Jan Bormans

Optimal memory organization for scalable texture codecs in MPEG-4

This paper addresses the problem of minimizing memory size and memory accesses in multiresolution texture coding architectures for discrete cosine transform (DCT) and wavelet-based schemes used, for example, in virtual-world walk-throughs or facial animation scenes of an MPEG-4 system. The problem of minimizing the memory cost is important since memory accesses, memory bandwidth limitations, and in general the correct handling of the data flows have become the true critical issues in designing high-speed and low-power video-processing architectures and in efficiently using multimedia processors. For instance, the straightforward implementation of a multiresolution texture codec typically needs an extra memory buffer of the same size as the image to be encoded/decoded. We propose a new calculation schedule that reduces this buffer memory size with up to two orders of magnitude, while still ensuring a number of external (off-chip) memory accesses that is very close to the theoretical minimum. The analysis is generic and is therefore useful for both wavelet and multiresolution DCT codecs.

Performance and complexity co-evaluation of the advanced video coding standard for cost-effective multimedia communications

The advanced video codec (AVC) standard, recently defined by a joint video team (JVT) of ITU-T and ISO/IEC, is introduced in this paper together with its performance and complexity co-evaluation. While the basic framework is similar to the motion-compensated hybrid scheme of previous video coding standards, additional tools improve the compression efficiency at the expense of an increased implementation cost. As a first step to bridge the gap between the algorithmic design of a complex multimedia system and its cost-effective realization, a high-level co-evaluation approach is proposed and applied to a real-life AVC design. An exhaustive analysis of the codec compression efficiency versus complexity (memory and computational costs) project space is carried out at the early algorithmic design phase. If all new coding features are used, the improved AVC compression efficiency (up to 50% compared to current video coding technology) comes with a complexity increase of a factor 2 for the decoder and larger than one order of magnitude for the encoder. This represents a challenge for resource-constrained multimedia systems such as wireless devices or high-volume consumer electronics. The analysis also highlights important properties of the AVC framework allowing for complexity reduction at the high system level: when combining the new coding features, the implementation complexity accumulates, while the global compression efficiency saturates. Thus, a proper use of the AVC tools maintains the same performance as the most complex configuration while considerably reducing complexity. The reported results provide inputs to assist the profile definition in the standard, highlight the AVC bottlenecks, and select optimal trade-offs between algorithmic performance and complexity.

Cost-Efficient C-Level Design of an MPEG-4 Video Decoder

Advanced multimedia systems intrinsically have a high memory cost, making the design of high performance, low power solutions a real challenge. Rather than spending most effort on implementation platform dependent optimization steps, we advocate a methodology and tool that involve C-level platform independent optimizations. This approach is applied to an MPEG-4 video decoder, leading to high performance, reusable C code. When mapped on (embedded) processors, this allows for lower clock rates, enabling low power realizations.

A Scalable Architecture for MPEG-4 Wavelet Quantization

Wavelet-based image compression has been adopted in MPEG-4 for visual texture coding. All wavelet quantization schemes in MPEG-4—Single Quantization (SQ), Multiple Quantization (MQ) and Bi-level Quantization—use Embedded Zero Tree (EZT) coding followed by an adaptive arithmetic coder for the compression and quantization of a wavelet image. This paper presents the OZONE chip, a dedicated hardware coprocessor for EZT and arithmetic coding. Realized in a 0.5 μm CMOS technology and operating at 32 MHz, the EZT coder is capable of processing up to 25.6 Mega pixel-bitplanes per second. This is equivalent to the lossless compression of 31.6 8-bit grayscale CIF images (352 × 288) per second. The adaptive arithmetic coder processes up to 10 Mbit per second. The combination of the performance of the EZT coder and the arithmetic coder allows the OZONE to perform visual-lossless compression of more than 30 CIF images per second. Due to its novel and scalable architecture, parallel operation of multiple OZONEs is supported. The OZONE functionality is demonstrated on a PC-based compression system.

Implementation of a scalable MPEG-4 wavelet-based visual texture compression system

The realization of new MPEG-4 functionality, applicable to 3D graphics texture compression and image database access over the Internet, is demonstrated in a PC-based compression system. Applying our system-level design methodologies effectively removes all implementation bottlenecks. A first-of-a-kind ASIC, called Ozone, accelerates the Embedded Zero Tree based encoding and is capable of compressing 30 color CIF images per second.

