Delphi中用多媒体库Bass.dll播放mp3 [9]

本例效果图:

代码文件:

unit Unit1;
interface
uses
　 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　 Dialogs, StdCtrls, ExtCtrls, ComCtrls;
type
　 TForm1 = class(TForm)
　　 OpenDialog1: TOpenDialog;
　　 PaintBox1: TPaintBox;
　　 Button1: TButton;
　　 Button2: TButton;
　　 Button3: TButton;
　　 ColorBox1: TColorBox;
　　 ColorBox2: TColorBox;
　　 procedure FormCreate(Sender: TObject);
　　 procedure Button1Click(Sender: TObject);
　　 procedure Button2Click(Sender: TObject);
　　 procedure Button3Click(Sender: TObject);
　　 procedure ColorBox1Change(Sender: TObject);
　　 procedure ColorBox2Change(Sender: TObject);
　　 procedure FormDestroy(Sender: TObject);
　　 procedure PaintBox1Paint(Sender: TObject);
　 private
　　 procedure Draw;
　 end;
var
　 Form1: TForm1;
implementation
{$R *.dfm}
uses Bass;
var
　 hs: HSTREAM;　{流句柄}
　 Data: array of Cardinal;
　 bit: TBitmap;
procedure TForm1.FormCreate(Sender: TObject);
begin
　 bit := TBitmap.Create;
　 PaintBox1.Align := alTop;
　 ColorBox1.Selected := clBlack;
　 ColorBox2.Selected := clLime;
　 if HiWord(BASS_GetVersion) <> BASSVERSION then
　　 MessageBox(0, '"Bass.dll" 文件版本不合适! ', nil, MB_ICONERROR);
　 if not BASS_Init(-1, 44100, 0, 0, nil) then ShowMessage('初始化错误');
end;
{打开}
procedure TForm1.Button1Click(Sender: TObject);
var
　 Mp3Path: AnsiString;
　 i: Cardinal;
　 time: Double;
　 hs2: HSTREAM;
begin
　 BASS_StreamFree(hs);
　 OpenDialog1.Filter := 'Mp3 文件(*.mp3)|*.mp3|Wav 文件(*.wav)|*wav';
　 if OpenDialog1.Execute then
　　 Mp3Path := AnsiString(OpenDialog1.FileName);
　 hs := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, 0);
　 if hs < BASS_ERROR_ENDED then
　　 Text := '打开失败'
　 else begin
　　 Text := string(Mp3Path);
　　 bit.Free;
　　 bit := TBitmap.Create;
　　 PaintBox1.Repaint;
　　 {下面几行不好理解}
　　 {重新建立文件流 hs2, 最后的参数是: BASS_STREAM_DECODE, 这样可以提前读取波 形数据}
　　 hs2 := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, BASS_STREAM_DECODE);
　　 {用 BASS_ChannelGetLevel 获取峰值时, 是以 20ms 为一个单位的; 先获取总时 间}
　　 time := BASS_ChannelBytes2Seconds(hs2, BASS_ChannelGetLength(hs, BASS_POS_BYTE));
　　 {time * 1000 div 20 + 1 是可以获取的总的峰值数据, 也是数组需要的大小}
　　 SetLength(Data, Trunc(time * 50 + 1));
　　 {遍历峰值数据填充数组}
　　 for i := 0 to Length(Data) - 1 do Data[i] := BASS_ChannelGetLevel (hs2);
　　 {hs2 此时已完成使命, 释放它}
　　 BASS_StreamFree(hs2);
　　 {调用绘制过程}
　　 Draw;
　 end;
end;
{播放}
procedure TForm1.Button2Click(Sender: TObject);
begin
　 BASS_ChannelPlay(hs, False);
end;
{暂停}
procedure TForm1.Button3Click(Sender: TObject);
begin
　 BASS_ChannelPause(hs);
end;
{背景色}
procedure TForm1.ColorBox1Change(Sender: TObject);
begin
　 Draw;
end;
{前景色}
procedure TForm1.ColorBox2Change(Sender: TObject);
begin
　 Draw;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
　 BASS_Free;
　 bit.Free;
end;
{刷新}
procedure TForm1.PaintBox1Paint(Sender: TObject);
begin
　 PaintBox1.Canvas.StretchDraw(Bounds(0, 0, PaintBox1.Width, PaintBox1.Height), bit);
end;
{绘制波形图}
procedure TForm1.Draw;
var
　 i,ch: Integer;
　 L,R: SmallInt;
begin
　 bit.Width := Length(Data);
　 bit.Height := PaintBox1.Height;
　 ch := bit.Height div 2;
　 bit.Canvas.Brush.Color := ColorBox1.Selected;
　 bit.Canvas.FillRect(Bounds(0, 0, bit.Width, bit.Height));
　 bit.Canvas.Pen.Color := ColorBox2.Selected;
　 for i := 0 to Length(Data) - 1 do
　 begin
　　 L := LoWord(Data[i]);
　　 R := HiWord(Data[i]);
　　 bit.Canvas.MoveTo(i, ch - Trunc(L/32768*ch));
　　 bit.Canvas.LineTo(i, ch + Trunc(R/32768*ch));
　 end;
　 PaintBox1.Repaint;
end;
end.