C / C++ / MFC

Re: Is USB camera video compressed and in what format??

10-May-12 6:55

SOLVED
Adding MJPEG driver to my box solved the problem.
Now I need to clean up the test mess I have added to my app!
Moral of the story - when working with OpenCV beware of lack of commnets in the code and always check the logic, it is not the best. I actually feel this is a (logical ) bug and has been in OpenCV since 1.1 and it is still in 2.4.0.

Thanks for all your help.
vaclav

I am trying to display image from USB connected camera.
I know the camera works – I can get a nice image using MS Scanner and Camera wizard.
My problem is that capGetVideoFormat fills the BITMAPINFO biCompression with a value I have no idea what it represents. MSDN is no help in defining this in video frame.
If it is a decompressor info it does not match any of 15 decompression installed on the system.
So
<b>how do I KNOW for sure the USB video is compressed and
how do I use this biCompression value for further processing?</b>

Here is the offending snippet from OpenCV library
BITMAPINFO vfmt;
memset( &vfmt, 0, sizeof(vfmt));
BITMAPINFOHEADER& vfmt0 = vfmt.bmiHeader; // input header
int sz, prevWidth, prevHeight;
if( !capWnd )
return 0;
this fills the biCompression value in question

sz = capGetVideoFormat( capWnd, &vfmt, sizeof(vfmt));
…..............
And this is where attempt to locate the decompressor driver fails

hic = ICLocate (ICTYPE_VIDEO, 0L, (LPBITMAPINFOHEADER) &vfmt,
NULL, ICMODE_DECOMPRESS);

Any suggestions are as always appreciated.
PS I need to stay with capAVI and OpenCV.
Thanks
Vaclav

CPallini10-May-12 7:10

CPallini

10-May-12 7:10

Vaclav_Sal wrote:
My problem is that capGetVideoFormat fills the BITMAPINFO biCompression with a value I have no idea what it represents.

What is its value?

Veni, vidi, vici.

Re: Is USB camera video compressed and in what format??

Vaclav_10-May-12 7:28

Re: Is USB camera video compressed and in what format??

10-May-12 7:28

1196444237

Graham Breach10-May-12 7:59

Graham Breach

10-May-12 7:59

If you convert that to hex you get 47504A4D - the characters "MJPG" backwards. So it looks like you need to use a motion JPEG codec.

Re: Is USB camera video compressed and in what format??

CPallini10-May-12 10:48

CPallini

10-May-12 10:48

As already suggested, is M-JPEG (in particular Pinnacle M-JPEG).

Veni, vidi, vici.

Re: Is USB camera video compressed and in what format??

Vaclav_10-May-12 11:03

Re: Is USB camera video compressed and in what format??

10-May-12 11:03

Ok, that is not one of the drivers in the system.
I hope is is no brainer to find it and add to the system.
I sure would like to know where did you find out how to decode this diCompressor value.
And of course how did MS determine that - where is it "advertized".
I did not see anything like that in device driver properties.
Thanks
Vaclav

Vaclav_10-May-12 12:14

image processing toolkits | batch image processing

10-May-12 12:14

I found this under FOURCC, I guess I just answered my own question.
Next time I'll test for the FOURCC code!

<a href="http://msdn.microsoft.com/en-us/library/windows/desktop/dd375802(v=vs.85).aspx">http://msdn.microsoft.com/en-us/library/windows/desktop/dd375802(v=vs.85).aspx</a>[<a href="http://msdn.microsoft.com/en-us/library/windows/desktop/dd375802(v=vs.85).aspx" target="_blank" title="New Window">^</a>]

DrawImage()

john563210-May-12 4:00

john5632

10-May-12 4:00

How to draw an image excepting balck pixel color using gdi DrawImage function?

Re: DrawImage()

C^hris L^osinger10-May-12 4:26

C^hris L^osinger

10-May-12 4:26

see TransparentBlt[^]

Re: DrawImage()

peilinok10-May-12 21:03

peilinok

10-May-12 21:03

u can select other pixel color when u create the CPen,
CPen(int nPenStyle,int nWidth,COLORREF crColor);

Issue with CreateControl after migration a workspace which was in VC6 to VS2010

V K 210-May-12 1:13

V K 2

10-May-12 1:13

We have migrated our workspace from VC6.0 to VS2010. There is a CreateControl api which is returning 0 after converting to VS2010. Before conversion this was working fine.

What could be the reason for failure.

Re: Issue with CreateControl after migration a workspace which was in VC6 to VS2010

Richard MacCutchan10-May-12 2:26

Richard MacCutchan

10-May-12 2:26

V K 2 wrote:
What could be the reason for failure.

At a guess, there is a bug in your code. Assuming you mean this function[^] then you can use your debugger to see what is happening. You could also check the value of GetLastError() on failures.

Binding 100,000 items to a list box can be just silly regardless of what pattern you are following. Jeremy Likness

what's means？

wangafei9-May-12 21:31

wangafei

9-May-12 21:31

int a:5;
int b:3;

Code-o-mat9-May-12 21:47

Code-o-mat

9-May-12 21:47

See here[^] for example.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> If it doesn't matter, it's antimatter.<

wangafei9-May-12 22:00

wangafei

9-May-12 22:00

thanks！

Malli_S10-May-12 0:29

Malli_S

10-May-12 0:29

Have a look at this[^] also.

[Delegates] [Virtual Desktop] [Tray Me !]

-Malli...!

wangafei10-May-12 16:47

wangafei

10-May-12 16:47

Malli_S

reference to const int

Aabid9-May-12 21:16

Aabid

9-May-12 21:16

void main()
{
const int i = 10;
int& j = (int&)i;

cout << "i= " << i << endl;
cout << "j= " << j << endl;
cout << "&i= " << &i << endl;
cout << "&j= " << &j << endl;

j++;

cout << "j= " << j << endl;
cout << "i= " << i << endl;
}

//output
i= 10
j= 10
&i= 0012FF60
&j= 0012FF60
j= 11
i= 10

Hi,

the code declares a const integer and a reference to it. incrementing a reference adds 1 to j and outputs as 11, that is fine. i was expecting "i" to get modified, since "i" and "j", both having a same memory address, as i print "i", it outputs 10 (or compiler should not allow to increment j). i could not understand the behavior. Could anybody explains me what is going on behind the scene?

regards
Abid

ThatsAlok9-May-12 21:18

ThatsAlok

9-May-12 21:18

Which compiler are you using is it VS or something else?

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow
Never mind - my own stupidity is the source of every "problem" - Mixture

cheers,
Alok Gupta
VC Forum Q&A :- I/IV
Support CRY- Child Relief and You

Aabid9-May-12 21:25

Aabid

9-May-12 21:25

VS 2010, VC++.

Richard MacCutchan9-May-12 22:32

Richard MacCutchan

9-May-12 22:32

If you generate the assembler listing for this code you can see that any reference to i in the code uses the constant value 10, but references to j use a memory variable, initially having a value of 10 but incremented as shown. I am not sure which language rule allows this but I would assume that since j is a reference to an integer then its target becomes a regular value.

I have tried changing j to const int&, but the compiler objects with error C3892.

Binding 100,000 items to a list box can be just silly regardless of what pattern you are following. Jeremy Likness

Code-o-mat9-May-12 22:35

Code-o-mat

9-May-12 22:35

Additionally to what Richard said, if you change your

const int i = 10;

to

volatile const int i = 10;

then you get the expected result (outputting both i and j gives you 11 in the end).

> The problem with computers is that they do what you tell them to do and not what you want them to do. <
> If it doesn't matter, it's antimatter.<