A scalable architecture for MPEG-4 embedded zero tree coding

Wavelet-based image compression has been adopted in emerging standards such as MPEG-4 and JPEG2000. An embedded zero tree (EZT) coding scheme enables the compression and the quantization of the wavelet coefficients. This paper presents the OZONE chip, a dedicated hardware solution for an EZT coding coprocessor. Realized in a 0.5 /spl mu/m CMOS technology, the OZONE performs visual-lossless compression of more than 30 CIF images per second. Due to its new scalable architecture, parallel operation of multiple OZONEs is supported.

View-dependent, scalable texture streaming in 3-D QoS with MPEG-4 visual texture coding

Multimedia applications are characterized by high resource demands (computing power, memory, network bandwidth, and power consumption). Efficient implementations aim at reducing these resources to a minimum, which is of the utmost importance for small, low-cost terminals in low-bandwidth networks. Resource savings can also be obtained by content adaptation without impeding the quality of the decoded audio-visual media. In this context, the paper analyzes texture adaptation and streaming for three-dimensional applications, using MPEG-4s Visual Texture Coding tool, in conjunction with eXtensible Markup Language (XML)-based description techniques. Augmented features for content adaptation are supported, such as region selection, accompanied by resolution and SNR settings. As a result, quality is optimized for the terminals computing capabilities and display resolution, taking the users viewing conditions into account. Moreover, the instantaneous bandwidth utilization is highly reduced in streaming scenarios.

Terminal QoS: advanced resource management for cost-effective multimedia appliances in dynamic contexts

Advanced multimedia applications such as those being developed within Ambient Intelligence typically share common characteristics, viz. the need to be able to access a wide variety of multimedia content using a heterogeneous communication and consumption infrastructure, in combination with low cost and low power requirements. The fact that a large variety of heterogeneous multimedia content has potentially to be dealt with (depending on user preferences and interaction) can lead to a cost inefficient overdimensioning of network and terminal resources. To tackle this issue, advanced resource management techniques are needed that make trade-offs on the fly to match the content bandwidth, the media coding and rendering complexity to the available network and terminal resources, while maximizing the overall perceived quality. This process is often referred to as Quality of Service (QoS) management. This paper illustrates the need to perform aspects of the overall QoS management on the terminal (Terminal QoS). The Terminal QoS for 3D graphics rendering on a software terminal (TriMedia set-top box) and reconfigurable platform is described in detail.

Implementation Aspects of FIR filtering in a Wavelet Compression Scheme

Publisher Summary The 2D fast wavelet transform of an image represents the original image by a hierarchy of wavelet images, corresponding to different quality or resolution levels. The image pyramid structure is generated by repeatedly filtering and subsampling the preceding image level, starting from the input image. This chapter analyzes the implication of some finite impulse response (FIR) filter implementation choices on the very-large-scale integration (VLSI) cost for the wavelet transform. Because the number of multiplications involved in the Wavelet decomposition represents a serious bottleneck, the chapter compares a number of techniques for reducing this number of multiplications. Traversing the search space along the minimal implementation cost path leads to the use of Sweldens Lifting Scheme, applied on wavelet filter banks with rational coefficients, having integer nominators and power-of-two denominators. Simulation results suggest that the VLSI area cost can be reduced with approximately a factor 3 when implementing fixed, instead of programmable filter coefficients. For large images or large filters, successive subimage convolutions should be applied using the overlap-add or overlap-save method, with some preference to the latter.

A scalable MPEG-4 wavelet-based visual texture compression system with optimized memory organization

The realization of new MPEG-4 functionality, applicable to three-dimensional graphics texture compression and image database access over the Internet, is demonstrated on a heterogeneous platform with several unique features. First, applying our system-level design methodologies effectively removes all data transfer and storage overhead that comprises the main bottleneck in the original system description. Second, a first-of-a-kind application specific solution, called Ozone, accelerates the embedded-zero-tree based encoding and is capable of compressing 30 color CIF images per second. The entire application is running on the Ozone coupled to a PC.