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  • How to get webcam video stream bytes in c++

    - by Mr Bell
    I am targeting windows machines. I need to get access to the pointer to the byte array describing the individual streaming frames from an attached usb webcam. I saw the playcap directshow sample from the windows sdk, but I dont see how to get to raw data, frankly, I don't understand how the video actually gets to the window. Since I don't really need anything other than the video capture I would prefer not to use opencv. Visual Studio 2008 c++

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  • Freeing memory twice

    - by benjamin button
    Hi, AFAIK, freeing a NULL pointer will result in nothing. I mean nothing is being done by the compiler/no functionality is performed. Still, I do see some statements where people say that one of the scenarios where memory corruption can occur is "freeing memory twice"? Is this still true?

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  • Pointers to threads

    - by viswanathan
    Suppose i have pointer to a thread like this CWinThread *m_pThread = AfxBeginThread(StartThread, this, THREAD_PRIORITY_NORMAL, 0, 0); Now in my StartThread function assume i did all operations and the function returned like this UINT CClassThread::StartThread(LPVOID pVoid) { return true; } Will my m_pThread be invalid when the return statement is executed?

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  • Creating a console in Java

    - by DeadMG
    When I try to use java.lang.System.console(), I get a null pointer. I can still write to out and read from in, but this only works when I run straight from my IDE. When I run the .jar file directly, nothing happens. How can I create a console like I'd see using std::cout for use in Java?

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  • Moving a unit precisely along a path in x,y coordinates

    - by Adam Eberbach
    I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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  • Are there any good books to learn C++ if you already know Java and C#

    - by JF LR
    Hi, I would like to know if you have any good books that teach C++ programming without repeating basic stuff. In fact, I already well know Java and C#. I also have a basic knowledge in C and assembly, so I understand a little bit pointer arithmetic, manual memory management and heap based allocation. I was looking at O'Reilly's C++ in a Nutshell and was also wondering if this book would be a good choice. Thank you

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  • Does the openssl command line do key strengthening?

    - by chotchki
    If I run the openssl command line in hmac mode (as below), is the key used for the hmac used directly or is it hashed before using it as the key? echo "foo" | openssl dgst -sha256 -binary -hmac "test" | openssl base64 Similarly, when encrypting a file with openssl (as below)is the pass phrase hashed with the salt? (If so how is it done? A pointer to the right source file would be even better.) openssl enc -salt

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  • Generic transparent Qt widget that can catch clicks?

    - by Pieter
    I've figured out how to use QPainter to draw rectangles. Now I want to have a drawing area where if the user clicks, a 1x1 rectangle is drawn where the mouse pointer is. To accomplish this, I assume I need a transparent Qt widget that supports the clicked() signal. How do I make such a transparent widget? Or is there something else I can use? Perhaps I can only use the window's clicked() signal?

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  • AVAudioPlayer error for Iphone Development

    - by KamalBhr
    Hello , I am developing an iphone application using "AVAudioPlayer" for playing a ".wav" file . For this i am adding header file "#import <AVFoundation/AVAudioPlayer.h>" . But while compiling i am getting error like : ".objc_class_name_AVAudioPlayer", referenced from: literal-pointer@__OBJC@__cls_refs@AVAudioPlayer in WebviewController.o ld: symbol(s) not found collect2: ld returned 1 exit status" . So can you please tell me the solution for this type of error.... Thanks & Regards, KamalBhr "

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  • Get specific process memory space

    - by Saul Rennison
    Hi, I have a pointer (void *) to a function and I want to know which process this function belongs to. I have no idea which way to go about it, but I think it's possible by using some form of VirtualQuery trickery. Any help would be appreciated. Thanks in advance,

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  • oprofile unable to produce call graph

    - by aaa
    hello I am trying to use oprofile to generate call graph. Compiler is g++, platform is linux x86-64, linker is gfortran C++ code is compiled with -fno- omit-frame-pointer. oprofile is started with --callgraph=25. report I run with --callgraph. the call graph is produced but it's only includes self time, which is not much use what am I missing?

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  • Setting clustered index in nhibernate

    - by SolBadguy
    Hi. I'm trying to define a property that is not the id as a clustered index in nhibernate, yet I've found no way of doing this. Could anyone give me a pointer of how this is done, or it is something not currently available in nhibernate? Thanks in advance

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  • dynamically bound elements don't subscribe to CSS rules

    - by user961627
    I'm using ajax to dynamically populate a menu. The problem is the dynamically created elements do not follow the CSS rules, although they're created with the right classname. This is surprising. Here's my HTML: <div id='menu1'> <ul class='menu'> <?php $sql = /// /* some sql string, which works */ $result = mysql_query($sql); while($row = mysql_fetch_array( $result )) { $prod_id = $row['product_id']; $prod_name = $row['product_name']; echo "<li data-title='$prod_id' class='menu1_item'>".$prod_name."</li> "; } ?> </ul> </div> <div id='menu2'> <ul class='menu'> </ul> </div> <div id='menu3'> <ul class='menu'> </ul> </div> Here's my jquery: $(".menu1_item").click( function() { $.ajax({ type: "POST", data: { m: '2', id: $(this).attr('data-title') }, url: "fetch_designs.php", success: function(msg){ if (msg != ''){ $("#menu2").html(msg).show(); $(".menu2_item").bind('click',function() { $.ajax({ type: "POST", data: { m: '3', id: $(this).attr('data-title') }, url: "fetch_designs.php", success: function(msg){ if (msg != ''){ $("#menu3").html(msg).show(); } } }); //end menu2 click }); //end if } //end success } }); //end menu1 click }); My CSS is as follows: ul.menu li { cursor:pointer; list-style: none; } #menu1, #menu2, #menu3 { margin:50px; position:relative; display:block; float:left; } .menu1-item .menu2-item .menu3-item { padding:4px; background-color:lightgray; color:black; cursor:pointer; }

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  • how to create media player on iphone?

    - by Jim
    I want to create my own media player. There is so much restriction with default media player control on iphone. I have written lots of applications using default media player. Now i want to write my own media player.If any one can give pointer from where to start to create custom media player. Thanks in advance. Jim.

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  • C question on functions

    - by benjamin button
    some times i see that functions are defined as below: read_dir(dir) char *dir; { DIR * dirp; struct dirent *d; /* open directory */ dirp = opendir(dir); ......... so on here what is the importance of the statement char *dir; what is the intension behind declaring the pointer soon after the function name and then starting the function body.

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  • Cocoa equivalent of diskEvt/kEventClassVolume?

    - by tewha
    We have a drop-down menu of volumes in our UI, and I'd like to update it when a new disk is mounted. In the Classic days, this would involve watching for a diskEvt event. In Carbon, I think this was kEventClassVolume. What's the Cocoa equivalent? (A pointer into Apple's documentation on this would satisfy the question. I've been unable to find anything!)

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  • return an address of a double

    - by bks
    i'm having an issue understanding why the following works: void doubleAddr(double* source, double** dest) { *dest = source; } i get a pointer to a double and want to change the double that dest points to: //usage: int main() { double* num; double* dest; doubleAddr(num, &dest); return 0; } thanks in advance

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  • Help with \0 terminated strings in C#

    - by Joshua
    I'm using a low level native API where I send an unsafe byte buffer pointer to get a c-string value. So it gives me // using byte[255] c_str string s = new string(Encoding.ASCII.GetChars(c_str)); // now s == "heresastring\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0(etc)"; So obviously I'm not doing it right, how I get rid of the excess?

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