Masking in video signal

Cilj ovog završnog rada je objasniti maskiranje u video signalu. Osim različitih tipova maskiranja, trebalo je objasniti i proučiti utjecaj maskiranja na kvalitetu prikazanog video signala. Maskiranje je objašnjeno kao smetnja kod promatranja ciljnog podražaja zbog umješanosti drugog maskirnog podražaja koji se u prostoru i vremenu nalazi blizu ciljnog podražaja. Glavni tipovi maskiranja su prostorno i vremensko maskiranje. Prostorno maskiranje objašnjava kako je zbog svojstva ljudskog vizualnog sustava šum (smetnja) u slici jasno vidljiv na „glatkim“ područjima u slici dok je na „grubim“ područjima gotovo neprimjetan. Zbog prevelike brzine izmjene okvira kod vremenskog maskiranja, ljudsko oko ne stigne pratiti sve promjene koje se dogode pa stoga ne primjećuje neke nepravilnosti kod izmjene okvira u videu. Utjecaj maskiranja na kvalitetu prikazanog video signala proučen je provođenjem subjektivnog i objektivnog ocjenjivanja kvalitete videa. Otkriveno je kako je subjektivna metoda pouzdanija. Naime, subjektivna metoda koja predstavlja ocjenu gledatelja puno je pouzdanija s obzirom da ljudsko oko ima sposobnost opažanja utjecaja maskiranja dok računalo to nije u stanju.Goal of this final work is to explain masking in video signal. Beside different types of masking, the influence of masking on quality of displayed video signal had to be explained and explored. Masking is explained as disturbance during observation of target stimulus because of interference of another masking stimulus which is near target stimulus in time and space. Main types of masking are spatial and temporal masking. Spatial masking explains that due to the characteristic of the human visual system, noise (disturbance) in an image is clearly visible on „smooth“ areas of the image while on „rough“ areas it is almost incospicuous. Due to very fast exchange of frames in temporal masking, human eye can't follow all changes that happen and therefore doesn't notice some irregularities at frame exchange in video. Masking effect on the quality of displayed video signal has been studied by conducting subjective and objective evaluation of video. It was revealed that subjective method is more reliable. Namely, subjective method that represents viewers evaluation is more reliable, considering that human eye has the ability to perceive the masking effect while the computer is not capable of such thing