![Chapter 2
Intra Prediction
Abstract Intra prediction is the first process of H.264/AVC intra encoding. It
predicts a macroblock by referring to its neighboring macroblocks to eliminate spa-
tial redundancy. There are 17 prediction modes for a macroblock: nine modes for
each of the 16 luma 4 4 blocks, four modes for a luma 16 16 block, and four
modes for each of the two chroma 8 8 blocks. Because there exists great similarity
among equations of generating prediction pixels across prediction modes, effective
hardware resource sharing is the main design consideration. Moreover, there exists
a long data-dependency loop among luma 4 4 blocks during encoding. Increasing
parallelism and skipping some modes are two of the popular methods to design
a high-performance architecture for high-end applications. However, to increase
throughput will require more hardware area and to skip some modes will degrade
video quality. We will present a novel VLSI implementation for intra prediction in
this chapter.
2.1 Introduction
H.264/AVC intra encoding achieves higher compression ratio and quality compared
with the latest still image coding standard JPEG2000 [1]. The intra prediction unit,
which is the first process of H.264/AVC intra encoding, employs 17 kinds of pre-
diction modes and supports several different block sizes. For baseline, main, and
extended profiles, it supports 4 4 and 16 16 block sizes. For high profile, it ad-
ditionally supports an 8 8 block size.
In this chapter, we focus on the intra prediction for baseline, main, and extended
profiles. The intra prediction unit refers to reconstructed neighboring pixels to gen-
erate prediction pixels. Therefore, its superior performance comes at the expense of
very high computational complexity.
We describe the detailed algorithm of intra prediction in Sect. 2.1.1 and address
some design considerations in Sect. 2.1.2.
Y.-L.S. Lin et al., VLSI Design for Video Coding: H.264/AVC Encoding from Standard
Specification to Chip, DOI 10.1007/978-1-4419-0959-6 2,
c
Springer Science+Business Media, LLC 2010
11](https://image.slidesharecdn.com/88030-250312045410-bd1aaa44/85/VLSI-Design-for-Video-Coding-2010th-Edition-Youn-24-320.jpg)
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VLSI Design for Video Coding 2010th Edition Youn
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- 5. VLSI Design for Video Coding 2010th Edition Youn Digital Instant Download Author(s): Youn,Long Steve Lin, Chao,Yang Kao, Hung,Chih Kuo, Jian,Wen Chen ISBN(s): 9781441909589, 1441909583 Edition: 2010 File Details: PDF, 29.76 MB Year: 2010 Language: english
- 7. VLSI Design for Video Coding
- 8. Youn-Long Steve Lin • Chao-Yang Kao Huang-Chih Kuo • Jian-Wen Chen VLSI Design for Video Coding H.264/AVC Encoding from Standard Specification to Chip 123
- 9. Prof. Youn-Long Steve Lin National Tsing Hua University Dept. Computer Science 101 Kuang Fu Road HsinChu 300 Section 2 Taiwan R.O.C. Chao-Yang Kao National Tsing Hua University Dept. Computer Science 101 Kuang Fu Road HsinChu 300 Section 2 Taiwan R.O.C. Huang-Chih Kuo National Tsing Hua University Dept. Computer Science 101 Kuang Fu Road HsinChu 300 Section 2 Taiwan R.O.C. Jian-Wen Chen National Tsing Hua University Dept. Computer Science 101 Kuang Fu Road HsinChu 300 Section 2 Taiwan R.O.C. ISBN 978-1-4419-0958-9 e-ISBN 978-1-4419-0959-6 DOI 10.1007/978-1-4419-0959-6 Springer New York Dordrecht Heidelberg London Library of Congress Control Number: 2009943294 c Springer Science+Business Media, LLC 2010 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)
- 10. Preface A video signal is represented as a sequence of frames of pixels. There exists vast amount of redundant information that can be eliminated with video compression technology so that its transmission and storage becomes more efficient. To facilitate interoperability between compression at the video producing source and decompres- sion at the consumption end, several generations of video coding standards have been defined and adapted. After MPEG-1 for VCD and MPEG-2 for DVD applications, H.264/AVC is the latest and most advanced video coding standard defined by the international standard organizations. Its high compression ratio comes at the expense of more computational-intensive coding algorithms. For low-end applications, software so- lutions are adequate. For high-end applications, dedicated hardware solutions are needed. This book describes an academic project of developing an application-specific VLSI architecture for H.264/AVC video encoding. Each subfunction is analyzed before a suitable parallel-processing architecture is designed. Integration of sub- functional modules as well as the integration into a bus-based SOC platform is presented. The whole encoder has been prototyped using an FPGA. Intended readers are researchers, educators, and developers in video coding sys- tems, hardware accelerators for image/video processing, and high-level synthesis of VLSI. Especially, those who are interested in state-of-the-art parallel architecture and implementation of intra prediction, integer motion estimation, fractional motion estimation, discrete cosine transform, context-adaptive binary arithmetic coding, and deblocking filter will find design ideas from this book. HsinChu, Taiwan, ROC Youn-Long Lin Chao-Yang Kao Huang-Chih Kuo Jian-Wen Chen v
- 11. Acknowledgments Cheng-Long Wu, Cheng-Ru Chang, Chun-Hsin Lee, Chun-Lin Chiu, Hao-Ting Huang, Huan-Chun Tseng, Huan-Kai Peng, Hui-Ting Yang, Jhong-Wei Gu, Kai-Hsiang Chang, Li-Cian Wu, Ping Chao, Po-Sheng Liu, Sheng-Tsung Hsu, Sheng-Yu Shih, Shin-Chih Lee, Tzu-Jen Lo, Wei-Cheng Huang, Yu-Chien Kao, Yuan-Chun Lin, and Yung-Hung Chan of the Theda.Design Group, National Tsing Hua University contribute to the development of the H.264 Video Encoder System described in this book. The authors appreciate financial support from Taiwan’s National Science Council under Contracts no. 95-2220-E-007-024, 96-2220-E-007-013, and 97-2220-E-007- 003 and Ministry of Economics Affairs under Contracts no. 94-EC-17-A-01-S1- 038, 95-EC-17-A-01-S1-038, and 96-EC-17-A-01-S1-038. Financial support from Taiwan Semiconductor Manufacturing Company Limited (TSMC) and Industry Technology Research Institute (ITRI) is also greatly appreciated. Global Unichip Corp. provided us with its UMVP multimedia SOC platform and consultation during the FPGA prototyping stage of the development. The authors are grateful to Chi Mei Optoelectronics for a 52-in. Quad Full HD display panel. Joint research with the Microprocessor Research Center (MPRC) of Peking University has been an important milestone of this project. vii
- 12. Contents 1 Introduction to Video Coding and H.264/AVC ............................. 1 1.1 Introduction ............................................................... 1 1.1.1 Basic Coding Unit ............................................... 2 1.1.2 Video Encoding Flow ........................................... 2 1.1.3 Color Space Conversion......................................... 2 1.1.4 Prediction of a Macroblock ..................................... 3 1.1.5 Intraframe Prediction............................................ 4 1.1.6 Interframe Prediction............................................ 4 1.1.7 Motion Vector ................................................... 4 1.1.8 Prediction Error.................................................. 4 1.1.9 Space-Domain to Frequency-Domain Transformation of Residual Error .............................. 5 1.1.10 Coefficient Quantization ........................................ 5 1.1.11 Reconstruction................................................... 5 1.1.12 Motion Compensation........................................... 5 1.1.13 Deblocking Filtering ............................................ 6 1.2 Book Organization ........................................................ 6 2 Intra Prediction ................................................................ 11 2.1 Introduction ............................................................... 11 2.1.1 Algorithm ........................................................ 12 2.1.2 Design Consideration ........................................... 16 2.2 Related Works ............................................................. 19 2.2.1 Prediction Time Reduction Approaches........................ 19 2.2.2 Hardware Area Reduction Approaches ........................ 19 2.3 A VLSI Design for Intra Prediction ...................................... 20 2.3.1 Subtasks Scheduling ............................................ 20 2.3.2 Architecture...................................................... 24 2.3.3 Evaluation ....................................................... 30 2.4 Summary .................................................................. 30 ix
- 13. x Contents 3 Integer Motion Estimation .................................................... 31 3.1 Introduction ............................................................... 31 3.1.1 Algorithms ....................................................... 33 3.1.2 Design Considerations .......................................... 36 3.2 Related Works ............................................................. 37 3.2.1 Architecture...................................................... 37 3.2.2 Data-Reuse Schemes ............................................ 43 3.3 A VLSI Design for Integer Motion Estimation .......................... 44 3.3.1 Proposed Data-Reuse Scheme .................................. 45 3.3.2 Architecture...................................................... 47 3.3.3 Data Flow ........................................................ 49 3.3.4 Evaluation ....................................................... 52 3.4 Summary .................................................................. 53 4 Fractional Motion Estimation ................................................ 57 4.1 Introduction ............................................................... 57 4.1.1 Algorithms ....................................................... 58 4.1.2 Design Considerations .......................................... 61 4.2 Related Works ............................................................. 61 4.3 A VLSI Design for Fractional Motion Estimation ...................... 63 4.3.1 Proposed Architecture........................................... 63 4.3.2 Proposed Resource Sharing Method for SATD Generator ............................................. 68 4.3.3 Evaluation ....................................................... 72 4.4 Summary .................................................................. 72 5 Motion Compensation ......................................................... 73 5.1 Introduction ............................................................... 73 5.1.1 Algorithms ....................................................... 73 5.1.2 Design Considerations .......................................... 75 5.2 Related Works ............................................................. 75 5.2.1 Memory Traffic Reduction...................................... 76 5.2.2 Interpolation Engine............................................. 76 5.3 A VLSI Design for Motion Compensation .............................. 77 5.3.1 Motion Vector Generator........................................ 77 5.3.2 Interpolator ...................................................... 79 5.3.3 Evaluation ....................................................... 83 5.4 Summary .................................................................. 83 6 Transform Coding ............................................................. 85 6.1 Introduction ............................................................... 85 6.1.1 Algorithms ....................................................... 85 6.1.2 Design Consideration ........................................... 97 6.2 Related Works ............................................................. 97 6.2.1 Multitransform Engine Approaches ............................ 97 6.2.2 Trans/Quan or InvQuan/InvTrans Integration Approaches .... 97
