Delphi 6 project:MP3 player [Archive]

_I_Play_Chess

12-06-2003, 10:05 AM

<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TBODY>
<TR>
<TD>Your first MP3 Delphi player </TD></TR>
<TR>
<TD bgColor=#cc0000 colSpan=2 height=1><IMG height=1 src="http://images.about.com/all/bullets/dot_clea.gif" width=1 border=0></TD></TR></TBODY></TABLE>Part 1: Delphi plays MP3? TMediaPlayer is all we need!

It's party time and Hollidays coming!!!!!.

You probably know this: MP3 is a music format where inaudible parts of music are left out, and the rest of the data are compressed. The results are quite impressive. A 64 MB song usually becomes 3-4 MB when converted to MP3 format.

MP3 is THE trend these days, and believe it or not, it seems that one of the first tasks of multimedia developers is to build a MPEG Layer 3 player.
What are we waiting for? Let's see how to use Delphi to build a MP3 player with the TMediaPlayer component. Let us not stop here. This article will show you how to extract (and even change) some more information about the MP3. The most popular tag encryption appears to be ID3. This tag holds the MP3's title, author, genre and some other information... Just for the records: to code a MP3 player with Delphi we have several possibilities. First: we could write a program that remotely controls another application like the WinAmp player. Second: we could use some third-party MP3 component like XAudio; and third: we could use DirectX with IMediaControl to build a player. MP3 with TMediaPlayer?
Remember the TMediaPlayer? Yep, even though it seems that our good-old TMediaPlayer is unable to playback a MP3 file, we'll see that this is, hopefully, wrong. TMediaPlayer component<IMG height=28 alt="TMediaPlayer icon" src="http://delphi.about.com/library/graphics/tmediaicon.gif" width=33 border=0>
VCL provides the TMediaPlayer component (located on the System tab of the Component palette) for all the major features of multimedia programming. If you look in the Delphi Help system you'll see that the "MediaPlayer component enables your application to control a media playing or recording device such as a CD-ROM player, video player/recorder, or MIDI sequencer."
<CENTER><IMG height=30 alt="MediaPlayer on Screen" src="http://delphi.about.com/library/graphics/tmediaplayer.gif" width=253 border=0></CENTER>One of the properties of the MediaPlayer is DeviceType. This property holds/contains the multimedia device types that can be opened by a TMediaPlayer component. Several multimedia device types are defined, but none of them is strict MP3. By default, when we put a MediaPlayer on a form, this property is set to dtAutoSelect to have the device type automatically selected based on the filename extension. At design time, we use a file open dialog box to specify the FileName property by clicking the ellipses button (...) in the Object Inspector. If we try to specify a MP3 file at design time we'll see that there is no *.MP3 selection; only AVI, MIDI, or WAVE. This will probably lead you to conclusion that TMediaPlayer is unable to reproduce a MP3 file - wrong!

_I_Play_Chess

12-06-2003, 10:10 AM

<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TBODY>
<TR>
<TD>Your first MP3 Delphi player </TD></TR>
<TR>
<TD bgColor=#cc0000 colSpan=2 height=1><IMG height=1 src="http://images.about.com/all/bullets/dot_clea.gif" width=1 border=0></TD></TR></TBODY></TABLE>Part 2: Building a MP3 player Delphi Project's GUI 

Step by step...
If you haven't already; this is the time to start Delphi - new project is created with one blank form (form1, by default). This will be the main and the only one form in the mp3 player project. As promissed, our player will not only play MP3 songs, we want the player to display (and even change) certain information about each file - the ID3 tag information. Why not even more: let there be a progress bar to show the current song's play progress. Add following components to form:
From the Standard tab:
one ListBox component, name it 'mp3List'
one GroupBox component containing six Edit components (names: edTitle, edArtist, edAlbum, edYear, edGenre, edComment),
From the Additional tab:
one BitBtn component, name it 'btnOpenFolder',
one StaticText component, name it 'txtFolder',
From the System tab
one Timer component, name it 'ProgresTimer'.
one ProgressBar component, name it 'Progres'.
and of course, one MediaPlayer component, name it 'mp3Player'.
<CENTER><IMG height=209 alt="mp3 player at design time" src="http://delphi.about.com/library/graphics/tmediaproject.gif" width=367 border=0></CENTER>Notice that when you place the MediaPlayer component on a form all 9 buttons are visible. Since we are only going to code a simple player some of the buttons are not required. Therefore, use the VisibleButtons property and hide all the buttons except this three: btPlay, btPause, btStop. The BitBtn and the StaticText are used to select and display the Folder where our MP3 songs are stored. All the MP3 files from the selected folder are listed in the ListBox. I have chosen BitBtn instead of the standard Button component simply because BitBtn has the glyph property - we can easily display a picture on it.

