mplayer + sqlite [SOLVED]
lazarus / 16-Databases

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Marcelo Confortino · 2016-09-04 13:39

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][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    {$IFDEF
Linux}   MPlayerControl1.MPlayerPath:=''; 
 //MPlayerControl1.StartParam:='-vo x11 -zoom -fs'; 
 MPlayerControl1.Filename := 'tv://
driver=v4l2:device=/dev/video0:gain=1:width=320:height=200:fps=25'; 
 MPlayerControl1.Play;  {$else $IFDEF Windows}   // Download MPlayer
generic for Windows and save under Programm Folder Directory   //
http://sourceforge.net/projects/mplayer-win32/   //Download MPlayer
WIN32-Generic   MPlayerControl1.MPlayerPath:=extractfilepath(applicati
on.exename)+'MPlayer\mplayer.exe' ; 
 //MPlayerControl1.StartParam:='-zoom -fs'; 
 MPlayerControl1.Filename:='tv://
driver=dshow:device=0:gain=1:width=320:height=200:fps=25'; 
 MPlayerControl1.Play;  {$endif}     
the code that takes the picture and saves the filename to the database
is here:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i       if
MPlayerControl1.Running then        begin         
MPlayerControl1.GrabImage;         
RegistroDataset.FieldByName('imagen').AsString :=
MPlayerControl1.LastImageFilename;        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.

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LacaK · 2016-09-05 08:51

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

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Marcelo Confortino · 2016-09-05 16:05

Sorry, LacaK. This is the relevant code:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i      
RegistroDataset.FieldByName('nrodni').AsInteger :=
StrToInt(Edit1.Text);     
RegistroDataset.FieldByName('fechahora').AsString :=
DateTimeToStr(Now);      if MPlayerControl1.Running then        begin 
        MPlayerControl1.GrabImage;         
RegistroDataset.FieldByName('imagen').AsString :=
MPlayerControl1.LastImageFilename;        end;     
RegistroDataset.Post;      RegistroDataset.ApplyUpdates; 
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.

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balazsszekely · 2016-09-05 16:48

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

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Marcelo Confortino · 2016-09-05 18:22

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

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balazsszekely · 2016-09-05 18:48

Apparently LastImageFilename is unique, so this should work:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i //... 
TForm1 = class(TForm)  private    function Wait(const DT: QWord; const
OldFileName: String): Boolean;  public  end;       //... function
TForm1.Wait(const DT: QWord; const OldFilename: String): Boolean;var 
TC: QWord;begin  Result := False;  TC := GetTickCount64;  while
(GetTickCount64 < TC + DT) and (not Application.Terminated) do  begin 
  if OldFilename <> MPlayerControl1.LastImageFilename then    begin  
  Result := True;      Break;    end;    Application.ProcessMessages; 
end;end; procedure TForm1.Button1Click(Sender: TObject);var 
OldFilename: String;begin  OldFilename:=
MPlayerControl1.LastImageFilename;  if MPlayerControl1.Running then 
begin     MPlayerControl1.GrabImage;     if Wait(5000, OldFilename)
then //wait until the filename changes, but no more then five seconds 
   begin        //do the saving here     end;  end;end;

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Marcelo Confortino · 2016-09-05 21:23

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.

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Marcelo Confortino · 2016-09-06 11:57

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.