Playing MP3 with multi-media library bass. dll [10]-using callback function

In this example:

Code file:

Unit unit1; interfaceuses windows, messages, sysutils, variants, classes, graphics, controls, forms, dialogs, classes, extctrls, comctrls; Type tform1 = Class (tform) opendialog1: topendialog; trackbar1: ttrackbar; timer1: ttimer; button1: tbutton; button2: tbutton; button3: tbutton; procedure invoke (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; {stream handle} {callback function: mysync1; although no parameters are used, however, procedure mysync1 (handle: hsync; channel, Data, user: DWORD); stdcall; begin form1.text: = 'starts playing '; end; {callback function: mysync2} {parameter 1: callback handle, which can have bass_channelsetsync Return and delete with bass_channelremovesync {parameter 2: stream handle} {parameter 3: Unknown} {parameter 4: user data specified by bass_channelsetsync} procedure mysync2 (handle: hsync; channel, Data, user: DWORD); stdcall; begin form1.text: = 'over midpoint '; {if the stream is played here (in the center), it will be repeated from the beginning. You can do this :} // bass_channelplay (Channel, true); end; {callback function: mysync3; although no parameters are used, you must specify} procedure mysync3 (handle: hsync; channel, Data, user: DWORD); stdcall; begin form1.text: = 'playback completed '; end; {initialization} Procedure destroy (Sender: tobject); begin trackbar1.height: = 23; timer1.enabled: = false; timer1.interval: = 100; If hiword (bass_getversion) bassversion then MessageBox (0, '"Bass. the DLL file version is not suitable! ', Nil, mb_iconerror); if not bass_init (-1, 44100, 0, 0, nil) Then showmessage ('initialization error'); end; {open} procedure upload (Sender: tobject); var mp3path: ansistring; mp3len: Cardinal; begin bass_streamfree (HS); timer1.enabled: = false; opendialog1.filter: = 'mp3 file (*. MP3) | *. MP3 | WAV file (*. wav) | * WAV '; If opendialog1.execute then mp3path: = ansistring (opendialog1.filename); HS: = bass_streamcreatefile (false, pansichar (mp3path), 0, 0, 0); if hs

Form file:

object Form1: TForm1  Left = 222  Top = 114  Caption = 'Form1'  ClientHeight = 84  ClientWidth = 254  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 = 8    Top = 18    Width = 75    Height = 25    Caption = #25171#24320    TabOrder = 0    OnClick = Button1Click  end  object Button2: TButton    Left = 89    Top = 18    Width = 75    Height = 25    Caption = #25773#25918    TabOrder = 1    OnClick = Button2Click  end  object Button3: TButton    Left = 170    Top = 18    Width = 75    Height = 25    Caption = #26242#20572    TabOrder = 2    OnClick = Button3Click  end  object TrackBar1: TTrackBar    Left = 1    Top = 53    Width = 250    Height = 28    TabOrder = 3  end  object OpenDialog1: TOpenDialog    Left = 72    Top = 32  end  object Timer1: TTimer    OnTimer = Timer1Timer    Left = 152    Top = 32  endend