Processing Decoded Video for LCD-LED Backlight Display:Post processing of decoded video and local backlight dimming for LCD technology with LED-based backlight

Abstract

Kvaliteten af digitale billeder og videosignaler pa visuelle medier såsom TV- og LCD-skærme bliver hovedsagligt påvirket af to faktorer: displayteknologien og kompressionsstandarder. Nøjagtig viden om karakteristikken af videosignalets visning kan bruges til at udvikle avancerede algoritmer til signalforbedring (billede eller video). Et anvendt tilfælde af sådanne algoritmer er LCD-skærme med dynamisk lokal baggrundsbelysning. Denne afhandling består af to hovedproblemer. For det frste, at designe en algoritme som forbedrer den opfattede visuelle kvalitet af billeder og video og som reducerer energiforbruget i LED-LCD med lokal baggrundsbelysning. For det andet, at fjerne digitale videokodeksartefakter som "blocking" og "ringing" artefakter ved hjlp af efterbehandlingsalgoritmer. Nye algoritmer baseret pa billedkendetegn med optimal balance mellem visuel kvalitet og energiforbrug er blevet udviklet. Derudover er et adaptivt filter til at fjerne flimreartefakter i LED-LCD skrme blevet foreslaet. Der er blevet foretaget adskillige eksperimenter for at teste og sammenholde de foreslaede algoritmer med de nyeste konkurrerende algoritmer. Der kan opsta forskellige typer af visuelle artefakter i en video vist pa en skrm. Det kan vre spatielle artefakter sasom "blocking" og "ringing" eller temporale artefakter såsom flimren eller "mosquito". I denne afhandling foreslås algoritmer til at reducere artefakter i MPEG-2 og H.264/AVC video.The quality of digital images and video signal on visual media such as TV screens and LCD displays is affected by two main factors; the display technology and compression standards. Accurate knowledge about the characteristics of display and the video signal can be utilized to develop advanced algorithms for signal (image or video) enhancement. One particular application of such algorithms is the case of LCDs with dynamic local backlight. The thesis addressed two main problems; first, designing algorithms that improve the visual quality of perceived image and video and reduce power consumption on local LED-LCD backlight. Second, removing the digital video codec artifacts such as blocking and ringing artifacts by post-processing algorithms. A novel algorithm based on image features with optimal balance between visual quality and power consumption was developed. In addition, to remove flickering artifact in LED-LCD display, an adaptive filter was proposed. Several experiments were performed to test and compare the proposed algorithms with the State of the Art algorithms. Different types of visual artifacts may occur in a video content shown on a display. They can be spatial artifacts such as blocking and ringing or temporal artifacts such as flickering or mosquito. In this thesis, some artifact reduction algorithms for MPEG-2 and H.264/AVC video are proposed