- 14. Contents xi 6.3 A VLSI Design for Transform Coding................................... 98 6.3.1 Subtasks Scheduling ............................................ 98 6.3.2 Architecture...................................................... 98 6.3.3 Evaluation .......................................................106 6.4 Summary ..................................................................106 7 Deblocking Filter...............................................................107 7.1 Introduction ...............................................................107 7.1.1 Deblocking Filter Algorithm....................................108 7.1.2 Subtasks Processing Order......................................112 7.1.3 Design Considerations ..........................................113 7.2 Related Works .............................................................115 7.3 A VLSI Design for Deblocking Filter....................................116 7.3.1 Subtasks Scheduling ............................................116 7.3.2 Architecture......................................................116 7.3.3 Evaluation .......................................................122 7.4 Summary ..................................................................124 8 CABAC Encoder ...............................................................125 8.1 Introduction ...............................................................125 8.1.1 CABAC Encoder Algorithm ....................................125 8.1.2 Subtasks Processing Order .....................................134 8.1.3 Design Consideration ...........................................134 8.2 Related Works .............................................................136 8.3 A VLSI Design for CABAC Encoder ....................................139 8.3.1 Subtasks Scheduling ............................................139 8.3.2 Architecture......................................................140 8.3.3 Evaluation .......................................................147 8.4 Summary ..................................................................148 9 System Integration .............................................................151 9.1 Introduction ...............................................................151 9.1.1 Algorithm ........................................................151 9.1.2 Design Consideration ...........................................153 9.2 Related Works .............................................................155 9.3 A VLSI Design for H.264/AVC Encoder ................................156 9.3.1 Subtasks Scheduling ............................................156 9.3.2 Architecture......................................................159 9.3.3 Evaluation .......................................................165 9.4 Summary ..................................................................166 References...........................................................................167 Index.................................................................................173
- 15. Chapter 1 Introduction to Video Coding and H.264/AVC Abstract A video signal is represented as a sequence of frames of pixels. There exists a vast amount of redundant information that can be eliminated with video compression technology so that transmission and storage becomes more efficient. To facilitate interoperability between compression at the video producing source and decompression at the consumption end, several generations of video coding standards have been defined and adapted. For low-end applications, software so- lutions are adequate. For high-end applications, dedicated hardware solutions are needed. This chapter gives an overview of the principles behind video coding in general and the advanced features of H.264/AVC standard in particular. It serves as an introduction to the remaining chapters; each covers an important coding tool and its VLSI architectural design of an H.264/AVC encoder. 1.1 Introduction A video encoder takes as its input a video sequence, performs compression, and then produces as its output a bit-stream data which can be decoded back to a video sequence by a standard-compliant video decoder. A video signal is a sequence of frames. It has a frame rate defined as the number of frames per second (fps). For typical consumer applications, 30 fps is adequate. However, it could be as high as 60 or 72 for very high-end applications or as low as 10 or 15 for video conferencing over a low-bandwidth communication link. A frame consists of a two-dimensional array of color pixels. Its size is called frame resolution. A standard definition (SD) frame has 720 480 pixels per frame whereas a full high definition (FullHD) one has 1,920 1,088. There are large num- ber of frame size variations developed by various applications such as computer monitors. A color pixel is composed of three elementary components: R, G, and B. Each component is digitized to an 8-bit data for consumer applications or a 12-bit one for high-end applications. Y.-L.S. Lin et al., VLSI Design for Video Coding: H.264/AVC Encoding from Standard Specification to Chip, DOI 10.1007/978-1-4419-0959-6 1, c Springer Science+Business Media, LLC 2010 1
- 16. 2 1 Introduction to Video Coding and H.264/AVC The data rate for a raw video signal is huge. For example, a 30-fps FullHD one will have a data rate of 30 1;920 1;088 3 8 D 1:5Gbps, which is impractical for today’s communication or storage infrastructure. Fortunately, by taking advantage of the characteristics of human visual system and the redundancy in the video signal, we can compress the data by two orders of magnitude without scarifying the quality of the decompressed video. 1.1.1 Basic Coding Unit In order for a video encoding or decoding system to handle video of different frame rates and simplify the implementation, a basic size of 16 16 has been popularly adopted. Every main stream coding standards from MPEG-1, MPEG-2, : : : to H.264 has chosen a macroblock of 16 16 pixels as their basic unit of processing. Hence, for video of different resolutions, we just have to process different number of mac- roblocks. For every 720 480 SD frame, we process 45 30 macroblocks while for every FullHD frame, we process 120 68 macroblocks. 1.1.2 Video Encoding Flow Algorithm 1.1 depicts a typical flow of video encoding. frame(t) is the current frame to be encoded. frame0 (t1) is the reconstructed frame for referencing or called ref- erence frame. frame0 (t) is the reconstructed current frame. We encode F.t/ one macroblock (MB) at a time starting from the leftmost MB of the topmost row. We called the MB being encoded as Curr MB. It can be encoded in one of the three modes: I for intra prediction, P or unidirectional interprediction, and B for bidirectional interprediction. The resultant MB from prediction is called Pred MB and the difference between Curr MB and Pred MB is called Res MB for residu- als. Res MB goes through space-to-frequency transformation and then quantization processes to become Res Coef or residual coefficients. Entropy coding then com- presses Res Coef to get final bit-stream. In order to prepare reconstructed current frame for future reference, we perform inverse quantization and inverse transform on Res Coef to get reconstructed residuals called Reconst res. Adding together Re- const res and Pred MB, we have Reconstruct MB for insertion into frame0 (t). 1.1.3 Color Space Conversion Naturally, each pixel is composed of R, G, and B 8-bit components. Applying the following conversion operation, it can be represented as one luminance (luma) com- ponent Y and two chrominance (chroma) components Cr and Cb. Since the human
- 17. 1.1 Introduction 3 Algorithm 1.1: Encode a frame. encode a frame (frame(t), mode) for I D 1, N do //** N: #rows of MBs per frame for I D 1, M do //** N: #rows of MBs per frame Curr MB D MB(frame(t), I, J); case (mode) I: Pred MB D Intra Pred (frame(t)’, I, J); P: Pred MB D ME (frame(t-1)’, I, J); B: Pred MB D ME (frame(t-1)’, frame(tC1)’, I, J); endcase Res MB D Curr MB - Pred MB; Res Coef D Quant(Transform(Res MB)); Output(Entropy code(Res Coef)); Reconst res D InverseTransform(InverseQuant(Res Coef)); Reconst MB D Reconst res C Pred MB; Insert(Reconst MB, frame(t)’); endfor endfor end encode a frame; visual system is more sensitive to luminance component than chrominance ones, we can subsample Cr and Cb to reduce the data amount without sacrificing the video quality. Usually one out of two or one out of four subsampling is applied. The for- mer is called 4:2:2 format and the later 4:2:0 format. In this book, we assume that 4:2:0 format is chosen. Of course, the inverse conversion will give us R, G, B com- ponents from a set of Y , Cr, Cb components. Y D 0:299R C 0:587G C 0:114B; Cb D 0:564.B Y /; Cr D 0:713.R Y /: (1.1) 1.1.4 Prediction of a Macroblock A macroblock M has 1616 D 256 pixels. It takes 2563 D 768 bytes to represent it in RGB format and 256.1C1=4C1=4/ D 384 bytes in 4:2:0 format. If we can find during decoding a macroblock M0 which is similar to M, then we only have to get from the encoding end the difference between M and M0 . If M and M0 are very similar, the difference becomes very small so does the amount of data needed to be transmitted/stored. Another way to interpret similarity is redundancy. There exist two types of redundancy: spatial and temporal. Spatial redundancy results from sim- ilarity between a pixel (region) and its surrounding pixels (regions) in a frame. Tem- poral redundancy results from slow change of video contents from one frame to the next. Redundancy information can be identified and removed with prediction tools.
