Ricardo De Queiroz

University of Brasília | UnB · Department of Computer Science

Point cloud compression (PCC) has been rapidly evolving in the context of international standards. Despite the inherent scalability of octree-based geometry descriptions, current attribute compression techniques prevent full scalability of compressed point clouds. We propose an improvement on an embedded attribute encoding method for point clouds b...

We study the use of predictive approaches alongside the region-adaptive hierarchical transform (RAHT) [1] in attribute compression of dynamic point clouds. The use of intra-frame prediction with RAHT was shown to improve attribute compression performance over pure RAHT [2] and represents the state-of-the-art in attribute compression of point clouds...

We present a method for post-processing point clouds’ geometric information by applying a previously proposed fractional super-resolution technique to clouds compressed and decoded with MPEG’s G-PCC codec. In some sense, this is a continuation of that previous work, which requires only a downscaled point cloud and a scaling factor, both of which ar...

Geometry-based point cloud compression (G-PCC) has been rapidly evolving in the context of international standards. Despite the inherent scalability of octree-based geometry description, current G-PCC attribute compression techniques prevent full scalability for compressed point clouds. In this paper, we present a solution to add scalability to att...

We present a method for post-processing point clouds' geometric information by applying a previously proposed fractional super-resolution technique to clouds compressed and decoded with MPEG's G-PCC codec. In some sense, this is a continuation of that previous work, which requires only a down-scaled point cloud and a scaling factor, both of which a...

Point cloud compression has been studied in standard bodies and we are here concerned with the Moving Picture Experts Group video-based point cloud compression (V-PCC) solution. Plenoptic point clouds (PPC) is a novel volumetric data representation wherein points are associated with colors in all viewing directions to improve realism. It is sampled...

We present a method to super-resolve voxelized point clouds downsampled by a fractional factor, using lookup-tables (LUT) constructed from self-similarities from their own downsampled neighborhoods. The proposed method was developed to densify and to increase the precision of voxelized point clouds, and can be used, for example, as improve compress...

Arithmetic coding is used in most media compression methods. Context modeling is usually done through frequency counting and look-up tables (LUTs). For long-memory signals, probability modeling with large context sizes is often infeasible. Recently, neural networks have been used to model probabilities of large contexts in order to drive arithmetic...

Point clouds have recently gained interest, especially for real-time applications and for 3D-scanned material, such as is used in autonomous driving, architecture, and engineering, to model real estate for renovation or display. Point clouds are associated with geometry information and attributes such as color. Be the color unique or direction-depe...

We propose an intra frame predictive strategy for compression of 3D point cloud attributes. Our approach is integrated with the region adaptive graph Fourier transform (RAGFT), a multi-resolution transform formed by a composition of localized block transforms, which produces a set of low pass (approximation) and high pass (detail) coefficients at m...

Algoritmos para a criação de mapas de saliência são bem estabelecidos para imagens, porém não há literatura sobre tais algoritmos para nuvens de pontos. Utilizamos então projeções ortográficas em planos bidimensionais para que possam ser aplicados os algoritmos já existentes na literatura para a criação de um mapa de saliência tridimensional. Os re...

Due to the large amount of data that point clouds represent and the differences in geometry of successive frames, the generation of motion vectors for an entire point cloud dataset may require a significant amount of time and computational resources. With that in mind, we provide a 3D motion vector database for all frames of two popular dynamic poi...

Recent trends in multimedia technologies indicate the need for richer imaging modalities to increase user engagement with the content. Among other alternatives, point clouds denote a viable solution that offers an immersive content representation, as witnessed by current activities in JPEG and MPEG standardization committees. As a result of such ef...

We present a method to compress geometry information of point clouds that explores redundancies across consecutive frames of a sequence. It uses octrees and works by progressively increasing resolution of the octree. At each branch of the tree, we generate an approximation of the child nodes by a number of methods which are used as contexts to driv...

Recent trends in multimedia technologies indicate a significant growth of interest for new imaging modalities that aim to provide immersive experiences by increasing the engagement of the user with the content. Among other solutions, point clouds denote an alternative 3D content representation that allows visualization of static or dynamic scenes i...

