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Cambios en la configuración de la cámara y del sistema

La administración y el uso de la configuración de la cámara y del sistema también se actualizaron en Extended View System (EVS) 1.1 Dado que EVS 1.0 no proporciona métodos para consultar información del dispositivo de la cámara y la configuración del sistema, el desarrollador de la app debe obtienen esa información ellos mismos. Por ejemplo, el cliente debe tener acceso de calibración si se implementan algunas apps de visión artificial.

Para aliviar esta circunstancia, EVS 1.1 extiende un descriptor de dispositivo de cámara con metadatos de la cámara y proporciona varios métodos que permiten a los clientes obtener la información de configuración del sistema y del dispositivo.

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;
};

Se extendió CameraDesc para que tenga metadatos de dispositivos con cámara y este tipo se importa de android.frameworks.cameraservice.device@2.0. Esta opción de diseño permite que los proveedores usen camera_metadata_t en sus implementaciones y aprovechar las APIs definidas en ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS. El conductor de EVS puede usar este tipo para identificar qué configuraciones de transmisión son compatibles con cada módulo de cámara. Además, los proveedores no pueden usar sus propios tipos de metadatos para proporcionar otra información que no esté definida en Android, como se explica en el ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS. El conductor de EVS puede usar este tipo para identificar qué configuraciones de transmisión son compatibles con cada módulo de cámara.

Abre un dispositivo de cámara con la configuración de transmisión deseada

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);

Uno de los campos de metadatos que Android define es ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS. El conductor de EVS puede usar este tipo para identificar las configuraciones de transmisión compatibles por cada módulo de la cámara. Por ejemplo, la implementación de referencia que se proporciona a continuación enumera los de cada configuración de transmisión admitida:

ID de flujo
Ancho
Altura
Dirección (entrada o salida)
Velocidad de fotogramas

Varios clientes en una sola instancia de hardware de cámara

Si un cliente solicita abrir un dispositivo de cámara ya activo, el EVS el administrador compara una configuración de transmisión solicitada con la configuración activa. Si difieren, el administrador de EVS devuelve un objeto IEvsCamera nulo. El cliente DEBE solucionar este posible error correctamente.

Archivo de configuración de referencia

El archivo de configuración de referencia incluido en EVS 1.1 está escrito en XML los proveedores pueden usar el archivo DTD incluido (que se muestra a continuación) para validar un mensaje (modificado) de configuración de muestra o usar su propio archivo si quieren usar el mismo formato. El archivo DTD también proporciona descripciones detalladas de cada elemento y atributo.

<?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/docs/core/interaction/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 is 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
        >

A continuación, se muestra un archivo de configuración de muestra (el ejemplo contiene datos numéricos ficticios).

<?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/docs/core/interaction/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>