浏览器集成Webcam实现人脸检测AI故障排查求助

问题概述 #

尝试复现YouTube上的人脸检测AI，目标是在浏览器中集成摄像头实时展示检测结果，使用VS Code的Live-Server预览代码，但功能无法正常运行。已完成以下排查：

• 修改代码中摄像头分辨率为支持参数
• 更换分辨率高于640×480的摄像头
• 授予浏览器全部权限
• 禁用所有浏览器扩展
• 更换不同浏览器
• 使用不同的摄像头视频调用函数

问题代码 #

JavaScript代码 #

const video = document.getElementById('video')

Promise.all([
  faceapi.nets.tinyFaceDetector.loadFromUri('/models'),
  faceapi.nets.faceLandmark68Net.loadFromUri('/models'),
  faceapi.nets.faceRecognitionNet.loadFromUri('/models'),
  faceapi.nets.faceExpressionNet.loadFromUri('/models')
]).then(startVideo)

function startVideo() {
  navigator.mediaDevices.getUserMedia(
    { video: true },
    stream => video.srcObject = stream,
    err => console.error(err)
  )
}

video.addEventListener('play', () => {
  const canvas = faceapi.createCanvasFromMedia(video)
  document.body.append(canvas)
  const displaySize = { width: video.width, height: video.height }
  faceapi.matchDimensions(canvas, displaySize)
  setInterval(async () => {
    const detections = await faceapi.detectAllFaces(video, new faceapi.TinyFaceDetectorOptions()).withFaceLandmarks().withFaceExpressions()
    const resizedDetections = faceapi.resizeResults(detections, displaySize)
    canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height)
    faceapi.draw.drawDetections(canvas, resizedDetections)
    faceapi.draw.drawFaceLandmarks(canvas, resizedDetections)
    faceapi.draw.drawFaceExpressions(canvas, resizedDetections)
  }, 100)
})

HTML代码 #

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script defer src="face-api.min.js"></script>
  <script defer src="script.js"></script>
  <style>
    body {
      margin: 0;
      padding: 0;
      width: 100vw;
      height: 100vh;
      display: flex;
      justify-content: center;
      align-items: center;
    }

    canvas {
      position: absolute;
    }
  </style>
</head>
<body>
  <video id="video" width="640" height="480" autoplay muted></video>
</body>
</html>

修复方案 #

1. 确认模型文件路径 #

确保/models文件夹与index.html处于同一层级，Live-Server的根目录即为项目根目录，若模型放在子文件夹中需调整loadFromUri路径（比如./models）。可打开浏览器开发者工具的Network面板，检查模型文件是否加载成功（状态码200）。

2. 优化摄像头调用逻辑 #

将getUserMedia改为async/await写法，确保错误能被完整捕获，同时指定明确的分辨率参数提升兼容性：

async function startVideo() {
  try {
    const stream = await navigator.mediaDevices.getUserMedia({
      video: { width: 640, height: 480 }
    });
    video.srcObject = stream;
  } catch (err) {
    console.error('摄像头调用失败:', err);
  }
}

3. 修正视频尺寸与事件监听逻辑 #

video.width/video.height是HTML属性设置的尺寸，实际播放的视频分辨率可能不同，应使用video.videoWidth/video.videoHeight获取真实分辨率；同时将play事件改为playing事件，确保视频已完成加载再启动检测：

video.addEventListener('playing', () => {
  const canvas = faceapi.createCanvasFromMedia(video);
  document.body.append(canvas);
  // 获取视频实际分辨率
  const displaySize = { width: video.videoWidth, height: video.videoHeight };
  faceapi.matchDimensions(canvas, displaySize);
  
  // 用requestAnimationFrame替代setInterval，性能更稳定
  async function detectFaces() {
    try {
      const detections = await faceapi.detectAllFaces(video, new faceapi.TinyFaceDetectorOptions())
        .withFaceLandmarks()
        .withFaceExpressions();
      const resizedDetections = faceapi.resizeResults(detections, displaySize);
      canvas.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
      faceapi.draw.drawDetections(canvas, resizedDetections);
      faceapi.draw.drawFaceLandmarks(canvas, resizedDetections);
      faceapi.draw.drawFaceExpressions(canvas, resizedDetections);
    } catch (err) {
      console.error('人脸检测失败:', err);
    }
    requestAnimationFrame(detectFaces);
  }
  detectFaces();
});

4. 验证face-api.js文件有效性 #

确保face-api.min.js已正确下载并放在项目根目录，可通过开发者工具的Console面板查看是否有faceapi未定义的报错。

内容的提问来源于stack exchange，提问作者N_Radziszewski