The assessment of station designs by applying pedestrian flow simulation models is addressed. In ... more The assessment of station designs by applying pedestrian flow simulation models is addressed. In particular, station design issues pertain to the way access gates will affect pedestrian flow operations in regard to levels of service, congestion levels, average walking times, ...
In this paper, we exploit a recently introduced coding algorithm called multidimensional multisca... more In this paper, we exploit a recently introduced coding algorithm called multidimensional multiscale parser (MMP) as an alternative to the traditional transform quantization-based methods. MMP uses approximate pattern matching with adaptive multiscale dictionaries that contain concatenations of scaled versions of previously encoded image blocks. We propose the use of predictive coding schemes that modify the source's probability distribution, in order to favour the efficiency of MMP's dictionary adaptation. Statistical conditioning is also used, allowing for an increased coding efficiency of the dictionaries' symbols. New dictionary design methods, that allow for an effective compromise between the introduction of new dictionary elements and the reduction of codebook redundancy, are also proposed. Experimental results validate the proposed techniques by showing consistent improvements in PSNR performance over the original MMP algorithm. When compared with state-of-the-art methods, like JPEG2000 and H.264/AVC, the proposed algorithm achieves relevant gains (up to 6 dB) for nonsmooth images and very competitive results for smooth images. These results strongly suggest that the new paradigm posed by MMP can be regarded as an alternative to the one traditionally used in image coding, for a wide range of image types.
The Multidimensional Multiscale Parser (MMP) algorithm has been proposed recently as a universal ... more The Multidimensional Multiscale Parser (MMP) algorithm has been proposed recently as a universal data coding method. MMP has proved to be a very powerful coding method for images, as for other types of signals. Experimental tests showed that MMP is able to achieve better results than the traditional transform-based image coding methods, particularly for images that do not have a low-pass nature. These promising results motivated the use of MMP for residual error encoding in hybrid video coding algorithms. This paper presents the first results of these experiments, performed using a H.264/AVC based video encoder, but using MMP to encode the motion compensated residual data, for the P and B slices. Experimental results show that, even in this not fully optimised version, this method is able to achieve an approximately equivalent performance to the H.264/AVC. This demonstrates that MMP is an alternative to the transform-quantisation paradigm for hybrid video coding that is worth investigating.
In this paper, we propose a new encoder for scanned compound documents, based upon a recently int... more In this paper, we propose a new encoder for scanned compound documents, based upon a recently introduced coding paradigm called multidimensional multiscale parser (MMP). MMP uses approximate pattern matching, with adaptive multiscale dictionaries that contain concatenations of scaled versions of previously encoded image blocks. These features give MMP the ability to adjust to the input image's characteristics, resulting in high coding efficiencies for a wide range of image types. This versatility makes MMP a good candidate for compound digital document encoding. The proposed algorithm first classifies the image blocks as smooth (texture) and nonsmooth (text and graphics). Smooth and nonsmooth blocks are then compressed using different MMP-based encoders, adapted for encoding either type of blocks. The adaptive use of these two types of encoders resulted in performance gains over the original MMP algorithm, further increasing the performance advantage over the current state-of-the-art image encoders for scanned compound images, without compromising the performance for other image types.
The Multidimensional Multiscale Parser (MMP) algorithm is an image encoder that approximates the ... more The Multidimensional Multiscale Parser (MMP) algorithm is an image encoder that approximates the image blocks by using recurrent patterns, from an adaptive dictionary, at different scales. This encoder performs well for a large range of image data. However, images encoded with MMP suffer from blocking artifacts. This paper presents the design of a deblocking filter that improves the performance the MMP. We present the results of our research, that aims to increase the performance of MMP, particularly for smooth images, without causing quality losses for other image types, where its performance is already up to 5 dB better than that of top transform based encoders. For smooth images, the proposed filter introduces relevant perceptual quality gains by efficiently eliminating the blocking effects, without introducing the usual blurring artifacts. Besides this, we show that, unlike traditional deblocking algorithms, the proposed method also improves the objective quality of the decoded image, achieving PSNR gains of up to about 0.3 dB. With such gains, MMP reaches an almost equivalent performance to that of the state-of-the-art image encoders (equal to that of JPEG2000 for higher compression ratios), for smooth images, while maintaining its gains for non-smooth images. In fact, for all image types, the proposed method provides significant perceptual improvements, without sacrificing the PSNR performance.
