WAVE音频文件格式分析--实现C语言读写文件头

本文将详细分析WAVE音频文件的格式,并通过C语言对wave文件头进行读写操作。

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WAVE音频文件格式分析–实现C语言读写文件头

WAVE音频文件

WAVE文件格式是一种由微软和IBM联合开发的用于音频数字存储的标准, 它采用RIFF(Resource Interchange File Format,资源交换文件标准)文件格式结构文件的扩展名为“WAV”, 所有的WAV都有一个文件头, 数据本身的格式为PCM或压缩型.

WAVE文件头

WAVE文件分成两部分:文件头和数据块. WAV格式文件主要有两种文件头: 标准的44字节文件头和经过了一些软件处理的58字节文件头. 
WAVE文件头包含RIFF数据块,一个“fmt”数据块和一个“data”数据块

本文所介绍的WAV文件头是标准的44字节文件头.

WAVE文件格式

纠正: ByteRate应该为每秒存储的字节数

通过WAVE文件头信息,我们可以计算出播放时长:

文件播放时长 = Subchunk2Size/ByteRate

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C语言实现对WAVE文件头的读写

这里我提供了几个接口供大家使用,handle_wave.c 和 handle_wave.h.

#ifndef _HANDLE_WAVE_H
#define _HANDLE_WAVE_H

typedef struct
{
    char  riff_id[4];                       //"RIFF"
    int   riff_datasize;                    // RIFF chunk data size,exclude riff_id[4] and riff_datasize,total - 8

    char  riff_type[4];                     // "WAVE"

    char  fmt_id[4];                        // "fmt "
    int   fmt_datasize;                     // fmt chunk data size,16 for pcm
    short fmt_compression_code;             // 1 for PCM
    short fmt_channels;                     // 1(mono) or 2(stereo)
    int   fmt_sample_rate;                  // samples per second
    int   fmt_avg_bytes_per_sec;            // sample_rate * channels * bit_per_sample / 8
    short fmt_block_align;                  // number bytes per sample, bit_per_sample * channels / 8
    short fmt_bit_per_sample;               // bits of each sample(8,16,32).

    char  data_id[4];                       // "data"
    int   data_datasize;                    // data chunk size,pcm_size - 44
}WaveHeader_t;

void init_wavheader(WaveHeader_t *wavheader);
int read_wavheader(FILE *fp,WaveHeader_t *wavheader);
int write_wavheader(FILE *fp,WaveHeader_t wavheader);
void print_wavheader(WaveHeader_t wavheader);

#endif

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#include <stdio.h>
#include <stdlib.h>
#include "handle_wave.h"

/* read and write integer from file stream */
static int get_int(FILE *fp)
{
    char *s;
    int i;
    s = (char *)&i;
    size_t len = sizeof(int);
    int n = 0;
    for(;n < len;n++)
    {
        s[n]=getc(fp);
        //printf("%x\n",s[n]);
    }
    return i;
}

static int put_int(int i,FILE *fp)
{
    char *s;
    s=(char *)&i;
    size_t len = sizeof(int);
    int n = 0;
    for(;n < len;n++)
    {
        putc(s[n],fp);
        //printf("%x\n",s[n]);
    }

    return i;
}

static short int get_sint(FILE *fp)
{
    char *s;
    short int i;
    s = (char *)&i;
    size_t len = sizeof(short);
    int n = 0;
    for(;n < len;n++)
    {
        s[n]=getc(fp);
        //printf("%x\n",s[n]);
    }

    return i;
}

static short int put_sint(short int i,FILE *fp)
{
    char *s;
    s=(char *)&i;
    size_t len = sizeof(short);
    int n = 0;
    for(;n < len;n++)
    {
        putc(s[n],fp);
        //printf("%x\n",s[n]);
    };

    return i;
}

void init_wavheader(WaveHeader_t *wavheader)
{
    sprintf(wavheader->riff_id,"RIFF");
    wavheader->riff_datasize = -1;

    sprintf(wavheader->riff_type,"WAVE");