We present a context-driven method to encode nodes of an octree, which is typically used to encode point cloud geometry. Instead of using one bit per node of the tree, the context allows for deriving probabilities for that node based on distances of the actual voxel to voxels in a reference point cloud. Accurate probabilities of the node state allo...

We propose a mixed-resolution point-cloud representation and an example-based super-resolution framework, from which several processing tools can be derived, such as compression, denoising and error concealment. By inferring the high-frequency content of low-resolution frames based on the similarities between adjacent full-resolution frames, the pr...

We introduce the polygon cloud, a compressible representation of three-dimensional geometry (including attributes, such as color), intermediate between polygonal meshes and point clouds. Dynamic polygon clouds, like dynamic polygonal meshes and dynamic point clouds, can take advantage of temporal redundancy for compression. In this paper, we propos...

Dynamic point clouds are a potential new frontier in visual communication systems. A few articles have addressed the compression of point clouds, but very few references exist on exploring temporal redundancies. This paper presents a novel motion-compensated approach to encoding dynamic voxelized point clouds at low bit rates. A simple coder breaks...

We propose using stationary Gaussian Processes (GPs) to model the statistics of the signal on points in a point cloud, which can be considered samples of a GP at the positions of the points. Further, we propose using Gaussian Process Transforms (GPTs), which are Karhunen-Lo`eve transforms of the GP, as the basis of transform coding of the signal. F...

We introduce the {\em polygon cloud}, also known as a polygon set or {\em soup}, as a compressible representation of 3D geometry (including its attributes, such as color texture) intermediate between polygonal meshes and point clouds. Dynamic or time-varying polygon clouds, like dynamic polygonal meshes and dynamic point clouds, can take advantage...

In free-viewpoint video, there is a recent trend to represent scene objects as solids rather than using multiple depth maps. Point clouds have been used in computer graphics for a long time and with the recent possibility of real time capturing and rendering, point clouds have been favored over meshes in order to save computation. Each point in the...

More than 70% of consumer mobile Internet traffic will be mobile video transmissions by 2019. The development of wireless video transmission technologies has been boosted by the rapidly increasing demand of video streaming applications. Although more and more videos are delivered for video analysis (e.g., object detection/tracking and action recogn...

This work presents a novel technique for image reconstruction applied to mixed-resolution video super-resolution. We segment an image into patches defined by the clustering of a vector flow generated from matching SIFT features. We reconstruct the segmented image by applying image projective transformation to a reference image. By varying the numbe...

Biometric systems based on face recognition have been shown unreliable under the presence of face-spoofing images. Hence, automatic solutions for spoofing detection became necessary. In this paper, face-spoofing detection is proposed by searching for Moiré patterns due to the overlap of the digital grids. The conditions under which these patterns a...

We propose a framework for optimal rate-allocation in free-viewpoint television (FVTV) for a general camera arrangement based on the attention the viewers are paying to each camera. In a recent letter [1], the authors proposed a FVTV broadcast architecture and an optimal bit-allocation approach, assuming a uniformly-spaced one-dimensional arrangeme...

In this paper, a fast transcoding solution from H.264/AVC to HEVC bitstreams is presented. This solution is based on two main modules: a coding unit (CU) classification module that relies on a machine learning technique in order to map H.264/AVC macroblocks into HEVC CUs; and an early termination technique that is based on statistical modeling of t...

In a free-viewpoint television network, each viewer chooses its point of view from which to watch a scene. We use the concept of total observed distortion, wherein we aim to minimize the distortion of the view observed by the viewers as opposed to the distortion of each camera, to develop an optimized bit-rate allocation for each camera. Our attent...

We present an example-based approach to general enhancement of degraded video frames. The method relies on building a dictionary with non-degraded parts of the video and to use such a dictionary to enhance the degraded parts. The image degradation has to originate from a “repeatable” process, so that the dictionary image patches (blocks) are equall...

Since the HEVC codec has become an ITU-T and ISO/IEC standard, efficient transcoding from previous standards, such as the H.264/AVC, to HEVC is highly needed. In this paper, we build on our previous work with the goal to develop a faster transcoder from H.264/AVC to HEVC. The transcoder is built around an established two-stage transcoding. In the f...

