ythen's profile - activity

I have solved the problem by installing the binaries from this download link provided by this answer.

It copied all opencv DLLs to C:\Python27 (or maybe other files). But I don't understand why it wouldn't work earlier as I have already included those DLLs into my PATH

As title, I am not able to read video using VideoCapture in python with the following code:

v = 'C:\\test.mp4'
import cv2
cap = cv2.VideoCapture(v)
if cap.isOpened():
  print "Finally"
else:
  print "BOOM"

BOOM is always being printed. sigh

Whereas in VS11, the following code works:

#include "stdafx.h"

#include <opencv2\highgui\highgui.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char* argv[])
{
    string v = "C:\\test.mp4";
    VideoCapture cap;
    cap.open(v);
    if (cap.isOpened()) {
        cout << "Yes!" << endl;
    } else {
        cout << "BOOM" << endl;
    }

    return 0;
}

I do realize there's a number solution in SO, but nothing works for me. I have the following dlls in C:\Python27 and C:\Python27\DLLs, as well as in PATH

• opencv_ffmpeg.dll
• opencv_ffmpeg_64.dll
• opencv_ffmpeg_245_64.dll
• opencv_ffmpeg_245.dll

I have no more idea what have not done.

Please help me. Thank you very much.

After digging into OpenCV's source code, I finally obtain answers to my own questions.

• Values enclosed withtin internalNodes tags

node.left node.right node.featureIdx node.threshold

I'm not sure what's node.left and node.right are for as I can't see them being called anywhere.

• The weights are used to calculate the feature as in below:

float ret = rect[0].weight * CALC_SUM(p[0], _offset) + rect[1].weight * CALC_SUM(p[1], _offset);

• As mentioned in the first bullet, the node.featureIdx are the index of the feature that's being evaluated at that particular node.

It would be best if someone could explain the numbers/values in the cascade.xml entirely. Example in:

<!-- stage 0 -->
<_>
  <maxWeakCount>3</maxWeakCount>
  <stageThreshold>-8.8384145498275757e-001</stageThreshold>
  <weakClassifiers>
    <_>
      <internalNodes>
        0 -1 66 5.1593100652098656e-003</internalNodes>
      <leafValues>
        -8.0555558204650879e-001 8.0694979429244995e-001</leafValues></_>
    <_>
      <internalNodes>
        0 -1 108 1.5044789761304855e-002</internalNodes>
      <leafValues>
        -6.2940740585327148e-001 7.5122624635696411e-001</leafValues></_>
    <_>
      <internalNodes>
        0 -1 99 -4.7172707127174363e-005</internalNodes>
      <leafValues>
        5.5112153291702271e-001 -8.6111217737197876e-001</leafValues></_></weakClassifiers></_>

What are the meanings of these values

      <internalNodes>
        0 -1 99 -4.7172707127174363e-005</internalNodes>

Another question is, how does the program know which feature to use for a particular stage? As far as I know, features are in the form as below

<_>
  <rects>
    <_>
      21 6 3 5 -1.</_>
    <_>
      22 6 1 5 3.</_></rects>
  <tilted>0</tilted></_>

Whereby it's the coordinates of two rectangles, forming something like below:

=-=    = Black colored rectangle
=-=    - White colored rectangle
=-=
=-=
=-=

What are the values -1. and 3. mean? I know it's weights but how is it used to calculate the feature?

Summary

1. What are the meaning of the values inside <internalNodes>?
2. How is the feature calculated? How are the weights in <rects> use?
3. Most importantly, which field denotes that which features are being used in a particular stage/node.

Thanks!

great find! i actually contacted adam yesterday and he provided me with some codes. Anyways, now that I know, I still need to know which features are being tested at a particular stage and node. I would be great if anyone able to help

Is there a way to display visually which Haar features are used at every stage of the classifier?

I have recently trained a classfier to detect vehicles, using opencv_traincascade.exe. For further analysis, I would like to see the features being evaluated at every stage.

Thanks for your help.

It will be great if anyone can supply information about the cascade.xml, what are the meaning of the nodes. Thanks

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