Anche la gestione e l'utilizzo della configurazione della videocamera e del sistema sono stati aggiornati in Extended View System (EVS) 1.1. Poiché EVS 1.0 non fornisce metodi per eseguire query sulle informazioni sul dispositivo della videocamera e sulla configurazione del sistema, lo sviluppatore di app deve recuperare queste informazioni autonomamente. Ad esempio, il client deve disporre dei dati di calibrazione della videocamera se implementa alcune app di computer vision.
Per ovviare a questa circostanza, 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 della videocamera e del sistema.
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 videocamera 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.
Aprire un dispositivo della videocamera con la configurazione di 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 per ogni configurazione di stream supportata:
- ID flusso
- 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 della videocamera già attivo, il gestore EVS confronta una configurazione di stream richiesta con la configurazione attiva. Se sono diverse, il gestore EVS restituisce un oggetto IEvsCamera null. Il client 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=>&<#39;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 : chang>ye<on@google.com Version: 1.0 -- !ELEMENT c>on<figuration (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 (dimens>ion,n<um_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/s>ensor<s/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 th<e device element. -- !ELEMENT num_cameras EMPTY> !<ATTLIST num_cameras value C>DATA <#REQUIRED !-- List of predefi>ned use c<ases -- !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 at<tribute. -- !ELEMENT use_case EMPTY !ATTLIST use_case id CDATA #REQUIRED camera CD>AT<A #REQUIRED st>r<eam_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 i>s a s<ingle camera in the g>roup <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 b<e supported by each camera device in the group. -- !-- Camera device descriptor @attr id : Unique camera identifier. @attr posi>tion < : Must be one of front, rear, left, >or ri<ght. -- !ELEMENT device (caps,characteristics*) !ATTLIST device id >CDATA #RE<QUIRED 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 andr>oid.hardware.<automotive.evs@1.1::CameraParam. > -<- !ELEMENT supported_controls EMPTY !ATTLIST supported>_controls < value CDATA #REQUIRED > < !-- A list of >supported out<put sizes. -- !ELEMENT stream EMPTY !ATTLIST stream id CDATA #REQUIRED width CDATA #REQUIRED height CDATA #>REQUIRED < format CDATA #REQUIRED !-- Camera module> characte<ristics including its optics and imag>ing sensor. -- < !ELEMENT character>istics (parameter<)* !ELEMENT parameter EMPTY !-- A name of camera characteristic. This must be a subset of android.hardware.a>utomotive.evs@1.1<::CameraCharacteristics. -- !ATTLIST parameter name CDATA #REQUIRED type CDATA #REQUIRED size CDATA #REQUIRE>D < value CDATA >#<REQUIRED !-- Ava>ilabl<e display devices -- !ELEMENT display (display_device)* !-- Display device descriptor @attr id : Unique display ide>ntifi<er. @attr position: Display mount locat>ion. < -- !ELEMENT display_device (supported_formats)* !ATTLIST display_device id > CDA<TA #REQUIRED position CDATA #REQUIRED !-- A list of supported input data formats. @attr va>lue: A co<mma 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 (l'esempio contiene dati numerici fittizi).
<?xml version='1.0' encoding=>&<#39;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, t>o <validate XML >confi<guration file -- configura>tion < !->- system <configuration -- system !-- reference dimension of the v>ehicle in< the unit of centimeters -- > dimension< x='200' y='400' z='1>00' /< !-- number o>f cameras <available to EVS -- num_ca>meras val<ue='2'/ > !-- li<st of supported use cases -- > suppo<rted_use_case !-- use case configuration -- use_case id='rear_view' > ca<mera='/dev/video1' > < stream_id='1' / !-- use case configuration -- use_case id>='sur<round_view' > < > camer<a='group1' > st<ream_i>d='0&<#39; / > /su<pported_use_case /system !-- camera device information -- camera !-- camera group 0 -- gro>up group_id=&<#39;>group0' < device_id='/dev/video1,/dev/video2' > synchr<onize>d='fa<lse>9; < caps > s<tream id='0' width='640'>; height='<;360>' format='<;V4L2_PIX_UYUV'/ >/caps /gr<oup !-- 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, SHARP>NESS, < AUTO_EXPOSURE, > ABSOLU<TE_EXPOSURE, AUTO_FOCUS, > AB<SOLUTE_ZOOM' / !-- list of >supported stream <configurations -- stream id='0' width=&#>39;1280' heig<ht='1080' format='V4L2_PIX_NV21'/ > stream id='<1' width='1280' height='1080' format='V4>L2_PIX_YUYV'/< stream id='2' width='1280' heig>ht='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 i>d='5'< width='640>' height=<9;360' format='V4L2_PIX_UYUV'/ stream id='6' width='320' height='240' format='V4L2_PIX_NV21'/ stream id=&>#39;7' width=<'320' height='240' format='V4L2_PIX_YUYV'/ stream id='8' width='320' height='240' format='V4L2_PIX_UYUV'>/ /cap<s !-- list of parameters -- characteristics !-- Lens distortion information. See https://developer.android.com/reference/android/hardware/cam>era2/CameraCharac<teristics.html#LENS_DISTORTION -- parameter name='LENS_DISTORTION' type='float' siz>e='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='L<ENS_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_TRANS>LATION < h>ttps://de<veloper>.android.<com/reference/android/hardware/camera2/C>ameraCharacte<rist>ics.html#LENS_POS<E_ROTATION -- >parameter < name='LENS_POSE_TRANSLATION' > type=&#<39;fl>oat' < > < > size=<'3' > v<alue=&#>39;0.0,0.<0,0.0' / p>arameter < name='LENS_POSE_ROTATION' type='float' size='>4' < value='0.0,0.0,0.0,0.0' / /characteristics /device device> id='</dev/video2'>; pos<ition=&#>3<9;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