HarmonyOS media.createAVImageGenerator的参数fdSrc 只能获取resource中的资源

const filePath = getContext().filesDir+"/VID_1716862918_000.mp4" 
const res = fs.accessSync(filePath) 
if (res) { 
  let fd = fs.openSync(filePath).fd 
  let size = fs.statSync(filePath).size 
  let fileSr: media.AVFileDescriptor = { 
    fd, 
    offset: 0, 
    length: size 
  } 
  let avIG = await media.createAVImageGenerator() 
  avIG.fdSrc = fileSr 
  let timeUs = 0 
  let queryOption = media.AVImageQueryOptions.AV_IMAGE_QUERY_NEXT_SYNC 
  let param: media.PixelMapParams = { 
    width : 300, 
    height : 300 
  } 
  this.pixelMap = await avIG.fetchFrameByTime(timeUs, queryOption, param); 
  let imageFile = fs.openSync(getContext().tempDir+"/VID_1716862918_000.jpg", fs.OpenMode.READ_WRITE|fs.OpenMode.CREATE) 
  image.createImagePacker().packToFile(this.pixelMap, imageFile.fd, { 
    format: "image/jpg", 
    quality: 98 
  }).then(res => { 
    console.log('asdasdsd') 
  }).catch((err: BusinessError) => { 
    console.log("-----"+JSON.stringify(err)) 
  }) 
  fs.closeSync(imageFile); 
  avIG.release();