Energy consumption has become a leading design constraint for computing devices in order to defray electric bills for individuals and businesses. Over the past years, digital video communication technologies have demanded higher computing power availability and, therefore, higher energy expenditure. In order to meet the challenge to provide softwar...

This paper presents a novel depth map enhancement method which takes as inputs a single view and an associated coarse depth estimate. The depth estimate is reconstructed according to the region boundaries proposed within a set of image partitions of the associated view. Image partitions are determined through a color-based region merging procedure...

We propose a mixed-resolution coding architecture for stereo color-plus-depth images, where encoding is performed at a low resolution, except for one of the color images. Super-resolution methods are proposed for the depth maps and for the low-resolution color image at the decoder side. Experiments are carried out for several real and synthetic ima...

We propose a video codec architecture based on mixed quality frames which allows for low-complexity intra-coded video to undergo inter-frame post-processing to improve its rate-distortion performance. The video sequence is divided into key and non-key frames by applying different quantization parameters among them. The application of different quan...

An architecture for free-viewpoint broadcast television transmission is proposed where all the views are transmitted at potentially different qualities and watched by a large number of viewers. The quality (or bit-rate) of each view is controlled by the distribution of viewpoints chosen by the viewers. For example, if most viewers are watching synt...

This paper proposes a hybrid pattern matching/transform-based compression method for scanned documents. The idea is to use regular video interframe prediction as a pattern matching algorithm that can be applied to document coding. We show that this interpretation may generate residual data that can be efficiently compressed by a transform-based enc...

We propose a mixed-resolution coding architecture for stereo color-plus-depth images, where encoding is performed at a low resolution, except for one of the color images. Super-resolution methods are proposed for the depth maps and for the low-resolution color image at the decoder side. Experiments are carried out for several real and synthetic ima...

As the most of the waste generated on the big cities are recyclable, it is necessary to establish a selective collection manner for correctly classifying them. The different kinds of bins available for recycling may confuse a not well-disciplined user who do not know where (in which trash) should discard his waste. This paper proposes a novel syste...

Example-based super-resolution (SR) is an attractive option to Bayesian approaches to enhance image resolution. We use a multiresolution approach to example-based SR and discuss codebook construction for video sequences. We match a block to be super-resolved to a low-resolution version of the reference high-resolution image blocks. Once the match i...

This paper proposes a hybrid pattern matching/transform-based compression engine for scanned compound documents. The novelty of this approach is demonstrated by using a modified version of the HEVC (High Efficiency Video Coding) Test Model as a compound document compressor, here conveniently referred to as HEDC (High Efficiency Document Coder). The...

This paper presents an algorithm for video super-resolution based on scale-invariant feature transform (SIFT) matching. SIFT features are known to be a robust method for locating keypoints. The matching of these keypoints from different frames in a video allows us to infer high-frequency information in order to perform example-based super-resolutio...

In stereoscopic and multiview video, binocular suppression theory states that the visual subjective quality of 3-D experience is not much affected by asymmetrical blurring of the individual views. Based on these studies, mixed-resolution frameworks applied for multiview systems offer great data-size reduction without incurring in significant qualit...

The mixed raster content (MRC) document-compression standard (ITU T.44) specifies a multilayer representation of a document image. The model is very efficient for representing sharp text and graphics over a background. However, its binary selection layer compromises the representation of scanned data and soft edges. Typical segmentation algorithms...

Encoding video sequences is a computation-demanding task in high-performance codecs. Optimizing this stage may result in a substantial encoding speed-up. In this paper, we propose a faster approach to encode sequences with the H.264/AVC codec, using mixed-resolution. By having some of the frames down-sampled, the overall computation is reduced, wit...

This paper presents a novel depth map enhancement method which takes as inputs a single view and an initial depth estimate. A region-based framework is introduced wherein a color-based partition of the image is created and depth uncertainty areas are identified according to the alignment of detected depth discontinuities and region borders. A color...

This paper presents a transform-based approach to semi-super resolution. The idea of semi-super resolution is to enhance low-resolution frames from a video sequence encoded with different resolutions among frames. The proposed framework uses a DCT-based down-sampling method at the encoder process. At the decoder, DCT-based up-sampling plus high-fre...

