Anche la gestione e l'utilizzo della configurazione della videocamera e del sistema sono stati aggiornati in EVS (Extended View System) 1.1. Poiché EVS 1.0 non fornisce metodi per eseguire query sulle informazioni del dispositivo della fotocamera e sulla configurazione di sistema, lo sviluppatore dell'app deve recuperare autonomamente queste informazioni. Ad esempio, il cliente deve disporre dei dati di calibrazione della fotocamera se implementa alcune app di visione artificiale.
Per ovviare a questa situazione, EVS 1.1 estende un descrittore del dispositivo della videocamera con i metadati della videocamera e fornisce diversi metodi che consentono ai client di ottenere informazioni sulla configurazione del dispositivo e del sistema della videocamera.
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 viene esteso per includere i metadati del dispositivo della fotocamera e questo tipo viene importato da android.frameworks.cameraservice.device@2.0.
Questa scelta di progettazione consente ai fornitori di utilizzare camera_metadata_t
nelle loro implementazioni e di sfruttare le API definite in ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS. Il driver EVS può utilizzare questo tipo per identificare le configurazioni di stream supportate da ciascun modulo della videocamera.
Inoltre, i fornitori non possono utilizzare i propri tipi di metadati per fornire altre informazioni non definite in Android, come spiegato in ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS. Il driver EVS può utilizzare questo tipo per identificare le configurazioni di stream supportate da ciascun modulo della videocamera.
Apri una videocamera con la configurazione dello stream desiderata
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 dei campi dei metadati definiti da Android è ANDROID_SCALER_AVAILABLE_STREAM_CONFIGURATIONS. Il driver EVS può utilizzare questo tipo per identificare le configurazioni di stream supportate da ciascun modulo della videocamera. Ad esempio, l'implementazione di riferimento fornita di seguito elenca le informazioni su ogni configurazione dello stream supportata:
- ID stream
- Larghezza
- Altezza
- Direzione (input o output)
- Frequenza fotogrammi
Più client su una singola istanza HW della videocamera
Se un client richiede di aprire un dispositivo videocamera già attivo, il gestore EVS confronta la configurazione dello stream richiesta con quella attiva. Se sono diversi, il gestore EVS restituisce un oggetto IEvsCamera null. Il cliente DEVE gestire correttamente questo possibile errore.
File di configurazione di riferimento
Il file di configurazione di riferimento incluso in EVS 1.1 è scritto in XML e i fornitori possono utilizzare il file DTD incluso (mostrato di seguito) per convalidare un file di configurazione di esempio (modificato) o utilizzare il proprio file se vogliono utilizzare lo stesso formato. Il file DTD fornisce anche descrizioni dettagliate per ogni elemento e attributo.
<?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 >
Di seguito è riportato un file di configurazione di esempio (che contiene dati numerici fittizi).
<?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>