draw() {
    const w = 300
    let h = 200
    const dpr = wx.getSystemInfoSync().pixelRatio
    wx.createSelectorQuery().select('#myVideo').context(res => {
      console.log('select video', res)
      const video = this.video = res.context
      wx.createSelectorQuery().selectAll('#cvs1').node(res => {
        console.log('select canvas', res)
        const ctx1 = res[0].node.getContext('2d')
        // console.error(ctx1)
        res[0].node.width = w * dpr
        res[0].node.height = h * dpr


        setInterval(() => {
          ctx1.drawImage(video, 0, 0, 960, 720, 0, 0, h * dpr, w * dpr);
        }, 1000 / 24)
      }).exec()
    }).exec()
  },