应用于JPEG2000的5/3提升小波的VLSI结构设计

提出一种基于提升算法（lifting scheme）实现JPEG2000编码系统中的二维离散小波变换（Discrete Wavelet Transform）的并行阵列式的VLSI结构设计方法.该结构由一个行处理器和一个列处理器组成,行、列处理器通过时分复用同时进行滤波,用优化的移位加操作替代乘法操作,采用嵌入式数据延拓算法处理边界延拓.整个结构采用流水线设计方法,减少了运算量,提高了硬件资源利用率,该结构可应用于JPEG2000图像编码芯片中.     

JPEG2000小波变换器的VLSI结构设计

新一代静止图像压缩标准JPEG2000将离散小波变换(DWT)作为其核心变换技术,并推荐采用推举体制(lifting)快速算法来实现.空间组合推举体制算法(SCLA)大大降低了lifting的运算量.当选用9/7小波滤波器时,SCLA的乘法运算量只有lifting的7/12.本文提出了一种实现SCLA算法的VLSI结构,降低了基于lifting实现的运算量, 加快了变换的速度,减小了电路的规模.本文的二维正反小波变换器已经作为单独的IP核应用于我们目前正在开发的JPEG2000图像编解码芯片中.     

An Efficient Pipeline Architecture and Memory Bit-Width Analysis for Discrete Wavelet Transform of the 9/7 Filter for JPEG 2000

In this paper, we propose an efficient pipeline architecture for the DWT 9/7 filter defined in JPEG 2000. The proposed architecture is composed of column and row processors to perform the separable 2-D DWT. Based on the rescheduling DWT algorithm, we derive a new data flow graph to shorten the critical path. The proposed 1-D column processor requires less pipeline registers to achieve about the same critical path compared with other lifting-based architectures. For the row processor, the data dependency of each lifting step is reduced to only two computation nodes and therefore more pipeline registers can be applied to achieve higher processing speed without increasing the internal memory size in the 2-D case. That is, for an N × N image, it only requires 4N internal memory to perform the row-wise transform. For the memory bit-width analysis, we use software simulation to reduce the memory bit-width for various compression ratios. Since a portion of information from least significant bits of DWT coefficients would be discarded after EBCOT-tier2 processing, one can decrease the data width of internal memory to perform various compression ratios of JPEG 2000 coding, especially at the low-bit rates. Our simulation results suggest that it is practically possible to design the energy-aware memory architecture to further reduce the power consumption in the future work.     

Two-Symbol FPGA Architecture for Fast Arithmetic Encoding in JPEG 2000

JPEG 2000 is one of the most popular image compression standards offering significant performance advantages over previous image standards. High computational complexity of the JPEG 2000 algorithms makes it necessary to employ methods that overcomes the bottlenecks of the system and hence an efficient solution is imperative. One such crucial algorithms in JPEG 2000 is arithmetic coding and is completely based on bit level operations. In this paper, an efficient hardware implementation of arithmetic coding is proposed which uses efficient pipelining and parallel processing for intermediate blocks. The idea is to provide a two-symbol coding engine, which is efficient in terms of performance, memory and hardware. This architecture is implemented in Verilog hardware definition language and synthesized using Altera field programmable gate array. The only memory unit used in this design is a FIFO (first in first out) of 256 bits to store the CX-D pairs at the input, which is negligible compared to the existing arithmetic coding hardware designs. The simulation and synthesis results show that the operating frequency of the proposed architecture is greater than 100 MHz and it achieves a throughput of 212 Msymbols/sec, which is double the throughput of conventional one-symbol implementation and enables at least 50% throughput increase compared to the existing two-symbol architectures.     

Optimization Design of Biorthogonal Wavelet Filter Banks for Extending JPEG 2000 Standard Part-2

A generic optimization design approach of biorthogonal wavelet filter banks (BWFB) for extending the JPEG 2000 standard part-2 is presented in this paper. This approach adopts Vaidyanathan optimal coding gain criterion to design the BWFB, and adopts peak signal-to-noise ratio (PSNR) as the criterion to optimize this BWFB. A functional relation between the general BWFB and their lifting scheme is derived in the first place with respect to one free variable, so that the optimization design of the BWFB is easier and more convenient. In addition, a general image model is formulated as a first-order Markov process driven by Gaussian white noise. It is taken as an input of two-channel filter banks which satisfy perfect reconstruction (PR) condition to realize subband coding for obtaining the optimal BWFB according to the Vaidyanathan optimal coding gain criterion. Finally, a new 9/7 BWFB with rational coefficients is proposed for extending the JPEG 2000 standard part-2, with PSNR of reconstructed images only 0.20 dB lower than standard CDF 9/7 BWFB for infrared thermal image compressions.     

