| 1. |
- Eriksson, Tomas, et al.
(författare)
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On the block size of trellis quantizers
- 2005
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Ingår i: Proceedings. DCC 2005. Data Compression Conference. - 0769523099 ; , s. 457-457
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. In this paper, we examine the effect of block size on the performance of trellis based quantization. In particular, the Viterbi and tailbiting BCJR algorithms are compared. It is shown that for short blocks of data, the T-BCJR algorithm achieves a superior performance over the Viterbi algorithm (VA). One approach is to use the maximum a posteriori probability (MAP) heuristic and the T-BCJR algorithm. If the MAP-encoder does not produce a tailbiting state sequence, the path is modified for a number of stages at the beginning and end of the block such that it tailbites. The enclosed figure shows MSE as a function of block size and sample position, respectively, for a rate R=1 bit per sample, 32-state trellis quantizer and an IID Gaussian source. The effects of start-up are clearly visible. For the T-BCJR algorithm, the distortion is evenly distributed across the whole block. The performance decrease for short blocks stems from the increase in the number of tailbiting violations for short blocks and the suboptimal modification to ensure tailbiting. The results presented here hold for a large class of trellis constructions, such as TCQ
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| 2. |
- Eriksson, Tomas, et al.
(författare)
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Short-block variable-length trellis quantization
- 2005
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Ingår i: Proc., 2005 IEEE Data Compression Conf., Snowbird. - 1068-0314. - 0769523099 ; , s. 251-260
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Konferensbidrag (refereegranskat)abstract
- We present two methods for variable-rate trellis quantization. Both methods utilize trellis codes based on linear congruential (LC) recursions. LC code trellises have good pseudo-random properties and are easily adapted to serve reconstruction alphabets of different sizes. The first method finds an entropy-constrained code only by optimizing over a scale factor. The scale factor modifies an initial reproducer alphabet in order to skew the associated set of codeword lengths. Using a Lagrangian formulation and the maximum a posteriori (MAP) heuristic, we also develop an entropy-constrained trellis quantizer suitable for short blocks of data. Here the tailbiting BCJR algorithm is used to find the MAP path in the trellis. Simulation results for the Gaussian and Laplacian distributions show that the proposed method is competitive with the best in the literature.
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| 3. |
- Eriksson, Tomas, et al.
(författare)
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Trellis based variable rate residual image coding over noisy channels
- 2006
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Ingår i: Proceedings. DCC 2006. Data Compression Conference. - 1068-0314. - 0769525458 ; , s. 252-261
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Konferensbidrag (refereegranskat)abstract
- We consider the lossy image compression problem and propose a model-residual approach. Polynomial basis images encode the model image and powerful new trellis codes quantize the residual part. A simple bit allocation scheme determines the residual bit rates and a variety of rates are attainable without entropy coding. The trellis structure is also used to form a joint source and channel coding scheme for the residual components. Results are shown for the 0.4-1.6 bits per pixel region. Comparisons are made to several state-of-the-art techniques and show that the proposed scheme is very competitive
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