- 18. 4 1 Introduction to Video Coding and H.264/AVC 1.1.5 Intraframe Prediction In an image region with smooth change, a macroblock is likely to be similar to its neighboring macroblocks in color or texture. For example, if all its neighbors are red, we can predict that a macroblock is also red. Generally, we can define sev- eral prediction functions; each takes pixel values from neighboring macroblocks as its input and produces a predicted macroblock as its output. To carry out in- traframe prediction, every function is evaluated and the one resulting in the smallest error is chosen. Only the function type and the error need to be encoded and stored/transmitted. This tool is also called intra prediction and a prediction func- tion is also called a prediction mode. 1.1.6 Interframe Prediction Interframe prediction, also called interprediction, identifies temporal redundancy between neighboring frames. We call the frame currently being processed the cur- rent frame and the neighboring one the reference frame. We try to find from the reference frame a reference macroblock that is very similar to the current macroblock of the current frame. The process is called motion estimation. A mo- tion estimator compares the current macroblock with candidate macroblocks within a search window in the reference frame. After finding the best-matched candi- date macroblock, only the displacement and the error need to be encoded and stored/transmitted. The displacement from the location of the current macroblock to that of the best candidate block is called motion vector (MV). In other words, motion estimation determines the MV that results in the smallest interprediction error. A bigger search window will give better prediction at the expense of longer estimation time. 1.1.7 Motion Vector A MV obtained from motion estimation is adequate for retrieving a block from the reference frame. Yet, we do not have to encode/transmit the whole of it because there exists similarity (or redundancy) among MVs of neighboring blocks. Instead, we can have a motion vector prediction (MVP) as a function of neighboring blocks’ MVs and just process the difference, called motion vector difference (MVD), between the MV and its MVP. In most cases, the MVD is much smaller than its associated MV. 1.1.8 Prediction Error We call the difference between the current macroblock and the predicted one as prediction error. It is also called residual error or just residual.
- 19. 1.1 Introduction 5 1.1.9 Space-Domain to Frequency-Domain Transformation of Residual Error Residual error is in the space domain and can be represented in the frequency domain by applying discrete cosine transformation (DCT). DCT can be viewed as representing an image block with a weighted sum of elementary patterns. The weights are termed as coefficients. For computational feasibility, a macroblock of residual errors is usually divided into smaller 4 4 or 8 8 blocks before applying DCT one by one. 1.1.10 Coefficient Quantization Coefficients generated by DCT carry image components of various frequencies. Since human visual system is more sensitive to low frequency components and less sensitive to high frequency ones, we can treat them with different resolution by means of quantization. Quantization effectively discards certain least significant bits (LSBs) of a coefficient. By giving smaller quantization steps to low frequency components and larger quantization steps to high frequency ones, we can reduce the amount of data without scarifying the visual quality. 1.1.11 Reconstruction Both encoding and decoding ends have to reconstruct video frame. In the encoding end, the reconstructed frame instead of the original one should be used as refer- ence because no original frame is available in the decoding end. To reconstruct, we perform inverse quantization and inverse DCT to obtain reconstructed residual. Note that the reconstructed residual is not identical to the original residual as quantization is irreversible. Therefore, distortion is introduced here. We then add prediction data to the reconstructed residual to obtain reconstructed image. For an intrapredicted macroblock, we perform predict function on its neighboring reconstructed mac- roblocks while for an interpredicted one we perform motion compensation. Both methods give a reconstructed version of the current macroblock. 1.1.12 Motion Compensation Given a MV, the motion compensator retrieves from the reference frame a re- constructed macroblock pointed to by the integer part of the MV. If the MV has fractional part, it performs interpolation over the retrieved image to obtain the final reconstructed image. Usually, interpolation is done twice, one for half-pixel accu- racy and the other for quarter-pixel accuracy.
- 20. 6 1 Introduction to Video Coding and H.264/AVC 1.1.13 Deblocking Filtering After every macroblock of a frame is reconstructed one by one, we obtain a reconstructed frame. Since the encoding/decoding process is done macroblock-wise, there exists blocking artifacts between boundaries of adjacent macroblocks or sub- blocks. Deblocking filter is used to eliminate this kind of artificial edges. 1.2 Book Organization This book describe a VLSI implementation of a hardware H.264/AVC encoder as depicted in Fig. 1.1. Inter Info Memory IME Engine TransCoding Engine FME Engine MC Engine IntraPred Engine IntraMD Engine Multiplexer Recons Engine DF Engine Unfilter Memory ReconsMB Memory CABAC Engine PE Engine DF MAU Encoder Core MB MAU SR MAU BIT MAU MAU Arbiter Command Receiver AMBA Slave AMBA Master AMBA MainCtrl Engine AMBA Interface Fig. 1.1 Top-level block diagram of the proposed design
- 21. 1.2 Book Organization 7 In Chap. 2, we present intra prediction. Intra prediction is the first process of H.264/AVC intra encoding. It predicts a macroblock by referring to its neighboring macroblocks to eliminate spatial redundancy. There are 17 prediction modes for a macroblock: nine modes for each of the 16 luma 4 4 blocks, four modes for a luma 16 16 block, and four modes for each of the two chroma 8 8 blocks. Because there exists great similarity among equations of generating prediction pixels across prediction modes, effective hardware resource sharing is the main design consider- ation. Moreover, there exists a long data-dependency loop among luma 4 4 blocks during encoding. Increasing parallelism and skipping some modes are two of the popular methods to design a high-performance architecture for high-end applica- tions. However, to increase throughput will require more hardware area and to skip some modes will degrade video quality. We will present a novel VLSI implementa- tion for intra prediction in this chapter. In Chap. 3, we present integer motion estimation. Interframe prediction in H.264/AVC is carried out in three phases: integer motion estimation (IME), frac- tional motion estimation (FME), and motion compensation (MC). We will discuss these functions in Chaps. 3, 4, and 5, respectively. Because motion estimation in H.264/AVC supports variable block sizes and multiple reference frames, high computational complexity and huge data traffic become main difficulties in VLSI implementation. Moreover, high-resolution video applications, such as HDTV, make these problems more critical. Therefore, current VLSI designs usually adopt parallel architecture to increase the total throughput and solve high computational complexity. On the other hand, many data-reuse schemes try to increase data-reuse ratio and, hence, reduce required data traffic. We will introduce several key points of VLSI implementation for IME. In Chap. 4, we present fractional motion estimation. Motion estimation in H.264/AVC supports quarter-pixel precision and is usually carried out in two phases: IME and FME. We have talked about IME in Chap. 3. After IME finds an integer motion vector (IMV) for each of the 41 subblocks, FME performs motion search around the refinement center pointed to by IMV and further refines 41 IMVs into fractional MVs (FMVs) of quarter-pixel precision. FME interpolates half- pixels using a six-tap filter and then quarter-pixels a two-tap one. Nine positions are searched in both half refinement (one integer-pixel search center pointed to by IMV and eight half-pixel positions) and then quarter refinement (one half-pixel position and eight quarter-pixel positions). The position with minimum residual error is chosen as the best match. FME can significantly improve the video quality (C0:3 to C0:5dB) and reduce bit-rate (20–37%) according to our experimental results. However, our profiling report shows that FME consumes more than 40% of the total encoding time. Therefore, an efficient hardware accelerator for fractional motion estimation is indispensable. In Chap. 5, we present motion compensation. Following integer and fractional motion estimation, motion compensation (MC) is the third stage in H.264/AVC interframe prediction (P or B frame). After the motion estimator finds MVs and related information for each current macroblock, the motion compensator generates
- 22. 8 1 Introduction to Video Coding and H.264/AVC compensated macroblocks (MBs) from reference frames. Due to quarter-pixel precision and variable-block-size motion estimation supported in H.264, motion compensation also needs to generate half- or quarter-pixels for MB compensation. Therefore, motion compensation also has high computational complexity and dom- inates the data traffic on DRAM. Current VLSI designs for MC usually focus on reducing memory traffic or increasing interpolator throughput. In this chapter, we will introduce several key points of VLSI implementation for motion compensation. In Chap. 6, we present transform coding. In H.264/AVC, both transform and quantization units consist of forward and inverse parts. Residuals are transformed into frequency domain coefficients in the forward transform unit and quantized in the forward quantization unit to reduce insignificant data for bit-rate saving. To gen- erate reconstructed pixels for the intra prediction unit and reference frames for the motion estimation unit, quantized coefficients are rescaled in the inverse quanti- zation unit and transformed back to residuals in the inverse transform unit. There are three kinds of transforms used in H.264/AVC: 4 4 integer discrete cosine transform, 2 2 Hadamard transform, and 4 4 Hadamard transform. To design an area-efficient architecture is the main design challenge. We will present a VLSI implementation of transform coding in this chapter. In Chap. 7, we present deblocking filter. The deblocking filter (DF) adopted in H.264/AVC reduces the blocking artifact generated by block-based motion- compensated interprediction, intra prediction, and integer discrete cosine transform. The filter for eliminating blocking artifacts is embedded within the coding loop. Therefore, it is also called in-loop filter. Expirically, it achieves up to 9% bit-rate saving at the expense of intensive computation. Even with today’s fastest CPU, it is hard to perform software-based real-time encoding of high-resolution sequences such as QFHD (3,840 2,160). Consequently, accelerating the deblocking filter by VLSI implementation is indeed required. Through optimizing processing cycle, ex- ternal memory access, and working frequency, we show a design that can support QFHD at 60-fps application by running at 195 MHz. In Chap. 8, we present context-based adaptive binary arithmetic coding. Context- based adaptive binary arithmetic coding (CABAC) adopted in H.264/AVC main profile is the state-of-the-art in terms of bit-rate efficiency. In comparison with context-based adaptive variable length coding (CAVLC) used in baseline profile, it can save up to 7% of the bit-rate. However, CABAC occupies 9.6% of total encoding time and its throughput is limited by bit-level data dependency. Moreover, for ultra- high resolution, such like QFHD (3,840 2,160), its performance is difficult to meet real-time requirement for a pure software CABAC encoder. Therefore, it is neces- sary to accelerate the CABAC encoder by VLSI implementation. In this chapter, a novel architecture of CABAC encoder will be described. Its performance is capable of real-time encoding QFHD video in the worst case of main profile Level 5.1. In Chap. 9, we present system integration. Hardware cost and encoding perfor- mance are the two main challenges in designing a high-performance H.264/AVC en- coder. We have proposed several high-performance architectures for the functional
- 23. 1.2 Book Organization 9 units in an H.264/AVC encoder. In addition, external memory management is another design issue. We have to access an external memory up to 3.3 GBps for real-time encoding 1080pHD video in our encoder. We propose several AMBA- compliant memory access units (MAUs) to efficiently access an external memory. We will present our H.264/AVC encoder in this chapter.
