海康NVR录像回放SDK原始流转FLV视频流：基于Java的流媒体转码（无需安装第三方插件ffmpeg）

wlinker-video-monitor
代码地址：https://gitee.com/wlinker/wlinker-video-monitor

背景与需求

在安防监控、智能楼宇等场景中，海康威视设备作为行业主流硬件，常需要将录像回放功能集成到Web系统中。然而，海康设备的原始视频流格式（如私有协议或MPEG）通常无法直接在浏览器中播放。本文通过一个真实案例，介绍如何利用 JavaCV、海康SDK 和 Spring Boot，实现设备录像回放流的实时转码与FLV格式输出，最终在浏览器中无缝播放。

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技术架构概览

核心组件

1. 海康SDK（HCNetSDK）：设备控制、录像回放流获取。

2. JavaCV（FFmpeg）：视频流抓取、转码（MPEG→FLV）。

3. Spring Boot：HTTP接口封装、异步任务处理。

4. 管道流（PipedStream）：跨线程数据传输。

流程示意图

[海康设备]│↓ (SDK回调流数据)
[HCNetTools] → PipedOutputStream│↓ (跨线程传输)
[PipedInputStream] → [FFmpegGrabber]│↓ (转码)
[FFmpegRecorder] → HTTP响应流(FLV)│↓
[浏览器/VLC播放器]

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关键技术实现

1. 海康SDK流获取与管道传输（HCNetTools）

海康SDK通过回调函数返回原始视频流数据，需将其写入管道流供后续处理。核心代码如下：

public class  HCNetTools {/*** 按时间回放录像* @param lChannel 通道号*/public void playBackByTime(LocalDateTime startTime, LocalDateTime endTime, int lChannel,Thread thread,PipedInputStream inputStream){playBackCallBack = null;try {pipeOutput = new PipedOutputStream(inputStream);} catch (Exception e) {StaticLog.error(e);}HCNetSDK.NET_DVR_VOD_PARA net_dvr_vod_para = new HCNetSDK.NET_DVR_VOD_PARA();net_dvr_vod_para.dwSize = net_dvr_vod_para.size();net_dvr_vod_para.struIDInfo.dwChannel = lChannel; //通道号//开始时间net_dvr_vod_para.struBeginTime = getHkTime(startTime);//停止时间net_dvr_vod_para.struEndTime = getHkTime(endTime);net_dvr_vod_para.hWnd = null; // 回放的窗口句柄，若置为空，SDK仍能收到码流数据，但不解码显示net_dvr_vod_para.write();iPlayBack = hCNetSDK.NET_DVR_PlayBackByTime_V40(lUserID, net_dvr_vod_para);if (iPlayBack <= -1) {System.out.println("按时间回放失败，错误码为" + hCNetSDK.NET_DVR_GetLastError());palybackFlay = true;return;}//开启取流IntByReference intP = new IntByReference(54962 * 1024);IntByReference intInlen1 = new IntByReference(0);boolean bCrtl = hCNetSDK.NET_DVR_PlayBackControl_V40(iPlayBack, HCNetSDK.NET_DVR_PLAYSTART, Pointer.NULL, 0, Pointer.NULL, intInlen1);if (bCrtl == false) {System.out.println("NET_DVR_PLAYSTART失败，错误码为" + hCNetSDK.NET_DVR_GetLastError());return;}playBackCallBack = new MyPlayDataCallBack(thread,pipeOutput);boolean bRet = hCNetSDK.NET_DVR_SetPlayDataCallBack(iPlayBack, playBackCallBack, Pointer.NULL);return;}class MyPlayDataCallBack implements HCNetSDK.FPlayDataCallBack{private final Thread thread;private boolean flag;private final PipedOutputStream pipeOutput;private AtomicInteger atomicInteger = new AtomicInteger(0);public MyPlayDataCallBack(Thread thread,PipedOutputStream pipeOutput){this.thread = thread;this.flag = false;this.pipeOutput = pipeOutput;}public void invoke(int lPlayHandle, int dwDataType, Pointer pBuffer, int dwBufSize, int dwUser) {//将设备发送过来的回放码流数据写入文件//StaticLog.info("回放码流回调次数:{}",atomicInteger.addAndGet(1));long offset = 0;ByteBuffer buffers = pBuffer.getByteBuffer(offset, dwBufSize);byte[] bytes = new byte[dwBufSize];buffers.rewind();buffers.get(bytes);try {this.pipeOutput.write(bytes);if(atomicInteger.addAndGet(1) % 50 == 0){int i = atomicInteger.get() / 50;//StaticLog.info("{},刷出通道：{}",atomicInteger.get(), i);this.pipeOutput.flush();if(i == 1){LockSupport.unpark(thread);}}} catch (IOException e) {stopPlayback();getPlaybacktimer().cancel();StaticLog.error(e,e.getLocalizedMessage());}}}}

关键设计：

• 多线程协作：通过 LockSupport 实现主线程阻塞与回调线程唤醒，确保FFmpeg在数据到达后开始处理。

• 缓冲控制：每50次写入刷新管道，平衡实时性与I/O开销。

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2. FFmpeg实时转码与HTTP流输出（NetPlayBackController）

