GB/T28181-2022之图像抓拍规范解读和设计实现

技术背景

GB/T28181-2022相对2016版，对图像抓拍有了明确的界定，图像抓拍在视频监控行业非常重要, Android平台GB28181设备接入端，无需实时上传音视频实时数据的情况下，就可以抓图上传到指定的图像存储服务器上。

图像抓拍基本要求如下：

1. 源设备向目标设备发送图像抓拍配置命令，需要携带传输路径、会话ID等信息。
2. 目标设备完成图像传输后，发送图像抓拍传输完成通知命令，采用IETF RFC3428中的MESSAGE方法实现。
3. 图像文件命名规则宜采用“设备编码(20位)、图像编码(2位)、时间编码(17位)、序列码(2位)”的形式
4. 图像格式宜使用JPEG，图像分辨率宜采用与主码流相同的分辨率。

需要注意的是，MESSAGE消息头Content-type头域为Content-type:Application/MANSCDP+xml，采用XML封装。设备收到图像抓拍配置命令后，发送配置响应命令，响应命令中包含执行结果信息。

图像抓拍流程如下：

技术实现

大牛直播SDK的SmartGBD已经完成GB28181设备接入侧的图像抓拍。

总体功能设计如下：

• ?[视频格式]H.264/H.265(Android H.265硬编码)；
• ?[音频格式]G.711 A律、AAC；
• ?[音量调节]Android平台采集端支持实时音量调节；
• ?[H.264硬编码]支持H.264特定机型硬编码；
• ?[H.265硬编码]支持H.265特定机型硬编码；
• ?[软硬编码参数配置]支持gop间隔、帧率、bit-rate设置；
• ?[软编码参数配置]支持软编码profile、软编码速度、可变码率设置；
• ?支持横屏、竖屏推流；
• ?Android平台支持后台service推送屏幕(推送屏幕需要5.0+版本)；
• 支持纯视频、音视频PS打包传输；
• 支持RTP OVER UDP和RTP OVER TCP被动模式（TCP媒体流传输客户端）；
• 支持信令通道网络传输协议TCP/UDP设置；
• 支持注册、注销，支持注册刷新及注册有效期设置；
• 支持设备目录查询应答；
• 支持心跳机制，支持心跳间隔、心跳检测次数设置；
• 支持移动设备位置(MobilePosition)订阅和通知；
• ?适用国家标准：GB/T 28181—2016；
• 支持语音广播；
• 支持语音对讲；
• 支持图像抓拍；
• 支持历史视音频文件检索；
• 支持历史视音频文件下载；
• 支持历史视音频文件回放；
• 支持云台控制和预置位查询；
• ?[实时水印]支持动态文字水印、png水印；
• ?[镜像]Android平台支持前置摄像头实时镜像功能；
• ?[实时静音]支持实时静音/取消静音；
• ?[实时快照]支持实时快照；
• ?[降噪]支持环境音、手机干扰等引起的噪音降噪处理、自动增益、VAD检测；
• ?[外部编码前视频数据对接]支持YUV数据对接；
• ?[外部编码前音频数据对接]支持PCM对接；
• ?[外部编码后视频数据对接]支持外部H.264数据对接；
• ?[外部编码后音频数据对接]外部AAC数据对接；
• ?[扩展录像功能]支持和录像SDK组合使用，录像相关功能。

图像抓拍相关信令处理如下：

/*
 * Author: daniusdk.com
 */
 
package com.gb.ntsignalling;
 
 
public interface GBSIPAgent {
    void setDeviceConfigListener(GBSIPAgentDeviceConfigListener deviceConfigListener);
 
 
    /*
     * 通知图像抓拍传输完成
     */
    boolean notifyUploadSnapShotFinished(String fromUserName, String fromUserNameAtDomain, String deviceID, String sessionID, java.util.List<String> snapShotList);
 
}

Device配置Listener如下：

package com.gb.ntsignalling;
 
public interface GBSIPAgentDeviceConfigListener {
    /*
     * 图像抓拍配置
     */
    void ntsOnDeviceSnapShotConfig(String from_user_name, String from_user_name_at_domain,
                                   String sn, String device_id, SnapShotConfig config,
                                   List<String> extra_info_list);
}

