directshow中获取码率

什么都不说了，看代码吧。（说明一下，这样得到的码率比文件属性中的码率是要小一点的，因为文件属性里标的码率包括了视频和音频，而这样得到的码率只包括视频，可是我又不知道怎么把音频的码率也得到，小就小一点吧^_^）

BOOL CDxGraph::GetBitRate(long *outBitRate)
...{
    if (NULL != outBitRate)
        *outBitRate = 0;

    if (NULL == m_pGraph)
        return FALSE;

    long lbitRate = 0;
    IEnumFilters* pEF = NULL;
    if (SUCCEEDED(m_pGraph->EnumFilters(&pEF)))
    ...{
        IBaseFilter*  pBF = NULL;
        while(S_OK == pEF->Next(1, &pBF, 0))
        ...{
            IEnumPins* pEnumPins = NULL;
            IPin     * pPin      = NULL;
            if (SUCCEEDED(pBF->EnumPins(&pEnumPins)))
            ...{
                while(S_OK == pEnumPins->Next(1, &pPin, 0))
                ...{
                    PIN_DIRECTION pinDirThis;
                    if (FAILED(pPin->QueryDirection(&pinDirThis)))
                    ...{
                        pPin->Release();
                        continue;
                    }
                    if (PINDIR_OUTPUT == pinDirThis)
                    ...{
                        pPin->Release();
                        break;
                    }

                    AM_MEDIA_TYPE mt;
                    if (FAILED(pPin->ConnectionMediaType(&mt)))
                    ...{
                        pPin->Release();
                        continue;
                    }
                    
                    if(mt.majortype == MEDIATYPE_Video)
                    ...{                        
                        if(mt.formattype == FORMAT_VideoInfo || mt.formattype == FORMAT_MPEGVideo)
                        ...{
                            VIDEOINFOHEADER* vih = (VIDEOINFOHEADER*)mt.pbFormat;
                            if(vih->dwBitRate)
                            ...{
                                if (lbitRate < vih->dwBitRate/1000)
                                    lbitRate = vih->dwBitRate/1000;
                            }
                        }
                        else if(mt.formattype == FORMAT_VideoInfo2)
                        ...{
                            VIDEOINFOHEADER2* vih = (VIDEOINFOHEADER2*)mt.pbFormat;
                            if(vih->dwBitRate)
                            ...{
                                if (lbitRate < vih->dwBitRate/1000)
                                    lbitRate = vih->dwBitRate/1000;
                            }
                        }
                    }                
                    pPin->Release();
                }

                pEnumPins->Release();
            }
            pBF->Release();    
        }
        pEF->Release();
    }

    if (NULL != outBitRate)
        *outBitRate = lbitRate;

    return TRUE;
}