_I_Play_Chess

12-06-2003, 10:14 AM

<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TBODY>
<TR>
<TD>Your first MP3 Delphi player </TD></TR>
<TR>
<TD bgColor=#cc0000 colSpan=2 height=1><IMG height=1 src="http://images.about.com/all/bullets/dot_clea.gif" width=1 border=0></TD></TR></TBODY></TABLE>Part 3: Building a MP3 player Delphi Project's Code 

Even the simpliest project needs some code to run. Till this moment we were only designing our projects GUI - it's time to see our player in action.

Select the folder with MP3 files
As stated before, the btnOpenFolder and the txtFolder are used to select and display the Folder where our MP3 songs are stored. To enable a user to select a list of mp3 songs from a directory on a system Delphi provides us with several possibilities. The OpenDialog component located on the Dialogs tab encapsulates the standard Windows dialog box for opening a file. Another approach is to use the

SHBrowseForFolder Windows API function and to invoke a Windows system dialog used to browse for files and folders on users hard drive as well as network computers and printers. This second approach is exactly what the btnOpenFolder hides in his OnClick event. For a full code see the last part of this article: Project's Code.

All the MP3 files from the selected folder are listed in the mp3List (that is the ListBox component). Display play progress
The trick is simple. The TMediaPlayer Position property holds the current position of a song. The Lenght property specifies the length of the song selected by using the current time format, which is specified by the TimeFormat property. When the user selects a song from the list the following assignement is made
<TABLE width="100%" bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>...
Progress.Max := 0;
{code to open a mp3 song}
Progress.Max := mp3player.Length;
...
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>and in the OnTimer event for the Timer (named 'ProgresTimer') component we have:
<TABLE width="100%" bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>procedure TForm1.ProgresTimerTimer
(Sender: TObject);
begin
if Progress.Max <> 0 then
Progress.Position := mp3player.Position;
end;
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>Play the MP3 file
You would not believe this, but this is the simplest part. Since, by default, TMediaPlayer knows what to do when the user chooses Play or Stop button - everything we have to do is to prepare the MediaPlayer to accept/open a MP3 file. I'll give you here the whole procedure - the one that is executed when the user select's a song from the list:
<TABLE width="100%" bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>procedure TForm1.mp3ListClick(Sender: TObject);
var mp3File:string;
begin
//if the list is empty don't do anything
if mp3List.Items.Count=0 then exit;
//file is FolderName + FileName
mp3File := Concat(txtFolder.Caption,
mp3List.Items.Strings
[mp3List.ItemIndex]);

//Chechk again if it exists
if not FileExists(mp3File) then begin
ShowMessage('MP3 file does not exist?!');
exit;
end;

//used to display the ID3 tag information
FillID3TagInformation (mp3File,
edTitle,
edArtist,
edAlbum,
edYear,
edGenre,
edComment);

Progress.Max:=0;

mp3player.Close;
mp3player.FileName:=mp3File;
mp3player.Open;

Progress.Max := mp3player.Length;
end;
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>
<CENTER><IMG height=208 alt="mp3Player at run time" src="http://delphi.about.com/library/graphics/tmediaruns.gif" width=367 border=0></CENTER>

_I_Play_Chess

12-06-2003, 10:22 AM

<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0>
<TBODY>
<TR>
<TD>Your first MP3 Delphi player </TD></TR>
<TR>
<TD bgColor=#cc0000 colSpan=2 height=1><IMG height=1 src="http://images.about.com/all/bullets/dot_clea.gif" width=1 border=0></TD></TR></TBODY></TABLE>Part 4: MP3 ID3 Tag Editing 

The thing that makes MP3 files even more great are ID3 tags. Every MP3 file has a little blurb of data on it, which is used to give informations about artist, title, album, publishing year and genre about a song. The "ID3" Tag is attached to most MP3 files these days. The tag is always 128 bytes long and is located at very end of the MP3-file.

