为什么要播放单声道?

问题描述

为什么要单声道播放?

Why play it mono?

#pragma comment (lib, "winmm.lib")
#include <windows.h>
#include <mmsystem.h>
#include <stdlib.h>

void CALLBACK waveInProc(HWAVEIN hwi,UINT uMsg,DWORD dwInstance,DWORD dwParam1,DWORD dwParam2);
bool addbuffer(WAVEHDR *pWaveHdr);

#define system_buf_len 4410
const int num_buff = 3;

HWAVEOUT hvo;
HWAVEIN hvi;

WAVEFORMATEX waveFormat;
WAVEHDR *whdrO;
WAVEHDR buffer[num_buff];

int main()
{
	whdrO=(WAVEHDR*)malloc(sizeof(WAVEHDR));

	waveFormat.wFormatTag      = WAVE_FORMAT_PCM;
	waveFormat.wBitsPerSample  = 16;
	waveFormat.nChannels       = 2;
	waveFormat.nSamplesPerSec  = 44100;
	waveFormat.nBlockAlign     = (waveFormat.nChannels * waveFormat.wBitsPerSample) / 8;
	waveFormat.nAvgBytesPerSec = (waveFormat.nSamplesPerSec * waveFormat.nBlockAlign);
	waveFormat.cbSize          = 0;

	UINT uDevice = 0;

	MMRESULT mmres;
	mmres = waveInOpen(&hvi,uDevice,&waveFormat,(DWORD)waveInProc,0,CALLBACK_FUNCTION);
	mmres = waveOutOpen(&hvo,WAVE_MAPPER,&waveFormat,0,0,CALLBACK_NULL);

	for (int i=0; i<num_buff; i++)
	{
		buffer[i].lpData          = (char*)malloc(system_buf_len);
		buffer[i].dwBufferLength  = system_buf_len;
		buffer[i].dwBytesRecorded = 0;
		buffer[i].dwUser          = 0;
		buffer[i].dwFlags         = 0;
		buffer[i].dwLoops         = 0;
		waveInPrepareHeader(hvi, &buffer[i], sizeof(WAVEHDR));
		waveInAddBuffer(hvi, &buffer[i], sizeof(WAVEHDR));
	}

	waveInStart(hvi);
	system("pause");
	waveInClose(hvi);
	waveOutClose(hvo);
	return 0;
}

void CALLBACK waveInProc(HWAVEIN hwi,UINT uMsg,DWORD dwInstance,DWORD dwParam1,DWORD dwParam2)
{
	WAVEHDR* pWaveHdr;
	switch(uMsg)
	{
		case MM_WIM_DATA:
			pWaveHdr = ((WAVEHDR*)dwParam1);
			if (pWaveHdr && hwi)
				if (pWaveHdr->dwFlags && WHDR_DONE == WHDR_DONE)
				{
					addbuffer(pWaveHdr);
					waveInAddBuffer(hwi, pWaveHdr, sizeof(WAVEHDR));
				}
		break;
	}
}

bool addbuffer(WAVEHDR *waveHdr)
{
	memcpy(whdrO,waveHdr,sizeof(WAVEHDR));
	waveInUnprepareHeader(hvi,waveHdr,sizeof(WAVEHDR));
	waveOutPrepareHeader(hvo,waveHdr,sizeof(WAVEHDR));
	waveOutWrite(hvo,whdrO, sizeof(WAVEHDR));

	return true;
}

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