用多媒体库 Bass.dll 播放 mp3 [8] - 实时显示左右声道的峰值

本例效果图:

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代码文件:

---

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls, ComCtrls;

type
  TForm1 = class(TForm)
    OpenDialog1: TOpenDialog;
    Timer1: TTimer;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    ProgressBar1: TProgressBar;
    ProgressBar2: TProgressBar;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Bass;

var
  hs: HSTREAM;  {流句柄}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer1.Interval := 100;
  Timer1.Enabled := False;
  ProgressBar1.Align := alLeft;
  ProgressBar2.Align := alRight;
  ProgressBar1.Orientation := pbVertical;
  ProgressBar2.Orientation := pbVertical;
  ProgressBar1.Width := 20;
  ProgressBar2.Width := 20;
  ProgressBar1.Max := MAXWORD div 2;
  ProgressBar2.Max := MAXWORD div 2;

  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);
  Timer1.Enabled := False;

  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
    Text := Mp3Path;
end;

{播放}
procedure TForm1.Button2Click(Sender: TObject);
begin
  BASS_ChannelPlay(hs, False);
  Timer1.Enabled := True;
end;

{暂停}
procedure TForm1.Button3Click(Sender: TObject);
begin
  BASS_ChannelPause(hs);
  Timer1.Enabled := False;
end;

{显示左右声道的峰值}
procedure TForm1.Timer1Timer(Sender: TObject);
var
  Level: Cardinal;
begin
  Level := BASS_ChannelGetLevel(hs); {其低16位为左声道峰值; 高16位为右声道峰值}
  ProgressBar1.Position := LoWord(Level);
  ProgressBar2.Position := HiWord(Level);
end;

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

end.

窗体文件:

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object Form1: TForm1
  Left = 222
  Top = 114
  Caption = 'Form1'
  ClientHeight = 113
  ClientWidth = 243
  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 Button1: TButton
    Left = 83
    Top = 17
    Width = 75
    Height = 25
    Caption = #25171#24320
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 83
    Top = 48
    Width = 75
    Height = 25
    Caption = #25773#25918
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 83
    Top = 79
    Width = 75
    Height = 25
    Caption = #26242#20572
    TabOrder = 2
    OnClick = Button3Click
  end
  object ProgressBar1: TProgressBar
    Left = 8
    Top = 74
    Width = 69
    Height = 17
    TabOrder = 3
  end
  object ProgressBar2: TProgressBar
    Left = 164
    Top = 74
    Width = 77
    Height = 17
    TabOrder = 4
  end
  object OpenDialog1: TOpenDialog
    Left = 192
    Top = 8
  end
  object Timer1: TTimer
    OnTimer = Timer1Timer
    Left = 40
    Top = 8
  end
end