Design of IIR orthogonal wavelet filter banks using lifting scheme

The lifting scheme is well known to be an efficient tool for constructing second generation wavelets and is often used to design a class of biorthogonal wavelet filter banks. For its efficiency, the lifting implementation has been adopted in the international standard JPEG2000. It is known that the orthogonality of wavelets is an important property for many applications. This paper presents how to implement a class of infinite-impulse-response (IIR) orthogonal wavelet filter banks by using the lifting scheme with two lifting steps. It is shown that a class of IIR orthogonal wavelet filter banks can be realized by using allpass filters in the lifting steps. Then, the design of the proposed IIR orthogonal wavelet filter banks is discussed. The designed IIR orthogonal wavelet filter banks have approximately linear phase responses. Finally, the proposed IIR orthogonal wavelet filter banks are applied to the image compression, and then the coding performance of the proposed IIR filter banks is evaluated and compared with the conventional wavelet transforms.     

Generalized block-lifting factorization of M-channel biorthogonal filter banks for lossy-to-lossless image coding

Generalized block-lifting factorization of M-channel (M > 2) biorthogonal filter banks (BOFBs) for lossy-to-lossless image coding is presented in this paper. Since the proposed block-lifting structure is more general than the conventional lifting factorizations and does NOT require many restrictions such as paraunitary, number of channels, and McMillan degree in each building block unlike the conventional lifting factorizations, its coding gain is higher than that of the previous methods. Several proposed BOFBs are designed and applied to image coding. Comparing the results with conventional lossy-to-lossless image coding structures, including the 5/3- and 9/7-tap discrete wavelet transforms in JPEG 2000 and a 4 × 8 hierarchical lapped biorthogonal transform in JPEG XR, the proposed BOFBs achieve better result in both objective measure and perceptual visual quality for the images with a lot of high-frequency components.     

JPEG2000并行阵列式小波滤波器的VLSI结构设计

提出一种基于提升算法实现JPEG2000编码系统中的二维离散小波变换(Discrete Wavelet Transform)的并行阵列式的VLSI结构设计方法.利用该方法所得结构由两个行处理器,一个列处理器以及少量行缓存组成;行列处理器内部是由并行阵列式的处理单元组成;能使行和列滤波器同时进行滤波,用优化的移位加操作替代乘法操作.整个结构采用流水线的设计方法处理,在保证同样的精度下,大大减少了运算量和提高了硬件资源利用率,几乎达到100％,加快了变换速度,也减少了电路的规模.该结构对于N×N大小的图像,处理速度达到O(N²/2)个时钟周期.二维离散小波滤波器结构已经过FPGA验证,并可作为单独的IP核应用于正在开发的JPEG2000图像编解码芯片中.     

Optimal wavelet filter design for remote sensing image compression

A new approach for designing the Biorthogonal Wavelet Filter Bank （BWFB） for the purpose of image compression is presented in this letter. The approach is decomposed into two steps. First, an optimal filter bank is designed in theoretical sense based on Vaidyanathan＇s coding gain criterion in SubBand Coding （SBC） system. Then the above filter bank is optimized based on the criterion of Peak Signal-to-Noise Ratio （PSNR） in JPEG2000 image compression system, resulting in a BWFB in practical application sense. With the approach, a series of BWFB for a specific class of applications related to image compression, such as remote sensing images, can be fast designed. Here, new 5/3 BWFB and 9/7 BWFB are presented based on the above approach for the remote sensing image compression applications. Experiments show that the two filter banks are equally performed with respect to CDF 9/7 and LT 5/3 filter in JPEG2000 standard; at the same time, the coefficients and the lifting parameters of the lifting scheme are all rational, which bring the computational advantage, and the ease for VLSI implementation.     

Arithmetic Unit for Finite Field ${rm GF}(2^{m})$

An arithmetic unit (AU) that performs all basic arithmetic operations in the finite field GF(2^m) is presented, where m is an arbitrary integer. The presented finite field AU consists of an arithmetic processor, an arithmetic logic unit, and a control unit. The proposed AU has low circuit complexity and is programmable, so that any error-correcting decoder that operates in GF(2^m) can be easily implemented with this AU.     