- 24. Chapter 2 Intra Prediction Abstract Intra prediction is the first process of H.264/AVC intra encoding. It predicts a macroblock by referring to its neighboring macroblocks to eliminate spa- tial redundancy. There are 17 prediction modes for a macroblock: nine modes for each of the 16 luma 4 4 blocks, four modes for a luma 16 16 block, and four modes for each of the two chroma 8 8 blocks. Because there exists great similarity among equations of generating prediction pixels across prediction modes, effective hardware resource sharing is the main design consideration. Moreover, there exists a long data-dependency loop among luma 4 4 blocks during encoding. Increasing parallelism and skipping some modes are two of the popular methods to design a high-performance architecture for high-end applications. However, to increase throughput will require more hardware area and to skip some modes will degrade video quality. We will present a novel VLSI implementation for intra prediction in this chapter. 2.1 Introduction H.264/AVC intra encoding achieves higher compression ratio and quality compared with the latest still image coding standard JPEG2000 [1]. The intra prediction unit, which is the first process of H.264/AVC intra encoding, employs 17 kinds of pre- diction modes and supports several different block sizes. For baseline, main, and extended profiles, it supports 4 4 and 16 16 block sizes. For high profile, it ad- ditionally supports an 8 8 block size. In this chapter, we focus on the intra prediction for baseline, main, and extended profiles. The intra prediction unit refers to reconstructed neighboring pixels to gen- erate prediction pixels. Therefore, its superior performance comes at the expense of very high computational complexity. We describe the detailed algorithm of intra prediction in Sect. 2.1.1 and address some design considerations in Sect. 2.1.2. Y.-L.S. Lin et al., VLSI Design for Video Coding: H.264/AVC Encoding from Standard Specification to Chip, DOI 10.1007/978-1-4419-0959-6 2, c Springer Science+Business Media, LLC 2010 11
- 25. 12 2 Intra Prediction 2.1.1 Algorithm All intra prediction pixels are calculated based on the reconstructed pixels of previously encoded neighboring blocks. Figure 2.1 lists all intra prediction modes with different block sizes. For the luma component, a 16 16 macroblock can be partitioned into sixteen 4 4 blocks or just one 16 16 block. The chroma com- ponent simply contains one 8 8 Cb block and one 8 8 Cr block. There are nine prediction modes for each of the 16 luma 4 4 blocks and four prediction modes for a luma 16 16 block and two chroma 8 8 blocks. Figure 2.2 illustrates the reference pixels of a luma macroblock. A luma 16 16 block is predicted by referring to its upper, upper-left, and left neighboring luma 16 16 blocks. For a luma 4 4 block, we utilize its upper, upper-left, left, and upper-right neighboring 4 4 blocks. There are 33 and 13 reference pixels for a luma 16 16 block and a luma 4 4 block, respectively. To predict a chroma 8 8 block is like to predict a luma 16 16 block by using its upper, upper-left, and left neighboring chroma blocks. There are 17 reference pixels for a chroma block. Figure 2.3 shows all the computation equations of luma 4 4 modes. Upper case letters from “A” to “M” denote the 13 reference pixels and lower case letters from “a” to “p” denote the 16 prediction pixels. Cr Cb 8x8 8x8 1 8x8 1 8x8 Y 16x16 1 16x16 Component Block Size Prediction Modes Abbreviation 16 4x4 0:vertical 1:horizontal 2:DC 3:plane L16_VER L16_HOR L16_DC L16_PLANE 0:vertical 1:horizontal 2:DC 3:diagonal down-left 4:diagonal down-right 5:vertical-right 6:horizontal-down 7:vertical-left 8:horizontal-up L4_VER L4_HOR L4_DC L4_DDL L4_DDR L4_VR L4_HD L4_VL L4_HU 2:vertical 1:horizontal 0:DC 3:plane CB8_VER CB8_DC CB8_PLANE CB8_HOR 2:vertical 1:horizontal 0:DC 3:plane CR8_VER CR8_DC CR8_PLANE CR8_HOR Fig. 2.1 Intra prediction modes
- 26. Other documents randomly have different content
- 27. By Jove, I can’t help laughing at myself, and it’s no joking matter, after I had laid myself out to make a deep impression. There, Scipio, draw the curtains and go. Stay; hand me the brandy-bottle and some cigars before you make your final exit. I might as well get drunk, and by that means bury my woes in a temporary oblivion, despite of all temperance societies. Give me my dressing-gown, and pitch this infernal coat out at the window. Ha! here’s another specimen of my undeniable taste. What man, save myself, would ever encase himself in a brocade of a pattern like a bed-curtain. No matter; your Persian says it is all takdeer—destiny. All this, I presume, was fore-ordained—it must have been predestined, this atrocious, villainous piece of business, and I suppose I can’t help it. Scipio, go to bed. Scipio retired, and I was left alone. The night was dark and confoundedly cold. I picked up a volume. It was Peter Schlemihl. I lighted a cigar, and mixing some strong brandy-and-water, I applied myself to the business which the reader has been previously informed I had in contemplation. But all would not do. I could not succeed in my intention. I smoked one Dos Amigos after another, and quaffed glass after glass of Seignette. The more I drank, in the more odious light did I appear to myself. I ruminated upon Julia’s flirtation with Fitzcrocky. I attempted to analyze the causes of my abominable want of taste in the components of costume. “Deuce take me!” at last I cried, exhausted, and half mad with vexation, “I wish to Heaven that I could exchange this unlucky carcass with some more fortunate individual, whose kinder stars may have granted him a comelier body and a more recherché taste in its decoration than my miserable self!” Scarcely had I spoken these words when a gentle cough attracted my attention. I looked up. Opposite to me there sat a gentleman of the most prepossessing exterior. He had drawn up a lounge to the side of the grate, and was seated, with patient politeness, as if in expectation of drawing my attention to himself. He was attired in a neat and elegant suit of black, which fitted him à merveille. A dark maroon velvet vest, buttoned tightly to his chest,
- 28. and falling over into a rolling collar, displayed his linen of superb make and texture, fastened by a small diamond pin. His cravat was tied with a prim precision; his boots and gloves would have driven Staub and Walker to despair. His hat was of the most appropriate block, and a cambric handkerchief, delicate as the web of Arachne, and scented with bouquet du roi, was occasionally applied to his nose, in the most graceful manner. The contour of his face was perfect Grecian, and a mass of wavy chestnut-hair was negligently disposed over his forehead. He wore neither whisker nor moustache. For some time I sat in silent amazement, wondering how my guest had procured his entreé, inasmuch as I knew that all the doors were locked and bolted, and that my janitor had gone to bed some hour and a half previous to the stranger’s appearance. He sat in equal silence. Presently he arose, and pouring out a glass of brandy, he swallowed it in a twinkling, bowing to me with infinite gravity. He next produced a long and slender meerschaum from his pocket, lighted it with a pastille ambreé and resuming his seat, his eyes traveled over my attire from head to foot, with an air of well-bred curiosity. My bile began to work. “May I ask, sir,” said I, “what is the meaning of this unusual visit?” The stranger, carelessly desisting from his investigation, expelled a mouthful of smoke, and with a kind of concealed chuckle, which I did not half like, replied, “Pray, sir, may I, without infringing upon propriety, inquire of you, who is your tailor?” My hand inadvertently sought the decanter, and I had a vague idea of hurling it at my visiter’s head. One moment’s reflection, together with a glance at the well-made and sinewy form before me, determined me to waive hostilities. “I cannot imagine, sir,” I replied, with severe dignity, “your motives in making any such inquiry.” “Oh, a mere trifle. I was anxious to become acquainted with the name of your fashioner, who, to judge from the appearance of your habiliments, must possess a most exquisite taste.”
