system>

    <!-- camera device information -->
    <camera>
        <!-- camera group 0 -->
        <group group_id='group0'
               device_id='/dev/video1,/dev/video2'
               synchronized='false'
        >
            <caps>
                <stream id='0' width='640' height='360' format='V4L2_PIX_UYUV'/>
            </caps>
        </group>

        <!-- camera device starts -->
        <device id='/dev/video1' position='rear'>
            <caps>
                <!-- list of supported controls -->
                <supported_controls
                    value='BRIGHTNESS,
                           CONTRAST,
                           AUTO_WHITE_BALANCE,
                           WHITE_BALANCE_TEMPERATURE,
                           SHARPNESS,
                           AUTO_EXPOSURE,
                           ABSOLUTE_EXPOSURE,
                           AUTO_FOCUS,
                           ABSOLUTE_ZOOM'
                />

                <!-- list of supported stream configurations -->
                <stream id='0' width='1280' height='1080' format='V4L2_PIX_NV21'/>
                <stream id='1' width='1280' height='1080' format='V4L2_PIX_YUYV'/>
                <stream id='2' width='1280' height='1080' format='V4L2_PIX_UYUV'/>
                <stream id='3' width='640'  height='360'  format='V4L2_PIX_NV21'/>
                <stream id='4' width='640'  height='360'  format='V4L2_PIX_YUYV'/>
                <stream id='5' width='640'  height='360'  format='V4L2_PIX_UYUV'/>
                <stream id='6' width='320'  height='240'  format='V4L2_PIX_NV21'/>
                <stream id='7' width='320'  height='240'  format='V4L2_PIX_YUYV'/>
                <stream id='8' width='320'  height='240'  format='V4L2_PIX_UYUV'/>
            </caps>

            <!-- list of parameters -->
            <characteristics>
                <!-- Lens distortion information. See
                     https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html#LENS_DISTORTION
                -->
                <parameter
                    name='LENS_DISTORTION'
                    type='float'
                    size='5'
                    value='0.0,0.0,0.0,0.0,0.0'
                />

                <!-- Camera intrinsic calibration matrix. See
                     https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html#LENS_INTRINSIC_CALIBRATION
                -->
                <parameter
                    name='LENS_INTRINSIC_CALIBRATION'
                    type='float'
                    size='5'
                    value='0.0,0.0,0.0,0.0,0.0'
                />

                <!-- Camera pose translation and rotation. See
                     https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html#LENS_POSE_TRANSLATION
                     https://developer.android.com/reference/android/hardware/camera2/CameraCharacteristics.html#LENS_POSE_ROTATION
                -->
                <parameter
                    name='LENS_POSE_TRANSLATION'
                    type='float'
                    size='3'
                    value='0.0,0.0,0.0'
                />
                <parameter
                    name='LENS_POSE_ROTATION'
                    type='float'
                    size='4'
                    value='0.0,0.0,0.0,0.0'
                />
            </characteristics>
        </device>
        <device id='/dev/video2' position='front'>
            <caps>
                <!-- list of supported stream configurations -->
                <stream id='0' width='1280' height='1080' format='V4L2_PIX_NV21'/>
            </caps>
        </device>
    </camera>

    <!-- display device starts -->
    <display>
        <display_device id='display0' position='driver'>
            <!-- list of supported input formats
                 This must be a subset of android_pixel_format_t enum.
            -->
            <supported_formats
                value='RGBA_8888,
                       YUYV,
                       UYVY'
            />
        </display_device>
    </display>
</configuration>