将16bit单声道WAV格式文件转为8bit PCM格式文件

1.扩展知识

wav文件格式分析与详解

PCM文件格式简单介绍

wav音频文件头解析

WAV文件头读取

 

2.代码（convert_sample_rate.c）

#include <stdio.h>
#include <string.h>
#include <errno.h>

int main(int argc, char **argv)
{
        FILE *from = NULL;
        FILE *to = NULL;
        int i, n, ret = 0;
        char path[256 + 1];
        char *src;
        char buf[4];
        char head_buff[44] = {0};

        printf("Convert sample rate 16000 -> 8000\n");

        if (argc == 1)
        {
                ret = -1;
                goto show_usage;
        }

        for (i = 1; i < argc; i++)
        {
                src = argv[i];
                snprintf(path, sizeof(path), "%s.pcm", src);
                from = fopen(src, "r");
                if (NULL == from)
                {
                        printf("error: open [%s] failed, %s\n", src, strerror(errno));
                        ret = -1;
                        goto next_file;
                }
                to = fopen(path, "w+");
                if (NULL == to)
                {
                        printf("error: open [%s] failed, %s\n", path, strerror(errno));
                        ret = -1;
                        goto next_file;
                }

                //去掉44字节文件头
                if(fread(head_buff, 1, 44, from) != 44)
                {
                    printf("Read Wav Head Error!\n");
                }

                printf("%2d: %60s -> %60s\n", i, src, path);
                while ((n = fread(buf, 1, 4, from)) == 4)
                {
                        if (2 != fwrite(buf, 1, 2, to))
                        {
                                printf("error: write failed\n");
                                break;
                        }
                }
next_file:
                if (NULL != from)
                        fclose(from);
                if (NULL != to)
                        fclose(to);
        }

        if (0 == ret)
                return 0;

show_usage:
        printf("Usage: %s [file_1] [file_n] [...] [file_n]\n", argv[0]);

        return 0;
}