c++ - 尝试从Win32 WASAPI C++使用 'Capturing a Stream"创建wav文件

Question

我在尝试解释(BYTE * pData)getBuffer函数返回的音频数据时遇到麻烦。我正在尝试将自己麦克风中捕获的音频写入到wav文件中，我本人正在构建这些文件是为了更好地了解音频设备，音频数据和音频格式。

下面是所有代码，其中大部分都来自Windows文档或从doc中引用:https://docs.microsoft.com/en-us/windows/win32/coreaudio/capturing-a-stream。试图使事情尽可能简单没有幻想。这段代码捕获了几秒钟的麦克风音频，您可以听到失真的声音，并且确实是静态的。失真是由于我将pData内容写入文件引起的吗？

Main.cpp
注意-请忽略所有地方的“cout”，仅用于调试

#pragma once
#include "MyAudioSink.h"
#include <windows.h>

// REFERENCE_TIME time units per second and per millisecond
#define REFTIMES_PER_SEC  10000000
#define REFTIMES_PER_MILLISEC  10000

#define EXIT_ON_ERROR(hres)  \
              if (FAILED(hres)) { goto Exit; }
#define SAFE_RELEASE(punk)  \
              if ((punk) != NULL)  \
                { (punk)->Release(); (punk) = NULL; }



const CLSID CLSID_MMDeviceEnumerator = __uuidof(MMDeviceEnumerator);
const IID IID_IMMDeviceEnumerator = __uuidof(IMMDeviceEnumerator);
const IID IID_IAudioClient = __uuidof(IAudioClient);
const IID IID_IAudioCaptureClient = __uuidof(IAudioCaptureClient);

HRESULT RecordAudioStream(MyAudioSink * pMySink);


int main() {

    HRESULT hr;
    hr = CoInitialize(nullptr);

    //declare MyAudioSink object
    MyAudioSink pMySink;

    hr = RecordAudioStream(&pMySink);

    cout << "done";

}


//-----------------------------------------------------------
// Record an audio stream from the default audio capture
// device. The RecordAudioStream function allocates a shared
// buffer big enough to hold one second of PCM audio data.
// The function uses this buffer to stream data from the
// capture device. The main loop runs every 1/2 second.
//-----------------------------------------------------------



HRESULT RecordAudioStream(MyAudioSink* pMySink)
{
    HRESULT hr;
    REFERENCE_TIME hnsRequestedDuration = REFTIMES_PER_SEC;
    REFERENCE_TIME hnsActualDuration;
    UINT32 bufferFrameCount;
    UINT32 numFramesAvailable;
    IMMDeviceEnumerator* pEnumerator = NULL;
    IMMDevice* pDevice = NULL;
    IAudioClient* pAudioClient = NULL;
    IAudioCaptureClient* pCaptureClient = NULL;
    WAVEFORMATEX* pwfx = NULL;
    UINT32 packetLength = 0;
    BOOL bDone = FALSE;
    BYTE* pData;
    DWORD flags;

    cout << "starting...";

    hr = CoCreateInstance(
        CLSID_MMDeviceEnumerator, NULL,
        CLSCTX_ALL, IID_IMMDeviceEnumerator,
        (void**)&pEnumerator);

    cout << "test1" ;
    EXIT_ON_ERROR(hr)

        hr = pEnumerator->GetDefaultAudioEndpoint(
            eCapture, eConsole, &pDevice);
    cout << "test2" ;
    EXIT_ON_ERROR(hr)

        hr = pDevice->Activate(
            IID_IAudioClient, CLSCTX_ALL,
            NULL, (void**)&pAudioClient);
    cout << "test3" ;
    EXIT_ON_ERROR(hr)

        hr = pAudioClient->GetMixFormat(&pwfx);
    cout << "test4" ;
    EXIT_ON_ERROR(hr)

        hr = pAudioClient->Initialize(
            AUDCLNT_SHAREMODE_SHARED,
            0,
            hnsRequestedDuration,
            0,
            pwfx,
            NULL);
    cout << "test5" ;
    EXIT_ON_ERROR(hr)

        // Get the size of the allocated buffer.
        hr = pAudioClient->GetBufferSize(&bufferFrameCount);
    cout << "test6" ;
    EXIT_ON_ERROR(hr)

        hr = pAudioClient->GetService(
            IID_IAudioCaptureClient,
            (void**)&pCaptureClient);
    cout << "test7" ;
    EXIT_ON_ERROR(hr)

