avicap32.dll issues (Is Ken Tucker Around?)

29 Jun 2005 2:59 AM

Jeremy

Hello

I am using a web cam service that saves images every five minutes based
off the example given by Ken Tucker. (hopefully I can catch him!) It
works great for the most part.

I need to handle a situation if the camera, or connection to the camera
become interupted. I am connecting through a device called a "dazzle"
which for some reason or another causes a few connection problems here
and there.

If the camera goes offline the image does not update, and the preview
window becomes frozen with the last frame before the connection was
interupted.

I noticed in the CAPSTATUS structure a few properties I could test for
to see if the image is "live". The problem is that "fLiveWindow" always
returns 1...even on a preview window with a still image. There is
another property "fCapturingNow" but it always returns 0. I could even
use "dwCurrentVideoFrame" and see if the count stopped but that too
always returns 0. What am I missing? How can I test if the preview
window has a live or moving image?

Public Structure CAPSTATUS
        Dim uiImageWidth As Integer
        Dim uiImageHeight As Integer
        Dim fLiveWindow As Integer
        Dim fOverlayWindow As Integer
        Dim fScale As Integer
        Dim ptScroll As POINTAPI
        Dim fUsingDefaultPalette As Integer
        Dim fAudioHardware As Integer
        Dim fCapFileExists As Integer
        Dim dwCurrentVideoFrame As Integer
        Dim dwCurrentVideoFramesDropped As Integer
        Dim dwCurrentWaveSamples As Integer
        Dim dwCurrentTimeElapsedMS As Integer
        Dim hPalCurrent As Integer
        Dim fCapturingNow As Integer
        Dim dwReturn As Integer
        Dim wNumVideoAllocated As Integer
        Dim wNumAudioAllocated As Integer
    End Structure

I use the following to access the structure...

Dim s As CAPSTATUS

bReturn = SendMessage(hHwnd, WM_CAP_GET_STATUS, Marshal.SizeOf(s), s)

Thanks a million for any assistance!

Thanks,
Jeremy

29 Jun 2005 1:23 PM

Supra

Function capGetStatus(ByVal lwnd As Integer, ByVal s As Integer, ByVal
wSize As Short) As Boolean
capGetStatus = SendMessage(lwnd, WM_CAP_GET_STATUS, wSize, s)
End Function

i haven't tried fLiveWindow yet. because i'm using winXp but doesn't
have capture card yet :-(
regards,

ken tucker is working on website project
regards

Jeremy wrote:

Show quoteHide quote

>Hello
>
>I am using a web cam service that saves images every five minutes based
>off the example given by Ken Tucker. (hopefully I can catch him!) It
>works great for the most part.
>
>I need to handle a situation if the camera, or connection to the camera
>become interupted. I am connecting through a device called a "dazzle"
>which for some reason or another causes a few connection problems here
>and there.
>
>If the camera goes offline the image does not update, and the preview
>window becomes frozen with the last frame before the connection was
>interupted.
>
>I noticed in the CAPSTATUS structure a few properties I could test for
>to see if the image is "live". The problem is that "fLiveWindow" always
>returns 1...even on a preview window with a still image. There is
>another property "fCapturingNow" but it always returns 0. I could even
>use "dwCurrentVideoFrame" and see if the count stopped but that too
>always returns 0. What am I missing? How can I test if the preview
>window has a live or moving image?
>
>Public Structure CAPSTATUS
>        Dim uiImageWidth As Integer
>        Dim uiImageHeight As Integer
>        Dim fLiveWindow As Integer
>        Dim fOverlayWindow As Integer
>        Dim fScale As Integer
>        Dim ptScroll As POINTAPI
>        Dim fUsingDefaultPalette As Integer
>        Dim fAudioHardware As Integer
>        Dim fCapFileExists As Integer
>        Dim dwCurrentVideoFrame As Integer
>        Dim dwCurrentVideoFramesDropped As Integer
>        Dim dwCurrentWaveSamples As Integer
>        Dim dwCurrentTimeElapsedMS As Integer
>        Dim hPalCurrent As Integer
>        Dim fCapturingNow As Integer
>        Dim dwReturn As Integer
>        Dim wNumVideoAllocated As Integer
>        Dim wNumAudioAllocated As Integer
>    End Structure
>
>I use the following to access the structure...
>
>Dim s As CAPSTATUS
>
>bReturn = SendMessage(hHwnd, WM_CAP_GET_STATUS, Marshal.SizeOf(s), s)
>
>Thanks a million for any assistance!
>
>Thanks,
>Jeremy
>
>
>

29 Jun 2005 3:01 PM

Jeremy

Thanks for your reply Supra,

I read an earlier discussion between you and Henry Wu:

http://groups-beta.google.com/group/microsoft.public.dotnet.languages.vb/browse_frm/thread/7c71088fb20b3293/960f363163cce7d1?q=WM_CAP_GET_STATUS&rnum=9&hl=en#960f363163cce7d1

Ken gave the following solution (which is what I am using to update
CAPSTATUS):

Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
        (ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As
Integer, _
        ByRef lParam As CAPSTATUS) As Boolean

        Dim bReturn As Boolean
        Dim wSize As Integer
        Dim s As CAPSTATUS
        bReturn = SendMessage(hHwnd, WM_CAP_GET_STATUS,
Marshal.SizeOf(s), s)
        Debug.WriteLine(String.Format("Video Size {0} x {1}",
s.uiImageWidth, s.uiImageHeight))

Of course not the Debug.WriteLine statement. Since fLiveWindow always
returns true ("1") even with the camera disconnected I am either using
it incorrectly, or it simply has limitations. I am guessing I am using
it incorrectly because many (not all) of the other CAPSTATUS structure
values return 0 no matter what the preview window state.

Is there an event I can use that will fire if the connection status to
the camera changes?

Thanks,
Jeremy