- 29. For a moment, I had suspicions that my amis inconnu was quizzing me. I eyed him narrowly, but the expression of his face was that of respectful earnestness, mingled with some curiosity. Not the slightest trace of a quiz could be detected upon his immovable aspect. “If you are really anxious to know,” said I, and I confess I fell naturally gratified, for it was the first compliment I had ever heard addressed to my taste, “I can refer you to Cabbage Stickem, Oxford street.” “I could almost wish to exchange my vile taste in costume for your more original and certainly more refined style,” said the stranger, without moving a single muscle of his face. “And I,” I cried, seizing him by the hand, “highly as I feel flattered by such a declaration, would willingly make such an exchange, if it were possible to do so.” “We shall find it very possible,” replied the stranger. “Come, let us take a glass to our better acquaintance. I am charmed to have it in my power to confer an obligation upon a gentleman like yourself, especially when it meets so exactly with my own inclinations.” “Egad,” said I, as we hob-nobbed very cordially together, “I am agreed to make the exchange directly.” I had no sooner said the word than I felt a most violent blow at the back of my head. On my recovery, for it almost stunned me, I was stupefied with astonishment, upon looking up, to behold myself sitting at my ease, and smoking with great insouciance, upon the very seat which I had previously occupied in propria persona. “Be so good, worthy sir,” said I, or the figure I saw seated in my- arm chair, “to look in yonder glass, and you will discover that your wishes have been complied with.” I stepped to the cheval, and to my unspeakable amazement and joy, viewed in the reflection the person of the elegant gentleman with whom I had exchanged exteriors. “I hope,” said the personage who rejoiced in my original ugliness and odious garments, “that this exchange is entirely to your satisfaction?”
- 30. I could have hugged him, for I was almost beside myself with delight. “How can I thank you for your kindness,” I exclaimed, for my old attire looked doubly ridiculous to my new optics. “I do assure you, sir, that I am forever at your service.” “That’s it,” said the gentleman with a peculiar smile, which in the plenitude of my joy I did not notice at the time, although I recollected it afterward perfectly well. “And now, as it grows late, I will bid you good evening.” As he spoke, I saw my ancient figure walk quietly out at the door. I don’t know, but I thought I heard him laugh a little after closing it. For my own part I was so elated, that I could not think of going to bed, so I sat drinking and singing, building castles in the air, and ruminating upon the magnificent figure which I should oppose against the fascinations of Fitzcrocky, in the eyes of Julia. I determined, with the afternoon of that day, to commence my triumphal progress in her affections. In fact, I never noticed how time slipped by, and when the entrance of some one at the door aroused me, and I collected my scattered senses, it was at least four hours after sunrise. “Gollamighty!” exclaimed the voice of Scipio. “What de debbil we got heah? Trange man in massa’s bed-room, and he not up yit. What you want, eh? He some tief—some robber.” “Why you old fool,” said I, “don’t you see it’s me—myself?” “Who me?—what dat, eh? Debbil tak me if I no b’lieve dat he has murdered massa and teal all de spoons! Help! murder!” “What do you mean, you old villain!” cried I. “Do you want to bring in the whole neighborhood?” and seizing a candlestick, I leveled it at his woolly pate. “What do you mean, you scoundrel, by abusing my servant?” roared a voice from the bed. I looked in that direction. There was my head protruded from the curtains, surmounted by a red night- cap, and a clenched fist was violently shaken at me from the same purlieu. “Turn him out, Scipio!” I shouted. “Turn him out!” repeated my Eidolon, if I may so term him.
- 31. “Turn who out!” queried Scipio, in a state of profound bewilderment. Perfectly frantic with rage, I flew toward the bed, eager for a pugilistic encounter, when the door was thrown open, and my old housekeeper, with pallid visage, peeped into the apartment. I determined to make an appeal to her. “Am I, or am I not your master, Nancy?” said I, in a very melancholy tone. “You my master! Come up, mister himperence,” replied Nancy. “My master is in yonder bed, young man. Run, Sip, and call a policeman. He’ll make you know your master, jail-bird.” “Ah!” thought I, “it’s all up, I see. That fellow’s me, and I’m somebody else, but hang me if I know who. Well, as I don’t choose to take a morning airing at Hatton Garden, I might as well abdicate at once. But,” cried I, “you scoundrel, you shall pay for this.” “Turn him out, Sip!” grunted my former voice from the bed. How hateful it sounded! “Turn him out, and don’t let me be disturbed till twelve. My head aches confoundedly.” I sneaked out of my own room like a detected pickpocket, Nancy and Scipio attending me down stairs, and delivering a brace of running lectures upon the evil courses which I was pursuing, admonishing me likewise of the certain and ignominious end which awaits such depraved and dissolute characters as I was presumed to be. At the foot of the stairs, Scipio insisted upon searching me, an operation to which, crest-fallen as I was, I did not pretend to make the slightest opposition. I was then dismissed in the same manner with Master Candide from the château of Thonderdentronck, namely with grands coups de pied dans le derrière, pretty well administered by a brace of sturdy valets, whom Scipio had summoned to his assistance from a neighboring area. This ejection from my own mansion took place about half past nine o’clock. In the first impulses of my rage and despair, I resolved to apply to my friends, in order to establish my identity by their testimonies. It was early; too early in fact to find any of them up, and I was fain to stroll the streets until the lingering hands of the clock should signify the proper and canonical hour of rising. So I
- 32. patrolled Hyde Park for an hour or so, until my insides began to give me very unequivocal tokens of their desire for breakfast. Rage, as well as love and all other sublunary matters, must yield to the calls of hunger. I entered a coffee-house in Upper Brook street, and ordered my morning meal. I drank a couple of cups of tea, ate a French roll and a modicum of raw beefsteak, and walked to the bar to pay my bill. I put my hand into my pocket in search of my purse. It was not there. I tried another, and another, and yet another pocket. Horrid to relate, I could not meet with the smallest coin of the realm! The waiter began to look very black, and I could overhear the monosyllable “bilk” ground out between his teeth in a tone which indicated profound aversion and contempt. My hair fairly stood on end. Nevertheless I thought it best to brazen it out. “Do you see, my good fellow,” said I, and I assure you, I spoke in a very bland and courteous tone, “I have most unaccountably forgotten my purse—” “Gammon!” was the very significant response of the Ganymede. “How d’ye know you ever had one?” “Confound your impudence, fellow!” said I, nettled by the coolness of the query. “What d’ ye mean by insulting a gentleman?” “More like a swell out o’ luck,” growled the servitor. “Come, young ’un, this here kind of a job’s no go. Post the cole, my boy, or it’ll be the worse for somebody.” As luck would have it, I thought of my diamond breastpin, and taking that article of jewelry from my shirt front, I offered it to the waiter. “Blast your Brummagem traps!” quoth that gentleman. “D’ ye think I don’t know a diamond from a Bristol stone, or gold from pinchbeck?” It was pinchbeck, by Jupiter! The waiter must have been touched by the despair depicted upon my countenance. With a grim smile, “Come, my fine chap,” said he, “if you are a bilk, it’s plain that you’re a new hand at the trade, and I don’t care about being too hard upon you. Give me your wipe, and I’ll let you off for this time,
- 33. but you take care you doesn’t come the swell mob again over this ’ere house, that’s all.” My heart was too full for speech. I gave him my handkerchief with a profound sigh, and throwing the pinchbeck breastpin into the coal-scuttle, I vanished with all convenient speed. Leaving the coffee-house, I espied my crony, Dick Buffers, across the street. To join him was but the work of a moment. “Hollo, Dick!” said I, slapping him heartily upon the shoulder. This was the irrepressible outpouring of a bosom, into which a ray of light, imparted by hope, had penetrated, cheering the darksome abode with its enlivening presence. Quickly was my joy turned into sorrow. “What do you mean, sir?” said Dick, drawing himself up with magnificent reserve. “Do you mean to insult me?” “Come, Dick,” said I, in a sort of whimper, for I was really becoming very much alarmed, “don’t put a strange face on the matter. It isn’t possible that you don’t know your old friend, Flashington Highflyer? Why we only parted at midnight, and dined together no later than yesterday.” “Highflyer!” said Buffers. “To be sure I know him, and very well, too. We undoubtedly did dine together yesterday, although I cannot account for your knowledge of the fact. But it will take even more than your impudence to convince me that you are the man. You must be either drunk or a fool. Flashington Highflyer! ha! ha! Your very dress convicts you of a lie.” Buffers might have spared this sarcasm. “Upon my honor, Richard Buffers,” said I, solemnly, while the tears actually stood in my eyes, “I am that most unfortunate man.” “You are? Why, the man’s mad! View that looking glass in yonder shop-window, and if you haven’t been looking into the glass too often this morning already, you will discover that your countenance bears not the slightest resemblance to that of Mr. Highflyer, that is, if you are at all acquainted with the physiognomy of the gentleman to whose name you have laid claim.” I stepped to the window. One glance was sufficient. Oh! how I cursed my super-lunatic folly, and how I longed for my former