        // Calculate the actual duration of the allocated buffer.
        hnsActualDuration = (double)REFTIMES_PER_SEC *
        bufferFrameCount / pwfx->nSamplesPerSec;

    // Notify the audio sink which format to use.
    hr = pMySink->SetFormat(pwfx);
    cout << "test8" ;
    EXIT_ON_ERROR(hr)

        //initialize the wav file with the specifications set by SetFormat
        hr = pMySink->_Initialize_File();
    cout << "test9" ;
    EXIT_ON_ERROR(hr)

        hr = pAudioClient->Start();  // Start recording.
    cout << "test10" ;
    EXIT_ON_ERROR(hr)

        cout << "about to run while...";

        // Each loop fills about half of the shared buffer.
        while (bDone == FALSE)
        {

            // Sleep for half the buffer duration.
            Sleep(hnsActualDuration / REFTIMES_PER_MILLISEC / 2);

            hr = pCaptureClient->GetNextPacketSize(&packetLength);
            EXIT_ON_ERROR(hr)

                while (packetLength != 0)
                {
                    // Get the available data in the shared buffer.
                    hr = pCaptureClient->GetBuffer(
                        &pData,
                        &numFramesAvailable,
                        &flags, NULL, NULL);
                    EXIT_ON_ERROR(hr)

                        if (flags & AUDCLNT_BUFFERFLAGS_SILENT)
                        {
                            cout << "silent";
                            pData = NULL;  // Tell CopyData to write silence.
                        }

                    // Copy the available capture data to the audio sink.
                    hr = pMySink->CopyData(
                        pData, numFramesAvailable, &bDone);
                    EXIT_ON_ERROR(hr)

                        hr = pCaptureClient->ReleaseBuffer(numFramesAvailable);
                    EXIT_ON_ERROR(hr)

                        hr = pCaptureClient->GetNextPacketSize(&packetLength);
                    EXIT_ON_ERROR(hr)
                }
        }
    hr = pMySink->_File_WrapUp();
    EXIT_ON_ERROR(hr)

        hr = pAudioClient->Stop();  // Stop recording.
    EXIT_ON_ERROR(hr)

        Exit:
    CoTaskMemFree(pwfx);
    SAFE_RELEASE(pEnumerator)
        SAFE_RELEASE(pDevice)
        SAFE_RELEASE(pAudioClient)
        SAFE_RELEASE(pCaptureClient)

        return hr;
}

MyAudioSink.cpp
注意**-这是问题所在。您可能会注意到，名为“write_word”的UDF是使用所有音频格式参数初始化wav文件的，但是，我无法弄清楚如何使用此函数来写入pData内容，因此尝试使用到目前为止，ostream写入功能产生了最佳效果(听我的声音)，但听起来非常静态且失真。

#pragma once

#include "MyAudioSink.h"
#include <string.h>


namespace little_endian_io
{
    template <typename Word>
    std::ostream& write_word(std::ostream& outs, Word value, unsigned size = sizeof(Word))
    {

        for (; size; --size, value >>= 8)
            outs.put(static_cast <char> (value & 0xFF));
        return outs;
    }
}
using namespace little_endian_io;

HRESULT MyAudioSink::_Initialize_File() {



    cout << "initializing file";

    // prepare our wav file
    mainFile.open("example.wav", ios::out | ios::binary);

    // Write the file headers and sound format
    mainFile << "RIFF----WAVEfmt ";     // (chunk size to be filled in later)
    write_word(mainFile, 16, 4);  // no extension data
    write_word(mainFile, 1, 2);  // PCM - integer samples
    write_word(mainFile, nChannels, 2);  // two channels (stereo file)
    write_word(mainFile, nSamplesPerSec, 4);  // samples per second (Hz)
    write_word(mainFile, nAvgBytesPerSec, 4);  // (Sample Rate * BitsPerSample * Channels) / 8
    write_word(mainFile, nBlockAlign, 2);  // data block size (size of two integer samples, one for each channel, in bytes)
    write_word(mainFile, wBitsPerSample, 2);  // number of bits per sample (use a multiple of 8)

    // Write the data chunk header
    data_chunk_pos = mainFile.tellp();
    mainFile << "data----";  // (chunk size to be filled in later)..

