用多媒体库 Bass.dll 播放 mp3 [11] 使用回调函数设置反复

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, Bass;

type
  TForm1 = class(TForm)
    OpenDialog1: TOpenDialog;
    Timer1: TTimer;
    PaintBox1: TPaintBox;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Shape1: TShape;
    Shape2: TShape;
    Shape3: TShape;
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure PaintBox1Paint(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure PaintBox1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
  private
    procedure Draw;
  end;

  procedure MySyncLoop(handle: HSYNC; channel, data, user: DWORD); stdcall;

var
  Form1: TForm1;

implementation

{$R *.dfm}

//uses Bass;

var
  hs: HSTREAM;  {流句柄}
  Data: array of Cardinal;
  bit: TBitmap;
  hSyncLoop: Cardinal; {回调函数句柄}
  Mp3Len: Cardinal;    {Mp3 总的字节长度}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Label1.Caption := '提示: 鼠标左键设置反复起始点(黄线); 右键设置反复拐点(红线).';
  Timer1.Enabled := False;
  Timer1.Interval := 100;

  Shape1.Pen.Style := psClear;
  Shape1.Brush.Color := clWhite;
  Shape1.Width := 3;
  Shape1.Height := PaintBox1.Height;
  Shape1.Top := 0;
  Shape1.Left := -1;

  Shape2.Pen.Style := psClear;
  Shape2.Brush.Color := clYellow;
  Shape2.Width := 3;
  Shape2.Height := PaintBox1.Height;
  Shape2.Top := 0;
  Shape2.Visible := False;

  Shape3.Pen.Style := psClear;
  Shape3.Brush.Color := clRed;
  Shape3.Width := 3;
  Shape3.Height := PaintBox1.Height;
  Shape3.Top := 0;
  Shape3.Visible := False;

  bit := TBitmap.Create;
  PaintBox1.Align := alTop;

  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;

    {获取波形数据}
    hs2 := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, BASS_STREAM_DECODE);
    time := BASS_ChannelBytes2Seconds(hs2, BASS_ChannelGetLength(hs, BASS_POS_BYTE));
    SetLength(Data, Trunc(time * 50 + 1));
    for i := 0 to Length(Data) - 1 do Data[i] := BASS_ChannelGetLevel(hs2);
    BASS_StreamFree(hs2);

    {Mp3 总字节长度}
    Mp3Len := BASS_ChannelGetLength(hs, BASS_POS_BYTE);

    {调用绘制过程}
    Draw;
  end;
end;

{播放}
procedure TForm1.Button2Click(Sender: TObject);
begin
  Timer1.Enabled := True;
  BASS_ChannelPlay(hs, False);
end;

{暂停}
procedure TForm1.Button3Click(Sender: TObject);
begin
  Timer1.Enabled := False;
  BASS_ChannelPause(hs);
end;

{从头播放}
procedure TForm1.Button4Click(Sender: TObject);
begin
  Timer1.Enabled := True;
  BASS_ChannelPlay(hs, True);
end;

{清除反复标记}
procedure TForm1.Button5Click(Sender: TObject);
begin
  Shape2.Visible := False;
  Shape3.Visible := False;
  BASS_ChannelRemoveSync(hs, hSyncLoop);
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 := clBlack;
  bit.Canvas.FillRect(Bounds(0, 0, bit.Width, bit.Height));
  bit.Canvas.Pen.Color := clLime;

  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;

{播放指针线}
procedure TForm1.Timer1Timer(Sender: TObject);
begin
  if BASS_ChannelIsActive(hs) = BASS_ACTIVE_PLAYING then
    Shape1.Left := Trunc(BASS_ChannelGetPosition(hs, BASS_POS_BYTE) / Mp3Len * PaintBox1.Width);
end;

{鼠标左键设定反复起始点, 右键设定反复拐点}
procedure TForm1.PaintBox1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  PosLoop: Cardinal;
begin
  case Button of
    mbLeft: begin
      Shape2.Left := X;
      Shape2.Visible := True;
    end;
    mbRight: begin
      Shape3.Left := X;
      Shape3.Visible := True;
      
      {删除上次的回调句柄}
      BASS_ChannelRemoveSync(hs, hSyncLoop);

      {指定反复点, 建立回调}
      PosLoop := Trunc(Shape3.Left / PaintBox1.Width * Mp3Len);
      hSyncLoop := BASS_ChannelSetSync(hs, BASS_SYNC_POS, PosLoop, @MySyncLoop, nil);
    end;
  end;
end;

{执行反复播放的回调函数}
procedure MySyncLoop(handle: HSYNC; channel, data, user: DWORD); stdcall;
var
  PosStart: Cardinal;
begin
  if not Form1.Shape2.Visible then
    PosStart := 0
  else
    PosStart := Trunc(Form1.Shape2.Left / Form1.PaintBox1.Width * Mp3Len);

  //BASS_ChannelPause(hs);
  BASS_ChannelSetPosition(hs, PosStart, BASS_POS_BYTE);
  BASS_ChannelPlay(hs, False);
end;

end.

窗体文件:

---

object Form1: TForm1
  Left = 222
  Top = 114
  Caption = 'Form1'
  ClientHeight = 177
  ClientWidth = 476
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesigned
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object PaintBox1: TPaintBox
    Left = 16
    Top = 0
    Width = 105
    Height = 105
    OnMouseDown = PaintBox1MouseDown
    OnPaint = PaintBox1Paint
  end
  object Shape1: TShape
    Left = 170
    Top = 24
    Width = 65
    Height = 65
  end
  object Shape2: TShape
    Left = 241
    Top = 24
    Width = 65
    Height = 65
  end
  object Shape3: TShape
    Left = 312
    Top = 24
    Width = 65
    Height = 65
  end
  object Label1: TLabel
    Left = 11
    Top = 156
    Width = 31
    Height = 13
    Caption = 'Label1'
  end
  object Button1: TButton
    Left = 8
    Top = 120
    Width = 75
    Height = 25
    Caption = #25171#24320
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 89
    Top = 120
    Width = 75
    Height = 25
    Caption = #25773#25918
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 170
    Top = 120
    Width = 75
    Height = 25
    Caption = #26242#20572
    TabOrder = 2
    OnClick = Button3Click
  end
  object Button4: TButton
    Left = 251
    Top = 120
    Width = 75
    Height = 25
    Caption = #20174#22836#25773#25918
    TabOrder = 3
    OnClick = Button4Click
  end
  object Button5: TButton
    Left = 375
    Top = 120
    Width = 93
    Height = 25
    Caption = #28165#38500#21453#22797#26631#35760
    TabOrder = 4
    OnClick = Button5Click
  end
  object OpenDialog1: TOpenDialog
    Left = 128
    Top = 24
  end
  object Timer1: TTimer
    OnTimer = Timer1Timer
    Left = 128
    Top = 72
  end
end