Mixed resolution formats have been employed in video encoding complexity reduction as well as data compression of stereoscopic video. High resolution frames within such formats may also be used as a means of enhancing lower resolution images. In this paper we present a super-resolution method for use in a mixed resolution, multiview video plus dept...

In order to enable real-time software-based video encoding, in this work we optimized the prediction stage of an H.264 video encoder, in the complexity sense. Thus, besides looking for the coding options which lead to the best coded representation in terms of rate and distortion (RD), we constrain to a complexity (C) budget. We present a complexity...

A new intra-prediction mode for the H.264/AVC standard is proposed. Each pixel within a block is predicted by a weighted sum of its neighbours, according to an N th order Markov linear model. The weights are obtained through a least-squares estimate from reconstructed data in the neighbouring blocks, so that no overhead is necessary to convey the w...

The joint usage of low- and full-resolution images in multiview systems provides an attractive opportunity for data size reduction while maintaining good quality in 3D applications. In this paper we present a novel application of a super-resolution method for usage within a mixed resolution multiview setup. The technique borrows high-frequency cont...

Real-time high-definition video encoding is a computation-hungry task that challenges software-based solutions. For that, in this work we adopted an Intel software implementation of an H.264 video encoder and optimized its prediction stage in the complexity sense (C). Thus, besides looking for the coding options which lead to the best coded represe...

Inspired by recent results showing that Wyner-Ziv coding using a combination of source and channel coding may be more efficient than pure channel coding, we have applied coset codes for the source coding part in the transform domain for Wyner-Ziv coding of video. The framework is a mixed-resolution approach where reduced encoding complexity is achi...

This paper proposes a hybrid approximate pattern matching/transform-based compression engine. The idea is to use regular video interframe prediction as a pattern matching algorithm that can be applied to document coding. We show that this interpretation may generate residual data that can be efficiently compressed by a transform-based encoder. The...

The concept of reversible conversion of color images to gray ones has been recently introduced. Colors are mapped to textures and from the textures the receiver can recover the colors. This was done using the wavelet transform and replacing high-frequency subbands by the down-sampled chrominance planes. The idea is to print a color image with a bla...

This work presents a new distributed multiview coding framework, based on the H.264/AVC standard operating with mixed resolution frames. It allows for a scalable complexity transfer from the encoder to the decoder, which is particularly suited for low-power video applications, such as multiview surveillance systems. Greater quality sequences are ge...

Many scalable video coding systems use variable resolution frames to enable different decoding layers. Some of these systems also use frame down-sampling along with enhancement layers to reduce complexity. In order to do that, super-resolution methods associated with efficient interpolation processes may help to increase the quality of low-resoluti...

Inaccurate depth map discontinuities are an impor-tant source of artifact and distortion in multiview systems and applications requiring depth-based view rendering such as 3DTV or free-viewpoint video. Such errors along depth discontinuities frequently occur during depth estimation and/or depth map coding. In this paper we present a novel method fo...

The Mixed Raster Content (MRC) document compression is a well documented standard. Its efficiency for representing sharp text and graphics over a background has been extensively presented. Scanned documents, however, are difficult to be dealt with because of soft transitions. In one of our previous works we presented a pre/post-processing algorithm...

H.264/AVC has brought an important increase in coding efficiency in comparison to previous video coding standards. One of its features is the use of macroblock partitioning in a tree-based structure. The use of macroblock partitions based in arbitrary line segments, like wedge partitions, has been reported to increase coding gains. The main problem...

Wyner-Ziv (WZ) coding of video utilizes simple encoders and highly complex decoders. A transcoder from a WZ codec to a traditional codec can potentially increase the range of applications for WZ codecs. We present a transcoder scheme from the most popular WZ codec architecture to a DPCM/DCT codec. As a proof of concept, we implemented this transcod...

We propose a framework for complexity scalability in H.264. The prediction is constrained so that only a subset of prediction modes are tested. The test subset is found by ranking the most ¿popular¿ modes (those the are most often picked as best) and selecting the modes that maximize their expected occurrence frequency given a complexity constrai...