h3a get no data??

dear all:
i use appro's dm355 platform. and i sure the aew_isr is registered, when i test the aew/af module, i found when the ccdc and sensor is working on 720p mode(video),the h3a never give up a interrupt, so aew didn't work. but when i change the ccdc and sensor working on 1944p mode(capture a picture),the h3a give up a interrupt,and the aew work ok. it is really strange.
 does anyone got the same question?

the appro's H3A demo is as below:
in the code,dm355_AEW_Read always return zero.
///////////////////////////////////////////////////////////////////
if(  ( aew_buff_size = dm355_AEW_open(resolution) )!=-1 )
    {
        printf("aew_buff_size = %d\n",aew_buff_size);
        pAew_buff = (unsigned short *)calloc( sizeof(char), aew_buff_size);
        Init_Aew_Param(pAew_buff);
        ApproWBSetPrm_xDM(resolution);
        printf("aew_appro wait for Rendezvous...\n");
        Rendezvous_meet(envp->hRendezvousInit);
        printf("aew enter main loop\n");
        while( !gblGetQuit() )
        {
                   
            if( dm355_AEW_Read( (void *)pAew_buff , aew_buff_size) )
            {

                DRVApproSend3A_xDM();
                Appro3Afunction_xDM();
            }

        }
        free( pAew_buff );