Browsing by Subject "Data compression (Telecommunication)."

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Open Access
Simulation of DigiCipher, an HDTV system proposal
(1991) Öktem, Levent
In this thesis, the digital video encoder-decoder parts of an American HDTV system proposal, DigiCipher^^'^ is simulated in an image sequencer, based on the system description sheets. Numerical and subjective performances are tested, by observing and making calculations on the decoder outputs of the system simulation. The performance tests show that the image quality does not have HDTV quality. Considering the very good picture quality in the demonstrations of the designer company (General Instruments), it is suspected that the description sheets do not mention all of the data compression methods used in the system.
Open Access
Three-dimensional facial motion and structure estimation in video coding
(1994) Bozdağı, Gözde
We propose a novel formulation where 3-D global and local motion estimation and the adaptation of a generic wire-frame model to a particular speaker are considered simultaneously within an optical flow based framework including the photometric effects of the motion. We use a flexible wire-frame model whose local structure is characterized by the normal vectors of the patches which are related to the coordinates of the nodes. Geometric constraints that describe the propagation of the movement of the nodes are introduced, which are then efficiently utilized to reduce the number of independent structure parameters. A stochastic relaxation algorithm has been used to determine optimum global motion estimates and the parameters describing the structure of the wire-frame model. For the initialization of the motion and structure parameters, a modified feature based algorithm is used whose performance has also been compared with the existing methods. Results with both simulated and real facial image sequences are provided.