mplayer + sqlite [SOLVED]

[Marcelo Confortino]

Good morning!

I am writing an application that must take a picture of the operator when some event is triggered. So far I have mplayer running and showing a webcam's output on screen (see attached screenshot):

Code: Pascal  [Select][+][-]

1.    {$IFDEF Linux}
2.    MPlayerControl1.MPlayerPath:='';
3.    //MPlayerControl1.StartParam:='-vo x11 -zoom -fs';
4.    MPlayerControl1.Filename := 'tv:// driver=v4l2:device=/dev/video0:gain=1:width=320:height=200:fps=25';
5.    MPlayerControl1.Play;
6.   {$else $IFDEF Windows}
7.    // Download MPlayer generic for Windows and save under Programm Folder Directory
8.    // http://sourceforge.net/projects/mplayer-win32/
9.    //Download MPlayer WIN32-Generic
10.    MPlayerControl1.MPlayerPath:=extractfilepath(application.exename)+'MPlayer\mplayer.exe' ;
11.    //MPlayerControl1.StartParam:='-zoom -fs';
12.    MPlayerControl1.Filename:='tv:// driver=dshow:device=0:gain=1:width=320:height=200:fps=25';
13.    MPlayerControl1.Play;
14.   {$endif}      

the code that takes the picture and saves the filename to the database is here:

Code: Pascal  [Select][+][-]

1.       if MPlayerControl1.Running then
2.         begin
3.           MPlayerControl1.GrabImage;
4.           RegistroDataset.FieldByName('imagen').AsString := MPlayerControl1.LastImageFilename;
5.         end;    

the problem is that the very first invocation of above code does not save the image filename in the database, later invocations work fine.

Am I missing something?

Thanks for your advice.

[LacaK]

You do not show whole database code 
There is missing at least ApllyUpdates and Commit ?

[Marcelo Confortino]

Sorry, LacaK. This is the relevant code:

Code: Pascal  [Select][+][-]

1.       RegistroDataset.FieldByName('nrodni').AsInteger := StrToInt(Edit1.Text);
2.       RegistroDataset.FieldByName('fechahora').AsString := DateTimeToStr(Now);
3.       if MPlayerControl1.Running then
4.         begin
5.           MPlayerControl1.GrabImage;
6.           RegistroDataset.FieldByName('imagen').AsString := MPlayerControl1.LastImageFilename;
7.         end;
8.       RegistroDataset.Post;
9.       RegistroDataset.ApplyUpdates;
10.  

The other fields in the record are saved fine, as is the full record in all but the first execution of the code.
Thank you.

[balazsszekely]

@Marcelo Confortino
Perhaps MPlayerControl1.GrabImage doesn't return the filename immediately. You should wait a few seconds before saving the data into the database.

[Marcelo Confortino]

Thank you, GetMem, I'll try that. Is there a way to know when the image file is ready?

[balazsszekely]

Apparently LastImageFilename is unique, so this should work:

Code: Pascal  [Select][+][-]

1. //...
2.   TForm1 = class(TForm)
3.   private
4.     function Wait(const DT: QWord; const OldFileName: String): Boolean;
5.   public
6.   end;      
7. //...
8.  
9. function TForm1.Wait(const DT: QWord; const OldFilename: String): Boolean;
10. var
11.   TC: QWord;
12. begin
13.   Result := False;
14.   TC := GetTickCount64;
15.   while (GetTickCount64 < TC + DT) and (not Application.Terminated) do
16.   begin
17.     if OldFilename <> MPlayerControl1.LastImageFilename then
18.     begin
19.       Result := True;
20.       Break;
21.     end;
22.     Application.ProcessMessages;
23.   end;
24. end;
25.  
26. procedure TForm1.Button1Click(Sender: TObject);
27. var
28.   OldFilename: String;
29. begin
30.   OldFilename:= MPlayerControl1.LastImageFilename;
31.   if MPlayerControl1.Running then
32.   begin
33.      MPlayerControl1.GrabImage;
34.      if Wait(5000, OldFilename) then //wait until the filename changes, but no more then five seconds
35.      begin
36.         //do the saving here
37.      end;
38.   end;
39. end;

[Marcelo Confortino]

Wow, that was fast, thank you. Sadly, it doesn't work. I even inserted Wait(5000) between grabimage and lastfilename, same result. Looks like some initialization is missing. Reading the wiki, it seems that TMPlayerControl.GrabImage is not fully dependable. I'll keep working on this.

[Marcelo Confortino]

Well. sort of. I added an additional GrabImage just after the initialization of TMplayerControl. Later, when I call GrabImage and LastFilename it is not the first invocation anymore, and it works as intended. Than you all.