- 34. shape. “Egad, it’s true,” I soliloquized. “It’s all correct, as my Yankee friends have it. That rascal has got into possession of my goods and chattels, as well as of my person, and has left me nothing in return but a most confoundedly disagreeable sense of my own individuality. What a horrid piece of business to be sure!” I turned. Dick was gone. “Who am I, then?” was my next very natural self interrogatory. It was needless to disturb my remaining acquaintance for proofs of my identity, as, indeed, if any body had demanded of me my address, I should have been amazingly puzzled to give it. I turned about, entirely reckless of whither I went. Twelve, one o’clock went by. I met many of my acquaintance, but there was no recognition. I was in despair, and could have sat down upon the curb-stone and wept. My walk procured me one thing, it is true, namely, a very good appetite; but I could have readily dispensed with that, inasmuch as I was painfully conscious that, without pawning my coat, I was utterly unable to satisfy the cravings of hunger. The hours rolled on. The force of habit, I presume, led me to Hyde Park once more. All the world was abroad. Beauty, rank and fashion were collected in one splendid, aristocratic mass. Carriages and four, with servants in gorgeous liveries; every variety of vehicle, from the dashing tandem to the humbler carriage and pair, tilburies, buggy-wagons, and cabs thronged and thundered around the ring. Horsemen dashed along the carriage-ways, and pedestrians crowded the footpaths. I sat down upon a bench and mechanically surveyed the scene. Every well-known face, which was wont to greet me with smiles, but which now bestowed upon me, en passant, but a vacant stare, struck a pang to my heart. My despair would have been uncontrollable, and I should have groveled and bit the ground with fury, but an innate self-respect, and a desire to appear to every possible advantage, qualities which I presume I gained together with my once admired, but now odiously detested figure, prevented me from making such an exhibition, although I verily believe that I was haunted with demoniac incitements to perform all manner of curious antics.
- 35. The crowd was now at its thickest. A chariot, with servants in splendid liveries, which I immediately recognized as my own, whirled onward. Julia was seated in it by myself, or the devil in my shape. There I was, perfectly plain to behold. The face, the form were the same, but the dress superlatively exquisite, and beautifully adapted to the figure. The turn-out of Fitzcrocky dashed by at the same time. He glared furiously upon my happy representative. With matchless insinuation this latter ogled and flirted with Julia. She returned his smiles with eyliads of incipient affection. As they passed me by, the fellow who had thus impudently usurped my figure and property winked—yes, he absolutely winked at me. My veins boiled with rage. Shrieking out a fearful oath, I seized a fragment of paving-stone and hurled it frantically at him. A scream, a rush, and I turned and fled, without stopping to ascertain the amount of damage inflicted by my missile, and ran as if the furies had been after me. But I ran not alone. A dense crowd of policemen, servants and gentleman on horseback dashed in pursuit. Never did fugitive from the galleys exert his legs with a better will, or with more effect, than I did. Timor additit alas. On I rushed, amidst the clamor, and dust, and clatter of the yelling multitude, as if the avenger of blood had been behind me. I had been a sportsman, and never did a Leicestershire fox lead a squad of Meltonians such a circumbendibus as I did my pursuers. One by one they gave in—the noise died away gradually, and I was safe. When partially recovered, I found myself within a queer, dark- looking old court, in the neighborhood of Hertford street and Brick Lane. I was surrounded by a multitude of crazy, loitering, reeking houses, apparently the abodes of no living beings, save Jew clothesmen, oyster venders, pawnbrokers, and gin dealers. A squalid, miserable, broken-down dog-kennel it was too! Tattered children ran about, dabbling in the filthy gutters, indulging in the mockery of play. Rough looking men, wrapped in heavy pea-coats and coarse jackets, with red and bloated faces, lounged about the doors of the various dealers, and haggard, wretched-looking women might have been descried entering the dens of the pawnbrokers, in hopes to raise some pittance of money for the purchase of food or
- 36. liquor, by pledging paltry articles of dress or furniture. I sat down on the pavement side and stared around me. The scene was altogether dissimilar to any thing I had been in the habit of witnessing, and it was an interesting though a painful novelty. Good God! the misery, and wretchedness, and grinding poverty, deadening to the heart, which exist in large cities, within ken of opulence, of luxury and of splendor! O! could the voice of these wretched throngs be heard, in its collected wailing, what a cry of despairful agony would go up to the throne of the Everlasting! Dead souls in living sepulchres, stalking their gloomy round of poverty, neglect and wo—uneducated, ungodly, famine-stricken—what hope is there for them in this world, and, word of horror, what in the next! As I sat in revery, some one tapped me on the shoulder. I looked up. A stout, heavily built man, with a pimpled and swollen face, attired in a rough drab over-coat, with leather gaiters and hob-nailed bootees, stood beside me. “Hollo, gen’l’mn Bill,” quoth this interesting parsonage. “Vy, vot brings you in these parts?” I knew the fellow at first glance, but, by Jupiter, I had never seen him before. “Well, old fellow,” said I, with a hilarity that disgusted me, although Heaven knows I couldn’t help it, “what news from your ken?” “I’tell thee vot,” said Gabriel Sooterkins, for the gentleman was familiarly known by that appellation, “a’ter this night, Billy, my bo, you had better change your tramp. The beaks ’ave nabbed Ikey about that ’ere job on Saffron Hill, and they say he’s peached upon it. Confound the trade, say I, if pals can’t be true to one another.” I recollected perfectly the matter he alluded to. It was a burglary committed upon an old miser, who had fixed his dwelling in that delicate abode, and I very well remembered, now that Mr. Gabriel Sooterkins mentioned it, that I had been the head and front of the offending, and that Ikey and himself were accomplices in the business. An exceedingly reputable exchange of persons I had made.
- 37. “Well,” said I, “if it’s done it can’t be helped, you know, and I’m off this night,” although I had not the most remote idea of where I was going. “If I’d a known vere you vos,” said Mr. Sooterkins, “I’d ha’ blowed this here spot o’ work afore. But step in here. I’ve a vord or two to say to you, for I s’pose there’s very little dust at the bottom of your fob.” Mr. Sooterkins plunged downward into a dingy cellar, and I followed him very obediently. The place into which I accompanied him was a filthy diving, or slap-bang shop, in which retreat was collected as motley an assemblage as the imagination of man can conceive. A long table extended from one end of the cellar to the other, covered with pewter mugs and dishes, cheap crockery ware, and knives and forks, which latter implements were chained to the table. A very satisfactory idea of the morals of the guests might be gathered from this circumstance; although, indeed, if that hint had been wanting, the variety of villany stamped upon the faces of the profligate crew which surrounded the table, gave proof satisfactory that they were not of that number who rank with the honest of this world. Mr. Sooterkins nodded to this amiable assembly upon entering, and I obeyed his example, inasmuch as I recognized among these gentlemen some very familiar acquaintances. We were received in a remarkably hilarious manner, and some of the most jovial of our friends pressed their regards rather closely, by playing off two or three practical jokes upon Mr. Sooterkins. The application of a quart pot to the head of the most forward of these wits sent him howling into a corner, and, to my unspeakable satisfaction, put a very sudden conclusion to the incipient merriment. “Take that,” growled Sooterkins, “and now, as you gen’l’mn seems to be so ’ighly delighted at this here cheerful occasion, you’ll just ’ave the goodness to leave me and my pal to our own cards for a brace of minnits. You see, Bill, ve must speak to Sal, and git posted up on this last score. Hollo! Sal! you old limb of Satan, move yer shanks this way, I tell ye!”
