Difference between revisions of "Using libvlc with Delphi"

From VideoLAN Wiki
Jump to navigation Jump to search
Line 87: Line 87:
 
   end;
 
   end;
 
end;
 
end;
−
</pre>  
+
</pre>
 +
=== Load libvlc library into memory ===
 +
 
 +
Next, load library libvlc.dll into memory
 +
<pre>// -----------------------------------------------------------------------------
 +
// Load libvlc library into memory
 +
// -----------------------------------------------------------------------------
 +
function LoadVLCLibrary(APath: string): integer;
 +
begin
 +
  Result := LoadLibrary(PWideChar(APath + '\libvlccore.dll'));
 +
  Result := LoadLibrary(PWideChar(APath + '\libvlc.dll'));
 +
end;
 +
 
 +
</pre>
 +
=== Get address of libvlc functions ===
 +
 
 +
This will get address of libvlc functions. Only neccessary functions loaded for this sample code, please refer to libvlc document if you need more functions
 +
<pre>// -----------------------------------------------------------------------------
 +
function GetAProcAddress(handle: integer; var addr: Pointer; procName: string; failedList: TStringList): integer;
 +
begin
 +
  addr := GetProcAddress(handle, PWideChar(procName));
 +
  if Assigned(addr) then Result := 0
 +
  else begin
 +
    if Assigned(failedList) then failedList.Add(procName);
 +
    Result := -1;
 +
  end;
 +
end;
 +
// -----------------------------------------------------------------------------
 +
// Get address of libvlc functions
 +
// -----------------------------------------------------------------------------
 +
function LoadVLCFunctions(vlcHandle: integer; failedList: TStringList): Boolean;
 +
begin
 +
  GetAProcAddress(vlcHandle, @libvlc_new, 'libvlc_new', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_new_location, 'libvlc_media_new_location', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_player_new_from_media, 'libvlc_media_player_new_from_media', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_release, 'libvlc_media_release', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_player_set_hwnd, 'libvlc_media_player_set_hwnd', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_player_play, 'libvlc_media_player_play', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_player_stop, 'libvlc_media_player_stop', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_player_release, 'libvlc_media_player_release', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_release, 'libvlc_release', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_player_is_playing, 'libvlc_media_player_is_playing', failedList);
 +
  GetAProcAddress(vlcHandle, @libvlc_media_new_path, 'libvlc_media_new_path', failedList);
 +
  // if all functions loaded, result is an empty list, otherwise result is a list of functions failed
 +
  Result := failedList.Count = 0;
 +
end;
 +
 
 +
</pre>
 +
=== Create form ===
 +
 
 +
Load library on form create. If you use a incompartible libvlc version (older or newer than this demo), some functions may not be correct (obsolete or agruments changed). In this case, program will display a list of functions failed to load, and you can correct these according to your libvlc version.
 +
<pre>// -----------------------------------------------------------------------------
 +
procedure TForm1.FormCreate(Sender: TObject);
 +
var sL: TStringList;
 +
begin
 +
  // load vlc library
 +
  vlclib := LoadVLCLibrary(GetVLCLibPath());
 +
  if vlclib = 0 then begin
 +
    Showmessage('Load vlc library failed');
 +
    Exit;
 +
  end;
 +
  // sL will contains list of functions fail to load
 +
  sL := TStringList.Create;
 +
  if not LoadVLCFunctions(vlclib, sL) then begin
 +
    Showmessage('Some functions failed to load : ' + #13#10 + sL.Text);
 +
    FreeLibrary(vlclib);
 +
    sL.Free;
 +
    Exit;
 +
  end;
 +
  sL.Free;
 +
end;
 +
 
 +
</pre>
 
[[Category:Coding]] [[Category:Delphi]]
 
[[Category:Coding]] [[Category:Delphi]]

Revision as of 06:43, 9 January 2012

This is a sample code to play media files using libvlc with Delphi (test with Delphi XE2 VCL form, VLC 1.1.11).

Form design

Use a simple form with 3 control : Panel1 (TPanel) to display video, btnPlay (TButton) to play media, and btnStop (TButton) to stop playing

Full source code

Implementations

unit Unit1;
interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls;

type
  TForm1 = class(TForm)
    btnPlay: TButton;
    btnStop: TButton;
    Panel1: TPanel;
    procedure btnPlayClick(Sender: TObject);
    procedure btnStopClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  plibvlc_instance_t        = type Pointer;
  plibvlc_media_player_t    = type Pointer;
  plibvlc_media_t           = type Pointer;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  libvlc_media_new_path              : function(p_instance : Plibvlc_instance_t; path : PAnsiChar) : Plibvlc_media_t; cdecl;
  libvlc_media_new_location          : function(p_instance : plibvlc_instance_t; psz_mrl : PAnsiChar) : Plibvlc_media_t; cdecl;
  libvlc_media_player_new_from_media : function(p_media : Plibvlc_media_t) : Plibvlc_media_player_t; cdecl;
  libvlc_media_player_set_hwnd       : procedure(p_media_player : Plibvlc_media_player_t; drawable : Pointer); cdecl;
  libvlc_media_player_play           : procedure(p_media_player : Plibvlc_media_player_t); cdecl;
  libvlc_media_player_stop           : procedure(p_media_player : Plibvlc_media_player_t); cdecl;
  libvlc_media_player_release        : procedure(p_media_player : Plibvlc_media_player_t); cdecl;
  libvlc_media_player_is_playing     : function(p_media_player : Plibvlc_media_player_t) : Integer; cdecl;
  libvlc_media_release               : procedure(p_media : Plibvlc_media_t); cdecl;
  libvlc_new                         : function(argc : Integer; argv : PAnsiChar) : Plibvlc_instance_t; cdecl;
  libvlc_release                     : procedure(p_instance : Plibvlc_instance_t); cdecl;

