Delphi中用多媒體庫Bass.dll播放mp3 [15] - 設置與獲取播放速度

本例效果圖:

代碼文件:

unit Unit1;
interface
uses
　 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　 Dialogs, StdCtrls, ComCtrls;
type
　 TForm1 = class(TForm)
　　 OpenDialog1: TOpenDialog;
　　 Button1: TButton;
　　 Button2: TButton;
　　 Button3: TButton;
　　 TrackBar1: TTrackBar;
　　 Label1: TLabel;
　　 Button4: TButton;
　　 procedure FormCreate(Sender: TObject);
　　 procedure Button1Click(Sender: TObject);
　　 procedure Button2Click(Sender: TObject);
　　 procedure Button3Click(Sender: TObject);
　　 procedure TrackBar1Change(Sender: TObject);
　　 procedure FormDestroy(Sender: TObject);
　　 procedure Button4Click(Sender: TObject);
　 end;
var
　 Form1: TForm1;
implementation
{$R *.dfm}
uses Bass;
var
　 hs: HSTREAM;　{流句柄}
procedure TForm1.FormCreate(Sender: TObject);
begin
　 TrackBar1.ShowSelRange := False;
　 TrackBar1.Height := 23;
　 TrackBar1.Max := 100000;
　 TrackBar1.Min := 100;
　 TrackBar1.Position := 44100;
　 if HiWord(BASS_GetVersion) <> BASSVERSION then
　　 MessageBox(0, '"Bass.dll" 文件版本不合適! ', nil, MB_ICONERROR);
　 if not BASS_Init(-1, 44100, 0, 0, nil) then
　　 ShowMessage('初始化錯誤');
end;
{打開}
procedure TForm1.Button1Click(Sender: TObject);
var
　 Mp3Path: AnsiString;
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 := '打開失敗'
　 else begin
　　 Text := string(Mp3Path);
　　 Button4.Click;
　 end;
end;
{播放}
procedure TForm1.Button2Click(Sender: TObject);
begin
　 BASS_ChannelPlay(hs, False);
end;
{暫停}
procedure TForm1.Button3Click(Sender: TObject);
begin
　 BASS_ChannelPause(hs);
end;
{原速}
procedure TForm1.Button4Click(Sender: TObject);
begin
　 TrackBar1.Position := 44100;
end;
{設置和獲取播放速度}
procedure TForm1.TrackBar1Change(Sender: TObject);
var
　 freq: Single;
begin
　 freq := 44100;
　 BASS_ChannelSlideAttribute(hs, BASS_ATTRIB_FREQ, TrackBar1.Position, 0);
　 BASS_ChannelGetAttribute(hs, BASS_ATTRIB_FREQ, freq);
　 Label1.Caption := Format('當前速度比例: %f%%', [freq/44100]);
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
　 BASS_Free;
end;
end.

窗體文件:

object Form1: TForm1
　 Left = 205
　 Top = 107
　 Caption = 'Form1'
　 ClientHeight = 119
　 ClientWidth = 286
　 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 Label1: TLabel
　　 Left = 32
　　 Top = 59
　　 Width = 31
　　 Height = 13
　　 Caption = 'Label1'
　 end
　 object Button1: TButton
　　 Left = 24
　　 Top = 17
　　 Width = 75
　　 Height = 25
　　 Caption = #25171#24320
　　 TabOrder = 0
　　 OnClick = Button1Click
　 end
　 object Button2: TButton
　　 Left = 105
　　 Top = 17
　　 Width = 75
　　 Height = 25
　　 Caption = #25773#25918
　　 TabOrder = 1
　　 OnClick = Button2Click
　 end
　 object Button3: TButton
　　 Left = 186
　　 Top = 17
　　 Width = 75
　　 Height = 25
　　 Caption = #26242#20572
　　 TabOrder = 2
　　 OnClick = Button3Click
　 end
　 object TrackBar1: TTrackBar
　　 Left = 24
　　 Top = 78
　　 Width = 237
　　 Height = 32
　　 TabOrder = 3
　　 OnChange = TrackBar1Change
　 end
　 object Button4: TButton
　　 Left = 186
　　 Top = 48
　　 Width = 75
　　 Height = 25
　　 Caption = #21407#36895
　　 TabOrder = 4
　　 OnClick = Button4Click
　 end
　 object OpenDialog1: TOpenDialog
　　 Left = 256
　 end
end