IonicのAngularでWebRTCなカメラ取得して画像を切り出しQR読み取り

<video #video autoplay muted playsinline"></video>

const elmVideo = this.video.nativeElement;
navigator.mediaDevices
  .getUserMedia({
    video: {
      width: { min: 160, ideal: 320, max: 640 },
      height: { min: 120, ideal: 240 },
      aspectRatio: 1.777777778,
      frameRate: { max: 30 },
      facingMode: 'environment',
      deviceId: "xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    },
  })
  .then((stream: MediaStream) => {
    elmVideo.srcObject = stream;
    // elmVideo.setAttribute('playsinline', true);
    elmVideo.play();
  })
  .catch((err: MediaStreamError) => {
    console.log(err);
  });

const elmVideo = this.video.nativeElement;
const elmCanvas = this.canvas.nativeElement;
elmCanvas.width = elmVideo.videoWidth;
elmCanvas.height = elmVideo.videoHeight;

const context2d = elmCanvas.getContext('2d');
context2d.drawImage(elmVideo, 0, 0, elmCanvas.width, elmCanvas.height);

const elmCanvas = this.canvas.nativeElement;
const context2d = elmCanvas.getContext('2d');
const imageData = context2d.getImageData(x, y, width, height);

const code = jsQR(imageData.data, imageData.width, imageData.height, {
 inversionAttempts: 'dontInvert',
});