用多媒体库 Bass.dll 播放 mp3 [12] - 绘制动态频谱 FFT

本例效果图:

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代码文件:

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unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    OpenDialog1: TOpenDialog;
    Timer1: TTimer;
    PaintBox1: TPaintBox;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure PaintBox1Paint(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Bass;

var
  hs: HSTREAM;  {流句柄}
  FFTData: array[0..512] of Single;
  bit: TBitmap;
  FFTPeacks  : array [0..128] of Integer;
  FFTFallOff : array [0..128] of Integer;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer1.Enabled := False;
  Timer1.Interval := 30;

  bit := TBitmap.Create;
  PaintBox1.Align := alTop;

  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);
    bit.Free;
    bit := TBitmap.Create;
    PaintBox1.Repaint;
  end;
end;

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

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

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

{刷新}
procedure TForm1.PaintBox1Paint(Sender: TObject);
begin
  PaintBox1.Canvas.StretchDraw(Bounds(0, 0, PaintBox1.Width, PaintBox1.Height), bit);
end;

{绘制 FFT}
procedure TForm1.Timer1Timer(Sender: TObject);
const
  w = 8;
var
  i,di: Integer;
begin
  if BASS_ChannelIsActive(hs) <> BASS_ACTIVE_PLAYING then Exit;

  BASS_ChannelGetData(hs, @FFTData, BASS_DATA_FFT1024);

  bit.Width := PaintBox1.Width;
  bit.Height := PaintBox1.Height;
  bit.Canvas.Brush.Color := clBlack;
  bit.Canvas.FillRect(Rect(0, 0, bit.Width, bit.Height));

  bit.Canvas.Pen.Color := clLime;
  for i := 0 to Length(FFTData) - 1 do
  begin
    di := Trunc(Abs(FFTData[i]) * 500);

    if di > bit.Height then di := bit.Height;
    if di >= FFTPeacks[i] then FFTPeacks[i] := di else FFTPeacks[i] := FFTPeacks[i] - 1;
    if di >= FFTFallOff[i] then FFTFallOff[i] := di else FFTFallOff[i] := FFTFallOff[i] - 3;
    if (bit.Height - FFTPeacks[i]) > bit.Height then FFTPeacks[i] := 0;
    if (bit.Height - FFTFallOff[i]) > bit.Height then FFTFallOff[i] := 0;

//    bit.Canvas.MoveTo(i, bit.Height);
//    bit.Canvas.LineTo(i, bit.Height - FFTFallOff[i]);
//    bit.Canvas.Pixels[i, bit.Height - FFTPeacks[i]] := bit.Canvas.Pen.Color;

    bit.Canvas.Pen.Color := bit.Canvas.Pen.Color;
    bit.Canvas.MoveTo(i * (w + 1), bit.Height - FFTPeacks[i]);
    bit.Canvas.LineTo(i * (w + 1) + w, bit.Height - FFTPeacks[i]);

    bit.Canvas.Pen.Color := bit.Canvas.Pen.Color;
    bit.Canvas.Brush.Color := bit.Canvas.Pen.Color;
    bit.Canvas.Rectangle(i * (w + 1), bit.Height - FFTFallOff[i], i * (w + 1) + w, bit.Height);
  end;

  BitBlt(PaintBox1.Canvas.Handle, 0, 0, PaintBox1.Width, PaintBox1.Height, bit.Canvas.Handle, 0, 0, SRCCOPY);
end;

end.

窗体文件:

---

object Form1: TForm1
  Left = 222
  Top = 114
  Caption = 'Form1'
  ClientHeight = 154
  ClientWidth = 476
  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 PaintBox1: TPaintBox
    Left = 16
    Top = 0
    Width = 105
    Height = 105
    OnPaint = PaintBox1Paint
  end
  object Button1: TButton
    Left = 109
    Top = 117
    Width = 75
    Height = 25
    Caption = #25171#24320
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 206
    Top = 117
    Width = 75
    Height = 25
    Caption = #25773#25918
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 303
    Top = 117
    Width = 75
    Height = 25
    Caption = #26242#20572
    TabOrder = 2
    OnClick = Button3Click
  end
  object OpenDialog1: TOpenDialog
    Left = 128
    Top = 24
  end
  object Timer1: TTimer
    OnTimer = Timer1Timer
    Left = 128
    Top = 72
  end
end