The ID3 tag is saved in the last 128 bytes of a MP3 file. ID3 tag should start with a "TAG" string. If this string is absent that means that ID3 information has been removed - or was never set. But don't worry - all we have to do is append it to the file. The ID3-Tag structure can be described as follows:
<TABLE bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>type
TID3Rec = packed record
Tag : array[0..2] of Char;
Title,
Artist,
Comment,
Album : array[0..29] of Char;
Year : array[0..3] of Char;
Genre : Byte;
end;
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>Note that genres are determined by one byte of data only. This byte has to be translated into text from the following declaration:
<TABLE width="100%" bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>const
MaxID3Genre=147;

ID3Genre: array[0..MaxID3Genre] of string = (
'Blues', 'Classic Rock', 'Country', 'Dance',
...
'Synthpop' {and probably more to come}
);
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>Read ID3
To read the ID3 tag from a MP3 song we have to go down to file system and use IO routines. Here goes the code to read the ID3 information:
<TABLE width="100%" bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>procedure FillID3TagInformation
(mp3File: string;
Title,Artist,Album,Year,Genre,Comment:TEdit);
var ID3 : TID3Rec;
fmp3: TFileStream;
begin
fmp3:=TFileStream.Create(mp3File, fmOpenRead);
try
fmp3.position:=fmp3.size-128;
fmp3.Read(ID3,SizeOf(ID3));
finally
fmp3.free;
end;

if ID3.Tag <> 'TAG' then begin
Title.Text:='Wrong or no ID3 tag information';
Artist.Text:='Wrong or no ID3 tag information';
Album.Text:='Wrong or no ID3 tag information';
Year.Text:='Wrong or no ID3 tag information';
Genre.Text:='Wrong or no ID3 tag information';
Comment.Text:='Wrong or no ID3 tag information';
end else begin
Title.Text:=ID3.Title;
Artist.Text:=ID3.Artist;
Album.Text:=ID3.Album;
Year.Text:=ID3.Year;
if ID3.Genre in [0..MaxID3Genre] then
Genre.Text:=ID3Genre[ID3.Genre]
else
Genre.Text:=IntToStr(ID3.Genre);
Comment.Text:=ID3.Comment
end;
end;
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>This code uses the TFileStream to access the information in MP3 file. Once we have successfully opened a Mp3 file set the position to EndOfFile-128 bytes and read the ID3 tag. The rest of the code in this procedure simply checks whether there is an ID3 tag information in a file and fills those Edit boxes (parameters in this procedure) with values. Write ID3
The writing part is simple too. This is the function declaration, the whole code can be found in the Project's code part of this article.
<TABLE width="100%" bgColor=#ffffcc border=1>
<TBODY>
<TR>
<TD><PRE>procedure ChangeID3Tag
(NewID3: TID3Rec; mp3FileName: string);
</PRE></TD><PRE></PRE></TR></TBODY></TABLE>Note that in the Project's code the call to this function is not covered. This is something I'll leave to you to implement. Before the end
Finally, we've made it! You have your own ready-to-play-and-get-some-money MP3 player working. What I want do to here is to suggest to "play" with it a little and modify it a lot. How about adding some kind of skin to this player in the means of Custom Shaped Forms? 

 

We will add to you this chapter after finishing page 5 with the complete source CODE of this project.

_I_Play_Chess

12-06-2003, 10:28 AM

**
Your first MP3 Delphi player

See how to build a full-blown mp3 player with Delphi
in just a few seconds. Even more: get the ID3 tag
information from a mp3 file and change it!

}

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    mp3player: TMediaPlayer;
    mp3List: TListBox;
    btnOpenFolder: TBitBtn;
    GroupBox1: TGroupBox;
    edTitle: TEdit;
    edArtist: TEdit;
    edAlbum: TEdit;
    edYear: TEdit;
    edGenre: TEdit;
    edComment: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    Label6: TLabel;
    txtFolder: TStaticText;
    Progress: TProgressBar;
    ProgresTimer: TTimer;
    procedure btnOpenFolderClick(Sender: TObject);
    procedure mp3ListClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure ProgresTimerTimer(Sender: TObject);
  private
    ** Private declarations }
  public
    ** Public declarations }
  end;

var
  Form1: TForm1;

