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From: Peter Haas <PeterJHaas@t-online.de>
Newsgroups: borland.public.delphi.multimedia
Subject: Re: Video capture frame rate
Date: Tue, 12 Jun 2001 18:32:52 +0200
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Hi Nick,

Nick Barrett wrote in <3b25fce2_2@dnews>:
> How does one set the capture frame rate when using capCaptureSequenceNoFile?
> I have tried changing CaptureParms.dwRequestMicroSecPerFrame in my program
> but there seem to be no change to the rate that VideoStreamCallback is
> called.

I have tested the following method in my demo, there are no problems. I
can set 1 frame per second and 50 frames per second, the frame rate will
realize.

UDFrameRate is a TUpDown.

var
  CaptureParms : TCaptureParms;
begin
  if FCapWnd <> 0 then
  begin
    capCaptureGetSetup(FCapWnd, @CaptureParms, SizeOf(CaptureParms));
    with CaptureParms do
    begin
      // frame rate
      dwRequestMicroSecPerFrame := 1000000 div UDFrameRate.Position;
      // background capture
      fYield := True;
      // abort by mouse click
      fAbortLeftMouse := True;
      fAbortRightMouse := True;
      // abort after 30 seconds
      fLimitEnabled := True;
      wTimeLimit := 30;
      // abort with space key
      vKeyAbort := vk_space;
    end;
    capCaptureSetSetup(FCapWnd, @CaptureParms, SizeOf(CaptureParms));
    capCaptureSequenceNoFile(FCapWnd);
  end;
end;


But, I know a effect from my program:

If the duration of the callback procedure to big, the next frame(s) will
skip. Use dwTimeCaptured to detect the correct position of the frame.


But this behavior can be dependant from the video card driver. I use a
miroMEDIA PCTV from miro (after the takeover to pinnacle the cards will
renamed in miroVIDEO PCTV and later in STUDIO PCTV). The driver based on
the BT848 driver Version 2.3.040.

Maybe your driver have a another behavior, if your computer too slow for
a frame rate.

Bye Peter.