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Question

What is a Delphi version of the C++ header for the DVP7010B video card DLL?

Answer 1

+1 A:

Well, the first thing I notice is that you're trying to convert a C++ class into a Delphi class. You can't do that. The object models are very different. Delphi is going to make certain assumptions about the way the object is laid out, and especially about the way the object's VMT is laid out, that are only valid for Delphi, not for C++.

What you need is either a non-object-oriented interface (plain C) or a COM object.

Mason Wheeler 2010-04-01 20:17:08

I need to connect witn Advantech DVP7010B video card (http://www.advantech.com/products/DVP-7010BE/mod_1-2JKF46.aspx). This card has samples only for C++. I do not know how to use dll for this card with Delphi. I read a lot about making translation dll header file to delphi but my result onlu get Access Violation. Could anybody help me what I must do to get proper file?

2010-04-01 20:34:48

C++ Classes do not cross DLL boundaries (Portably anyway). You need to lookup the C API to use that DLL.

Billy ONeal 2010-04-01 20:36:18

Does this mean that there is no possibility to use this card in Delphi? Manufacturer provides only the header file as above.

2010-04-01 20:46:08

@grzegorz1 - I suspect that it CAN work, but whether it WILL work depends on whether the vendor will cooperate with you. I agree with @BillyONeal, they should provide a native C header. As a seemingly unnecessary work-around, you could write a "shim" wrapper in C++, which exposes a more paletable API.

Chris Thornton 2010-04-01 20:51:45

Thank you for your help. Unfortunately, I do not know enough C++ to deal with this problem. Anyway I wish you all a good night (I go to sleep) or a nice day.

2010-04-01 21:03:17

Answer 2

+1 A:

Apparently AdvDVP_CreateSDKInstence does some Magic(tm) to create a VMT that is then used to dispatch the virtual function calls.

You should leave behind the c++ header file and program directly to the DLL, wrapping them in a Delphi class if you wish. There are tons of tutorials out there that you can pick from, for starters, try this one. It also shows how to create enums in Delphi, and it has a handy little tool to create a unit from the functions the DLL exports.

Ozan 2010-04-01 21:01:12

I read this totorial and many more but I don't know how to solve problem. I tried solve problem with help from Rudy's Delphi Corner (Using C++ objects in Delphi) but without success. Could you give me few sample lines ?

2010-04-01 21:13:21

@grzegorz1: Please edit your question and post the unit you have after following one of those tutorials, and the error you get when compiling or running it.

Ozan 2010-04-01 22:10:14

Answer 3

+2 A:

I agree with Mason you should not use a class (at least at the beginning when you are building the wrapper and testing it)
the first objective here is to have calls to the library functions working.

so try like this :

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  public
    procedure DisplayStatus(r:integer);
  end;

  Function AdvDVP_InitSDK():Integer ; stdcall;  external 'DVP7010B.dll';

var
  Form1: TForm1;
  DVP_DLL_Handle:THandle;

const
   SUCCEEDED = 1;
   FAILED = 0;
   SDKINITFAILED = -1;
   PARAMERROR = -2;
   NODEVICES = -3;
   NOSAMPLE = -4;
   DEVICENUMERROR = -5;
   INPUTERROR = -6;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var r:integer;
begin
   if DVP_DLL_Handle <>0 then begin
       r := AdvDVP_InitSDK();
       DisplayStatus(r);
   end else begin
     showmessage('error loading library');
   end;
end;

procedure TForm1.DisplayStatus(r: integer);
begin
   case r of
     SUCCEEDED:showmessage('SUCCEEDED');
     FAILED:showmessage('FAILED');
     SDKINITFAILED:showmessage('SDKINITFAILED');
     PARAMERROR:showmessage('PARAMERROR');
     NODEVICES:showmessage('NODEVICES');
     NOSAMPLE:showmessage('NOSAMPLE');
     DEVICENUMERROR:showmessage('DEVICENUMERROR');
     INPUTERROR:showmessage('INPUTERROR');
   end;
end;

initialization
  DVP_DLL_Handle:=LoadLibrary('DVP7010B.dll');

finalization
  if DVP_DLL_Handle <>0 then begin
     FreeLibrary(DVP_DLL_Handle);
  end;

end.

it's an incomplete conversion, and I put all into one single unit...

but I downloaded the SDK and tried it : it works : i get 'NODEVICES' when i push the button.