- 38. A withered crone, who seemed to be the mistress of the cellar, came hobbling forward, being thus politely conjured to appear. “Wot!” said she, extending her wrinkled hand to me. “Gentleman Bill here! Here’s a sight for sore eyes!” “Dight your gab,” interrupted Sooterkins. “Bill’s here, but he’ll be obliged to cut and run this darkey, for the beaks are a’ter him ’bout that job of Ikey’s. Now he’s got no stump, and the devil a mag have I, so you must fork over, for the purchase wot come in vos fairly vorth double as much nor you paid for it. Bill, and Ikey, and I, are all in fur the business, but the blackguard daren’t peach on me, ’cause if he gits off from this scrape, I knows enough of other matters about him to bring him to a hemp crawat wery speedily. You’ve got the plunder, you old hag, and it’s only fair as you should come down with the tin for the tramp.” “Ah, Gabe,” said the old woman, “you will drive hard bargains with me. But I can’t well refuse for the pretty face of him.” Singular as it may appear. I felt gratified by the compliment of the hag. “Yes, mother,” said I, “change of air is good for the constitution, and I’ll cheat Jack Ketch of his fees in spite of fate for this bout.” “How much can you do vith?” queried Mr. Sooterkins, who had lighted a fragment of a clay pipe, and commenced to smoke most industriously. “Ten pounds will carry me on to Portsmouth,” said I, for the localities and resources of roguery were fast becoming familiar to me. “Too much,” grumbled the crone. Gabe was about to make a savage reply, when two females descended the ladder, and entered the cellar. “By my forks!” whistled Gabe. “This ’ere is just wot I hoped vouldn’t ’appen; but these cussed gals is everlastin’ly a riggin a man, till he trots over the Old Bailey valls on a vooden oss.” “Bill!” cried one of the females, recognizing and running to me. “Is it you, Bill? I’ve been over the whole of this blessed town after you, for I heard that Ikey Solomon had let all out, and I feared that you were caught. But, thank Heaven, you’re safe—you’re safe!”
- 39. With an hysterical burst of laughter, the girl threw her arms around me and embraced me tightly. Her laughter gradually ceased, and gave way to a violent fit of weeping. Amazed at first, and not knowing what she could mean, the truth began to break upon me. Poor girl! The burglar’s mistress! What a world of guilt and wo are in those words! Her face was handsome, but oh! how deadly pale, save on the summit of the cheek-bones, where the fire of the hectic blazed. Her large, dark orbs were sunken, and gleamed like the reflected glow of a furnace from their deep cavities. Her apparel, which was a shade or two better than that of her companion, and her language, which showed her to be superior to the wretched assemblage around us, told a tale of sorrow—which, although a common tale, struck deeply on my heart. “Hang it, Bess,” said Sooterkins, endeavoring to push the girl away, “vot dost mean, crying and sniveling about a chap ven his wery life hangs on his speed in gettin’ out o’Lunnun? Stand aside, thou foolish jade, and let me have my say out vith him.” “Stand by, Bess dear,” said I, “and I will speak with you directly.” The girl obeyed. “Now then,” said Sooterkins, “As I’ve vormed the ten pounds out o’ Sal, all you’ve got to do is this. Be off now, d’rectly, and take all the by cuts till you’re out o’ town, snug in the fields. I’ve a friend as goes down on the mail in the morning, and mind, give him this jark. He’ll be down on the sly with you, for my sake. Then pull for Common Hard, and off over the Channel, till this ’ere job blows by. Lose no time, the night’s dark, and make forward like the wind.” “And Bess?” said I, for the girl’s affection had interested me, and the emotions of my burglar friend began to quicken in my breast. “Pshaw!” said Sooterkins, “why canst not mind thine own affairs, and let the girl alone?” “I must speak to her before I go, Gabe,” I replied. “What she is, I have made her, and it would break my heart to leave her thus.” “Speak, then, fool, and be spry about it.” “Bess,” said I, stealing my arm around the waist of the unfortunate girl, “I must be off for Portsmouth.”
- 40. “Are you going, Bill?” she said, in a low and tremulous voice, as she lifted her eyes anxiously to mine; and that expression cut me to the soul, keen as a knife, “I never shall see you again.” “Hush, dearest, you must not speak so. We shall see each other soon, and live as happy days as ever.” The eyes of the young girl became suffused with tears. “Happy! No, Bill, I never shall know happiness again. I have been weak and ill of late. I’m dying, Bill, and I know it. Before you will dare to return here, I shall be laid, in the parish shell, cold enough in the grave of a pauper. Do you remember the little cottage near the Downs? Ah! those were my happy days. Then I was innocent, but you—but I wont speak of that, dearest, for I would not distress you.” “Nay, Bess, compose yourself—” “In the sleep of death? There is no other composure for me. You are going, and the strings of my heart snap as I look upon you for the last time. Oh! through misery and crime, Bill—and we have been miserable and criminal—I have loved you, dearer than the light of heaven! But, dearest, if you do escape and return, quit this awful life, for the sake of her whom you once vowed never to abandon— quit this den of villainy, and for God’s sake, oh, never enter it again!” The tears gushed from my eyes at this appeal, and my whole frame was shaken. “I promise—I swear it,” whispered I. “Thank you, dearest. Take this little ring. You know its history. And now, for the last time, this kiss. Farewell!” Her head sunk upon her breast. Bestowing an embrace upon her, I darted from her side, and sprang up the steps of the cellar. At the foot I paused for a moment. Bess had hidden her face in her lap, and the heaving of her breast, plainly perceptible through its thin covering, testified the agony of her spirit. The labyrinths of the dark and dingy by-streets seemed familiar to me as the interior of my own house. In fact, I was becoming rapidly identified with the character, as well as with the person of the burglar. But as I sped on, the recollection of my former condition was forcibly recalled, as I came upon a tailor’s shop, ostentatiously placed at the corner of a well lighted street. The view of that shop
- 41. acted as a talisman. It recalled me to a due sense, and to a most painful recollection of the transactions of the preceding night, and of my rencontre in Hyde Park with the usurper of my rights. I recollected perfectly well that I had received an invitation to a grand gala at Lord Flannery’s for this evening, of which I doubted not for an instant that my representative would avail himself. Julia, I also knew, had promised to be there. Curiosity, no less than jealousy, spurred me on. I felt a strong desire to see in what manner and to what advantage I should appear. I determined to make my way to his lordship’s, forgetting that if the police laid eyes upon me, I should dangle most loftily from the front of Newgate or the Old Bailey. Onward I strode until I reached Grosvenor Square, from near which point I had started on my morning peregrinations. It was past eleven o’clock. I stationed myself in front of Lord Flannery’s mansion, where the glow of lights, crowds of liveried menials, and the sound of music indicated the commencement of the rout. Equipage after equipage rolled up, and depositing their inmates at the door, drove off in rapid succession. Crowds of fashionables swarmed the apartments. I waited for Julia’s arrival until my patience was nearly exhausted, and I was upon the point of giving the matter up in despair, when a magnificent turn-out drove up to the door, and Flashington Highflyer, Esquire, descended from the vehicle, attired in a most recherché evening dress, and handed out— proh pudor!—the Honorable Miss Julia Adeliza Dashleigh! I was petrified with astonishment. There was the figure which had excited her laughter but the previous night, and which was evidently the present object of her favorable regard. As the pair passed me, the light from the hall shone strongly upon my features. My representative gave me, en passant, a most facetious dig in the small ribs with his elbow, and suddenly clapping his hands upon his pockets, exclaimed, “There are thieves here! I have lost my snuff-box and my handkerchief!” “Dear Mr. Highflyer!” said Julia, with a winning glance.
