Why amcap shows no data when preview, but still can captured video?

Dear Sir,
I have wrote a AVStream driver for a pc-camera. It has a problem. The
device is described with a capture pin. Amcap can preview and capture
videos. The problem is sometimes amcap preview is nothing, video is
black. I have look into my driver, and my driver transfers image
successfully to upper layer. The data is valid. I also try to capture
a file while the preview window is black. The captured video is fine!
So it looks driver is OK.
My question is why amcap shows nothing? I don't know where is the
problem. Is there any condition that driver feeds images to amcap, but
amcap will not show it on screen?

Maxim
Mon Apr 23 08:34:36 CDT 2007

Can preview in MSN Messenger work?

I remember that some apps (MSN Messenger included) run preview by _querying
the still image bitmap_, not the movie, from the driver, and doing it in a loop
once per some time.

Ensure that your driver has the still image preview bitmap path (forgotten
how is it called, but there was such a path in DirectShow and even VfW)
properly supported.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com

<SaxenKo@gmail.com> wrote in message
news:1177325403.790986.177450@p77g2000hsh.googlegroups.com...
> Dear Sir,
> I have wrote a AVStream driver for a pc-camera. It has a problem. The
> device is described with a capture pin. Amcap can preview and capture
> videos. The problem is sometimes amcap preview is nothing, video is
> black. I have look into my driver, and my driver transfers image
> successfully to upper layer. The data is valid. I also try to capture
> a file while the preview window is black. The captured video is fine!
> So it looks driver is OK.
> My question is why amcap shows nothing? I don't know where is the
> problem. Is there any condition that driver feeds images to amcap, but
> amcap will not show it on screen?
>

Anatoly
Mon Apr 23 16:26:49 CDT 2007

Yes, there is such condition. If the renderer does not support the video
format produced by your driver. What happens when you build a graph in
graphedit, can you successfully build and run preview graph?

Anatoly.

<SaxenKo@gmail.com> wrote in message
news:1177325403.790986.177450@p77g2000hsh.googlegroups.com...
> Dear Sir,
> I have wrote a AVStream driver for a pc-camera. It has a problem. The
> device is described with a capture pin. Amcap can preview and capture
> videos. The problem is sometimes amcap preview is nothing, video is
> black. I have look into my driver, and my driver transfers image
> successfully to upper layer. The data is valid. I also try to capture
> a file while the preview window is black. The captured video is fine!
> So it looks driver is OK.
> My question is why amcap shows nothing? I don't know where is the
> problem. Is there any condition that driver feeds images to amcap, but
> amcap will not show it on screen?
>

Tulup
Tue Apr 24 01:06:44 CDT 2007

hmmm. stupid check, did you turn on "preview" ?)

<SaxenKo@gmail.com> wrote in message
news:1177325403.790986.177450@p77g2000hsh.googlegroups.com...
> Dear Sir,
> I have wrote a AVStream driver for a pc-camera. It has a problem. The
> device is described with a capture pin. Amcap can preview and capture
> videos. The problem is sometimes amcap preview is nothing, video is
> black. I have look into my driver, and my driver transfers image
> successfully to upper layer. The data is valid. I also try to capture
> a file while the preview window is black. The captured video is fine!
> So it looks driver is OK.
> My question is why amcap shows nothing? I don't know where is the
> problem. Is there any condition that driver feeds images to amcap, but
> amcap will not show it on screen?
>

Dave
Tue Apr 24 14:36:31 CDT 2007

Have youe stepped through AMCAP with a debugger to see WHY it's not
previewing...

A good bet is your formant isn't supported directly by the renderer and the
InteligentConnect (which isn't so inteligent) isn't supplying a proper color
space converter....

Are you providing a preview pin or are you forcing Intelignet connect to
insert a tee.

--.- Dave



<SaxenKo@gmail.com> wrote in message
news:1177325403.790986.177450@p77g2000hsh.googlegroups.com...
> Dear Sir,
> I have wrote a AVStream driver for a pc-camera. It has a problem. The
> device is described with a capture pin. Amcap can preview and capture
> videos. The problem is sometimes amcap preview is nothing, video is
> black. I have look into my driver, and my driver transfers image
> successfully to upper layer. The data is valid. I also try to capture
> a file while the preview window is black. The captured video is fine!
> So it looks driver is OK.
> My question is why amcap shows nothing? I don't know where is the
> problem. Is there any condition that driver feeds images to amcap, but
> amcap will not show it on screen?
>

SaxenKo
Tue Apr 24 21:56:04 CDT 2007

After these trying, I found the problem is amcap doesn't refresh its
preview window. When preview is black, I move the amcap window that
makes amcap repaint its window. And the image comes out just one
frame. The situation seems amcap forget to refresh its content. But as
far as I know, amcap uses DShow's IVideoWindow to do previewing. I
doubt there are something I missed when preview just starting. I am
still looking and searching for a solution..

Saxen
Wed Apr 25 01:14:02 CDT 2007

Woo, I solve the problem! I add KSSTREAM_HEADER_OPTIONSF_FLUSHONPAUSE flag to
KSSTREAM_HEADER. And it works fine now ^_^

Actually, I never think about changing this flag and just set it as DDK
sample does. But in fact, it really affects a lot.

"SaxenKo@gmail.com" wrote:

> After these trying, I found the problem is amcap doesn't refresh its
> preview window. When preview is black, I move the amcap window that
> makes amcap repaint its window. And the image comes out just one
> frame. The situation seems amcap forget to refresh its content. But as
> far as I know, amcap uses DShow's IVideoWindow to do previewing. I
> doubt there are something I missed when preview just starting. I am
> still looking and searching for a solution..
>
>

Andy
Mon May 07 05:16:01 CDT 2007

Dear Sir:
I trapped with this situation almost one month. I can preiew with MJPG
and RGB24 successfully, but when I change data format to I420 or YUY2, AmCap
shows nothing sometimes. Thanks for your help.

"Saxen Ko" wrote:

> Woo, I solve the problem! I add KSSTREAM_HEADER_OPTIONSF_FLUSHONPAUSE flag to
> KSSTREAM_HEADER. And it works fine now ^_^
>
> Actually, I never think about changing this flag and just set it as DDK
> sample does. But in fact, it really affects a lot.
>
> "SaxenKo@gmail.com" wrote:
>
> > After these trying, I found the problem is amcap doesn't refresh its
> > preview window. When preview is black, I move the amcap window that
> > makes amcap repaint its window. And the image comes out just one
> > frame. The situation seems amcap forget to refresh its content. But as
> > far as I know, amcap uses DShow's IVideoWindow to do previewing. I
> > doubt there are something I missed when preview just starting. I am
> > still looking and searching for a solution..
> >
> >