DamienD 2010-04-02 10:23:58

Unfortunately your solution not working with real card. Function AdvDVP_InitSDK causes Access Violation. Thank you for help.

2010-04-02 14:07:42

you should check dll dependencies...just an example : in the past I had similar problems playing with Delphi and SketchupReader.dll (access violations) because this dll in fact need Microsoft Visual C++ 2005 Redistributable Package to be installed.

DamienD 2010-04-02 19:36:42

Answer 4

A:

unit IDVP7010BDLL_h;

interface

uses
  Windows;

const
  DVP7010B          = 'DVP7010B.dll';

  MAXBOARDS         = 4;
  MAXDEVS           = 4;
  MAXMUXS           = 4;
  ID_NEW_FRAME      = 37810;
  ID_MUX0_NEW_FRAME = 37800;
  ID_MUX1_NEW_FRAME = 37801;
  ID_MUX2_NEW_FRAME = 37802;
  ID_MUX3_NEW_FRAME = 37803;

  // TRec
  SUCCEEDED       = 1;
  FAILED          = 0;
  SDKINITFAILED   = -1;
  PARAMERROR      = -2;
  NODEVICES       = -3;
  NOSAMPLE        = -4;
  DEVICENUMERROR  = -5;
  INPUTERROR      = -6;
  // TRec

  // TAnalogVideoFormat
  Video_None      = $00000000;
  Video_NTSC_M    = $00000001;
  Video_NTSC_M_J  = $00000002;
  Video_PAL_B     = $00000010;
  Video_PAL_M     = $00000200;
  Video_PAL_N     = $00000400;
  Video_SECAM_B   = $00001000;
  // TAnalogVideoFormat

  // TCapState
  STOPPED       = 1;
  RUNNING       = 2;
  UNINITIALIZED = -1;
  UNKNOWNSTATE  = -2;
  // TCapState

type
  TCapState = Longint;
  TRes = Longint;
  TtagAnalogVideoFormat = DWORD;
  TAnalogVideoFormat = TtagAnalogVideoFormat;
  PAnalogVideoFormat = ^TAnalogVideoFormat;
  TVideoSize = (SIZEFULLPAL = 0, SIZED1, SIZEVGA, SIZEQVGA, SIZESUBQVGA);
  PVideoSize = ^TVideoSize;
  P_Pointer = ^Pointer;