type
  TID3Rec = packed record
    Tag     : array[0..2] of Char;
    Title,
    Artist,
    Comment,
    Album   : array[0..29] of Char;
    Year    : array[0..3] of Char;
    Genre   : Byte;
  end;

const
  MaxID3Genre=147;
  ID3Genre: array[0..MaxID3Genre] of string = (
    'Blues', 'Classic Rock', 'Country', 'Dance', 'Disco', 'Funk', 'Grunge',
    'Hip-Hop', 'Jazz', 'Metal', 'New Age', 'Oldies', 'Other', 'Pop', 'R&B',
    'Rap', 'Reggae', 'Rock', 'Techno', 'Industrial', 'Alternative', 'Ska',
    'Death Metal', 'Pranks', 'Soundtrack', 'Euro-Techno', 'Ambient',
    'Trip-Hop', 'Vocal', 'Jazz+Funk', 'Fusion', 'Trance', 'Classical',
    'Instrumental', 'Acid', 'House', 'Game', 'Sound Clip', 'Gospel',
    'Noise', 'AlternRock', 'Bass', 'Soul', 'Punk', 'Space', 'Meditative',
    'Instrumental Pop', 'Instrumental Rock', 'Ethnic', 'Gothic',
    'Darkwave', 'Techno-Industrial', 'Electronic', 'Pop-Folk',
    'Eurodance', 'Dream', 'Southern Rock', 'Comedy', 'Cult', 'Gangsta',
    'Top 40', 'Christian Rap', 'Pop/Funk', 'Jungle', 'Native American',
    'Cabaret', 'New Wave', 'Psychadelic', 'Rave', 'Showtunes', 'Trailer',
    'Lo-Fi', 'Tribal', 'Acid Punk', 'Acid Jazz', 'Polka', 'Retro',
    'Musical', 'Rock & Roll', 'Hard Rock', 'Folk', 'Folk-Rock',
    'National Folk', 'Swing', 'Fast Fusion', 'Bebob', 'Latin', 'Revival',
    'Celtic', 'Bluegrass', 'Avantgarde', 'Gothic Rock', 'Progressive Rock',
    'Psychedelic Rock', 'Symphonic Rock', 'Slow Rock', 'Big Band',
    'Chorus', 'Easy Listening', 'Acoustic', 'Humour', 'Speech', 'Chanson',
    'Opera', 'Chamber Music', 'Sonata', 'Symphony', 'Booty Bass', 'Primus',
    'Porn Groove', 'Satire', 'Slow Jam', 'Club', 'Tango', 'Samba',
    'Folklore', 'Ballad', 'Power Ballad', 'Rhythmic Soul', 'Freestyle',
    'Duet', 'Punk Rock', 'Drum Solo', 'Acapella', 'Euro-House', 'Dance Hall',
    'Goa', 'Drum & Bass', 'Club-House', 'Hardcore', 'Terror', 'Indie',
    'BritPop', 'Negerpunk', 'Polsk Punk', 'Beat', 'Christian Gangsta Rap',
    'Heavy Metal', 'Black Metal', 'Crossover', 'Contemporary Christian',
    'Christian Rock', 'Merengue', 'Salsa', 'Trash Metal', 'Anime', 'Jpop',
    'Synthpop'  {and probably more to come}
  );

implementation

uses ShellAPI, ShlObj;  // needed for the BrowseForFolder function

**$R *.DFM}

procedure FillID3TagInformation(mp3File:string; Title,Artist,Album,Year,Genre,Comment:TEdit);
var //fMP3: file of Byte;
    ID3 : TID3Rec;
    fmp3: TFileStream;
begin
  fmp3:=TFileStream.Create(mp3File, fmOpenRead);
  try
    fmp3.position:=fmp3.size-128;
    fmp3.Read(ID3,SizeOf(ID3));
  finally
    fmp3.free;
  end;

