检索结果-内蒙古大学图书馆

low complexity deblocking method for DCT coded video signals

iee PROCEEDINGS-VISION image AND SIGNAL PROCESSING 2006年第1期153卷 46-56页

作者： Tai, SC Chen, YR Chen, CY Chen, YH Natl Cheng Kung Univ Dept Elect Engn Tainan 70101 Taiwan Natl Cheng Kung Univ Inst Comp & Commun Tainan 70101 Taiwan

A new method to remove blocking artefacts in low bit-rate block-based video coding, such as MPEG-4 and H.264, is presented. A low computational deblocking filter with five modes is proposed, including three frequency-related modes (smooth mode, intermediate mode, and complex mode for low-frequency, mid-frequency, and high-frequency regions, respectively), one special mode (steep mode for a large offset between two blocks) and a refined mode (corner mode for the corner of four blocks). A mode decision procedure is also needed to decide which mode is given by observing pixel behaviour around the block boundary. To take the masking effect of the human visual system (HVS) into consideration, the filter for smooth mode is designed to be much stronger than that for complex mode, because human eyes are more sensitive to smooth regions. Experimental results show that, in most cases, the proposed algorithm removes more blocking artefacts than MPEG-4 deblocking filters do, and improves both subjective and objective image quality. The proposed algorithm keeps the computation lower than MPEG-4 and is suitable for most block-based image and video coding systems.

关键词： SIGNAL processing image processing SIGNAL processing -- Digital techniques DIGITAL image processing MPEG (Video coding standard) DIGITAL video -- Standards VIDEO compression -- Standards VIDEO equipment DIGITAL electronics

来源：评论

学校读者我要写书评

暂无评论

Strategies to improve the performance of very low bit rate speech coders and application to a variable rate 1.2 kb/s codec

引用

iee PROCEEDINGS-VISION image AND SIGNAL PROCESSING 2005年第1期152卷 74-86页

作者： de Lamare, RC Alcaim, A CETUC PUC RIO BR-22453900 Rio De Janeiro Brazil

This paper presents several strategies to improve the performance of very low bit rate speech coders and describes a speech codec that incorporates these strategies and operates at an average bit rate of 1.2 kb/s. The encoding algorithm is based on several improvements in a mixed multiband excitation (MMBE) linear predictive coding (LPC) structure. A switched-predictive vector quantiser technique that outperforms previously reported schemes is adopted to encode the LSF parameters. Spectral and sound specific low rate models are used in order to achieve high quality speech at low rates. An MMBE approach with three sub-bands is employed to encode voiced frames, while fricatives and stops modelling and synthesis techniques are used for unvoiced frames. This strategy is shown to provide good quality synthesised speech, at a bit rate of only 0.4 kb/s for unvoiced frames. To reduce coding noise and improve decoded speech, spectral envelope restoration combined with noise reduction (SERNR) postfifter is used. The contributions of the techniques described in this paper are separately assessed and then combined in the design of a low bit rate codec that is evaluated against the North American Mixed Excitation Linear Prediction (MELP) coder. The performance assessment is carried out in terms of the spectral distortion of LSF quantisation, mean opinion score (MOS), A/B comparison tests and the ITU-T P.862 perceptual evaluation of speech quality (PESQ) standard. Assessment results show that the improved methods for LSF quantisation, sound specific modelling and synthesis and the new postfiltering approach can significantly outperform previously reported techniques. Further results also indicate that a system combining the proposed improvements and operating at 1.2 kb/s, is comparable (slightly outperforming) a MELP coder operating at 2.4kb/s. For tandem connection situations, the proposed system is clearly superior to the MELP coder.

关键词： ALGORITHMS PARAMETER estimation ESTIMATION theory SPEECH codes theory coding theory SPEECH -- Study & teaching

来源：评论

学校读者我要写书评

暂无评论

Novel embedded image coding algorithms based on wavelet difference reduction

引用

iee PROCEEDINGS-VISION image AND SIGNAL PROCESSING 2005年第1期152卷 9-19页

作者： Yuan, Y Mandal, MK Univ Alberta Dept Elect & Comp Engn Multimedia Comp & Commun Lab Edmonton AB T6G 2V4 Canada

Wavelet difference reduction (WDR) has recently been proposed as a method for efficient embedded image coding. In this paper, the WDR algorithm is analysed and four new techniques are proposed to either reduce its complexity or improve its rate distortion (RD) performance. The first technique, dubbed modified WDR-A (MWDR-A), focuses on improving the efficiency of the arithmetic coding (AC) stage of the WDR. Based on experiments with the statistics of the output symbol sequence, it is shown that the symbols can either be arithmetic coded under different contexts or output without AC. In the second technique, MWDR-B, the AC stage is dropped from the coder. By employing MWDR-B, up to 20% of coding time can be saved without sacrificing the RD performance, when compared to WDR. The third technique focuses on the improvement of RD performance using context modelling. A low-complexity context model is proposed to exploit the statistical dependency among the wavelet coefficients. This technique is termed context-modelled WDR (CM-WDR), and acts without the AC stage to improve the RD performance by up to 1.5 dB over WDR on a set of test images, at various bit rates. The fourth technique combines CM-WDR with AC and achieves a 0.2 dB improvement over CM-WDR in terms of PSNR. The proposed techniques retain all the features of WDR, including low complexity, region-of-interest capability, and embeddedness.