- 42. “Secure this fellow,” said the hateful scoundrel, for whose crimes I was penitently atoning, pointing to me. “He has a suspicious look. Bring him into the hall. Come, dearest Julia, I will attend you to the dressing-room, and will then return to examine this man.” Instantly I was pounced upon by a police officer, assisted by a dozen servants, and in spite of my cries and protestations of innocence, was dragged into the hall. Mr. Highflyer was not long in making his appearance. “Search him, officer,” said he, as he drew out his tooth-pick, and planted himself in a very Lara-like style, with his back to the banisters. “You infernal, thieving, rope-cracking black-guard!” I roared, goaded to the very verge of insanity by these accumulated misadventures. “Gag him,” said my tormentor. “Have you found any thing, officer?” “All right, sir,” replied that functionary, “Is this here vipe yours?” Shocking to relate, the missing articles were found upon me! “That handkerchief is mine, as well as the snuff-box. I shall appear to prosecute. Off with him to Bow Street. A p-r-e-e-tt-y good- looking chap for a pickpocket,” continued he, as he turned his head with a supercilious smile, and examined me through his eye-glass. The smile gave way to a sneer of the most diabolical description as he ascended the staircase. I had never thought myself so confoundedly ugly as I did at that moment. Of course I was dragged off to the police-office, upon the charge of robbing myself. All that I could say would be of no avail, therefore I kept a most stoical silence. Having arrived at our destination, I was walked in before the head of the police, who, after a long and scrutinizing survey of my person, whispered an officer, who went out. I was then desired, or rather commanded, to extend my wrists to another officer, who placed upon them a very ornamental, but not very agreeable appendage, in the shape of a pair of manacles. I had subsided into a dogged, sullen, almost unconscious state of mind, and was becoming, in fact, very careless as regarded consequences. Half an hour had elapsed, when the officer who had spoken with the
- 43. chief of police, returned. He whispered the presiding functionary, who grinned approvingly. “Well, my kiddy,” said he, “the Saffron-Hill job warn’t enough for you, eh? But I’ve caged you now, bird, and you’ll be made to sing plenty loud for that matter, outcepting this altogether.” “I never heerd the like of this lark,” said the under-strapper. “It’s a rigler demeanin’ of the trade. Here’s one of your Jimmy burglary swells come down to a-sneak of a pickpocket!” It would be a work of supererogation to detail the variety of insults and the tortures of mind that I was forced to undergo from my appearance before the magistrate the next morning, until my final trial at the Old Bailey upon the charge of burglary. I had heard nothing of my ingenious tyrant, who was evidently, at the time I saw him last, in a very fair way to lead my lady-love to the altar. Nor, indeed, had I any opportunity of hearing from him. I saw no persons save my keeper, and a little, seedy, Jew attorney, whom I discovered to be in pay of the gang of which I was a worthy member. After various consultations with this gentleman, who informed me that he would be able, in spite of the veracious testimony of the respectable Mr. Ikey Solomons, to produce a satisfactory alibi, it was decided that I was to put in the plea of Not Guilty. The day of trial arrived, after a weary and solitary residence within the walls of my prison of a month. None of the gang came near me, and I could never learn any tidings of Bess. At the appointed time, I was escorted into the court, and being duly arraigned, the charge was read to me, in that agreeable nasality of tone peculiar to the clerks of all legal tribunals. During this process, to which I paid not the least attention, I espied a newspaper lying by the side of the dock. I picked it up, and was vacantly pouring over the columns, unseen by my jailers, when my attention was riveted by the following paragraph, which filled my breast with horror and despair. “Married, by the Right Rev. Doctor Dumfungle, at St. Martin’s in the Fields, Flashington Highflyer, Esq., to the Hon. Julia Adeliza, daughter of Sir Poins Dashleigh, Bart.”
- 44. The climax to my sorrows had then arrived. The whole man was quelled within me. Spectators, judge and jury were all forgotten, and the tide of my woes rushed irresistibly onward, overwhelming me in the vortex. The question was put in the usual form, “guilty or not guilty?” Life had cloyed with me. I longed to occupy a resting place where I should be secure from the scorn and the persecutions of the world. The grave offered this refuge, and I gladly embraced it. I therefore rose from my seat, and replied to the query of the clerk, “guilty.” My attorney fairly fell under the table with astonishment. The whole assemblage seemed utterly confounded at my audacity, and a voice was heard above the general buz of tongues, which I recognized as appertaining to my acquaintance, Mr. Sooterkins. “Vell, by blazes, h’aint you gone and done it!” Of course I was sentenced to be hanged. Day after day dragged on its weary course, and as I gazed at the gray walls of my dungeon, my heart seemed to harden like the stone itself. In vain did the ministers of the gospel strive to arouse me from my apathy. All was cold and dead within me. The day before that which was fixed for my execution, to my extreme surprise, Mr. Flashington Highflyer entered my cell. For some time indignation chained up my tongue. I experienced a choking sensation as I stared furiously upon my visiter, whose countenance was drawn out into the most hypocritical length. This did not very long continue, for the solemn visage which he had chosen to exhibit at his entrance soon gave place to a most malicious and devilish sneer. “Well,” said he, with an odious chuckle, “my fine fellow, how d’ye like your bargain?” “Avaunt, fiend!” I exclaimed. He certainly manifested no symptoms of departure, but lolling upon my bunk, produced a Havana from his mother-of-pearl cigar-case, and igniting it by means of a Lucifer, commenced to smoke with great sang froid. “Pretty pleasant lodgings, those of yours, my old chap, but your wardrobe was horridly low and vulgar. In fact, I was compelled to
- 45. make a bonfire of all your old clothes, before I could manage to put it into tolerable order.” “You infernal scoundrel!” I roared, goaded to madness by this last insult. “I told you that you should pay for your rascality, and, by heaven, you shall pay for it now!” As I spoke, I rushed upon him and grappled tightly with him. He resisted strenuously, but rage had nerved me with the strength of a dozen men, and seizing him by the throat, we rolled upon the ground together. “Ya—ya—yough! Gollamity, massa, what you do? Want fur choke Sip?—oh, murder! murder!” I looked with bewildered eyes around me. I had upset the table, tumbled from my chair upon the floor, and had grappled poor Scipio by the throat, until his eye-balls protruded an inch from his head. “Hollo!” I cried, “where the devil am I?” “Why, you home, be sure, massa,” replied Scipio, whimpering from the effects of the rough salutation I had bestowed upon him, “and be broad daylight, and you no bin to bed yit.” I looked at the decanter. It was empty. “Oh!” ejaculated I. The odious apparel of the preceding night still decked my person and strewed the room. There was a sickening odor of stale tobacco- smoke hovering through the chamber, and, with a very clear perception that I should require a tumbler of Hock and soda to reinvigorate the inner man, I arrived at the comfortable conclusion that I was still in propria persona, the “man who could never dress well.” P. S. I’m off to Paris. Fitzcrocky has Julia’s promise. A pea-green coat with gilt buttons, and a scarlet satin lining has done my business.
- 46. SUMMER’S BACCHANAL. ——— BY J. BAYARD TAYLOR. ———
- 47. Fill the cup from some secretest fountain, Under granite ledges, deep and low, Where the crystal vintage of the mountain Runs in foam from dazzling fields of snow! Some lost stream, that in a woodland hollow Coils, to sleep its weariness away, Hid from prying stars, that fain would follow, In the emerald glooms of hemlock spray. Fill, dear friend, a goblet cool and sparkling As the sunlight of October morns— Not for us the crimson wave, that darkling Stains the lips of olden drinking-horns! We will quaff, beneath the noontide glowing, Draughts of nectar, sweet as faery dew; Couched on ferny banks, where light airs blowing, Shake the leaves between us and the blue. We will pledge, in breathless, long libation, All we have been, or have sworn to be— Fame, and Joy, and Love’s dear adoration— Summer’s lusty bacchanals are we! Fill again, and let our goblets, clashing, Stir the feathery ripples on the brim: Let the light, within their bosoms flashing, Leap like youth to every idle limb! Round the white roots of the fragrant lily And the mossy hazels, purple-stained, Once the music of these waters chilly Gave return for all the sweetness drained. How that rare, delicious, woodland flavor
- 48. Mocked my palate in the fever hours, When I pined for springs of coolest savor, As the burning Earth for thunder-showers! In the wave, that through my maddened dreaming Flowed to cheat me, fill the cups again! Drink, dear friend, to life which is not seeming— Fresh as this to manhood’s heart and brain! Fill, fill high! and while our goblets, ringing, Shine with vintage of the mountain-snow, Youth’s bright Fountain, clear and blithely springing. Brims our souls to endless overflow! THE PLANTATION OF GENERAL TAYLOR. [SEE ENGRAVING.] We present our readers this month with the first of a series of views which, by permission, we have caused to be engraved expressly for this Magazine, from Mr. John R. Smith’s celebrated Panorama of the Mississippi River. It represents the cotton plantation belonging to the recently elected President of the U. S., General Zachary Taylor. It is situated on the eastern branch of the Mississippi River, in Jefferson county, Mississippi, seven miles below the town of Rodney, between the estates of James Suggett, on the north, and Colonel Barker, on the south. The view embraces the overseer’s house, the cottages of the laborers, with a small portion of the broad acres which are comprised in the plantation. The spot is interesting, not only as being the property and the occasional residence of a distinguished public man, but as affording a specimen of those cotton estates, the culture of which exerts so important an influence on the commercial and financial destinies of the republic.
- 49. Plantation of General Taylor FANCIES ABOUT A LOCK OF HAIR. ——— BY S. D. ANDERSON. ———
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