Flipping structure: an efficient VLSI architecture for lifting-based discrete wavelet transform

In this paper, an efficient very large scale integration (VLSI) architecture, called flipping structure, is proposed for the lifting-based discrete wavelet transform. It can provide a variety of hardware implementations to improve and possibly minimize the critical path as well as the memory requirement of the lifting-based discrete wavelet transform by flipping conventional lifting structures. The precision issues are also analyzed. By case studies of the JPEG2000 default lossy (9,7) filter, an integer (9,7) filter, and the (6,10) filter, the efficiency of the proposed flipping structure is demonstrated.     

JPEG2000算术编码器的改进算法与实现

作为新一代静止图像压缩标准的JPEG2000标准拥有压缩比高,支持多分辨率等优点。JPEG2000的编码方式采用了嵌入式码块编码(EBCOT)方式,在编码过程中采用了MQ算术编码。文中分析了它对内容单一、信息量少图像编解码的不足,针对这些不足提出了一种对MQ算术编码器流程的改进算法。这种算法提高了JPEG2000对简单图像压缩的PSNR值,使解码后的图像更加清晰。     

Automated optimization of JPEG 2000 encoder options based on model observer performance for detecting variable signals in X-ray coronary angiograms

Image compression is indispensable in medical applications where inherently large volumes of digitized images are presented. JPEG 2000 has recently been proposed as a new image compression standard. The present recommendations on the choice of JPEG 2000 encoder options were based on nontask-based metrics of image quality applied to nonmedical images. We used the performance of a model observer [non-prewhitening matched filter with an eye filter (NPWE)] in a visual detection task of varying signals [signal known exactly but variable (SKEV)] in X-ray coronary angiograms to optimize JPEG 2000 encoder options through a genetic algorithm procedure. We also obtained the performance of other model observers (Hotelling, Laguerre-Gauss Hotelling, channelized-Hotelling) and human observers to evaluate the validity of the NPWE optimized JPEG 2000 encoder settings. Compared to the default JPEG 2000 encoder settings, the NPWE-optimized encoder settings improved the detection performance of humans and the other three model observers for an SKEV task. In addition, the performance also was improved for a more clinically realistic task where the signal varied from image to image but was not known a priori to observers [signal known statistically (SKS)]. The highest performance improvement for humans was at a high compression ratio (e.g., 30:1) which resulted in approximately a 75% improvement for both the SKEV and SKS tasks.     

一种基于流水线的MQ编码器FPGA设计

提出了一种应用于JPEG2000标准的4级流水线MQ编码器设计方案.采用状态超前更新,前导0位超前检测和字节输出缓冲策略,解决了在上下文(CX)状态表更新、归一化及字节输出过程中的反馈和循环等问题,提高了编码效率.同时,对关键路径处算法进行优化,提高了系统工作的时钟频率.该设计使用VHDL语言在RTL级描述,并在FPGA上对其进行了仿真验证.实验表明,在Altera的StratixⅡ EP2S601020C4上,编码器的工作效率可以达到1CxD/cycle,最高工作时钟频率可达99.66 MHz.     

CORDIC-lifting factorization of paraunitary filter banks based on the quaternionic multipliers for lossless image coding

Quaternions have offered a new paradigm to the signal processing community: to operate directly in a multidimensional domain. We have recently introduced the quaternionic approach to the design and implementation of paraunitary filter banks: four- and eight-channel linear-phase paraunitary filter banks, including those with pairwise-mirror-image symmetric frequency responses. The hypercomplex number theory is utilized to derive novel lattice structures in which quaternion multipliers replace Givens (planar) rotations. Unlike the conventional algorithms, the proposed computational schemes maintain losslessness regardless of their coefficient quantization. Moreover, the one regularity conditions can be expressed directly in terms of the quaternion lattice coefficients and thus easily satisfied even in finite-precision arithmetic. In this paper, a novel approach to realizing CORDIC-lifting factorization of paraunitary filter banks is presented, which is based on the embedding of the CORDIC algorithm inside the lifting scheme. Lifting allows for making multiplications invertible. The 2D CORDIC engine using sparse iterations and asynchronous pipeline processor architecture based on the embedded CORDIC engine as stage of processor is reported. Also it is necessary to notice, that the quaternion multiplier lifting scheme based on the 2D CORDIC algorithm is the structural decision for the lossless digital signal processing. This approach applies to very practical filter banks, which are essential for image processing, and addresses interesting theoretical questions.     

