Fire Detection Algorithms Using Multimodal ... - Bilkent University

CHAPTER 2. FLAME DETECTION IN VISIBLE RANGE VIDEO 122.2 Steps of Video Flame Detection AlgorithmThe proposed video-based fire detection algorithm consists of four sub-algorithms:(i) moving pixels or regions in the current frame of a video are determined, (ii)colors of moving pixels are checked to see if they match to pre-specified fire colors.Afterwards, wavelet analysis in (iii) temporal and (iv) spatial domains are carriedout to determine high-frequency activity within these moving regions. Each stepof the proposed algorithm is explained in detail in the sequel.2.2.1 Moving Region DetectionBackground subtraction is commonly used for segmenting out moving objectsin a scene for surveillance applications. There are several methods in the literature[19], [3], [77]. The background estimation algorithm described in [19]uses a simple IIR filter applied to each pixel independently to update the backgroundand use adaptively updated thresholds to classify pixels into foregroundand background.Stationary pixels in the video are the pixels of the background scene becausethe background can be defined as temporally stationary part of the video.If thescene is observed for some time, then pixels forming the entire background scenecan be estimated because moving regions and objects occupy only some partsof the scene in a typical image of a video. A simple approach to estimate thebackground is to average the observed image frames of the video. Since movingobjects and regions occupy only a part of the image, they conceal a part of thebackground scene and their effect is canceled over time by averaging. Our mainconcern is real-time performance of the system. In Video Surveillance and Monitoring(VSAM) Project at Carnegie Mellon University [19] a recursive backgroundestimation method was developed from the actual image data using l1-norm basedcalculations.Let I(x, n) represent the intensity value of the pixel at location x in the n−thvideo frame I. Estimated background intensity value, B(x, n + 1), at the same