用多媒体库 Bass.dll 播放 mp3 [15] - 设置与获取播放速度

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;
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);
Button4.Click;
end;
end;

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

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

{原速}
procedure TForm1.Button4Click(Sender: TObject);
begin
TrackBar1.Position := 44100;
end;

{设置和获取播放速度}
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('当前速度比例: %f%%', [freq/44100]);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
BASS_Free;
end;

end.

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