如何获得每帧的平均时间？ [英] How to get the Average Time Per Frame?

问题描述

我试图在vc ++中使用DirectShow获取视频的每帧平均时间。

我使用IBasicVideo接口获取该值，它具有get_AvgTimePerFrame函数。但是我没有从中获得任何价值。

I am trying to get the Average time per frame of the video using DirectShow in vc++.
And am using the IBasicVideo interface to get that value,it is having the get_AvgTimePerFrame function. But am not getting any value from it.

hr = pGraph->QueryInterface(IID_IBasicVideo,(void **)&pVideo);
hr = InitWindowlessVMR(AfxGetMainWnd()->m_hWnd, pGraph, &pWc);
// Build the graph. 
hr = pGraph->RenderFile(L"Video.mp4", NULL);
double df;
hr=pVideo->get_AvgTimePerFrame(&df);

如果我在pGraph-> RenderFile（video.mp4之后调用get_AvgTimePerFrame函数，NULL函数正在获取值。如果我指定过滤器形成我的返回值为E_NOINTERFACE。

我需要做什么来获得每帧平均时间的值？



提前告诉你。

If i call the get_AvgTimePerFrame function after the pGraph->RenderFile("video.mp4",NULL) function am getting the value. If i specify the filter formation am getting the return value as E_NOINTERFACE.
What i need to do to get the value of the average time per frame?

Thaking you in advance.

推荐答案

您应该获得渲染器的连接媒体类型并获取信息来自VIDEOINFOHEADER结构。

You should get connected media type of your renderer and get information from VIDEOINFOHEADER structure.

double GetFPS(IBaseFilter * _filter)
{
    double _fps = 0;
    if (_filter) // Check if the filter passed
    {
        IEnumPins * _enum;
        // Query Enum pins
        if (S_OK == _filter->EnumPins(&_enum))
        {
            IPin * _pin;
            // While we have pins or fps not setted yet
            while (_fps == 0 && _enum->Next(1,&_pin,NULL) == S_OK)
            {
                PIN_DIRECTION _direction;
                // Here we check for pin direction
                // Assume that we pass the renderer filter as argument
                // But checking direction not mandatory
                _pin->QueryDirection(&_direction);
                if (_direction == PINDIR_INPUT)
                {
                    AM_MEDIA_TYPE mt;
                    // We try to retrieve connection media type
                    // In case if connected it returns type and S_OK result
                    if (S_OK == _pin->ConnectionMediaType(&mt))
                    {
                        // We have video type and have format
                        // At least format shoudl be size of VIDEOINFOHEADER structure
                        // As all other well known format structures are higher size
                        if (mt.majortype == MEDIATYPE_Video 
                            && mt.pbFormat 
                            && mt.cbFormat >= sizeof(VIDEOINFOHEADER))
                        {
                            // We cast directly here without checking format type
                            // This possible because we had check the size and we need
                            // only "AvgTimePerFrame" field
                            // NOTE: do not do this for bmiHeader field
                            REFERENCE_TIME _time = ((VIDEOINFOHEADER*)mt.pbFormat)->AvgTimePerFrame;
                            if (_time > 0)
                            {
                                // Calculate fps = second / time per frame
                                _fps = ((double)UNITS / (double)(_time));
                            }
                        }
                        // Free format block
                        FreeMediaType(mt);
                    }
                }
                // Release pin
                _pin->Release();
            }
            // Release enum
            _enum->Release();
        }
    }
    return _fps;
}

Maxim。

Maxim.

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