利用Mpegplayer控件编写简单的mp3播放程序

       mp3因其较高的压缩率,较好的音质,成为越来越多的使用者的喜爱,用自己编制的mp3播放器听mp3音乐一定很有乐趣.我以下介绍一个用delphi编制的简单mp3播放器,因为mp3音乐的解码比较复杂,普通的程序员很难编制其解码程序,但不要紧,我们可以用别人写好的解码程序来完成我们的程序.
       我们使用mpegdll.dll来解码(很多国产的mp3播放器都用它),mpegdll.dll的作者提供了它的delphi的控件,在各大delphi网站都有下载,,在component中选择install component,安装控件包中的mpegplayer.dcu,安装完成后在控件栏里多出一个add-ons来,控件就在里面.
1.介绍一下用到的参数

   mpeg.streamname   所要播放的文件名
   mpeg.length       文件程度
   mpeg.bitrate      压缩位率
   mpeg.frequency    压缩频率
   mpeg.layer        压缩层次
   mpeg.mode         压缩模式
   mpeg.pathtodll    dll文件的路径
2.新建一个from,放入6个label,5个button,1个checkbox,1个mpeg,1个time,1个trackbar,1个opendialog控件调整为适当的布局,点击opendialog1使*.mp3成为打开文件的后缀名.调整5个button,把其属性name改为 openbutton,pausebutton,stopbutton,playbutton和exitbutton,并把caption改为播放,暂停,停止,打开,和退出. 使3个label的caption成为,压缩位率,压缩频率,压缩层次,调整其他3个label使label4对应label1,label5对应label2,label6对应label3 caption为空,autosize为true,trackbar的tickstyle设为tsNone,chickbox的caption设为循环播放,timer的ontimer设为timer1timer
3.程序清单如下

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes,
  Graphics, Controls, Forms, Dialogs,
  ExtCtrls, MPEGPlayer,Gauges,
  ComCtrls,Mask, StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    openButton: TButton;
    playButton: TButton;
    pauseButton: TButton;
    stopButton: TButton;
    exitButton: TButton;
    CheckBox1: TCheckBox;
    TrackBar1: TTrackBar;
    MPEG: TMPEGPlayer;
    Timer1: TTimer;
    OpenDialog1: TOpenDialog;
    Label6: TLabel;
    procedure exitButtonClick(Sender: TObject);
    procedure openButtonClick(Sender: TObject);
    procedure playButtonClick(Sender: TObject);
    procedure pauseButtonClick(Sender: TObject);
    procedure stopButtonClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure FormClose(Sender:
TObject; var Action: TCloseAction);
  private
    { Private declarations }
    dontseek:boolean;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}


procedure TForm1.exitButtonClick(Sender: TObject);
begin
close;
end;

procedure TForm1.openButtonClick(Sender: TObject);
var s:string;
begin
if not opendialog1.execute then exit;
mpeg.autoplay:=false;
mpeg.streamname:=opendialog1.filename;
mpeg.open;
trackbar1.Max:=mpeg.length;
trackbar1.position:=0;
str(trackbar1.max,s);
playbutton.Enabled:=true;
stopbutton.enabled:=true;
pausebutton.Enabled:=true;
end;

procedure TForm1.playButtonClick(Sender: TObject);
var a,b,c:string;
begin
playbutton.Enabled:=false;
openbutton.Enabled:=false;
mpeg.Play;
str(mpeg.Bitrate,a);
label4.Caption:=a;
str(mpeg.Frequency,b);
label5.caption:=b;
str(mpeg.layer,c);
label6.caption:=c;
end;
procedure TForm1.pauseButtonClick(Sender: TObject);
begin
mpeg.paused:=not (mpeg.Paused);
end;

procedure TForm1.stopButtonClick(Sender: TObject);
begin
if mpeg.mode>2 then
begin
mpeg.stop;
mpeg.close;
end;
trackbar1.Position:=0;
openbutton.Enabled:=true;
playbutton.enabled:=false;
stopbutton.enabled:=false;
pausebutton.enabled:=false;
label4.Caption:='';
label5.Caption:='';
label6.Caption:='';
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
mpeg.pathtodll:='';  
//存放dll闻家的路径本例程序和dll在同一路径下
//dll一定要放在程序同一目录,否则不能编译
mpeg.init;
playbutton.Enabled :=false;
pausebutton.enabled:=false;
stopbutton.enabled:=false;
end;
procedure TForm1.FormClose(Sender:
TObject; var Action: TCloseAction);
begin
mpeg.deinit;
end;
procedure TForm1.TrackBar1Change(Sender: TObject);
begin
if not(dontseek) then
    if (mpeg.mode=3)or((mpeg.mode=4))
      then mpeg.CurrentPosition:=trackbar1.Position;
end;
procedure TForm1.Timer1Timer(Sender: TObject);
var a,b,c:string;
begin
if (mpeg.mode=3) then
  begin
   dontseek:=true;
   trackbar1.Position:=mpeg.CurrentPosition;
   dontseek:=false;
   
end;
if mpeg.PlayStopped then
begin
if checkbox1.Checked then
begin
mpeg.Play;
playbutton.Enabled:=false;
openbutton.Enabled:=false;
str(mpeg.Bitrate,a);
label4.Caption:=a;
str(mpeg.Frequency,b);
label5.caption:=b;
str(mpeg.layer,c);
label6.caption:=c;
end
else
begin
mpeg.close;
trackbar1.Position:=0;
openbutton.Enabled:=true;
playbutton.Enabled :=false;
pausebutton.enabled:=false;
stopbutton.enabled:=false;
label4.Caption:='';
label5.Caption:='';
label6.Caption:='';
end;
end;
end;
end.
---- 以上是一个简单的mp3播放器的例程,mpegplayer是一个强大的控件可以实现很多功能,如多曲播放。