Reduction of transients during lifting based spatial switching of two-channel filter banks

Time/space varying filter banks (FBs) are useful for non-stationary images. Lifting factorization of FBs results in structural perfect reconstruction even during the transition from one FB to other. This allows spatial switching between arbitrary FBs, avoiding the need to design border FBs. However, we show that lifting based switching between arbitrarily designed FBs induces spurious transients in the subbands during the transition. In this paper, we study the transients in lifting based switching of two-channel FBs. We propose two solutions to overcome the transients. One solution consists of a boundary handling mechanism to switch between any arbitrarily designed FBs, while the other solution proposes to design the FBs with a set of conditions applied on lifting steps. Both solutions maintain good frequency response during the transition and eliminate the transients. Using the proposed methods, we develop a spatial adaptive transform by switching between the long length FBs (either the JPEG2000 9/7 FB or the newly designed 13/11 FB) and the short length FBs (JPEG2000 5/3 FB) for lossy image compression. This adaptive transform shows PSNR improvement for images over JPEG2000 9/7 FB in low bit rate region (up to 0.2 bpp) and subjective improvements with reduced ringing up to medium bit rates (up to 0.6 bpp).     

基于OpenMP的JPEG2000并行解码算法的实现

为了提高JPEG2000的解码速度,在多核处理器平台上利用OpenMP（Open specifications for Multi Processing）实现了JPEG2000的高速并行解码。即利用OpenMP对JPEG2000解码过程中的T1解码器和离散小波逆变换进行多路并行解码,减少了这两部分的运行时间,从而降低JPEG2000的整体解码时间。实验结果表明,OpenMP是一种简单而有效的并行化编程工具,在保证解码图像质量不变的前提下,相对单线程串行算法,所提出的并行解码算法,解码速度有显著提高。     

JPEG2000中高速Tier1编码器的VLSI设计

提出并实现了一种用于JPEG2000编码芯片中高速Tier1编码器的并行流水结构。该编码器采用了双位平面并行编码、通道扫描的流水控制、状态变量实时产生电路以及列内并行上下文生成等技术,实现了一种0状态存储器的多并行流水位平面编码器;并行同步流水的多记号输入算术编码器以及不定算术编码周期下的多输入同步读取电路,使算术编码速度平均为1.3上下文编码记号对/时钟;对算术编码产生的压缩码流存储呈高效的宏流水线结构。该编码器在100MHz工作时钟下,最高编码速度为85M小波系数/s。用SMIC0.25μm工艺库综合时,门电路为6.3万门,片上存储器为26kb(码块大小32×32),关键路径为5.2ns。     

一种新型的样本并行JPEG2000编码器EB COT体系

提出了一种新型的用于JPEG2000的、基于样本并行(sample-parallel)的低时钟数EBCOT编码器体系,有效降低了处理时间.体系包括1个每周期完成4个样本编码的位平面编码器,和3个每周期完成2位比特编码的内容自适应二进制算术编码器.其中的位平面编码器在码通并行(pass-parallel)的基础上进一步并行了每列4位样本的编码操作.二进制算术编码器通过采用流水线技术来匹配位平面编码器的高吞吐量.     

A methodology for implementing decimator FIR filters on FPGA

This paper presents a methodology which can be used to implement any decimator symmetric/antisymmetric (S/A) finite impulse response (FIR) filter. Two varieties are developed: a classic distributed arithmetic (CDA) based and a modified distributed arithmetic (MDA) based one. Both exploit the polyphase structure and the symmetry/antisymmetry of the filter and are evaluated in terms of area efficiency, speed and power consumption. The choice of the algorithm depends on the performance metrics targeted. The methodology has been applied to implement the filter bank CDF9/7 which constitutes a one dimensional (1D) and one level discrete wavelet transform (DWT). The filter bank also known as the bior4.4 biorthogonal wavelets is recommended by the JPEG2000 standard for lossy compression of images and video. The architecture has been implemented on an Altera field programmable gate array (FPGA) and the simulations run in Matlab, Modelsim and Altera Quartus II. The results prove the efficiency of the algorithms and show the tradeoff between the area occupied, the throughput and the power consumption.