Browsing by Subject "Video Coding"
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Item Open Access Issues in developing a very low bit rate videophone coder(Bilkent University, 1993) Mickos, Roy MikaelThe issues of a suitable transmission image size, general behaviour, and buffer control of a very low bitrate videophone video signal coder to be used in future mobile and public switched telephone networks are addressed. A software simulator of the coder was built so that the performance of the coder and the various alternative methods under consideration could be tested by subjective evaluation. In the case of transmission image size a clear choice between the two alternatives, QCIF and NCIF. is achieved: QCIF. The behaviour of the coder is explained on the basis of some statistical parameters extracted from it. With head-and-shoulders sequences without buffer regulation the coder is succesfiil in allocating bits to those regions in the image containing the most important information. Finally, the buffer control scheme of the coder is analyzed and an alternative method, based on framewise analysis of the bits created for that frame, is developed which is shown to be better than the original.Item Open Access Regularized motion estimation techniques and their applications to video coding(Bilkent University, 1996) Kıranyaz, SerkanNovel regularized motion estimation techniques and their possible applications to video coding are presented. A block matching motion estimation algorithm which extracts better block motion field by forming and ininimizing a suitable energy function is introduced. Based on ciri ¿idciptive structure onto block sizes, cui cidvcinced block matching ¿ilgorithm is presented. The block sizes are adaptively ¿idjusted according to the motion. Blockwise coarse to fine segmentation based motion estimation algorithm is introduced for further reduction on the number of bits that are spent lor the coding of the block motion vectors. Motion estiiricition algorithms which can be used lor ¿iverage motion determination and artificial frame generation by fractional motion compensation are ¿ilso developed. Finallj^, an alternative motion estimation cind compensation technique which defines feciture based motion vectors on the ob ject boundciries and reconstructs the decoded frame from the interpolation of the compensated object boundaries is presented. All the algorithms developed in this thesis are simulated on recil or synthetic images cind their performance is demonstrcited.