  //TAdvDVP_CreateSDKInstence = function(var p: PIDVP7010BDLL): Integer of object; stdcall; // not needed in class
  TAdvDVP_InitSDK = function(): Integer of object; stdcall;
  TAdvDVP_CloseSDK = function(): Integer of object; stdcall;
  TAdvDVP_GetNoOfDevices = function(var pNoOfDevs: Integer): Integer of object; stdcall;
  TAdvDVP_Start = function(nDevNum: Integer; SwitchingChans: Integer; Main: HWND; hwndPreview: HWND): Integer of object; stdcall;
  TAdvDVP_Stop = function(nDevNum: Integer): Integer of object; stdcall;
  TAdvDVP_GetCapState = function(nDevNum: Integer): Integer of object; stdcall;
  TAdvDVP_IsVideoPresent = function(nDevNum: Integer; var VPresent: Bool): Integer of object; stdcall;
  TAdvDVP_GetCurFrameBuffer = function(nDevNum: Integer; VMux: Integer; var bufSize: LongInt; buf: PByte): Integer of object; stdcall;
  TAdvDVP_SetNewFrameCallback = function(nDevNum: Integer; callback: Integer): Integer of object; stdcall;
  TAdvDVP_GetVideoFormat = function(nDevNum: Integer; var vFormat: TAnalogVideoFormat): Integer of object; stdcall;
  TAdvDVP_SetVideoFormat = function(nDevNum: Integer; vFormat: TAnalogVideoFormat): Integer of object; stdcall;
  TAdvDVP_GetFrameRate = function(nDevNum: Integer; nFrameRate: Integer): Integer of object; stdcall;
  TAdvDVP_SetFrameRate = function(nDevNum: Integer; SwitchingChans: Integer; nFrameRate: Integer): Integer of object; stdcall;
  TAdvDVP_GetResolution = function(nDevNum: Integer; var Size: TVideoSize): Integer of object; stdcall;
  TAdvDVP_SetResolution = function(nDevNum: Integer; Size: TVideoSize): Integer of object; stdcall;
  TAdvDVP_GetVideoInput = function(nDevNum: Integer; var input: Integer): Integer of object; stdcall;
  TAdvDVP_SetVideoInput = function(nDevNum: Integer; input: Integer): Integer of object; stdcall;
  TAdvDVP_GetBrightness = function(nDevNum: Integer; input: Integer; var pnValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_SetBrightness = function(nDevNum: Integer; input: Integer; nValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_GetContrast = function(nDevNum: Integer; input: Integer; var pnValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_SetContrast = function(nDevNum: Integer; input: Integer; nValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_GetHue = function(nDevNum: Integer; input: Integer; var pnValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_SetHue = function(nDevNum: Integer; input: Integer; nValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_GetSaturation = function(nDevNum: Integer; input: Integer; var pnValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_SetSaturation = function(nDevNum: Integer; input: Integer; nValue: LongInt) :Integer of object; stdcall;
  TAdvDVP_GPIOGetData = function(nDevNum: Integer; DINum: Integer; var value: Bool): Integer of object; stdcall;
  TAdvDVP_GPIOSetData = function(nDevNum: Integer; DONum: Integer; value: Boolean): Integer of object; stdcall;


  TIDVP7010BDLL = class
  public
    //AdvDVP_CreateSDKInstence: TAdvDVP_CreateSDKInstence; // not needed in class
    AdvDVP_InitSDK: TAdvDVP_InitSDK;
    AdvDVP_CloseSDK: TAdvDVP_CloseSDK;
    AdvDVP_GetNoOfDevices: TAdvDVP_GetNoOfDevices;
    AdvDVP_Start: TAdvDVP_Start;
    AdvDVP_Stop: TAdvDVP_Stop;
    AdvDVP_GetCapState: TAdvDVP_GetCapState;
    AdvDVP_IsVideoPresent: TAdvDVP_IsVideoPresent;
    AdvDVP_GetCurFrameBuffer: TAdvDVP_GetCurFrameBuffer;
    AdvDVP_SetNewFrameCallback: TAdvDVP_SetNewFrameCallback;
    AdvDVP_GetVideoFormat: TAdvDVP_GetVideoFormat;
    AdvDVP_SetVideoFormat: TAdvDVP_SetVideoFormat;
    AdvDVP_GetFrameRate: TAdvDVP_GetFrameRate;
    AdvDVP_SetFrameRate: TAdvDVP_SetFrameRate;
    AdvDVP_GetResolution: TAdvDVP_GetResolution;
    AdvDVP_SetResolution: TAdvDVP_SetResolution;
    AdvDVP_GetVideoInput: TAdvDVP_GetVideoInput;
    AdvDVP_SetVideoInput: TAdvDVP_SetVideoInput;
    AdvDVP_GetBrightness: TAdvDVP_GetBrightness;
    AdvDVP_SetBrightness: TAdvDVP_SetBrightness;
    AdvDVP_GetContrast: TAdvDVP_GetContrast;
    AdvDVP_SetContrast: TAdvDVP_SetContrast;
    AdvDVP_GetHue: TAdvDVP_GetHue;
    AdvDVP_SetHue: TAdvDVP_SetHue;
    AdvDVP_GetSaturation: TAdvDVP_GetSaturation;
    AdvDVP_SetSaturation: TAdvDVP_SetSaturation;
    AdvDVP_GPIOGetData: TAdvDVP_GPIOGetData;
    AdvDVP_GPIOSetData: TAdvDVP_GPIOSetData;

    constructor Create; // For method 2
  end;
  PIDVP7010BDLL = ^TIDVP7010BDLL;
  PPIDVP7010BDLL = ^PIDVP7010BDLL;