    //start by setting our complete variable to False, main func will turn to true
    bComplete = false;
    //testing
    test = 0;

    return S_OK;

}

HRESULT MyAudioSink::SetFormat(WAVEFORMATEX* pwfx) {



    //Update our format variables
    wFormatTag = pwfx->wFormatTag;
    nChannels = pwfx->nChannels;
    nSamplesPerSec = pwfx->nSamplesPerSec;
    nAvgBytesPerSec = pwfx->nAvgBytesPerSec;
    nBlockAlign = pwfx->nBlockAlign;
    wBitsPerSample = pwfx->wBitsPerSample;
    cbSize = pwfx->cbSize;

    return S_OK;

}

HRESULT MyAudioSink::CopyData(BYTE* pData, UINT32 numFramesAvailable, BOOL* bDone) {
    //TODO

    //forgot how to do this part, figure it out
    for (int i = 0; i < numFramesAvailable; i++) {
        mainFile.write((const char*) pData+(i* nBlockAlign), nBlockAlign);
    }


    //test
    test++;
    if (test >= nBlockAlign * 120) bComplete = true;

    //check if our main function is done to finish capture
    if (bComplete) *bDone = true;


    return S_OK;
}

HRESULT MyAudioSink::_File_WrapUp() {



    // (We'll need the final file size to fix the chunk sizes above)
    file_length = mainFile.tellp();

    // Fix the data chunk header to contain the data size
    mainFile.seekp(data_chunk_pos + 4);
    write_word(mainFile, file_length - data_chunk_pos + 8);

    // Fix the file header to contain the proper RIFF chunk size, which is (file size - 8) bytes
    mainFile.seekp(0 + 4);
    write_word(mainFile, file_length - 8, 4);

    mainFile.close();

    cout << "finalized file";

    return S_OK;
}

MyAudioSink.h

#pragma once

//
#include <audioclient.h>
#include <Mmdeviceapi.h>
#include <fstream>
#include <iostream>
#include <cmath>



using namespace std;

class MyAudioSink
{

private:

    size_t data_chunk_pos;
    size_t file_length;
    ofstream mainFile;

    //sample format
    WORD  wFormatTag;
    WORD  nChannels;
    DWORD nSamplesPerSec;
    DWORD nAvgBytesPerSec;
    WORD  nBlockAlign;
    WORD  wBitsPerSample;
    WORD  cbSize;
    int test;

public:

    bool bComplete;

    HRESULT _Initialize_File();
    HRESULT SetFormat(WAVEFORMATEX* pwfx);
    HRESULT CopyData(BYTE* pData, UINT32 numFramesAvailable, BOOL* bDone);
    HRESULT _File_WrapUp();
};

Answer 1

我怀疑的问题是您的程序仅处理PCM格式，而不处理可扩展格式。最终的 header 将不是WAVE Specifications

Add this code to confirm :

    pAudioClient->GetMixFormat(&pwfx);

    switch(pwfx->wFormatTag)
    {
        case WAVE_FORMAT_PCM:
            cout << "WAVE_FORMAT_PCM";
            break;

        case WAVE_FORMAT_IEEE_FLOAT:
            cout << "WAVE_FORMAT_IEEE_FLOAT";
            break;

        case WAVE_FORMAT_EXTENSIBLE:
            cout << "WAVE_FORMAT_EXTENSIBLE";

            WAVEFORMATEXTENSIBLE *pWaveFormatExtensible = reinterpret_cast<WAVEFORMATEXTENSIBLE *>(pwfx);

            if(pWaveFormatExtensible->SubFormat == KSDATAFORMAT_SUBTYPE_PCM)
            {
                cout << "KSDATAFORMAT_SUBTYPE_PCM";
            }
            else if(pWaveFormatExtensible->SubFormat == KSDATAFORMAT_SUBTYPE_IEEE_FLOAT)
            {
                cout << "KSDATAFORMAT_SUBTYPE_IEEE_FLOAT";
            }
            break;
    }

我认为最常见的情况是WAVE_FORMAT_EXTENSIBLE和KSDATAFORMAT_SUBTYPE_IEEE_FLOAT ...

编辑

我在这里做了一个简单的示例: WasapiCapture