求救

各位好，请教下，我想实现视频电子变倍的效果，现在对输入通道进行扩展（先裁剪然后缩放），可是无法对扩展通道进行操作，显示Set vi ext-chn attr err:0xa0108008错误（操作不支持），我用的050sdk；
s32Ret = SAMPLE_COMM_VI_StartVi(pstViConfig);
    if (HI_SUCCESS != s32Ret)
    {
        SAMPLE_PRT("start vi failed!\n");
    }
#if 1
    VI_EXT_CHN_ATTR_S stExtChnAttr;
    stExtChnAttr.s32BindChn = 0;
    stExtChnAttr.stDestSize.u32Width = 1920;
    stExtChnAttr.stDestSize.u32Height = 1080;
    stExtChnAttr.s32DstFrameRate = -1;
    stExtChnAttr.s32SrcFrameRate = -1;
    stExtChnAttr.enPixFormat = PIXEL_FORMAT_YUV_SEMIPLANAR_420;
    stExtChnAttr.enCompressMode = COMPRESS_MODE_NONE;
    s32Ret=HI_MPI_VI_SetExtChnAttr(1, &stExtChnAttr);
    if (HI_SUCCESS != s32Ret)
    {
    printf("Set vi ext-chn attr err:0x%x\n", s32Ret);
    return s32Ret;
    }

    CROP_INFO_S stExtChnCrop;

    stExtChnCrop.bEnable = HI_TRUE;
    stExtChnCrop.stRect.s32X = 0;
    stExtChnCrop.stRect.s32Y = 0;
    stExtChnCrop.stRect.u32Height = 720;
    stExtChnCrop.stRect.u32Width = 1080;
    s32Ret=HI_MPI_VI_SetExtChnCrop(1, &stExtChnCrop);
    if (HI_SUCCESS != s32Ret)
    {
            printf("Set vi ext-chn crop attr err:0x%x\n", s32Ret);
        return s32Ret;
    }

    s32Ret = HI_MPI_VI_EnableChn (1);
    if (HI_SUCCESS != s32Ret)
    {
    printf("Enable chn failed with error code %#x!\n", s32Ret);
    return s32Ret;
    }

#endif
    stVpssGrpAttr.bDciEn    = HI_FALSE;
    stVpssGrpAttr.bHistEn   = HI_FALSE;
    stVpssGrpAttr.bIeEn     = HI_FALSE;
    stVpssGrpAttr.bNrEn     = HI_TRUE;
    stVpssGrpAttr.enDieMode = VPSS_DIE_MODE_NODIE;
    stVpssGrpAttr.enPixFmt  = PIXEL_FORMAT_YUV_SEMIPLANAR_420;

    stVpssGrpAttr.u32MaxW = stSize.u32Width;
    stVpssGrpAttr.u32MaxH = stSize.u32Height;


    /******************************************
     step 5: start vpss group
    ******************************************/
    s32Ret = SAMPLE_COMM_VPSS_StartGroup(VpssGrp, &stVpssGrpAttr);
    if (HI_SUCCESS != s32Ret)
    {
        SAMPLE_PRT("start VPSS GROUP failed!\n");
    }