Question

我想用C ++读取音频（.wav）文件。

到目前为止，我已经阅读了wav文件的标题。如何循环进入wav文件的数据部分，将其转换为-1和1，然后将其写入txt文件。

我已经完成了以下操作，但是当我使用MATLAB绘制生成的txt文件时，信号似乎失真了。

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <fstream>
using namespace std;
//double byteToDouble( char firstByte, char secondByte );

// WAVE PCM soundfile format (you can find more in https://ccrma.stanford.edu/courses/422/projects/WaveFormat/ )
typedef struct header_file
{
    char chunk_id[4];
    int chunk_size;
    char format[4];
    char subchunk1_id[4];
    int subchunk1_size;
    short int audio_format;
    short int num_channels;
    int sample_rate;            // sample_rate denotes the sampling rate.
    int byte_rate;
    short int block_align;
    short int bits_per_sample;
    char subchunk2_id[4];
    int subchunk2_size; // subchunk2_size denotes the number of samples.
    //char data; // actual data : Added by tarmizi
} header;

typedef struct header_file* header_p;




int main()

{
    ofstream myFile;
    myFile.open("mizi.txt");


    FILE * infile = fopen("0BF1S1T0.wav","rb");     // Open wave file in read mode
    FILE * outfile = fopen("Output.txt","wb");      // Create output ( wave format) file in write mode;
    FILE * svFile;

    int BUFSIZE = 256;                  // BUFSIZE can be changed according to the frame size required (eg:512)
    int count = 0;                      // For counting number of frames in wave file.
    short int buff16[BUFSIZE];              // short int used for 16 bit as input data format is 16 bit PCM audio
    header_p meta = (header_p)malloc(sizeof(header));   // header_p points to a header struct that contains the wave file metadata fields
    int nb;                         // variable storing number of bytes returned

    if (infile)
    {
        fread(meta, 1, sizeof(header), infile);
        //fwrite(meta,1, sizeof(*meta), outfile);


        cout << "first chunk is :" << sizeof(meta->chunk_id) << " bytes in size" << endl;
        cout << "The file is a :" << meta->chunk_id << " format" << endl;
        cout << " Size of Header file is "<<sizeof(*meta)<<" bytes" << endl;
        cout << " Sampling rate of the input wave file is "<< meta->sample_rate <<" Hz" << endl;
        cout << " Number of bits per sample is: "<< meta->bits_per_sample <<"bits" << endl;
        cout << " Size of data in the audio is: " << sizeof(meta->subchunk2_size)<< " bytes" << endl;
        cout << " The number of channels of the file is "<< meta->num_channels << " channels" << endl;
        cout << " The audio format is PCM:"<< meta->audio_format << endl;
        //cout << " The size of actual data is "<< sizeof(meta->data) << "bytes" << endl;



        while (!feof(infile))          //(nb = fread(buff16,1,BUFSIZE,infile))>0
        {
                    // Reading data in chunks of BUFSIZE
            //cout << nb <<endl;
            nb = fread(buff16,1,BUFSIZE,infile);
            count++;
                            // Incrementing > of frame
            for (int i = 0; i<BUFSIZE; i+=meta->num_channels) //  BUFSIZE = 256, meta->num_channels = 1
                {



                        int c = (buff16[i]<<8) | buff16[1+i];
                        double t = c/32768.0;

                        myFile << t<< endl;

                    }



        }

    cout << " Number of frames in the input wave file are " <<count << endl;


/
return 0;
}
}

有什么想法吗？我认为我不会循环数据并正确转换。任何人都可以帮我在这里展示正确的方法吗？提前谢谢......

Answer 1

将两个字节组合成int的方式总是会产生正结果。为了正确处理符号，您应该将字节组合成short而不是int。

Answer 2

问题似乎在于：

nb = fread(buff16,1,BUFSIZE,infile);

它实际上读取1 * BUFSIZE个字节，而它应该读取2 * BUFSIZE个字节（每个元素2个字节）。将该行更改为以下内容：

nb = fread(buff16,sizeof(short int),BUFSIZE,infile);

另外，在

行

int c = (buff16[i]<<8) | buff16[1+i];

buff16[i]应该移位16位。

我对音频格式知之甚少。所以可能还有其他错误。

Answer 3

此代码看起来不对：

int c = (buff16[i]<<8) | buff16[1+i];
double t = c/32768.0;

您应该将缓冲区声明为unsigned char[32]。

的数组

然后为每个频道计算t：

int hi = (signed char) buffer[i + 1]; // always little endian
int c = (hi << 8) | buffer[i + 0];
double t = c / 32768.0;
i += 2;

用C ++读取音频文件

3 个答案: