《计算机世界月刊》1995.3期曾刊登了《在DOS下使用Windows *.WAV文件》一文，根据《在》文中所附的源程序重放WAV文件，发现其音质确实较差；又用文中所提及的第二种延时方法，效果并无改善(大概是循环次数int(vol[counter]/256)≡0)。究其原因，可能是重放时将原WAV文件中127/128的有用信息抛弃了。
实际上，我们是可以把原来抛弃的127/128的有用信息捡回来的。我们知道，WAV文件中所存的是采样时的电压幅值信号，只要将电压信号重现在PC的小喇叭上，就可以逼真地重放WAV文件了。
喇叭上发出的声音，其实就是驱动喇叭的电压变化。而对PC上的数字开关喇叭，只有“0”和“1”两种状态:“1”时喇叭纸盆向外运动，“0”则纸盆向内运动而回复正常位置。
但是向喇叭发送“1”信号时，喇叭向外运动有一个延迟时间，当喇叭还没到达最外位置时，立即再发送“0”信号，纸盆来不及运动到最外位置而转向向内运动。根据这一原理，我们控制喇叭向外运动的时间，就可以间接地控制纸盆运动的幅度，从而根据WAV文件的采样值来控制喇叭的声音大小。
对于PC时钟，显然来不及控制纸盆运动的幅度(即使对8253定时器重新编程，也无法使纸盆从正常位置到最外位置有若干个int08h发生)，因此，对于WAV文件的延时，只能采用loop指令。实际上，Windows也正是用这种方法来延时的(以标准模式和增强模式分别启动时，Windows要重新建立延迟时间而发出测试的声音)。
程序中读WAV文件头信息和WAV数据与《在》文相同，发声子程序重新改写了。若发出的声音在频率上有失真，可以修改wave函数中cx的初值(386增强模式、386DX33微机上Windows使用0x13)。
程序运行环境:386兼容机，DOS6.2，Twrbo C++3.0编译系统。
#include<dos.h>
#include<stdio.h>
#include<string.h>
#include<conio.h>
#include<stdlib.h> お
#define MAXSIZE 50000 お
unsigned int a[]=
{
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,
0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff81,0xff83,
0xff88,0xff8d,0xff92,0xff97,0xff9c,0xffa1,0xffa6,0xffab,
0xffb0,0xffb5,0xffba,0xffbf,0xffc4,0xffc9,0xffce,0xffd3,
0xffd8,0xffdd,0xffe2,0xffe7,0xffec,0xfff1,0xfff6,0xfffb,
0x0000,0x0005,0x000a,0x000f,0x0014,0x0019,0x001e,0x0023,
0x0028,0x002d,0x0032,0x0037,0x003c,0x0041,0x0046,0x004b,
0x0050,0x0055,0x005a,0x005f,0x0064,0x0069,0x006e,0x0073,
0x0078,0x007d,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,
0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f,0x007f
=======================================================
}; お
struct wave-file-head
{
char riff-id[4];
long size0;
char wave-fmt[8];
long size1;
int fmttag;
int channel;
long samplespersec;
long bytepersec;
int blockalign;
int bitpersamples;
} filehead; お
long datasize;
unsigned char vol[MAXSIZE];
void wave(void); お
void wave()
{
unsigned int i; お
for(i=0;i<datasize;i++)
{
_BL=vol[i];
asm {
xor bh,bh
shl bx,1
mov bx,a[bx];
xor di,di;
xor dx,dx;
in al,0x61;
and al,0xfc;
out 0x61,al;
mov cx,17;
}
loc33:
asm{
add di,bx;
jge loc34
and al,0xfc;
sub di,0xff81;
out 0x61,al;
loop loc33;
jmp loc35;
}
loc34:
asm{
or al,3;
sub di,0x7f;
out 0x61,al;
loop loc33;
}
loc35;
}
} お
void main(int argc,char *argv[])
{
long j;
int key;
char *s;
FILE *fp; お
if (argc==1)
{
printf("Required parameter missing\n");
exit(0);
>}
if((fp=fopen(argv[1],"rb"))==NULL)
{
printf("File not open\n");
exit(0);
}
if(fread(&filehead,sizeof(struct wave-file-head),1,fp) ==NULL)
{
prinft("File read error\n");
exit(0);
}
fseek(fp,4,SEEK-CUR);
fread(&datasize,4,1,fp); お
for(j=0;j<datasize;j++)
vol[j]=getc(fp);
fclose(fp);
printf("%s\n","Press[ESC] to stop\nSounding...");
while(bioskey(1)==0)wave();
nosound();
}
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