windows DirectShow pcm to mp3 代码实现

以下是使用DirectShow将PCM转换为MP3的C++代码示例：

#include <dshow.h>
#include <stdio.h>

int main(int argc, char* argv[])
{
    // 初始化COM组件
    CoInitialize(NULL);

    // 创建FilterGraph对象
    IGraphBuilder* pGraph = NULL;
    CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void**)&pGraph);

    // 创建WAV解码器
    IBaseFilter* pWAVDecoder = NULL;
    CoCreateInstance(CLSID_DSoundRender, NULL, CLSCTX_INPROC_SERVER, IID_IBaseFilter, (void**)&pWAVDecoder);

    // 创建MP3编码器
    IBaseFilter* pMP3Encoder = NULL;
    CoCreateInstance(CLSID_MPEG1Layer3Encoder, NULL, CLSCTX_INPROC_SERVER, IID_IBaseFilter, (void**)&pMP3Encoder);

    // 创建文件写入过滤器
    IFileSinkFilter* pFileSink = NULL;
    CoCreateInstance(CLSID_FileWriter, NULL, CLSCTX_INPROC_SERVER, IID_IFileSinkFilter, (void**)&pFileSink);

    // 打开PCM文件
    HANDLE hPCMFile = CreateFile("test.pcm", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hPCMFile == INVALID_HANDLE_VALUE)
    {
        printf("Failed to open PCM file.\n");
        return -1;
    }

    // 创建PCM文件流
    IStream* pPCMStream = NULL;
    CreateStreamOnHGlobal(NULL, TRUE, &pPCMStream);

    // 读取PCM数据
    BYTE buffer[4096];
    DWORD bytesRead;
    while (ReadFile(hPCMFile, buffer, sizeof(buffer), &bytesRead, NULL) && bytesRead > 0)
    {
        pPCMStream->Write(buffer, bytesRead, NULL);
    }

    // 关闭PCM文件
    CloseHandle(hPCMFile);

    // 将PCM流封装为WAV文件
    WCHAR filename[MAX_PATH];
    MultiByteToWideChar(CP_ACP, 0, "test.wav", -1, filename, MAX_PATH);
    AM_MEDIA_TYPE mt;
    mt.majortype = MEDIATYPE_Audio;
    mt.subtype = MEDIASUBTYPE_PCM;
    mt.formattype = FORMAT_WaveFormatEx;
    mt.cbFormat = sizeof(WAVEFORMATEX);
    mt.pbFormat = (BYTE*)CoTaskMemAlloc(mt.cbFormat);
    ZeroMemory(mt.pbFormat, mt.cbFormat);
    ((WAVEFORMATEX*)mt.pbFormat)->wFormatTag = WAVE_FORMAT_PCM;
    ((WAVEFORMATEX*)mt.pbFormat)->nChannels = 2;
    ((WAVEFORMATEX*)mt.pbFormat)->nSamplesPerSec = 44100;
    ((WAVEFORMATEX*)mt.pbFormat)->nAvgBytesPerSec = 176400;
    ((WAVEFORMATEX*)mt.pbFormat)->nBlockAlign = 4;
    ((WAVEFORMATEX*)mt.pbFormat)->wBitsPerSample = 16;
    IFileSinkFilter* pWAVSink = NULL;
    pGraph->QueryInterface(IID_IFileSinkFilter, (void**)&pWAVSink);
    pWAVSink->SetFileName(filename, &mt);
    CoTaskMemFree(mt.pbFormat);
    pGraph->AddFilter(pWAVDecoder, L"WAV Decoder");
    pGraph->ConnectDirect(pWAVDecoder, L"Output", pWAVSink, NULL);

    // 将WAV解码器输出连接到MP3编码器输入
    IPin* pWAVOutput = NULL;
    pWAVDecoder->FindPin(L"Output", &pWAVOutput);
    IPin* pMP3Input = NULL;
    pMP3Encoder->FindPin(L"In", &pMP3Input);
    pGraph->ConnectDirect(pWAVOutput, pMP3Input, NULL);

    // 设置MP3编码器参数
    ICodecAPI* pCodecAPI = NULL;
    pMP3Encoder->QueryInterface(IID_ICodecAPI, (void**)&pCodecAPI);
    VARIANT val;
    val.vt = VT_UI4;
    val.ulVal = 192000;  // 设置比特率为192Kbps
    pCodecAPI->SetValue(&CODECAPI_AVEncMP3BitRate, &val);

    // 将MP3编码器输出连接到文件写入过滤器
    IPin* pMP3Output = NULL;
    pMP3Encoder->FindPin(L"Out", &pMP3Output);
    pFileSink->SetFileName(L"test.mp3", NULL);
    pGraph->AddFilter(pMP3Encoder, L"MP3 Encoder");
    pGraph->AddFilter((IBaseFilter*)pFileSink, L"File Writer");
    pGraph->ConnectDirect(pMP3Output, (IPin*)pFileSink, NULL);

    // 开始转换
    IMediaControl* pControl = NULL;
    pGraph->QueryInterface(IID_IMediaControl, (void**)&pControl);
    pControl->Run();

    // 等待完成
    IMediaEvent* pEvent = NULL;
    pGraph->QueryInterface(IID_IMediaEvent, (void**)&pEvent);
    long evCode;
    pEvent->WaitForCompletion(INFINITE, &evCode);

    // 释放资源
    pControl->Release();
    pEvent->Release();
    pPCMStream->Release();
    pWAVDecoder->Release();
    pMP3Encoder->Release();
    pFileSink->Release();
    pGraph->Release();
    CoUninitialize();

    return 0;
}

这段代码中使用了DSoundRender作为WAV解码器，使用了MPEG1Layer3Encoder作为MP3编码器，使用了FileWriter作为文件写入过滤器。需要注意的是，不同的解码器和编码器可能有不同的接口和参数，需要根据实际情况进行调整。