Snapshot配置接口如下：

public interface SnapShotConfig {
    int snap_num();
    int interval();
    String upload_url();
    String session_id();
}

图像抓拍JNI接口设计如下：

public class SmartPublisherJniV2 {
 
     /**
	 * 截图接口, 支持JPEG和PNG两种格式
	 * @param compress_format: 压缩格式, 0:JPEG格式, 1:PNG格式, 其他返回错误
	 * @param quality: 取值范围:[0, 100], 值越大图像质量越好, 仅对JPEG格式有效, 若是PNG格式,请填100
	 * @param file_name: 图像文件名, 例如:/dirxxx/test20231113100739.jpeg, /dirxxx/test20231113100739.png
	 * @param user_data_string: 用户自定义字符串
	 * @return {0} if successful
	 */
	 public native int CaptureImage(long handle, int compress_format, int quality, String file_name, String user_data_string);
	 
}

Device Snap Shot Listener 核心代码如下：

/*
 * Author: daniusdk.com
 */
 
public class GBDeviceSnapShotListenerImpl implements GBSIPAgentDeviceControlListener {
 
   @Override
    public void ntsOnDeviceSnapShotConfig(String from_user_name, final String from_user_name_at_domain,
                                          String sn, String device_id, final SnapShotConfig config,
                                          List<String> extra_info_list) {
        if (null == config)
            return;
 
        handler_.postDelayed(new Runnable() {
            @Override
            public void run() {
                Log.i(TAG, "ntsOnDeviceSnapShotConfig device_id:" + device_id_ + " session_id:" + config.session_id()
                        + ", snap_num:" + config.snap_num() + ", interval:" + config.interval() + ", upload_url:" + config.upload_url());
 
                if (null == gb28181_agent_)
                    return;
 
                if (null == snap_shot_impl_) {
                    snap_shot_impl_ = new SnapShotGBImpl(image_path_, context_, handler_, lib_publisher_jni, snap_shot_publisher_);
                    snap_shot_impl_.start();
                }
 
                snap_shot_impl_.add_config(gb28181_agent_, from_user_name_, from_user_name_at_domain_, sn_,
                        device_id_, snap_shot_config_, extra_info_list_);
            }
 
            private String from_user_name_;
            private String from_user_name_at_domain_;
            private String sn_;
            private String device_id_;
            private SnapShotConfig snap_shot_config_;
            private List<String> extra_info_list_;
 
            public Runnable set(String from_user_name, String from_user_name_at_domain,
                                String sn, String device_id, SnapShotConfig config,
                                List<String> extra_info_list) {
                this.from_user_name_ = from_user_name;
                this.from_user_name_at_domain_ = from_user_name_at_domain;
                this.sn_ = sn;
                this.device_id_ = device_id;
                this.snap_shot_config_ = config;
                this.extra_info_list_ = extra_info_list;
                return this;
            }
 
        }.set(from_user_name, from_user_name_at_domain, sn, device_id, config, extra_info_list), 0);
    }
}
 
 
public class SnapShotGBImpl extends SnapShotImpl {
    private List<SnapConfig> config_list_ = new LinkedList<>();
  
    public SnapShotGBImpl(String dir, Context context, android.os.Handler handler,
                                      SmartPublisherJniV2 lib_sdk, LibPublisherWrapper publisher) {
        super(dir, context, handler, lib_sdk, publisher);
    }
 
    public boolean add_config(GBSIPAgent agent, String from_user_name, String from_user_name_at_domain, String sn,
                              String device_id, SnapShotConfig config, List<String> extra_info_list) {
        if (null == agent)
            return false;
 
        if (is_null_or_empty(device_id))
            return false;
 
        if (null == config)
            return false;
 
        if (config.snap_num() < 1)
            return false;
 
        if (config.interval() < 1)
            return false;
 
        if (is_null_or_empty(config.session_id()))
            return false;
 
        SnapConfig c = new SnapConfig(agent, from_user_name, from_user_name_at_domain, sn, device_id, config, extra_info_list);
        config_list_.add(c);
 
        return true;
    }
 
    public void on_captured_image(long result, String file_name, long file_date_time_ms, String user_data) {
        SnapConfig config = find_config(user_data);
        if (null == config) {
            super.on_captured_image(result, file_name, file_date_time_ms, user_data);
            return;
        }
 