  vlcLib: integer;
  vlcInstance: plibvlc_instance_t;
  vlcMedia: plibvlc_media_t;
  vlcMediaPlayer: plibvlc_media_player_t;

Get VLC installation path

Normally, the library libvlc.dll is in "C:\Program files\Videolan\VLC\". This function read registry to get the correct VLC installation path, stored in key HKEY_LOCAL_MACHINE\Software\VideoLAN\VLC. 

// -----------------------------------------------------------------------------
// Read registry to get VLC installation path
// -----------------------------------------------------------------------------
function GetVLCLibPath: String;
var
  Handle: HKEY;
  RegType: Integer;
  DataSize: Cardinal;
  Key: PWideChar;
begin
  Result := '';
  Key := 'Software\VideoLAN\VLC';
  if RegOpenKeyEx(HKEY_LOCAL_MACHINE, Key, 0, KEY_READ, Handle) = ERROR_SUCCESS then
  begin
    if RegQueryValueEx(Handle, 'InstallDir', nil, @RegType, nil, @DataSize) = ERROR_SUCCESS then
    begin
      SetLength(Result, DataSize);
      RegQueryValueEx(Handle, 'InstallDir', nil, @RegType, PByte(@Result[1]), @DataSize);
      Result[DataSize] := '\';
    end
    else Showmessage('Error on reading registry');
    RegCloseKey(Handle);
    Result := String(PChar(Result));
  end;
end;

Load libvlc library into memory

Next, load library libvlc.dll into memory 

// -----------------------------------------------------------------------------
// Load libvlc library into memory
// -----------------------------------------------------------------------------
function LoadVLCLibrary(APath: string): integer;
begin
  Result := LoadLibrary(PWideChar(APath + '\libvlccore.dll'));
  Result := LoadLibrary(PWideChar(APath + '\libvlc.dll'));
end;

Get address of libvlc functions

This will get address of libvlc functions. Only neccessary functions loaded for this sample code, please refer to libvlc document if you need more functions 

// -----------------------------------------------------------------------------
function GetAProcAddress(handle: integer; var addr: Pointer; procName: string; failedList: TStringList): integer;
begin
  addr := GetProcAddress(handle, PWideChar(procName));
  if Assigned(addr) then Result := 0
  else begin
    if Assigned(failedList) then failedList.Add(procName);
    Result := -1;
  end;
end;
// -----------------------------------------------------------------------------
// Get address of libvlc functions
// -----------------------------------------------------------------------------
function LoadVLCFunctions(vlcHandle: integer; failedList: TStringList): Boolean;
begin
  GetAProcAddress(vlcHandle, @libvlc_new, 'libvlc_new', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_new_location, 'libvlc_media_new_location', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_player_new_from_media, 'libvlc_media_player_new_from_media', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_release, 'libvlc_media_release', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_player_set_hwnd, 'libvlc_media_player_set_hwnd', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_player_play, 'libvlc_media_player_play', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_player_stop, 'libvlc_media_player_stop', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_player_release, 'libvlc_media_player_release', failedList);
  GetAProcAddress(vlcHandle, @libvlc_release, 'libvlc_release', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_player_is_playing, 'libvlc_media_player_is_playing', failedList);
  GetAProcAddress(vlcHandle, @libvlc_media_new_path, 'libvlc_media_new_path', failedList);
  // if all functions loaded, result is an empty list, otherwise result is a list of functions failed
  Result := failedList.Count = 0;
end;

Create form

Load library on form create. If you use a incompartible libvlc version (older or newer than this demo), some functions may not be correct (obsolete or agruments changed). In this case, program will display a list of functions failed to load, and you can correct these according to your libvlc version. 

// -----------------------------------------------------------------------------
procedure TForm1.FormCreate(Sender: TObject);
var sL: TStringList;
begin
  // load vlc library
  vlclib := LoadVLCLibrary(GetVLCLibPath());
  if vlclib = 0 then begin
    Showmessage('Load vlc library failed');
    Exit;
  end;
  // sL will contains list of functions fail to load
  sL := TStringList.Create;
  if not LoadVLCFunctions(vlclib, sL) then begin
    Showmessage('Some functions failed to load : ' + #13#10 + sL.Text);
    FreeLibrary(vlclib);
    sL.Free;
    Exit;
  end;
  sL.Free;
end;
Retrieved from "https://wiki.videolan.org/index.php?title=Using_libvlc_with_Delphi&oldid=21164"