用多媒體庫 Bass.dll 播放 mp3 [13] - 混響(Reverb)效果

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;
　　procedure FormCreate(Sender: TObject);
　　procedure Button1Click(Sender: TObject);
　　procedure Button2Click(Sender: TObject);
　　procedure Button3Click(Sender: TObject);
　　procedure FormDestroy(Sender: TObject);
　　procedure TrackBar1Change(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses Bass;
var
　hs: HSTREAM;　{流句柄}
　reverb: BASS_DX8_REVERB; {混響的參數結構, 不能是局部變量; 本例只測試了結構中的 fReverbTime 參數}
　fx: HFX; {DX 的效果句柄}
procedure TForm1.FormCreate(Sender: TObject);
begin
　{reverb.fReverbTime: 0.001 - 3000.0; 默認 1000}
　TrackBar1.Min := 1;
　TrackBar1.Max := 3000;
　TrackBar1.Position := 1000;
　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);
　{實現混響等效果, 需要指定 BASS_SAMPLE_FX 參數}
　hs := BASS_StreamCreateFile(False, PAnsiChar(Mp3Path), 0, 0, BASS_SAMPLE_FX);
　if hs < BASS_ERROR_ENDED then
　　Text := '打開失敗'
　else begin
　　Text := string(Mp3Path);
　　{設置並返回效果句柄}
　　fx := BASS_ChannelSetFX(hs, BASS_FX_DX8_REVERB, 0);
　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;
procedure TForm1.FormDestroy(Sender: TObject);
begin
　BASS_Free;
end;
procedure TForm1.TrackBar1Change(Sender: TObject);
begin
　reverb.fReverbTime := TrackBar1.Position;
　BASS_FXSetParameters(fx, @reverb);
　Label1.Caption := Format('混響