HI3516中OSD叠加之后前面几秒正常画面，后面的画面却好像进行了压缩，快进播放

HI_S32 SAMPLE_REGION_VI_VPSS_VENC(HI_S32 HandleNum,RGN_TYPE_E  enType,MPP_CHN_S *pstChn)
{
    HI_S32         i;
    HI_S32         s32Ret;
    HI_S32         MinHandle;
    pthread_t      gtpid;

    s32Ret = SAMPLE_REGION_MPP_VI_VPSS_VENC_START();
    if(HI_SUCCESS != s32Ret)
    {
        return  s32Ret;
    }
    s32Ret = SAMPLE_COMM_REGION_Create(HandleNum,enType);
    if(HI_SUCCESS != s32Ret)
    {
        SAMPLE_PRT("SAMPLE_COMM_REGION_Create failed!\n");
        goto EXIT1;
    }
    s32Ret = SAMPLE_COMM_REGION_AttachToChn(HandleNum,enType,pstChn);
    if(HI_SUCCESS != s32Ret)
    {
        SAMPLE_PRT("SAMPLE_COMM_REGION_AttachToChn failed!\n");
        goto EXIT2;
    }

    MinHandle = SAMPLE_COMM_REGION_GetMinHandle(enType);
    status_RGN = HI_TRUE;

    pthread_create(&gtpid,0,UpdateBMP,(HI_VOID*)&MinHandle);
    PAUSE();

    status_RGN = HI_FALSE;
    pthread_join(gtpid,NULL);

 EXIT2:
    s32Ret = SAMPLE_COMM_REGION_DetachFrmChn(HandleNum,enType,pstChn);
    if(HI_SUCCESS!= s32Ret)
    {
        SAMPLE_PRT("SAMPLE_COMM_REGION_AttachToChn failed!\n");
    } 
EXIT1:
    s32Ret = SAMPLE_COMM_REGION_Destroy(HandleNum,enType);
    if(HI_SUCCESS != s32Ret)
    {
        SAMPLE_PRT("SAMPLE_COMM_REGION_AttachToChn failed!\n");
    }
    SAMPLE_REGION_MPP_VI_VPSS_VENC_END();
    return s32Ret;
}

下面是我的字库线程函数处理部分重要代码
        temp = SDL_ConvertSurface(text, fmt, 0);
        if(text == NULL)
        {
            printf("%s:[%d] The text is NULL !\n",__FUNCTION__,__LINE__);
            return NULL;
        }

        SDL_SaveBMP(temp, "./res/mm.bmp");


        if (OVERLAY_RGN == *arg || OVERLAYEX_RGN == *arg)
        {
            for (i = 0; i < 1; i++)
            {
                s32Ret = SAMPLE_COMM_REGION_SetBitMap(i, PIXEL_FORMAT_ARGB_1555);
                if (HI_SUCCESS != s32Ret)
                {
                    SAMPLE_PRT("SAMPLE_COMM_REGION_SetBitMap failed!\n"); 
                }
            }
        }

出现的具体状况就是程序运行后，前面10秒左右的画面是正常的，并且OSD显示的时间戳也是跟着变换的，但是10s后，写入文件的数据变得极其缓慢。后面打开视频文件发现后面的内存全部压缩到一块，画面跟快进一样。