视频遮挡程序卡在阻塞程序后不运行，哪位大神帮忙看看，谢谢

      HI_S32 s32MilliSec = 20000;
      VPSS_GRP s32VpssGrp = 0;
      VPSS_CHN as32VpssChn[] = {VPSS_CHN0, VPSS_CHN1};

      VIDEO_FRAME_INFO_S stExtFrmInfo;
      VIDEO_FRAME_INFO_S stBaseFrmInfo;


  while (HI_FALSE == s_bStopSignal)
    {

        s32Ret = HI_MPI_VPSS_GetChnFrame(s32VpssGrp, as32VpssChn[1], &stExtFrmInfo, s32MilliSec);
        if (HI_SUCCESS != s32Ret)
        {
            SAMPLE_PRT("HI_MPI_VPSS_GetChnFrame fail,Error(%#x)\n", s32Ret);
            continue;
        }
               
                s32Ret = HI_MPI_VPSS_GetChnFrame(s32VpssGrp, as32VpssChn[0], &stBaseFrmInfo, s32MilliSec);               
                SAMPLE_CHECK_EXPR_GOTO(HI_SUCCESS!=s32Ret, EXT_RELEASE,
                        "HI_MPI_VPSS_GetChnFrame failed, VPSS_GRP(%d), VPSS_CHN(%d), Error(%#x)!\n",
                        s32VpssGrp, as32VpssChn[0], s32Ret);





其中HI_MPI_VPSS_GetChnFrame为阻塞函数，时间参数设置为20000毫秒，可时间过了，程序也一直卡在那里不运行，哪位大神帮忙解答下。