        SnapItem item = config.find_capturing_item(file_name);
        if (null == item) {
            super.on_captured_image(result, file_name, file_date_time_ms, user_data);
            return;
        }
 
        if (result != 0) {
            item.set_status(SnapItem.ERROR_STATUS);
            item.set_error_info("capture failed");
            Log.e(TAG, "capture failed, file:" + file_name + ", session_id:" + user_data);
            return;
        }
 
        item.set_status(SnapItem.CAPTURE_COMPLETION_STATUS);
    }
 
    public void on_uploaded(boolean is_ok, String file_name, String session_id, String gb_name) {
        SnapConfig config = find_config(session_id);
        if (null == config) {
            Log.w(TAG, "on_uploaded cannot find config, session_id:" + session_id + ", gb_name:" + gb_name);
            return;
        }
 
        SnapItem item = config.find_uploading_item(gb_name);
        if (null == item) {
            Log.w(TAG, "on_uploaded cannot find item, session_id:" + session_id + ", gb_name:" + gb_name);
            return;
        }
 
        if (is_ok) {
            item.set_status(SnapItem.UPLOAD_COMPLETION_STATUS);
            Log.i(TAG, "on_uploaded ok, session_id:" + session_id + ", file:" + file_name);
        }else {
            item.set_status(SnapItem.ERROR_STATUS);
            item.set_error_info("upload failed");
            Log.e(TAG, "on_uploaded failed, session_id:" + session_id + ", file:" + file_name);
        }
    }
 
    @Override
    public void on_stop() {
        this.config_list_.clear();
        shutdown(200, TimeUnit.MILLISECONDS);
    }
 
    private void process_upload() {
        android.os.Handler app_handler = os_handler();
        for(SnapConfig c : config_list_)
            c.upload_files(app_handler, this);
    }
 
    private void process_finished() {
        List<String> notified_files = null;
 
        Iterator<SnapConfig> iterator = config_list_.iterator();
        while(iterator.hasNext()) {
            SnapConfig c = iterator.next();
            if (!c.is_can_notify_server())
                continue;
 
            iterator.remove();
 
            if (null == notified_files)
                notified_files = new LinkedList<>();
 
            c.notify_server(notified_files);
        }
		
        // 暂时删除这些文件, 根据业务需求随时调整就好
        if(notified_files != null && !notified_files.isEmpty())
            execute(new DeleteFilesTask(notified_files));
    }
 
    private static class SnapItem {
        private int status_ = INITIALIZATION_STATUS;
 
        private final String device_id_;
        private final int sn_; // 序列码, 40~41
        private final String dir_;
        private String file_name_;
    }
 
    private static class SnapConfig {
        private WeakReference<GBSIPAgent> agent_;
        private final String from_user_name_;
        private final String from_user_name_at_domain_;
        private final String sn_;
        private final String device_id_;
        private final String session_id_;
        private final int snap_num_;
        private final String upload_url_;
        private final int interval_sec_;
        private final List<String> extra_info_list_;
 
        private ArrayList<SnapItem> items_;
 
       
        public final String session_id() {
            return this.session_id_;
        }
 
        public void upload_files(android.os.Handler os_handler, SnapShotGBImpl snap) {
            if (null == items_)
                return;
 
            for (SnapItem i : items_) {
                if (i.is_capture_completion_status()) {
                    i.set_status(SnapItem.UPLOADING_STATUS);
 
                    BaseUploadTask upload_task = new MyUploadTask(upload_url_, i.file_name(), i.gb_snap_shot_file_id(),
                            session_id(), i.gb_name(), os_handler, snap);
 
                    if (!snap.submit(upload_task) ) {
                        i.set_status(SnapItem.ERROR_STATUS);
                        i.set_error_info("submit upload task failed");
                    }
                }
            }
        }
 
        public void notify_server(List<String> notified_files) {
            ArrayList<String> snap_shot_list = new ArrayList(items_.size());
            for (SnapItem i : items_) {
                if (SnapItem.UPLOAD_COMPLETION_STATUS == i.status())
                    snap_shot_list.add(i.gb_snap_shot_file_id());
 
                if (notified_files != null)
                    notified_files.add(i.file_name());
            }
 
            if (null == agent_)
                return;
 