The multidimensional multiscale parser (MMP) is a lossy multidimensional signal encoder, that use... more The multidimensional multiscale parser (MMP) is a lossy multidimensional signal encoder, that uses an adaptive dictionary for approximating the original signal using multiscale recurrent pattern matching. In previous work we have shown the efficiency of MMP for image coding and we have also described new techniques to improve its performance, using predictive coding (MMP-Intra) and innovative strategies for reducing the dictionary redundancy. The combination of these methods for image coding achieves much better results than the state-of-the-art JPEG2000 and H.264/AVC Intra image encoders for text and compound images, but for smooth natural images it still presents small losses. In this work we present a new technique to improve the dictionary adaptation process of the MMP-Intra, based on enhanced updating techniques. Experimental results have showed that, when combined with dictionary growth control methods, this technique achieves consistent image quality gains for all image types. Furthermore we present some methods that eliminate the intrinsic substantial increase of the computational complexity associated with more rapidly growing dictionaries, without compromising the final quality of the decoded image.
Abstractó MMP-Intra was recently proposed as a recurrent patterns based image encoder that combin... more Abstractó MMP-Intra was recently proposed as a recurrent patterns based image encoder that combines the Multidimen- sional Multiscale Parser (MMP) algorithm with intra prediction techniques. Our results show that this method is able to achieve considerable gains over state-of-the-art transform-based image encoders for a wide variety of types of images, like text, composed (text and graphics) and texture images, while
The assessment of station designs by applying pedestrian flow simulation models is addressed. In ... more The assessment of station designs by applying pedestrian flow simulation models is addressed. In particular, station design issues pertain to the way access gates will affect pedestrian flow operations in regard to levels of service, congestion levels, average walking times, ...
In this paper, we exploit a recently introduced coding algorithm called multidimensional multisca... more In this paper, we exploit a recently introduced coding algorithm called multidimensional multiscale parser (MMP) as an alternative to the traditional transform quantization-based methods. MMP uses approximate pattern matching with adaptive multiscale dictionaries that contain concatenations of scaled versions of previously encoded image blocks. We propose the use of predictive coding schemes that modify the source's probability distribution, in order to favour the efficiency of MMP's dictionary adaptation. Statistical conditioning is also used, allowing for an increased coding efficiency of the dictionaries' symbols. New dictionary design methods, that allow for an effective compromise between the introduction of new dictionary elements and the reduction of codebook redundancy, are also proposed. Experimental results validate the proposed techniques by showing consistent improvements in PSNR performance over the original MMP algorithm. When compared with state-of-the-art methods, like JPEG2000 and H.264/AVC, the proposed algorithm achieves relevant gains (up to 6 dB) for nonsmooth images and very competitive results for smooth images. These results strongly suggest that the new paradigm posed by MMP can be regarded as an alternative to the one traditionally used in image coding, for a wide range of image types.
The Multidimensional Multiscale Parser (MMP) algorithm has been proposed recently as a universal ... more The Multidimensional Multiscale Parser (MMP) algorithm has been proposed recently as a universal data coding method. MMP has proved to be a very powerful coding method for images, as for other types of signals. Experimental tests showed that MMP is able to achieve better results than the traditional transform-based image coding methods, particularly for images that do not have a low-pass nature. These promising results motivated the use of MMP for residual error encoding in hybrid video coding algorithms. This paper presents the first results of these experiments, performed using a H.264/AVC based video encoder, but using MMP to encode the motion compensated residual data, for the P and B slices. Experimental results show that, even in this not fully optimised version, this method is able to achieve an approximately equivalent performance to the H.264/AVC. This demonstrates that MMP is an alternative to the transform-quantisation paradigm for hybrid video coding that is worth investigating.
