| Paper: | SPCOM-P3.5 | ||
| Session: | Joint Source/Channel Coding and Quantization | ||
| Time: | Wednesday, May 19, 09:30 - 11:30 | ||
| Presentation: | Poster | ||
| Topic: | Signal Processing for Communications: Compression, Coding, and Modulation | ||
| Title: | ANALYSIS OF QUANTIZATION NOISE FEEDBACK IN CAUSAL TRANSFORM CODING | ||
| Authors: | David Mary; Université de Nice | ||
| Dirk Slock; Institut Eurécom | |||
| Abstract: | The performances of the LDU (Lower-Diagonal-Upper (LDU) factorization) transform were recently shown to be equivalent tothose of the Karhunen-Loeve Transform (KLT, which is optimalfor Gaussian sources) in the limit of high rates. In thispaper, we further investigate both theoretically and empiricallythe performances of the LDU for actual transform coding (TC) schemes. Previous results showed that the LDU should be implemented in closed loop around the quantizers, though this leads to a noise feedback effect, similar to that occuring in DPCM systems. We develop in this paper novel analyses of these effects on the distortion-rate functions and coding gains. The proposed analyses compare previous results obtained for an hypothetical TC system for which the bit allocation is optimal and the rate is high, to those obtained for practical TC systems whose bit allocation is nearly optimal. By means of a theorem and numerical results, evidence is given that ordering the subsignals in the source vector by order of decreasing variances minimizes the quantization noise feedback. For the investigated practical systems, we show that deviations from the high rate assumptionsarise below 3 b/s. The effects of the noise feedback become non negligible below 2 b/s. The LDU competes with the KLT above 2.5 b/s. | ||
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