在两个通道上播放单声道 WAV

Question

我创建了一个随机的单声道 WAV，但是当我播放它时，我可以通过两个声道（左和右）听到音频。这是我的代码：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>

struct wav{
    char ChunkID[4];
    unsigned int ChunkSize;
    char Format[4];
    char Subchunk1ID[4];
    unsigned int Subchunk1Size;
    unsigned short int AudioFormat;
    unsigned short int NumChannels;
    unsigned int SampleRate;
    unsigned int ByteRate;
    unsigned short int BlockAlign;
    unsigned short int BitsPerSample;
    char SubChunk2ID[4];
    unsigned int Subchunk2Size;
};

int main(){

    struct wav wavHdr;
    FILE *fp;

    fp = fopen("MonoSound.wav", "wb");

    strcpy(wavHdr.ChunkID, "RIFF");
    strcpy(wavHdr.Format, "WAVE");
    strcpy(wavHdr.Subchunk1ID, "fmt ");
    wavHdr.Subchunk1Size = 16;
    wavHdr.AudioFormat = 1;
    wavHdr.NumChannels = 1;
    wavHdr.SampleRate = 220505;
    wavHdr.ByteRate = 441010;   //(SampleRate*NumChannels*BitsPerSample/8)
    wavHdr.BlockAlign = 2;     //(NumChannels*BitsPerSample/8)
    wavHdr.BitsPerSample = 16;
    strcpy(wavHdr.SubChunk2ID, "data");
    /* multiplied by 5 because there's 5 seconds of audio */
    wavHdr.Subchunk2Size = (5 * wavHdr.ByteRate);
    wavHdr.ChunkSize = (wavHdr.Subchunk2Size + 36);

    fwrite(&wavHdr, 44, 1, fp);

    int i, randVal;
    unsigned int audio;
    float freq = 50.0;
    int amp = 32600;
    float w;

    srand(time(NULL));

    for(i = 0; i < (5 * wavHdr.SampleRate); i++){
        randVal = (rand() % 1) + 1;
        amp += randVal;
        w = 2.0 * 3.141592 * freq;
        audio = amp * sin(w * i / 220505.0);
        fwrite(&audio, 2, 1, fp);
    }

    return 0;
}

我做错了什么？音频只能通过其中一个扬声器输出。在此先感谢您的帮助。

Answer 1

"The audio should only come out through one of the speakers"

不是真的。当你有单声道文件时，即你在录制音频时有一个麦克风，你将在两个输出通道上获得相同的数据。如果你只想听到一个通道的音频，制作 2 个通道的 wav，其中一个通道全为零

Answer 2

The audio should only come out through one of the speakers

你为什么这么认为？可能音频驱动程序试图变得聪明并通过两个扬声器播放单声道信号（就像所有其他消费类音频硬件一样）。

如果您想确保只在左声道播放信号，您必须创建一个立体声信号并将右声道设置为静音（全为零） .

Answer 3

为了实现您的目标，您可以欺骗您的声卡（默认情况下将单声道文件播放到两个扬声器声道），或者您可以创建一个具有一个空声道的立体声文件。为此，您必须更改通道数（使用 wavHdr.NumChannels 设置为 2）并且您必须编写一个空通道与 good 通道交替（参见代码末尾的第二个命令 fwrite。）

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <cstring>

struct wav{
    char ChunkID[4];
    unsigned int ChunkSize;
    char Format[4];
    char Subchunk1ID[4];
    unsigned int Subchunk1Size;
    unsigned short int AudioFormat;
    unsigned short int NumChannels;
    unsigned int SampleRate;
    unsigned int ByteRate;
    unsigned short int BlockAlign;
    unsigned short int BitsPerSample;
    char SubChunk2ID[4];
    unsigned int Subchunk2Size;
};

int main(){

    struct wav wavHdr;
    FILE *fp;

    fp = fopen("MonoSound.wav", "wb");

    strcpy(wavHdr.ChunkID, "RIFF");
    strcpy(wavHdr.Format, "WAVE");
    strcpy(wavHdr.Subchunk1ID, "fmt ");
    wavHdr.Subchunk1Size = 16;
    wavHdr.AudioFormat = 1;
    wavHdr.NumChannels = 2;
    wavHdr.BitsPerSample = 16;
    wavHdr.SampleRate = 220505;
    wavHdr.ByteRate = wavHdr.SampleRate * wavHdr.NumChannels * wavHdr.BitsPerSample/8;
    wavHdr.BlockAlign = wavHdr.NumChannels * wavHdr.BitsPerSample/8;
    strcpy(wavHdr.SubChunk2ID, "data");
    /* multiplied by 5 because there's 5 seconds of audio */
    wavHdr.Subchunk2Size = (5 * wavHdr.ByteRate);
    wavHdr.ChunkSize = (wavHdr.Subchunk2Size + 36);

    fwrite(&wavHdr, 44, 1, fp);

    int i, randVal;
    unsigned int audio, empty=0;
    float freq = 50.0;
    int amp = 32600;
    float w;

    srand(time(NULL));

    for(i = 0; i < (5 * wavHdr.SampleRate); i++){
        randVal = (rand() % 1) + 1;
        amp += randVal;
        w = 2.0 * 3.141592 * freq;
        audio = amp * sin(w * i / 220505.0);
        // write LEFT channel
        fwrite(&audio, 2, 1, fp);
        // write RIGHT channel
        fwrite(&empty, 2, 1, fp);
    }

    return 0;
}

您编写两个频道的顺序很重要。如果你想让空通道成为左边的通道，你必须反转两个 fwrite 命令。此外，您必须更改 ByteRate 和 BlockAlign 以考虑新频道。

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