In this paper, we propose a new encoder for scanned compound documents, based upon a recently int... more In this paper, we propose a new encoder for scanned compound documents, based upon a recently introduced coding paradigm called multidimensional multiscale parser (MMP). MMP uses approximate pattern matching, with adaptive multiscale dictionaries that contain concatenations of scaled versions of previously encoded image blocks. These features give MMP the ability to adjust to the input image's characteristics, resulting in high coding efficiencies for a wide range of image types. This versatility makes MMP a good candidate for compound digital document encoding. The proposed algorithm first classifies the image blocks as smooth (texture) and nonsmooth (text and graphics). Smooth and nonsmooth blocks are then compressed using different MMP-based encoders, adapted for encoding either type of blocks. The adaptive use of these two types of encoders resulted in performance gains over the original MMP algorithm, further increasing the performance advantage over the current state-of-the-art image encoders for scanned compound images, without compromising the performance for other image types.
The Multidimensional Multiscale Parser (MMP) algorithm is an image encoder that approximates the ... more The Multidimensional Multiscale Parser (MMP) algorithm is an image encoder that approximates the image blocks by using recurrent patterns, from an adaptive dictionary, at different scales. This encoder performs well for a large range of image data. However, images encoded with MMP suffer from blocking artifacts. This paper presents the design of a deblocking filter that improves the performance the MMP. We present the results of our research, that aims to increase the performance of MMP, particularly for smooth images, without causing quality losses for other image types, where its performance is already up to 5 dB better than that of top transform based encoders. For smooth images, the proposed filter introduces relevant perceptual quality gains by efficiently eliminating the blocking effects, without introducing the usual blurring artifacts. Besides this, we show that, unlike traditional deblocking algorithms, the proposed method also improves the objective quality of the decoded image, achieving PSNR gains of up to about 0.3 dB. With such gains, MMP reaches an almost equivalent performance to that of the state-of-the-art image encoders (equal to that of JPEG2000 for higher compression ratios), for smooth images, while maintaining its gains for non-smooth images. In fact, for all image types, the proposed method provides significant perceptual improvements, without sacrificing the PSNR performance.
The multidimensional multiscale parser (MMP) is a lossy multidimensional signal encoder, that use... more The multidimensional multiscale parser (MMP) is a lossy multidimensional signal encoder, that uses an adaptive dictionary for approximating the original signal using multiscale recurrent pattern matching. In previous work we have shown the efficiency of MMP for image coding and we have also described new techniques to improve its performance, using predictive coding (MMP-Intra) and innovative strategies for reducing the dictionary redundancy. The combination of these methods for image coding achieves much better results than the state-of-the-art JPEG2000 and H.264/AVC Intra image encoders for text and compound images, but for smooth natural images it still presents small losses. In this work we present a new technique to improve the dictionary adaptation process of the MMP-Intra, based on enhanced updating techniques. Experimental results have showed that, when combined with dictionary growth control methods, this technique achieves consistent image quality gains for all image types. Furthermore we present some methods that eliminate the intrinsic substantial increase of the computational complexity associated with more rapidly growing dictionaries, without compromising the final quality of the decoded image.
Abstractó MMP-Intra was recently proposed as a recurrent patterns based image encoder that combin... more Abstractó MMP-Intra was recently proposed as a recurrent patterns based image encoder that combines the Multidimen- sional Multiscale Parser (MMP) algorithm with intra prediction techniques. Our results show that this method is able to achieve considerable gains over state-of-the-art transform-based image encoders for a wide variety of types of images, like text, composed (text and graphics) and texture images, while
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Papers by Nuno Rodrigues