C++ Beep()演奏简谱的改进以及实现背景音乐_c++演奏音乐平凡之路

看到Beep()就会想起上世纪90年代初在8086的机器或者稍后的286、386机器上用解释型Basic编简谱玩的情景，这便是那个声霸卡还没上市的年代里，几乎是人们在PC上唯一可编的声音了。

Beep的函数原型：
BOOL Beep(
DWORD dwFreq;  /*指定要发出的频率(HZ)*/
DWORD dwDuration;  /*指定发音的时长，以毫秒为单位*/
);

通常先把do re mi ...的频率预定义好，再照着简谱把频率和时长编入两个数组或一个结构体数组。
#define do 523
#define re 578
#define mi 659
#define fa 698
#define so 784
#define la 880
#define si 988
......
int freq[] = { do,re,mi,do,do,re,mi,do,...}
int duration[] = {300,300,300,300,300,300,300,300,...}
最后用Beep()循环输出。

对此我做了些小改进：把频率定入一个结构体数组便于反复调用；简谱放入一个vector容器就不用管谱子的长短不用管数组的下标，只要按顺序push_back()每一个音符，还能随时插入删除某个音符，重复的小节可以用循环多次输出以缩短代码长度；简谱转代码时“所见即所得”看到什么数字就写入什么数字；音符的时长也以“拍”为单位，每个小节后加个空行便于检查每节的总时长。源代码如下：

#include <array>
#include <vector>
#include <iostream>
#include <windows.h>
 
using namespace std;
 
#define PAI 300  //一拍的时长，可以自行调整 
 
struct tone{
	short a; short d; short g;  //中音;低音;高音 
	short b; short e; short f;  //半阶音 
};
 
struct tune{
	short t;	//唱名 
	float l;	//音长 
	short b;	//音调 
};
 
array<tone,8>m;
 
short t(short a,short b)
{
	switch(b){
		case 0: return m[a].a;
		case 1: return m[a].d;
		case 2: return m[a].g;
		case 3: return m[a].b;
		case 4: return m[a].e;
		case 5: return m[a].f;
	}
}
 
short p(float p)
{
	return (short)(PAI*p);
}
 
void initTone(void)
{	//把各音符的频率写入数组，一劳永逸可以随时调用
	m.at(0)={0,0,0,0,0,0};
	m.at(1)={523,262,1046,554,277,1109};
	m.at(2)={578,294,1175,622,311,1245};
	m.at(3)={659,330,1318,659,330,1318};
	m.at(4)={698,349,1493,740,370,1556};
	m.at(5)={784,392,1568,831,415,1661};
	m.at(6)={880,440,1760,932,466,1865};
	m.at(7)={988,494,1976,988,494,1976};
}
 
void initTune(vector<tune>&s)
{
	for (int i=0;i<2;i++){	
	    s.push_back({1,1,0});
    	s.push_back({2,1,0});
	    s.push_back({3,1,0});
    	s.push_back({1,1,0});
    }
 
	for (int i=0;i<2;i++){	
    	s.push_back({3,1,0});
	    s.push_back({4,1,0});
    	s.push_back({5,2,0});
    }
	
   	for (int i=0;i<2;i++){	
    	s.push_back({5,0.75,0});
    	s.push_back({6,0.25,0});
    	s.push_back({5,0.75,0});
	    s.push_back({4,0.25,0});
	    s.push_back({3,1,0});
	    s.push_back({1,1,0});
    }
 
	for (int i=0;i<2;i++){	
	    s.push_back({1,1,0});
	    s.push_back({5,1,1});
	    s.push_back({1,2,0});
    }
	
	//以上根据简谱上的拍子和音调编入容器，方法如下： 
	//第一个参数 1~7 对应do re mi fa so la si 0=休止符
	//第二个参数 1拍=1；半拍=0.5 四分之一拍=0.25 以此类推 
	//第三个参数 一般就为0，低音=1 高音=2 对应的半阶音=3 4 5 
	//转简谱时看到什么数字就是什么，不用记频率数方便编辑和排错 
}
 
int main()
{
	vector<tune>music;
	initTone();
	initTune(music);
		
	cout<<"开始演奏《两只老虎》"<<endl;	
	for (auto m:music) Beep(t(m.t,m.b),p(m.l));
	
	return 0; 
}

 背景音乐的实现

一个程序独占控制台CPU时间来演奏音乐，没有一点实用性。我们再来编一首《送别》并实现“后台演奏”，注意：碰到简谱中有重复的小节可多放几个子函数以供多次调用。

实际上，演奏的同时还要做其他工作，就是要创建多个线程来完成几个不同的工作：先调用<pthread.h>库函数pthread_create()创建一个线程来播放背景音乐，然后让主程序开始做其它工作，并且可以按需要来选择哪项任务先结束。源代码如下：

#include <array>
#include <vector>
#include <iostream>
#include <ctime>
#include <sstream>
#include <windows.h>
#include <pthread.h>
 
using namespace std;
 