** or the non Stream approach - as in ChangeID3Tag procedure
try
   AssignFile(fMP3, mp3File);
   Reset(fMP3);
   try
     Seek(fMP3, FileSize(fMP3) - 128);
     BlockRead(fMP3, ID3, SizeOf(ID3));
   finally
   end;
finally
   CloseFile(fMP3);
end;
}

if ID3.Tag <> 'TAG' then begin
   Title.Text:='Wrong or no ID3 tag information';
   Artist.Text:='Wrong or no ID3 tag information';
   Album.Text:='Wrong or no ID3 tag information';
   Year.Text:='Wrong or no ID3 tag information';
   Genre.Text:='Wrong or no ID3 tag information';
   Comment.Text:='Wrong or no ID3 tag information';
end else begin
   Title.Text:=ID3.Title;
   Artist.Text:=ID3.Artist;
   Album.Text:=ID3.Album;
   Year.Text:=ID3.Year;
   if ID3.Genre in [0..MaxID3Genre] then
     Genre.Text:=ID3Genre[ID3.Genre]
   else
     Genre.Text:=IntToStr(ID3.Genre);
   Comment.Text:=ID3.Comment
end;
end;

procedure ChangeID3Tag(NewID3: TID3Rec; mp3FileName: string);
var
  fMP3: file of Byte;
  OldID3 : TID3Rec;
begin
  try
    AssignFile(fMP3, mp3FileName);
    Reset(fMP3);
    try
      Seek(fMP3, FileSize(fMP3) - 128);
      BlockRead(fMP3, OldID3, SizeOf(OldID3));
      if OldID3.Tag = 'TAG' then
        ** Replace old tag }
        Seek(fMP3, FileSize(fMP3) - 128)
      else
        ** Append tag to file because it doesn't exist }
        Seek(fMP3, FileSize(fMP3));
      BlockWrite(fMP3, NewID3, SizeOf(NewID3));
    finally
    end;
  finally
    CloseFile(fMP3);
  end;
end;

procedure FillMP3FileList(Folder: string; sl: TStrings);
var Rec : TSearchRec;
begin
sl.Clear;
if SysUtils.FindFirst(Folder + '*.mp3', faAnyFile, Rec) = 0 then
  try
    repeat
      sl.Add(Rec.Name);
    until SysUtils.FindNext(Rec) <> 0;
  finally
    SysUtils.FindClose(Rec);
  end;
end;

function BrowseDialog(const Title: string; const Flag: integer): string;
var
  lpItemID : PItemIDList;
  BrowseInfo : TBrowseInfo;
  DisplayName : array[0..MAX_PATH] of char;
  TempPath : array[0..MAX_PATH] of char;
begin
  Result:='';
  FillChar(BrowseInfo, sizeof(TBrowseInfo), #0);
  with BrowseInfo do begin
    hwndOwner := Application.Handle;
    pszDisplayName := @DisplayName;
    lpszTitle := PChar(Title);
    ulFlags := Flag;
  end;
  lpItemID := SHBrowseForFolder(BrowseInfo);
  if lpItemId <> nil then begin
    SHGetPathFromIDList(lpItemID, TempPath);
    Result := IncludeTrailingBackslash(TempPath);
    GlobalFreePtr(lpItemID);
  end;
end;

procedure TForm1.btnOpenFolderClick(Sender: TObject);
var mp3Folder : string;
begin
mp3Folder := BrowseDialog('Choose a folder with mp3 files', BIF_RETURNONLYFSDIRS);
if mp3Folder = '' then Exit;

txtFolder.Caption := mp3Folder;

FillMP3FileList(mp3Folder, mp3List.Items);
end;

procedure TForm1.mp3ListClick(Sender: TObject);
var mp3File: string;
begin
  if mp3List.Items.Count=0 then exit;
  mp3File := Concat(txtFolder.Caption, mp3List.Items.Strings[mp3List.ItemIndex]);
  if not FileExists(mp3File) then begin
   ShowMessage('MP3 file '+#13#10+ mp3File +#13#10+'does not exist!');
   exit;
  end;

  FillID3TagInformation(mp3File, edTitle, edArtist, edAlbum, edYear, edGenre, edComment);

  Progress.Max:=0;

  mp3player.Close;
  mp3player.FileName:=mp3File;
  mp3player.Open;

  Progress.Max := mp3player.Length;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  txtFolder.Caption := ExtractFilePath(Application.ExeName);
  FillMP3FileList(txtFolder.Caption, mp3List.Items);
  Progress.Max:=0;
end;

procedure TForm1.ProgresTimerTimer(Sender: TObject);
begin
  if Progress.Max<>0 then
    Progress.Position := mp3player.Position;
end;
end.

Realged13

12-06-2003, 11:28 AM

Damn that is a lot of stuff to remember.