Lucas's profile - activity

Hi,

Just a silly question. If I compile an app using OpenCV so as to run it on another computer, do I need to install OpenCV on the target computer, or add some .dll ?

Thanks for your answer

Lucas

Hey!

I tried to store my files in several directories (I switch directory every 25 000 frames) and it works now! Thanks a lot for the idea SR, but do you know from where this issue comes from ? It's a problem to save files in a flooded folder?

in one big directory, each file is named frame_n.tiff where n is the number of the frame

I'm using Windows XP SP3 with a NTFS HDD and the second HDD i tried was an external storage (also in NTFS)

Hi,

I'm currently facing a problem using imwrite function to save frames from a camera (in .tiff format).

My application needs to save 20 frames per second. Everything works fine for the 50 000 first images but after my FPS decrease drastically and increase again around 100 000 images saved.

Here is an image showing the behaviour :

The problem is exactly reproducible (same shape, decrease at 50 000 and increase again at 100 000), and I try my application on a different HDD (with a different size) with the same issue. By putting timers in my code I know that's the imwrite function which is slower during some periods but I don't know why.

I really can't figure out why I get this behaviour. Then if you've got some ideas or solutions to offer...

Thanks for your help

Lucas

Hi,

Is tiff format compressed using imwrite? If it is, what is the compression scheme, and is it lossy ?

Thanks

Lossless jpeg actually exists, that's why I was wondering. If imwrite(test.jpg,CV_IMWRITE_JPEG_QUALITY,100) is lossy, is it possible to have a lossless jpeg compression with OpenCV?

Hi, Do you know how compression parameters works in imwrite. I mean if I choose CV_IMWRITE_JPEG_QUALITY equal to 100 for a jpeg saving or CV_IMWRITE_PNG_COMPRESSION equal to 0 for a png saving, will I have a lossless compression? Thanks

Lucas

Moreover when I add flags I can't open a image with imread and save it to png anymore...

I have still the same issue adding compression info. Thanks anyway for advice.

Hi,

I'm currently working on a video acquisition project in which I have to save frames from a video camera. My software works when I save frames in bmp format but so as to use less space on the hard drive I would like to save them in png format. But when I change the format my application doesn't work anymore (xxx.exe encountered a problem and needs to close). Then I reduced the code to its minimum to save only one image from the video camera (see code below) and I don't understand why it works perfectly in bmp and bugs in png :

#include "stdafx.h"
#include "cv.h"
#include "highgui.h"

using namespace std;
using namespace cv;

int main()
{
    VideoCapture cap(0);
    if(!cap.isOpened())
        return -1;

    Mat frame;
    cap >> frame;
    // Mat frameC;
    // frame.convertTo(frameC,CV_16UC3);
    imwrite("C:\\Frames\\frame.png",frame);

    return 0;
}

It also doesn't work in jpg format. I'm working with Visual Studio 2005 on Windows XP and OpenCV2.1. I tried to convert the image before saving it, but no change (comments in the code) And if I just open and save a png image (without using the video camera) then it works.

Debugging indicates that the problem is in malloc.c (l. 163) :

res = _heap_alloc(size);

And the error is "Unhandled exception at 0x70100fcd in TestOpenCV.exe: 0xC0000005: Access violation reading location 0x00000000" I don't know what is "size" in this function but its type is size_t and its value 32. Then the program stops with the code -1073741819.

I've no idea how to fix this problem or even if it's possible. Maybe the problem comes from the camera or the acquisition card (Intensity Pro from BlackMagicDesign). Any ideas?

Your help or advices are welcome, I'm really stuck with this issue.

Thanks a lot.

Lucas