控制器从管道流读取数据并转码为FLV格式，通过HTTP响应流式输出：

@Slf4j
@Api(tags = "海康网络设备-录像回放原始流转flv流输出")
@RestController
@RequestMapping("/api/hikNet")
public class NetPlayBackController {@ResourceHikCameraAspect aspect;@GetMapping(value = "/playBackVideoOne")@ApiOperation(value = "海康网络设备-录像回放（基于原始流）-通道不复用",  notes = "响应通道不复用，但较稳定")@Asyncpublic void playBackVideo2(@RequestParam String id, @RequestParam String startTime, @RequestParam String endTime, HttpServletResponse httpServletResponse) throws InterruptedException, IOException {//设置响应头httpServletResponse.setContentType("video/x-flv");httpServletResponse.setHeader("Connection", "keep-alive");httpServletResponse.setStatus(HttpServletResponse.SC_OK);httpServletResponse.flushBuffer();Thread mainThread = Thread.currentThread();MonitorDeviceDTO monitorDeviceDTO = VideoKeyUtils.getMonitorDeviceDtoById(id);String deviceCode = monitorDeviceDTO.getDeviceCode();String accessPlatform = monitorDeviceDTO.getAccessPlatform();if (!HikVisionAccessPlatformEnum.net.getAccessPlatform().equals(accessPlatform)) {throw new RuntimeException("不支持该平台");}LocalDateTime startLocalTime = DateUtil.parseLocalDateTime(startTime);LocalDateTime endLocalTime = DateUtil.parseLocalDateTime(endTime);//单次录像下载时长范围不能超过一小时if (startLocalTime.isAfter(endLocalTime)) {throw new RuntimeException("开始时间不能大于结束时间");}if (startLocalTime.plusHours(1).isBefore(endLocalTime)) {throw new RuntimeException("时间区间不能超过一小时");}Integer channelNo = monitorDeviceDTO.getChannelNo();aspect.logout(deviceCode);aspect.login(deviceCode);FFmpegFrameGrabber grabber = null;FFmpegFrameRecorder recorder = null;HCNetTools hcNetTools = NetDeviceCacheUtils.getHcNetTools(deviceCode);try (PipedInputStream inputStream = new PipedInputStream(1024 * 1024);) {Thread thread = Thread.currentThread();// 启动下载线程：将数据写入管道输出流hcNetTools.playBackByTime(startLocalTime, endLocalTime, channelNo, thread, inputStream);// 最多等待5秒（配置响应超时时间）long delayNanos = TimeUnit.SECONDS.toNanos(5);LockSupport.parkNanos(delayNanos);// 配置日志级别avutil.av_log_set_level(avutil.AV_LOG_FATAL);// 配置FFmpegFrameGrabber从管道输入流读取grabber = new FFmpegFrameGrabber(inputStream);// 明确指定输入格式（部分流需要）grabber.setFormat("mpeg");grabber.setOption("stimeout", "500000");//设置缓存大小，提高画质、减少卡顿花屏grabber.setOption("buffer_size", "1024000");grabber.start();// 配置FFmpegFrameRecorder直接输出FLV到HTTP响应流//创建转码器recorder = new FFmpegFrameRecorder(httpServletResponse.getOutputStream(), grabber.getImageWidth(),grabber.getImageHeight(),grabber.getAudioChannels());//配置转码器recorder.setFrameRate(grabber.getFrameRate());recorder.setSampleRate(grabber.getSampleRate());if (grabber.getAudioChannels() > 0) {recorder.setAudioChannels(grabber.getAudioChannels());recorder.setAudioBitrate(grabber.getAudioBitrate());recorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);//设置视频比例//recorder.setAspectRatio(grabber.getAspectRatio());}recorder.setFormat("flv");recorder.setVideoBitrate(grabber.getVideoBitrate());recorder.setVideoCodec(avcodec.AV_CODEC_ID_H264);recorder.setVideoOption("color_range", "tv");recorder.start();Frame frame;while ((frame = grabber.grab()) != null) {recorder.record(frame);}} catch (Exception e) {log.error("播放视频时发生异常：{}", e.getMessage());} finally {// 释放资源if (recorder != null) {try {recorder.close();} catch (Exception e) {log.error("关闭recorder发生异常：{}", e.getMessage());}}if (grabber != null) {try {grabber.close();} catch (Exception e) {log.error("关闭grabber发生异常：{}", e.getMessage());}}hcNetTools.stopPlayback();hcNetTools.deviceLogout();}}}

关键优化：

• 低延迟：直接传递帧对象，避免内存复制。

• 自适应参数：从原始流继承分辨率、帧率等属性，确保兼容性。

总结与展望

本文方案通过 海康SDK + JavaCV + 管道流 的组合，实现了设备录像回放流的实时转码与Web输出。其优势在于：

• 高实时性：从设备到浏览器的端到端延迟可控。

• 轻量级：无需中间服务器转存视频文件。