#define PAI 400  //一拍的时长，可以自行调整 
 
struct tone{
	short a; short d; short g;  //中音;低音;高音 
	short b; short e; short f;  //半阶音 
};
 
struct tune{
	short t;	//唱名 
	float l;	//音长 
	short b;	//音调 
};
 
array<tone,8>m;
 
short t(short a,short b)
{
	switch(b){
		case 0: return m[a].a;
		case 1: return m[a].d;
		case 2: return m[a].g;
		case 3: return m[a].b;
		case 4: return m[a].e;
		case 5: return m[a].f;
	}
}
 
short p(float p)
{
	return (short)(PAI*p);
}
 
void initTone(void)
{	
	m.at(0)={0,0,0,0,0,0};
	m.at(1)={523,262,1046,554,277,1109};
	m.at(2)={578,294,1175,622,311,1245};
	m.at(3)={659,330,1318,659,330,1318};
	m.at(4)={698,349,1493,740,370,1556};
	m.at(5)={784,392,1568,831,415,1661};
	m.at(6)={880,440,1760,932,466,1865};
	m.at(7)={988,494,1976,988,494,1976};
}
 
void repeat1(vector<tune>&s)
{
	s.push_back({5,1,0});
	s.push_back({3,0.5,0});
	s.push_back({5,0.5,0});
}
 
void repeat2(vector<tune>&s)
{
	s.push_back({6,1,0});
	s.push_back({1,1,2});
	s.push_back({5,2,0});
}
 
void repeat3(vector<tune>&s, short i)
{
	s.push_back({i,2,0});
	s.push_back({0,1,0});
	s.push_back({0,1,0});
}
 
void initTune(vector<tune>&s)
{
	for (int i=0;i<2;i++){
 
		repeat1(s);
		s.push_back({1,2,2});
		repeat2(s);
 
		s.push_back({5,1,0});
		s.push_back({1,0.5,0});	
		s.push_back({2,0.5,0});
		s.push_back({3,1,0});
		s.push_back({2,0.5,0});
		s.push_back({1,0.5,0});
	
		repeat3(s,2);
	
		repeat1(s);
		s.push_back({1,1.5,2});
		s.push_back({7,0.5,0});	
		repeat2(s);	
	
		s.push_back({5,1,0});
		s.push_back({2,0.5,0});	
		s.push_back({3,0.5,0});
		s.push_back({4,1.5,0});
		s.push_back({7,0.5,1});
	
		repeat3(s,1);
	
		s.push_back({6,1,0});
		s.push_back({1,1,2});
		s.push_back({1,2,2});
	
		s.push_back({7,0.5,0});
		s.push_back({6,0.5,0});
		s.push_back({7,0.5,0});
		s.push_back({1,2,2});		
	
		s.push_back({6,0.5,0});
		s.push_back({7,0.5,0});
		s.push_back({1,0.5,2});
		s.push_back({6,0.5,0});
		s.push_back({6,0.5,0});
		s.push_back({5,0.5,0});
		s.push_back({3,0.5,0});
		s.push_back({1,0.5,0});
 
		repeat3(s,2);
	
		repeat1(s);
		s.push_back({1,1.5,2});
		s.push_back({7,0.5,0});	
		repeat2(s);	
	
		s.push_back({5,1,0});
		s.push_back({2,0.5,0});
		s.push_back({3,0.5,0});
		s.push_back({4,1.5,0});
		s.push_back({7,0.5,1});
 
	    repeat3(s,1);
 
	}
}
 
void gotoXY(short x, short y)
{
    COORD position = {x, y};
    HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
    SetConsoleCursorPosition(hConsole, position);
}
 
bool play_not_end=true;  //设置演奏标记 
 
void* play(void* args)
{
	vector<tune>music;
	initTone();
	initTune(music);
	gotoXY(28,8);
	cout<<"背景音乐：《送别》";
	for (auto v:music)
		if (play_not_end) Beep(t(v.t,v.b),p(v.l));
		else break;
 
	play_not_end=false;
}
 
char strTime[20];
 
void* coutTime(void* args)
{
	time_t lt;
	while (play_not_end){
		time(&lt);
		strftime(strTime,sizeof(strTime),"%Y-%m-%d %H:%M:%S",localtime(&lt));
		Sleep(300);
	}
	play_not_end=false;
}
 
int main()
{
	pthread_t pt;
	int ret = pthread_create(&pt, NULL, play, NULL);  //创建一个线程，play()变相成为背景音乐 
	if (ret!=0) cout<<"create thread_1 error: error_code="<<ret<<endl;
	
	ret = pthread_create(&pt, NULL, coutTime, NULL);  //再创建一个线程，用于显示当前系统时间 
	if (ret!=0) cout<<"create thread_2 error: error_code="<<ret<<endl;
	
	//在 pthread_create()与 pthread_exit()之间，便是程序工作的主场 
	Sleep(100);
	gotoXY(28,10);
	cout<<"工作开始：循环次数 ";
	for(int i=1;play_not_end;i++){
		gotoXY(48,10);
		cout<<i<<endl;
		gotoXY(60,0);
		cout<<strTime; //显示另外一个线程取回的时间 
		Sleep(300);
		if (i==100) play_not_end=false;  //工作在音乐演奏完之前结束，只要把标记设为false即可 
	}
	gotoXY(28,12);
	cout<<"工作结束！"<<endl;
	
	pthread_exit(NULL);
	return 0; 
}

注意：本程序在Dev-C++ 5.11/编译器TDM-GCC 4.9.2 64-bit 上通过编译，若用VS编译找不到头文件<pthread.h>，请搜索“如何在vs2017上使用pthread.h”并自行安装库文件。

附：《两只老虎》、《送别》简谱