  TIAdvDVP_CreateSDKInstence = function(var p: PIDVP7010BDLL): Integer; stdcall;

var
  hDVP7010B: THandle;
  IAdvDVP_CreateSDKInstence: TIAdvDVP_CreateSDKInstence;

implementation

{ TIDVP7010BDLL }

constructor TIDVP7010BDLL.Create;
begin
  if hDVP7010B <> 0 then
  begin
    //@IAdvDVP_CreateSDKInstence := GetProcAddress(hDVP7010B, 'AdvDVP_CreateSDKInstence'); // not needed
    @AdvDVP_InitSDK := GetProcAddress(hDVP7010B, 'AdvDVP_InitSDK');
    @AdvDVP_CloseSDK := GetProcAddress(hDVP7010B, 'AdvDVP_CloseSDK');
    @AdvDVP_GetNoOfDevices := GetProcAddress(hDVP7010B, 'AdvDVP_GetNoOfDevices');
    @AdvDVP_Start := GetProcAddress(hDVP7010B, 'AdvDVP_Start');
    @AdvDVP_Stop := GetProcAddress(hDVP7010B, 'AdvDVP_Stop');
    @AdvDVP_GetCapState := GetProcAddress(hDVP7010B, 'AdvDVP_GetCapState');
    @AdvDVP_IsVideoPresent := GetProcAddress(hDVP7010B, 'AdvDVP_IsVideoPresent');
    @AdvDVP_GetCurFrameBuffer := GetProcAddress(hDVP7010B, 'AdvDVP_GetCurFrameBuffer');
    @AdvDVP_SetNewFrameCallback := GetProcAddress(hDVP7010B, 'AdvDVP_SetNewFrameCallback');
    @AdvDVP_GetVideoFormat := GetProcAddress(hDVP7010B, 'AdvDVP_GetVideoFormat');
    @AdvDVP_SetVideoFormat := GetProcAddress(hDVP7010B, 'AdvDVP_SetVideoFormat');
    @AdvDVP_GetFrameRate := GetProcAddress(hDVP7010B, 'AdvDVP_GetFrameRate');
    @AdvDVP_SetFrameRate := GetProcAddress(hDVP7010B, 'AdvDVP_SetFrameRate');
    @AdvDVP_GetResolution := GetProcAddress(hDVP7010B, 'AdvDVP_GetResolution');
    @AdvDVP_SetResolution := GetProcAddress(hDVP7010B, 'AdvDVP_SetResolution');
    @AdvDVP_GetVideoInput := GetProcAddress(hDVP7010B, 'AdvDVP_GetVideoInput');
    @AdvDVP_SetVideoInput := GetProcAddress(hDVP7010B, 'AdvDVP_SetVideoInput');
    @AdvDVP_GetBrightness := GetProcAddress(hDVP7010B, 'AdvDVP_GetBrightness');
    @AdvDVP_SetBrightness := GetProcAddress(hDVP7010B, 'AdvDVP_SetBrightness');
    @AdvDVP_GetContrast := GetProcAddress(hDVP7010B, 'AdvDVP_GetContrast');
    @AdvDVP_SetContrast := GetProcAddress(hDVP7010B, 'AdvDVP_SetContrast');
    @AdvDVP_GetHue := GetProcAddress(hDVP7010B, 'AdvDVP_GetHue');
    @AdvDVP_SetHue := GetProcAddress(hDVP7010B, 'AdvDVP_SetHue');
    @AdvDVP_GetSaturation := GetProcAddress(hDVP7010B, 'AdvDVP_GetSaturation');
    @AdvDVP_SetSaturation := GetProcAddress(hDVP7010B, 'AdvDVP_SetSaturation');
    @AdvDVP_GPIOGetData := GetProcAddress(hDVP7010B, 'AdvDVP_GPIOGetData');
    @AdvDVP_GPIOSetData := GetProcAddress(hDVP7010B, 'AdvDVP_GPIOSetData');
  end
  else
    MessageBox(0, 'DVP7010B.dll not found!', 'Error', MB_ICONERROR);
end;

