用多媒体库 Bass.dll 播放 mp3 [11] - 使用回调函数设置反复

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.

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