smart210 的h264硬编码的帧率设置为30，播放时为什么显示25？

smart210 的h264硬编码的帧率设置为30，播放时为什么显示25？
参数设置
    //common parameters
    param->codecType = H264_ENC;
    param->SourceWidth = 640;
    param->SourceHeight = 480;
    param->IDRPeriod = 100;
    param->SliceMode = 0; // 0,1,2,4
    param->RandomIntraMBRefresh = 0;
    param->EnableFRMRateControl = 1; // this must be 1 otherwise init error
    param->Bitrate = 10 * 1000 * 1000;
    param->FrameQp = 20; //<=51, the bigger the lower quality
    param->FrameQp_P = 20;
    param->QSCodeMin = 10; // <=51
    param->QSCodeMax = 51; // <=51
    param->CBRPeriodRf = 120;
    param->PadControlOn = 0;
    param->LumaPadVal = 0; // <=255
    param->CbPadVal = 0; //<=255
    param->CrPadVal = 0; //<=255
    param->FrameMap = 0; // encoding input mode (0=linear, 1=tiled)

    // H264 specific
    param->ProfileIDC = 1; // 0=main,1=high,2=baseline
    param->LevelIDC = 40; // level 4.0
    param->FrameQp_B = 20;
    param->FrameRate = 30000; // real frame rate = FrameRate/1000 (refer to S5PV210 datasheet Section 6.3.4.2.2)
    param->SliceArgument = 0;
    param->NumberBFrames = 0; //<=2
    param->NumberReferenceFrames = 2; // <=2
    param->NumberRefForPframes = 2; // <=2
    param->LoopFilterDisable = 1; // 0=enable, 1=disable
    param->LoopFilterAlphaC0Offset = 0; // <=6
    param->LoopFilterBetaOffset = 0; // <=6
    param->SymbolMode = 1; // 0=CAVLC, 1=CABAC
    param->PictureInterlace = 0; // Picture AFF 0=frame coding, 1=field coding, 2=adaptive
    param->Transform8x8Mode = 1; // 0=only 4x4 transform, 1=allow 8x8 trans, 2=only 8x8 trans
    param->EnableMBRateControl = 0;
    param->DarkDisable = 0;
    param->SmoothDisable = 0;
    param->StaticDisable = 0;
    param->ActivityDisable = 0;