Imed Bouchrika Blog

Convert images to a VLF video

admin — Wed, 17 Mar 2010 09:39:59 +0000

ffmpeg -i image%07d.png -s 640×480 -qscale 10 video.flv

On Using Gait in Forensic Biometrics

admin — Thu, 14 Jan 2010 15:42:27 +0000

As biometrics can now identify people based on individual measures, it appears prudent to translate these techniques for forensic use. As subjects can conceal features associated with identification, prior convictions have used gait and posture to identify suspect. The locations of human vertices are used within instantaneous posture matching. To derive a measure of confidence in this match, we use an automated analysis to determine the variation in the match measure as a function of increasing database size. We can match subjects between videos and assess the confidence in the match measure. We describe how we can derive a match for suspects recorded performing the same criminal act, in surveillance footage, and assess the confidence. As this is the first study of its kind, it raises many points to consider which can aid refinement not just of the matching procedure, but also constraints on the placement of cameras in surveillance.

View-invariant Gait Biometrics

admin — Thu, 05 Mar 2009 16:00:19 +0000

We present a new method for view-point independent gait biometrics. The system relies on a single camera, does not require camera calibration and works with a wide range of camera-views. This is achieved by a formulation where the gait is self-calibrating. These properties make the proposed method particularly suitable for identification by gait, where the advantages of completely unobtrusiveness, remoteness and covertness of the biometric system preclude the availability of camera information and specific walking directions. Moreover, tests on the multi-view CASIA-B database, composed of more than 2270 video sequences with 65 different subjects walking freely along different walking directions have been performed. The obtained results show that human identification by gait can be achieved without any knowledge of internal or external camera parameters with a mean CCR of 73.6% using purely dynamic gait features. The performance of the proposed method is particularly encouraging for application in surveillance scenarios.

Replacing Text in files using Perl

admin — Wed, 18 Feb 2009 19:22:43 +0000

perl -pi.bak -e “s/pattern/new_string/g” *

Ways to promote a site

admin — Thu, 01 Jan 2009 14:02:46 +0000

http://www.wilsonweb.com/articles/checklist.htm

Using FFMPEG to extract or convert videos to Images

admin — Fri, 12 Dec 2008 10:56:24 +0000

The simple command to use to convert a given video video.ext to a set of images preferably with the naming format XXXX.png is :

ffmpeg -i video.ext %4d.png

It will produce images with the naming : 0001.png 0002.png and so on. You can try different image format if needed ( Jpeg, bmp…)

In case you want to extract and convert only a specific portion of the video :

ffmpeg -ss hh:mm:ss -t hh:mm:ss -i video.ext %4d.png
-ss option is the starting point whilst -t option is the duration to be converted.

SQL : Using Count within the Where clause

admin — Mon, 08 Dec 2008 10:53:17 +0000

As trying to make a condition inside an SQL where clause based on the COUNT function or other functions, the trivial one is to use :

SELECT count(items) as cnt from user_items where cnt>3

This is not going to work, and therefore you need to use the following one instead :

SELECT count(items) as cnt from user_items having count(items)>3

In case you want to add a where clause to the SQL statement, here is how it should look :

SELECT count(items) as cnt from user_items where id>1000 having count(items)>3

selinux and HTTPD & svftps under CentOS

admin — Tue, 05 Aug 2008 18:59:15 +0000

to make httpd work and avoid the selinux headaches :

setsebool httpd_disable_trans 1 setsebool httpd_can_network_connect_db=1 service httpd restart

For the FTP server ( vsftpd )

setsebool -P ftpd_disable_trans 1 service vsftpd restart

Mela Festival in Southampton

admin — Sun, 20 Jul 2008 12:06:30 +0000

Took Asma to see the Mela Asian Festival in Southampton, but looks that she didn’t like the sound of music ? or wanted to have some sleep by putting her fingers into her ears.

Asma : now 19 months

admin — Sat, 12 Jul 2008 17:56:52 +0000

A photo taken using an SLR camera.