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

　Bass.dll 功能非常強大, 做了上面 15 個例子, 已經夠我的程序用了; 利用 Bass 還可以錄音、下載並播放網上的音樂等等, 沒時間繼續學習了.

　　另外:

　　1、如果喜歡動態引入函數, 可以使用其中的 DelphidynamicDynamic_Bass.pas 單元;

　　2、建議使用 mp3-freebass.dll, 這是免費的;

　　3、有不少的音樂播放器使用了不同版本的 Bass.dll, 所以程序發布時注意它的發布地址, 不然會覆蓋或被覆蓋!