Why FVID_exchange() failed?

Hi all：

      I am using DM6437 connect with TVP5158 decoder to get 2-ch D1 image(line-interleaved mode). I refer to the examle of in the path of \dvsdk_1_01_00_15\psp_1_00_02_00\pspdrivers.....\loopback\.But when it runs into :

   if(IOM_COMPLETED != FVID_exchange(CcdcHandle,&FBAddr))
    {
          VPSS_DBG("VPSS  :CCDC Exchange.......FAILED \r\n");
    }

   FVID_exchange() faied.

 I config the CCDC like this:

PSP_VPFECcdcConfigParams ccdcParams =
{
    FVID_CCDC_YCBCR_8,                  /* dataFlow     */
    FVID_FRAME_MODE,                    /* ffMode       */
    1250,// 480,                                /* height       */
    736,                                /* width        */
    (736 *2),                           /* pitch        */
    0,                                  /* horzStartPix */
    0,                                  /* vertStartPix */
    NULL,                               /* appCallback  */
    {
        PSP_VPFE_TVP5158_Open,         /* extVD Fxn    */
        PSP_VPFE_TVP5158_Close,
        PSP_VPFE_TVP5158_Control,
    },
    0                                   /*segId         */
};

I have two questions ：

1. Why did FVID_exchange() fail?How can I corrected?

2. I found if  the input mode of VPFE is configed FVID_FIELD_MODE,FVID_creat() will fail .But if it is configed  FVID_FRAME_MODE,the FVID_exchange will fail.  the data stream of input should be FVID_FIELD_MODE.

Could you help me?