    sprintf(wavheader->fmt_id,"fmt ");
    wavheader->fmt_datasize = 16;
    wavheader->fmt_compression_code = 1;
    wavheader->fmt_channels = -1;
    wavheader->fmt_sample_rate = -1;
    wavheader->fmt_avg_bytes_per_sec = -1;
    wavheader->fmt_block_align = -1;
    wavheader->fmt_bit_per_sample = 16;

    sprintf(wavheader->data_id,"data");
    wavheader->data_datasize = -1;
}

int read_wavheader(FILE *fp,WaveHeader_t *wavheader)
{
    if (fp ==NULL)
        return -1;

    fread(wavheader->riff_id,4,1,fp);
    wavheader->riff_datasize = get_int(fp);
    fread(wavheader->riff_type,4,1,fp);
    fread(wavheader->fmt_id,4,1,fp);
    wavheader->fmt_datasize = get_int(fp);
    wavheader->fmt_compression_code = get_sint(fp);
    wavheader->fmt_channels = get_sint(fp);
    wavheader->fmt_sample_rate = get_int(fp);
    wavheader->fmt_avg_bytes_per_sec = get_int(fp);
    wavheader->fmt_block_align = get_sint(fp);
    wavheader->fmt_bit_per_sample = get_sint(fp);
    fread(wavheader->data_id,4,1,fp);
    wavheader->data_datasize = get_int(fp);

    return 0;
}

int write_wavheader(FILE *fp,WaveHeader_t wavheader)
{
    if (fp ==NULL)
        return -1;

    fwrite(wavheader.riff_id,4,1,fp);
    put_int(wavheader.riff_datasize,fp);
    fwrite(wavheader.riff_type,4,1,fp);
    fwrite(wavheader.fmt_id,4,1,fp);
    put_int(wavheader.fmt_datasize,fp);
    put_sint(wavheader.fmt_compression_code,fp);
    put_sint(wavheader.fmt_channels,fp);
    put_int(wavheader.fmt_sample_rate,fp);
    put_int(wavheader.fmt_avg_bytes_per_sec,fp);
    put_sint(wavheader.fmt_block_align,fp);
    put_sint(wavheader.fmt_bit_per_sample,fp);
    fwrite(wavheader.data_id,4,1,fp);
    put_int(wavheader.data_datasize,fp);

    return 0;
}

void print_wavheader(WaveHeader_t wavheader)
{
    printf("wavheader.riff_id: %c%c%c%c\n",wavheader.riff_id[0],wavheader.riff_id[1],wavheader.riff_id[2],wavheader.riff_id[3]);
    printf("wavheader.riff_datasize: %d\n",wavheader.riff_datasize);
    printf("wavheader.riff_type: %c%c%c%c\n",wavheader.riff_type[0],wavheader.riff_type[1],wavheader.riff_type[2],wavheader.riff_type[3]);
    printf("wavheader.fmt_id: %c%c%c%c\n",wavheader.fmt_id[0],wavheader.fmt_id[1],wavheader.fmt_id[2],wavheader.fmt_id[3]);
    printf("wavheader.fmt_datasize: %d\n",wavheader.fmt_datasize);
    printf("wavheader.fmt_compression_code: %hd\n",wavheader.fmt_compression_code);
    printf("wavheader.fmt_channels: %hd\n",wavheader.fmt_channels);
    printf("wavheader.fmt_sample_rate: %d\n",wavheader.fmt_sample_rate);
    printf("wavheader.fmt_avg_bytes_per_sec: %d\n",wavheader.fmt_avg_bytes_per_sec);
    printf("wavheader.fmt_block_align: %hd\n",wavheader.fmt_block_align);
    printf("wavheader.fmt_bit_per_sample: %hd\n",wavheader.fmt_bit_per_sample);
    printf("wavheader.data_id: %c%c%c%c\n",wavheader.data_id[0],wavheader.data_id[1],wavheader.data_id[2],wavheader.data_id[3]);
    printf("wavheader.data_datasize: %d\n",wavheader.data_datasize);
}