关键词： ALGORITHMS INFORMATION theory MATHEMATICAL analysis WAVELETS (Mathematics) coding theory RATE distortion theory HARMONIC analysis (Mathematics)

来源：评论

学校读者我要写书评

暂无评论

Efficient low bit-rate embedded colour video coding with 3D-spiht

Efficient low bit-rate embedded colour video coding with 3D-...

引用

iee International Conference on Visual Information Engineering, VIE 2005

作者： Khelifi, Fouad Bouridane, Ahmed School of Computer Science Queen's University Belfast United Kingdom

This paper proposes an extension of 3D-SPIHT for low bit-rate embedded colour video coding. The aim is to increase the efficiency and keep the full embeddedness of the coding. The extended technique is inspired from our previous work for still images [7]. Since the chrominance components U and V in the YUV colour image format are sufficiently less significant in terms of energy when compared to the luminance components, a large number of trees at the same spatio-temporal location in the chrominance planes are insignificant for a given threshold. We propose to join the chrominance components in the list of insignificant sets by using a composite spatio-temporal trees structure specific to the chrominance. Our proposed technique has been assessed and compared against the independent spatio-temporal orientation trees method when applied on YUV 4:4:4 colour space and the results have shown a significant improvement in terms of PSNR especially at low bit-rate coding.

关键词： image coding

来源：评论

学校读者我要写书评

暂无评论

Smooth side-match weighted vector quantiser with variable block size for image coding

Smooth side-match weighted vector quantiser with variable bl...

引用

作者： Yang, S.-B. Department of Computer Science and Information Engineering Leader University No. 188 Sec. 5 An-Chung Rd. Tainan City Taiwan

Although side-match vector quantisation (SMVQ) reduces the bit rate, the quality of image coding using SMVQ generally degenerates as the grey level transition across the boundaries of neighbouring blocks increases or decreases. The author proposes a smooth side-match weighted method to yield a state codebook according to the smoothness of the grey levels between neighbouring blocks. When a block is encoded, a corresponding weight is assigned to each neighbouring block to represent its relative importance using the smooth side-match weighted method. This smooth side-match weighted vector quantisation (SSMWVQ) achieves a higher PSNR than SMVQ at the same bit rate. Also, each block can be pre-encoded in an image, allowing each encoded block to use all neighbouring blocks to yield the state codebook in SSMWVQ, rather than using only two neighbouring blocks, as in SMVQ. Moreover, SSMWVQ selects many highdetail blocks as basic blocks to enhance the coding quality, and merges many low-detail blocks into a larger one to reduce further the bit rate. Experimental results reveal that SSMWVQ has a higher PSNR and lower bit rate than other methods.

关键词： Vector quantization

来源：评论

学校读者我要写书评

暂无评论

Recent developments in audio coding

Recent developments in audio coding

引用

12th International Workshop on Systems, Signals and image Processing

作者： Bartkowiak, M Poznan Tech Univ Div Multimedia Telecommun & Radioelect PL-60965 Poznan Poland

ISBN: (纸本)0907776205

A tremendous progress has taken place in audio coding technologies in recent years. Perceptual coding paradigm became ubiquitous among standard and proprietary techniques for compressed audio storage and delivery in applications ranging from narrowband internet streaming of music and speech to high definition multichannel home theatre. coding scenarios make heavy use of psychoacoustics, especially masking phenomena that render some components of the sound inaudible in the presence of other strong components with similar spectra. Departing from 1st generation basic subband coding scheme with perceptually controlled uniform scalar quantization, modern algorithms of 2nd and 3rd generation have evolved into sophisticated forms of transform coding with switched time and frequency resolution and temporal shaping of quantization noise. Several additional tools have been introduced to model and remove the redundant and perceptually irrelevant components of audio signal, thus increasing the coding efficiency. These tools include variants of prediction in time and frequency domain, perceptual substitution of noise components, diverse quantization schemes (including vector quantization) and refined entropy coding. Although the original 1st and 2nd generation techniques were aimed at near-CD or broadcast quality, there was a strong demand for codecs offering decent quality at reduced bit rate. At very low bit rates however, traditional waveform coding methods are no longer able to hide the quantization noise below the threshold of audibility and coding artefacts become apparent because the masking conditions of the perceptual models are heavily violated. The 4th generation audio codec recently standardized by ISO uses two new model-based tools to describe parametrically the high frequency content and spatial information instead of coding them. Spectral band replication and parametric stereo encoding allow reducing the bit rate required for good quality audio down to a range whi

关键词： Audio acoustics

来源：评论

学校读者我要写书评

暂无评论

Visual perception of content-prioritised sign language video quality

Visual perception of content-prioritised sign language video...

