EVS 1.1介绍

EVS在Android 11 的时候进行了版本迭代

1、事件和帧通知机制

上个版本1.0中，IEvsCameraStream接口定义了一个回调方法，仅用于传递捕获的视频帧

无法识别一些突发事件，1.1版本中增加了一个用于传递流式传输事件的额外回调。

package [email protected];

import @1.0::IEvsCameraStream;

/**
 * Implemented on client side to receive asynchronous video frame deliveries.
 */
interface IEvsCameraStream extends @1.0::IEvsCameraStream {
    /**
     * Receives calls from the HAL each time a video frame is ready for inspection.
     * Buffer handles received by this method must be returned via calls to
     * IEvsCamera::doneWithFrame_1_1(). When the video stream is stopped via a call
     * to IEvsCamera::stopVideoStream(), this callback may continue to happen for
     * some time as the pipeline drains. Each frame must still be returned.
     * When the last frame in the stream has been delivered, STREAM_STOPPED
     * event must be delivered. No further frame deliveries may happen
     * thereafter.
     *
     * @param buffer a buffer descriptor of a delivered image frame.
     */
    oneway deliverFrame_1_1(BufferDesc buffer);

    /**
     * Receives calls from the HAL each time an event happens.
     *
     * @param  event EVS event with possible event information.
     */
    oneway notify(EvsEvent event);
};

2、控制摄像头参数

之前1.0版本，摄像头设备被视为只读设备，不存在任何可让应用更改摄像头控制参数的方法

1.1版本中可以在app中更改摄像头控制参数，这些参数定义在enum CameraParam 中

/**
 * EVS Camera Parameter
 */
enum CameraParam : uint32_t {
    /**
     * The brightness of image frames
     */
    BRIGHTNESS,
    /**
     * The contrast of image frames
     */
    CONTRAST,
    /**
     * Automatic gain/exposure control
     */
    AUTOGAIN,
    /**
     * Gain control
     */
    GAIN,
    /**
     * Automatic Whitebalance
     */
    AUTO_WHITE_BALANCE,
    /**
     * Manual white balance setting as a color temperature in Kelvin.
     */
    WHITE_BALANCE_TEMPERATURE,
    /**
     * Image sharpness adjustment
     */
    SHARPNESS,
    /**
     * Auto Exposure Control modes; auto, manual, shutter priority, or
     * aperture priority.
     */
    AUTO_EXPOSURE,
    /**
     * Manual exposure time of the camera
     */
    ABSOLUTE_EXPOSURE,
    /**
     * Set the focal point of the camera to the specified position. This
     * parameter may not be effective when auto focus is enabled.
     */
    ABSOLUTE_FOCUS,
    /**
     * Enables continuous automatic focus adjustments.
     */
    AUTO_FOCUS,
    /**
     * Specify the objective lens focal length as an absolute value.
     */
    ABSOLUTE_ZOOM,
};

3、调整相机和系统配置

1.0版本中未提供查询相机设备信息和系统配置方法，1.1版本针对此问题，使用相机元数据扩展相机

设备描述符。

参考配置文件

EVS 1.1中包含的参考配置文件是采用XML格式编写的，且供应商可以使用包含DTD文件来验证

总归就是说，1.1版本中使用的是XML文件来配置相机的，不再是json文件

4、显示这块的更改

提供了新的简单框架服务，允许供应商在HAL实现中使用Sufaceflinger/EGL，无需链接libgui，

AOSP 提供此服务的默认实现，功能完善。但是，供应商还必须实现 API，以便在其平台上提供此服务。

后续更新1.1版本的代码流程！！！

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