            GBSIPAgent agent = agent_.get();
            if (null == agent)
                return;
 
            agent.notifyUploadSnapShotFinished(from_user_name_, from_user_name_at_domain_, device_id_, this.session_id(), snap_shot_list);
        }
    }
 
    private static class DeleteFilesTask implements Runnable {
        private List<String> file_name_list_;
 
        public DeleteFilesTask(List<String> file_name_list) {
            this.file_name_list_ = file_name_list;
        }
 
        @Override
        public void run() {
            if (null == file_name_list_)
                return;
 
            if (file_name_list_.isEmpty()) {
                file_name_list_ = null;
                return;
            }
 
            for (String i : file_name_list_) {
                try  {
                    File f = new File(i);
                    if (!f.exists()||!f.isFile() )
                        continue;
 
                    if (f.delete())
                        Log.i(TAG, "delete file:" + i);
                    else
                        Log.w(TAG, "delete file failed, " + i);
                }
                catch(Exception e) {
                    Log.e(TAG, "DeleteFilesTask.run Exception:", e);
                }
            }
 
            file_name_list_.clear();
            file_name_list_ = null;
        }
    }
 
    public static class BaseUploadTask extends CancellableTask {
        private final String upload_url_;
        private final String file_name_;
        private final String gb_snap_shot_file_id_;
        private final String session_id_;
        private final String gb_name_;
 
        private WeakReference<android.os.Handler> os_handler_;
        private WeakReference<SnapShotGBImpl> snap_;
 
        public BaseUploadTask(String upload_url, String file_name, String gb_snap_shot_file_id,
                              String session_id, String gb_name, android.os.Handler os_handler, SnapShotGBImpl snap) {
            this.upload_url_ = upload_url;
            this.file_name_ = file_name;
            this.gb_snap_shot_file_id_ = gb_snap_shot_file_id;
            this.session_id_ = session_id;
            this.gb_name_ = gb_name;
 
            if (os_handler !=null)
                this.os_handler_ = new WeakReference<>(os_handler);
 
            if (snap != null)
                this.snap_ = new WeakReference<>(snap);
        }
 
        protected final String upload_url() {
            return this.upload_url_;
        }
 
        protected final String file_name() {
            return this.file_name_;
        }
 
        protected final String gb_snap_shot_file_id() {
            return this.gb_snap_shot_file_id_;
        }
 
        protected final String session_id() {
            return this.session_id_;
        }
 
        protected final String gb_name() { return this.gb_name_; }
 
        protected final android.os.Handler os_handler() {
            if (os_handler_ != null)
                return os_handler_.get();
 
            return null;
        }
 
        protected final SnapShotGBImpl snap() {
            if (snap_ != null)
                return snap_.get();
 
            return null;
        }
 
        private static class ResultRunnable implements Runnable {
            private final boolean result_;
            private final String file_name_;
            private final String session_id_;
            private final String gb_name_;
            private WeakReference<SnapShotGBImpl> snap_;
 
            public ResultRunnable(boolean result, String file_name, String session_id,
                                  String gb_name, SnapShotGBImpl snap) {
                this.result_ = result;
                this.file_name_ = file_name;
                this.session_id_ = session_id;
                this.gb_name_ = gb_name;
 
                if (snap != null)
                    this.snap_ = new WeakReference<>(snap);
            }
 
            @Override
            public void run(){
                if (null == this.snap_)
                    return;
 
                SnapShotGBImpl snap = this.snap_.get();
                if (null == snap)
                    return;
 
                snap.on_uploaded(result_, file_name_, session_id_, gb_name_);
            }
        }
 
        protected void post_result(boolean is_ok) {
            android.os.Handler handler = os_handler();
            if (null == handler)
                return;
 
            SnapShotGBImpl gb_snap = snap();
            if (null == gb_snap)
                return;
 
            handler.post(new ResultRunnable(is_ok, file_name_,session_id_, gb_name_, gb_snap));
        }
    }
}
 

总结

以上是GB28181图像抓拍大概的流程和设计参考，权当抛砖引玉，Android终端除支持常规的音视频数据接入外，还可以支持移动设备位置(MobilePosition)订阅和通知、图像抓拍、语音广播和语音对讲、历史视音频下载和回放。感兴趣的开发者，可以单独跟我探讨。