用多媒体库 Bass.dll 播放 mp3 [4] - 显示与设置播放进度

//获取文件流的长度, 单位是字节
function BASS_ChannelGetLength(
  handle: DWORD; {流句柄}
  mode: DWORD    {获取模式; 有两种选择, 但对 HSTREAM 流只能使用 BASS_POS_BYTE}
): QWORD; stdcall; external bassdll;

//获取流的当前指针位置, 单位是字节
function BASS_ChannelGetPosition(
  handle: DWORD; {流句柄}
  mode: DWORD    {获取模式; 有两种选择, 但对 HSTREAM 流只能使用 BASS_POS_BYTE}
): QWORD; stdcall; external bassdll;

//根据流的指针位置来获取时间点, 单位是秒, 是非常精确的浮点数
function BASS_ChannelBytes2Seconds(
  handle: DWORD; {流句柄}
  pos: QWORD     {流的指针位置, 单位是字节, QWORD = Int64}
): Double; stdcall;external bassdll;

//和 BASS_ChannelBytes2Seconds 相反, BASS_ChannelSeconds2Bytes 可以通过时间获取流的指针位置.
function BASS_ChannelSeconds2Bytes(
  handle: DWORD;
  pos: Double
): QWORD; stdcall;external bassdll;

//和 BASS_ChannelGetPosition 相反, BASS_ChannelSetPosition 可以设置流的指针位置.
function BASS_ChannelSetPosition(
  handle: DWORD;
  pos: QWORD;
  mode: DWORD
): BOOL; stdcall; external bassdll;



//要获取音乐的总时间可以:
BASS_ChannelBytes2Seconds(hs, BASS_ChannelGetLength(hs, BASS_POS_BYTE));

//要获取音乐播放的当前时间可以:
BASS_ChannelBytes2Seconds(hs, BASS_ChannelGetPosition(hs, BASS_POS_BYTE));

本例效果图:

---

代码文件:

---

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    OpenDialog1: TOpenDialog;
    Timer1: TTimer;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    ScrollBar1: TScrollBar;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure ScrollBar1Scroll(Sender: TObject; ScrollCode: TScrollCode;
      var ScrollPos: Integer);
    procedure FormDestroy(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Bass;

var
  hs: HSTREAM;  {流句柄}
  time: Double; {乐曲总时间}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Timer1.Interval := 100;
  Timer1.Enabled := False;
  ScrollBar1.Enabled := False;

  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;
  ScrollBar1.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 begin
    Text := string(Mp3Path);
    time := BASS_ChannelBytes2Seconds(hs, BASS_ChannelGetLength(hs, BASS_POS_BYTE)); {总秒数}
    ScrollBar1.Max := Trunc(time * 1000);
    ScrollBar1.Enabled := True;
  end;
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
  Timer1.Enabled := False;
  BASS_ChannelPause(hs);
end;

{播放时需要的显示}
procedure TForm1.Timer1Timer(Sender: TObject);
var
  s: Double; {当前秒数}
begin
  s := BASS_ChannelBytes2Seconds(hs, BASS_ChannelGetPosition(hs, BASS_POS_BYTE));
  Text := Concat(FloatToStr(time), ' / ', FloatToStr(s));
  ScrollBar1.Position := Trunc(s * 1000);
end;

{调整播放位置}
procedure TForm1.ScrollBar1Scroll(Sender: TObject; ScrollCode: TScrollCode;
  var ScrollPos: Integer);
var
  Position: Int64;
begin
  Button3.Click;
  Position := BASS_ChannelSeconds2Bytes(hs, ScrollPos / 1000);
  BASS_ChannelSetPosition(hs, Position, BASS_POS_BYTE);
  Text := Concat(FloatToStr(time), ' / ', FloatToStr(Position / 1000));
  Timer1Timer(nil);
end;

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

end.

窗体文件:

---

object Form1: TForm1
  Left = 205
  Top = 107
  Caption = 'Form1'
  ClientHeight = 88
  ClientWidth = 393
  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 = 65
    Top = 17
    Width = 75
    Height = 25
    Caption = #25171#24320
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 161
    Top = 17
    Width = 75
    Height = 25
    Caption = #25773#25918
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 257
    Top = 17
    Width = 75
    Height = 25
    Caption = #26242#20572
    TabOrder = 2
    OnClick = Button3Click
  end
  object ScrollBar1: TScrollBar
    Left = 8
    Top = 56
    Width = 377
    Height = 17
    PageSize = 0
    TabOrder = 3
    OnScroll = ScrollBar1Scroll
  end
  object OpenDialog1: TOpenDialog
    Left = 40
    Top = 40
  end
  object Timer1: TTimer
    OnTimer = Timer1Timer
    Left = 80
    Top = 48
  end
end