CodeBook background subtraction with moving objects - opencv

Question

I am trying to use CodeBook method for OpenCV to subtract the background. So far so good, but I am not sure if I can update the codebook for moving objects after some time span, say 5 minutes, I need to update the codebook after which I get lots of moving objects. How do I make sure that after 5 minutes I have a background that needs to be updated?
Thanks for the tips!

Answer 1

kim's algorithm supposedly has a cache layer, i did not dig deep enough into opencv implementation to know how to have a workable version that works with exposure problem.
notes
opencv book(which i havent read) should have the info you need if it's there at all
this is only 1 channel and not in yuv although it can be extended
needs more work on speed/testing (you can of course turn on optimization in compiler)
background subtraction is a buzzy word. try "change detection"
bgfg_cb.h
#ifndef __bgfg_cb_h__
#define __bgfg_cb_h__
//http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.148.9778&rep=rep1&type=pdf
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
#include <time.h>
using namespace cv;
using namespace std;
struct codeword {
float min;
float max;
float f;
float l;
int first;
int last;
bool isStale;
};
extern int alpha ;
extern float beta ;
extern int Tdel ,Tadd , Th;
void initializeCodebook(int w,int h);
void update_cb(Mat& frame);
void fg_cb(Mat& frame,Mat& fg);
#endif
bgfg_cb.cpp
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <iostream>
#include <time.h>
#include "bgfg_cb.h"
using namespace cv;
using namespace std;
vector<codeword> **cbMain;
vector<codeword> **cbCache;
int t=0;
int alpha = 10;//knob
float beta =1;
int Tdel = 200,Tadd = 150, Th= 200;//knobs
void initializeCodebook(int w,int h)
{
cbMain = new vector<codeword>*[w];
for(int i = 0; i < w; ++i)
cbMain[i] = new vector<codeword>[h];
cbCache = new vector<codeword>*[w];
for(int i = 0; i < w; ++i)
cbCache[i] = new vector<codeword>[h];
}
void update_cb(Mat& frame)
{
if(t>10) return;
for(int i=0;i<frame.rows;i++)
{
for(int j=0;j<frame.cols;j++)
{
int pix = frame.at<uchar>(i,j);
vector<codeword>& cm =cbMain[i][j];
bool found = false;
for(int k=0;k<cm.size();k++)
{
if(cm[k].min<=pix && pix<=cm[k].max && !found)
{
found=true;
cm[k].min = ((pix-alpha)+(cm[k].f*cm[k].min))/(cm[k].f+1);
cm[k].max = ((pix+alpha)+(cm[k].f*cm[k].max))/(cm[k].f+1);
cm[k].l=0;
cm[k].last=t;
cm[k].f++;
}else
{
cm[k].l++;
}
}
if(!found)
{
codeword n={};
n.min=max(0,pix-alpha);
n.max=min(255,pix+alpha);
n.f=1;
n.l=0;
n.first=t;
n.last=t;
cm.push_back(n);
}
}
}
t++;
}
void fg_cb(Mat& frame,Mat& fg)
{
fg=Mat::zeros(frame.size(),CV_8UC1);
if(cbMain==0) initializeCodebook(frame.rows,frame.cols);
if(t<10)
{
update_cb(frame);
return;
}
for(int i=0;i<frame.rows;i++)
{
for(int j=0;j<frame.cols;j++)
{
int pix = frame.at<uchar>(i,j);
vector<codeword>& cm = cbMain[i][j];
bool found = false;
for(int k=0;k<cm.size();k++)
{
if(cm[k].min<=pix && pix<=cm[k].max && !found)
{
cm[k].min = ((1-beta)*(pix-alpha)) + (beta*cm[k].min);
cm[k].max = ((1-beta)*(pix+alpha)) + (beta*cm[k].max);
cm[k].l=0;
cm[k].first=t;
cm[k].f++;
found=true;
}else
{
cm[k].l++;
}
}
cm.erase( remove_if(cm.begin(), cm.end(), [](codeword& c) { return c.l>=Tdel;} ), cm.end() );
fg.at<uchar>(i,j) = found?0:255;
if(found) continue;
found = false;
vector<codeword>& cc = cbCache[i][j];
for(int k=0;k<cc.size();k++)
{
if(cc[k].min<=pix && pix<=cc[k].max && !found)
{
cc[k].min = ((1-beta)*(pix-alpha)) + (beta*cc[k].min);
cc[k].max = ((1-beta)*(pix+alpha)) + (beta*cc[k].max);
cc[k].l=0;
cc[k].first=t;
cc[k].f++;
found=true;
}else
{
cc[k].l++;
}
}
if(!found)
{
codeword n={};
n.min=max(0,pix-alpha);
n.max=min(255,pix+alpha);
n.f=1;
n.l=0;
n.first=t;
n.last=t;
cc.push_back(n);
}
cc.erase( remove_if(cc.begin(), cc.end(), [](codeword& c) { return c.l>=Th;} ), cc.end() );
for(vector<codeword>::iterator it=cc.begin();it!=cc.end();it++)
{
if(it->f>Tadd)
{
cm.push_back(*it);
}
}
cc.erase( remove_if(cc.begin(), cc.end(), [](codeword& c) { return c.f>Tadd;} ), cc.end() );
}
}
}
main.cpp
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "bgfg_cb.h"
#include <iostream>
using namespace cv;
using namespace std;
void proc()
{
Mat frame,fg,gray;
VideoCapture cap("C:/Downloads/S2_L1.tar/S2_L1/Crowd_PETS09/S2/L1/Time_12-34/View_001/frame_%04d.jpg");
cap >> frame;
initializeCodebook(frame.rows,frame.cols);
for(;;)
{
cap>>frame;
cvtColor(frame,gray,CV_BGR2GRAY);
fg_cb(gray,fg);
Mat cc;
imshow("fg",fg);
waitKey(1);
}
}
int main(int argc, char ** argv)
{
proc();
cin.ignore(1);
return 0;
}