After the cnierynce of nunierous Internet streaming applications. rate-distortion (R-I)) modeling of scalable video encalers has bceonie an iniportant issue. In this paper. we examine the performance of existing R-D niodels in scalable coders hy using the example of MPEG-4 FGS antl PIGS, and propose a novel U-D niodel based on approximation theory. Experinientd results denionstrate that the proposed nlMlel is very accurate antl significantly oulperforms those in previous work. Since R-D curves are central to a wide range of video applications (e.g., optimal hits allocation [IS]. constant quality control [17], etc.), they continuously attract significant attention in research literature. R-D models can be classified into two categories based on the theory they apply: models based on Shannon's rate-distortion theory 151 and [hose derived from high-rate quanrindtion theory [I]. The former assumes that sources are coded using very long (infinite) blocks. while the latter assumes that the encoding rate is arbitrarily high [14]. These two theories are complementary and, as shown in [ 6 ] , converge to the same lower hound D N e-= when the input block size goes to infinity. However. since block length cannot be infinite in real coding systems, it is widely recognized that classical rate-distortion theory is often not suitable for accurate modeling of actual R-D curves (141. In addition, current transform-based encoders achieve high compression ratios and often produce low-bitrate signals 1131, which means that the high-bitrate assumption of the quantization theory no longer holds [Z]. [13]. Therefore, adjustable parameters are often incorporated into the theoretical R-D models to keep up with the complexity of coding systems and the diversity of video sources (e.g., [9]. Recall that most current R-D models are built for images or non-scolrible video coders. (1) where mz is the variance of the source and ( I -care constants. This paper is o r p i z e d as follows. In Section 2. we brieHy overview current R-D models and show their perfomrance in scalable coders. In Section 3. we analyze distortion in scalable coders and derive a novel K-D model from the angle of approximation theory. We also denionstrate the accuracy of the proposed R-D model in various scalable video sequences. Section 4 concludes In this section, we give a brief Overview of related work and analyze the applicability of current R-D models to scalable coders. In rate-distortion theory, there arenoexplicit R-D models. but only upper and lower bounds for general sources Ill]: this paper. where Q is the entropy power and U; is the variance of a Gaussian distributed source. In contrast, there are two kinds of lower bounds in high-rate quantization theory [SI: the minimum distortion D I ( N ) attainable for a constrained number of quantization levels N , and the mininium distortion Dz(R) attainable for a constrained bitrate R. However, in bath quantization and rate-
In and REF , the authors compared their new R-D models against nonscalable and layered R-D models for accuracy.
Rate-distortion modeling of scalable video coders
2004 International Conference on Image Processing, 2004. ICIP '04.
2004 International Conference on Image Processing, 2004. ICIP '04.
Computer Science