initialization
  hDVP7010B := LoadLibrary(DVP7010B);
  // For method 1
  if hDVP7010B <> 0 then
  begin
    @IAdvDVP_CreateSDKInstence := GetProcAddress(hDVP7010B, 'AdvDVP_CreateSDKInstence');
    if @IAdvDVP_CreateSDKInstence = nil then
      MessageBox(0, 'AdvDVP_CreateSDKInstence not found in DVP7010B.dll', 'Error', MB_ICONERROR);
  end
  else
    MessageBox(0, 'DVP7010B.dll not found!', 'Error', MB_ICONERROR);

finalization
  FreeLibrary(hDVP7010B);

end.

Test code:

procedure TForm8.Button1Click(Sender: TObject);
var
  pDVPSDK: PIDVP7010BDLL;
  res: Integer;
begin
  // Method 1
  pDVPSDK := nil;
  res := IAdvDVP_CreateSDKInstence(pDVPSDK);
  if not (res = SUCCEEDED) then
  begin
    Application.MessageBox('AdvDVP_CreateSDKInstence error!', 'Error', MB_ICONERROR);
  end
  else
  begin
    Application.MessageBox('AdvDVP_CreateSDKInstence will not work for this!!!', 'Error', MB_ICONERROR);
  end;
end;

Why it will not work with Delphi: An empty Delphi 2009 class has 8 bytes (see http://blogs.teamb.com/craigstuntz/2009/03/25/38138/ for more info) and so AdvDVP_InitSDK & AdvDVP_CloseSDK offset get eaten and bug the rest functions and my guess it also bug the class itself.

Take a look at Local Variables while debugging:

pDVPSDK $1C71100
+AdvDVP_InitSDK ($10001253,$1000123A)
+AdvDVP_CloseSDK ($1000101E,$10001285)
+AdvDVP_GetNoOfDevices ($100011D1,$1000112C)
+....

And from IDA:

.text:10001253 public AdvDVP_GetNoOfDevices

AdvDVP_InitSDK points to TAdvDVP_GetNoOfDevices !!!

Try this if you have a card yourself:

procedure TForm8.Button2Click(Sender: TObject);
var
  DVPSDK: TIDVP7010BDLL;
  res: Integer;
  nDevCount: Integer;
  i: Integer;
begin
  // Method 2
  DVPSDK := TIDVP7010BDLL.Create;
  try
    res := DVPSDK.AdvDVP_InitSDK;
    if res = SUCCEEDED then
    begin
      if not (DVPSDK.AdvDVP_GetNoOfDevices(nDevCount) = SUCCEEDED) then
        Exit;

      if (nDevCount > MAXBOARDS*MAXDEVS) then
        Exit;

      for i := 0 to nDevCount - 1 do
      begin
        m_DevNum.Items.Add(Format('Device_%d', [i])); // TComboBox
      end;
    end
    else
    begin
      case res of
        FAILED: Application.MessageBox('SDK function failed!', 'Error', MB_ICONERROR);
        SDKINITFAILED: Application.MessageBox('SDK initiation failed!', 'Error', MB_ICONERROR);
        PARAMERROR: Application.MessageBox('Number of the devices out of the range!', 'Error', MB_ICONERROR);
        NODEVICES: Application.MessageBox('No device be found!', 'Error', MB_ICONERROR);
      end;
    end;
  finally
    DVPSDK.Free;
  end;
end;

I don't know if events need a different calling conversion other than stdcall, but you can try with cdecl and others depending of what data you get from the functions.

Good luck.

pani 2010-04-03 03:06:49

Unfortunately, despite your help, we still have no success. Calling a function "AdvDVP_InitSDK" generate Access Violation. Last night I tried connect card with TVideoGrabber component - it works perfectly - so probably I give up fight. Once again, thank you very much for help.

2010-04-06 09:41:50

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What is a Delphi version of the C++ header for the DVP7010B video card DLL?

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