引用

iee International Conference on Visual Information Engineering, VIE 2005

作者： Muir, L.J. Richardson, I.E.G. Hamilton, K. Image Communication Technology Group Robert Gordon University Schoolhill Aberdeen United Kingdom

Video communication systems currently provide poor quality and performance for deaf people using sign language, particularly at low bit rates. Our previous work, involving eye movement tracking experiments and analysis of visual attention mechanisms for sign language, demonstrated a consistent characteristic response which could be exploited to enable optimisation of video coding systems performance by prioritising content for deaf users. This paper describes an experiment designed to test the perceived quality of selectively prioritised video for sign language communication. A series of selectively degraded video clips was shown to individual deaf viewers. Participants subjectively rated the quality of the modified video on a Degradation Category Rating (DCR) scale adapted for sign language users. The results demonstrate the potential to develop content-prioritised coding schemes, based on viewing behaviour, which can reduce bandwidth requirements and provide best quality for the needs of the user. We propose selective quantisation to reduce compression in visually important regions of video images, which require spatial detail for small slow motion detection, and increased compression of regions regarded in peripheral vision where large rapid movements occur in sign language communication.

关键词： Communication systems

来源：评论

学校读者我要写书评

暂无评论

Advanced DSP based system for image transmission over GSM/GPRS networks

Advanced DSP based system for image transmission over GSM/GP...

引用

12th International Workshop on Systems, Signals and image Processing

作者： Mohorko, J Gleich, D Planinsic, P Ultra Advanced Research Center Ultra D.o.o. Co. Cesta Otona Zupancica 23a Slovenia Faculty of Electrical Engineering and Computer Science University of Maribor 2000 Maribor Gosposvetska ulica 84 Slovenia University of Maribor Slovenia Ultra D.o.o Co. Slovenia IEEE Slovenia Laboratory for Signal Processing and Remote Control University of Maribor Slovenia DLR Institute in Oberpfaffenhofen Germany SPIE

ISBN: (纸本)0907776205

In this article the development of the prototype of complex hierarchical organized sensor/control system that enables the capture and transmission of high quality images through mobile networks is described. Compression methods (codecs) for image information contents are used for effective image transfer through bandwidth limited communication channel. JPEG method is one of the implemented methods. It is the most known standard method on the field of lossy methods, but it gives poor results at high compression rations. The best compression methods are based on Wavelet transformation. In our implementation lifting scheme for a 9/7-filter bank was used to compute wavelet transform and the novel coding process and ordering of bit plane bits is presented which is comparable with a JPEG2000 codec in rate-distortion sense and has lower computational complexity as JPEG2000. A trade-off between a complexity and efficiency has been made to meet the cannel capacity of the GSM/GPPS network. Coder prototype is realized in compact DSP video module with relatively low cornputational power. Usability of the described methods is demonstrated on Internet based application 'Information system for image data collecting and distribution.

关键词： image compression wavelet transform coding internet protocol JPEG GSM GPRS DSP

来源：评论

学校读者我要写书评

暂无评论

Efficient compressed domain target image search and retrieval

Efficient compressed domain target image search and retrieva...

引用

4th International Conference on image and Video Retrieval, CIVR 2005

作者： Bracamonte, Javier Ansorge, Michael Pellandini, Fausto Farine, Pierre-Andreá Institute of Microtechnology University of Neuchâtel Rue A.-L Breguet 2 2000 Neuchâtel Switzerland

In this paper we introduce a low complexity and accurate technique for target image search and retrieval. This method, which operates directly in the compressed JPEG domain, addresses two of the CBIR challenges stated by The Benchathlon Network regarding the search of a specific image: finding out if an exact same image exists in a database, and identifying this occurrence even when the database image has been compressed with a different coding bit-rate. The proposed technique can be applied in feature-containing or featureless image collections, and thus it is also suitable to search for image copies that might exist on the Web for law enforcement of copyrighted material. The reported method exploits the fact that the phase of the Discrete Cosine Transform coefficients contains a significant amount of information of a transformed image. By processing only the phase part of these coefficients, a simple, fast, and accurate target image search and retrieval technique is achieved. © Springer-Verlag Berlin Heidelberg 2005.

关键词： image retrieval

来源：评论

学校读者我要写书评

暂无评论

EFFICIENT low bit-RATE EMBEDDED COLOUR VIDEO coding WITH 3D-SPIHT

EFFICIENT LOW BIT-RATE EMBEDDED COLOUR VIDEO CODING WITH 3D-...

引用

iee International Conference on Visual Information Engineering (VIE 2005)

作者： Fouad Khelifi Ahmed Bouridane School of Computer Science Queen's university Belfast UK

关键词： 3-D Wavelet transform Luminance Chrominance SPIHT Scalability

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：