docs: function (id, canva, video, altCanvas) {
  
      const date = new Date();
      canva.resize(video);
      canva.copy(video);
  
      // handle alternative canvas:
      altCanvas = altCanvas === undefined ? [] : altCanvas;
      this.altScreenShots = [];
      if (altCanvas.length > 0) {
          for (let i = 0; i < altCanvas.length; i++) {
              let canvaEl = altCanvas[i].el;
              canvaEl.resize(video, altCanvas[i].width);
              canvaEl.copy(video);
  
              this.altScreenShots.push({
                  dataURI: canvaEl.extractImage(),
                  name: altCanvas[i].name
              });
          }
      }
  
      this.id = id;
      this.timestamp = date.getTime();
      this.dataURI = canva.extractImage();
      this.videoTime = video.getCurrentTime();
  
  }