1,720,967 research outputs found
High Dynamic Range Images Coding: Embedded and Multiple Description
No full textThe aim of this work is to highlight and discuss a new paradigm for representing high-dynamic range (HDR) images that can be used for both its coding and describing its multimedia content. In particular, the new approach defines a new representation domain that, conversely from the classical compressed one, enables to identify and exploit content metadata. Information related to content are used here to control both the encoding and the decoding process and are directly embedded in the compressed data stream. Firstly, thanks to the proposed solution, the content description can be quickly accessed without the need of fully decoding the compressed stream. This fact ensures a significant improvement in the performance of search and retrieval systems, such as for semantic browsing of image databases. Then, other potential benefits can be envisaged especially in the field of management and distribution of multimedia content, because the direct embedding of content metadata preserves the consistency between content stream and content description without the need of other external frameworks, such as MPEG-21. The paradigm proposed here may also be shifted to Multiple description coding, where different representations of the HDR image can be generated accordingly to its content. The advantages provided by the new proposed method are visible at different levels, i.e. when evaluating the redundancy reduction. Moreover, the descriptors extracted from the compressed data stream could be actively used in complex applications, such as fast retrieval of similar images from huge databases
Flexible and Effective High Dynamic Range Image Coding
No full textThis paper presents an algorithm based on a two-layer coding scheme, where the original information is represented by means of a Low Dynamic Range (LDR) image, obtained by applying a tone mapping operator to the original HDR (High Dynamic Range), plus an enhancement layer, which allows to recover the full dynamic range. More specifically, the original HDR is represented with a format similar to the well known RGBE, which uses a shared exponent to compactly represent floating point numbers. With respect to the original RGBE, here the mantissa is composed by an approximation of the LDR image while the shared exponent represents the enhancement layer. This particular choice allows to split the original HDR into a color image, the mantissa, and a grayscale image, the exponent, which are very smooth signals that can be efficiently compressed by conventional image coding methods. With respect to already proposed similar schemas, two desirable features are then provided: a high coding efficiency, combined with the possibility to retrieve a displayable version of the original content
High Dynamic Range Image Tone Mapping Based on Local Histogram Equalization
No full textHigh Dynamic Range (HDR) images can represent the acquired scene with a greater dynamic range of luminance than classical Low Dynamic Range (LDR) ones. Despite the recent diffusion of some HDR camera models, HDR displays are not yet in the market. For this reason HDR images need to be adapted in order to be properly rendered through conventional devices. This operation mainly consists in a dynamic range compression realized by applying a Tone Mapping Operator (TMO). In this work, a new tone map algorithm, derived from the Contrast Limited Adaptive Histogram Equalization (CLAHE) technique, is presented. With respect to the original CLAHE, in the proposed implementation an adaptive contrast limit and a new strategy for the determination of local tone mapping functions have been introduced. The comparison between the obtained LDR images, and those produced by applying State of the Art TMOs, evidences how the main characteristic of the proposed algorithm is the ability to equally enhance visibility in both dark and bright areas. This could be, for example, a key feature in video surveillance applications and automotive safety camera systems
An Optimal Video-Surveillance Approach for HDR Videos Tone Mapping
Get PDFRecently, a new type of camera, which allows the recording of almost the entire range of luminosity of the acquired scene, has been introduced to the market. The produced High Dynamic Range images (HDRi), can simplify some video-surveillance tasks, such as object detection, recognition an tracking, since they can simultaneously capture the visual scene content of both dark and bright areas. Applications where lighting conditions cannot be controlled can greatly benet from the adoption of HDR cameras. For example, the achievement of a good and constant visual quality of images is one of the key aspects in video-surveillance applications, because it allows to robustly detect salient events in the captured scenes. However, the use of HDR images in traditional video-surveillance systems requires the reduction of their dynamic range appropriately, by applying a tone mapping operator. In this paper a fast method for tone mapping HDR
videos, which combines the benets of both local and global operators, is presented. It is applied in the context of object detection and tracking. It also enhances the visual quality of the image in all light conditions, which facilitated surveillance tasks for both human and automatic operators
Image Coding with Face Descriptors Embedding
No full textContent descriptors, useful for browsing and retrieval tasks, are generally extracted and treated as a separate entity with respect to the nature of the content itself. At the same time, conventional coding processes do not take into account information carried out by content descriptors. Content descriptors are closely related to the content itself, and they potentially can be used to exploit redundancy in entropy coding processes. Embedding content descriptors in the bitstream can reduce content description extraction load, and at the same time, it can reduce the rate associated to the compressed content and its description. In this paper an effective implementation of this approach is presented, where image descriptors are actively used in the coding process for exploiting redundancy. First of all, image areas containing faces are detected and encoded using a scalable method, where the base layer is represented by the corresponding eigenface, and the enhancement layer is formed by the prediction error. The remaining areas are then encoded by using a traditional approach. Simulations show that achievable compression performances are comparable with those provided by conventional, making the proposed approach very convenient for source coding and content description
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Scalable Coding of Image Collections with Embedded Descriptors
No full textWith the increasing popularity of repositories of personal images, the problem of effective encoding and retrieval of similar image collections has become very important. In this paper we propose an efficient method for the joint scalable encoding of image-data and visual-descriptors, applied to collections of similar images. From the generated compressed bit stream, it is possible to extract and decode the visual information at different granularity levels, enabling the so called ldquomidstream content accessrdquo. The proposed approach is based on the appropriate combination of vector quantization (VQ) and JPEG2000 image coding. Specifically, the images are encoded at a first draft level using an optimal visual-codebook, while the residual errors are encoded using a JPEG2000 approach. In this way, the codebook of the VQ is freely available as an efficient visual descriptor of the considered image collection. This scalable representation supports fast browsing and retrieval of image collections providing also a coding efficiency comparable with those of standard image coding methods
Embedded indexing in scalable video coding
No full textEffective encoding and indexing of audiovisual documents are two key aspects for enhancing the multimedia user experience. In this paper we propose the embedding of low-level content descriptors into a scalable video-coding bitstream by jointly optimizing encoding and indexing performance. This approach provides a new type of bitstream where part of the information is used for both content encoding and content description, allowing the so called "Midstream Content Access". To support this concept, a novel technique based on the appropriate combination of Vector Quantization and Scalable Video Coding has been developed and evaluated. More specifically, the key-pictures of each video Group Of Pictures (GOP) are encoded at a first draft level by using a suitable visual-codebook, while the residual errors are encoded using a conventional approach. The same visual-codebook is also used to encode all the key-pictures of a video shot, where boundaries are dynamically estimated. In this way, the visual-codebook is freely available as an efficient visual descriptor of the considered video shot. Moreover, since a new visual-codebook is introduced every time a new shot is detected, also an implicit temporal segmentation is provided
- …
