Adaptive Multi-Pattern Fast Block-Matching Algorithm Based on Motion Classification Techniques

Motion estimation is the most time-consuming subsystem in a video codec. Thus, more efficient methods of motion estimation should be investigated. Real video sequences usually exhibit a wide-range of motion content as well as different degrees of detail, which become particularly difficult to manage by typical block-matching algorithms. Recent developments in the area of motion estimation have focused on the adaptation to video contents. Adaptive thresholds and multi-pattern search algorithms have shown to achieve good performance when they success to adjust to motion characteristics. This paper proposes an adaptive algorithm, called MCS, that makes use of an especially tailored classifier that detects some motion cues and chooses the search pattern that best fits to them. Specifically, a hierarchical structure of binary linear classifiers is proposed. Our experimental results show that MCS notably reduces the computational cost with respect to an state-of-the-art method while maintaining the qualityPublicad

Aplicación de la técnica SVM en el análisis forense de imágenes de dispositivos móviles

Uno de los problemas a tratar dentro del análisis forense digital es la identificación de la cámara que se ha usado para obtener una determinada imagen. Debido al aumento en el uso de teléfonos móviles con cámara integrada durante los últimos años, el trabajo está orientado a este tipo de dispositivos, proporcionando al investigador forense una herramienta específica para el análisis de este tipo de imágenes. En este trabajo se analiza la información EXIF contenida en un archivo de imagen y se comprueba porque no es una fuente fiable a la hora de obtener la marca y modelo de la cámara. Por eso desarrollamos un algoritmo que utiliza la información de los píxeles de la imagen. Está basado en las diferencias existentes en los métodos de procesamiento de la imagen que utilizan los distintos fabricantes, como el algoritmo de interpolación del color que tiene lugar en la matriz CFA del sensor, la corrección gamma o la corrección de puntos blancos. Estas diferencias originan un conjunto de huellas en la imagen que nos permitirían diferenciar la marca y modelo de la camara fuente. Para obtener estas huellas, extraemos un conjunto de características de las imagenes, entre las que se encuentran características de color, métricas de la calidad de la imagen y estadísticas wavelet. Para realizar la predicción de la marca y modelo de la camara utilizamos un clasificador SVM. Siguiendo un procedimiento análogo, se desarrolla otro algoritmo que permite saber si una imagen procede de una cámara o de un escáner. Finalmente, llevamos a cabo un conjunto de experimentos que demuestran la efectividad del algoritmo implementado. [ABSTRACT] One of the issues involved in digital forensics is the identification of the camera used to obtain a particular image. Due to the increase use of mobile phones with integrated camera in recent years, this work is aimed at this type of devices, providing to forensic investigator a specific tool for the analysis of images taken with mobile phones. In this work we analyze the EXIF information contained in an image file and we explain because it is not a reliable source if we want to extract the make and model of the camera from it. So we develop an algorithm that uses information from the pixels of the image. It is based on dferences in the image processing methods used by diferent manufacturers, such as color interpolation algorithm which takes place in the color filter array, gamma correction or white point correction. These diferences originate a set of footprints in the image that allow us to diferentiate the brand and model of the source camera. To obtain these footprints, we extract a feature set from the images, among which are color characteristics, image quality metrics and wavelet statistics. To predict the make and the model of camera we use an SVM classifier. Following a similar procedure, we develop another algorithm that let us know if an image comes from a camera or a scanner. Finally, we perform a series of experiments to prove the efectiveness of the implemented algorithm

Colección de prácticas de tratamiento digital de audio para telecomunicaciones

Grado en Ingeniería de Sistemas Audiovisuales. Asignatura: Tratamiento digital de audio para Telecomunicacione

In-layer multi-buffer framework for rate-controlled scalable video coding

Temporal scalability is supported in scalable video coding (SVC) by means of hierarchical prediction structures, where the higher layers can be ignored for frame rate reduction. Nevertheless, this kind of scalability is not totally exploited by the rate control (RC) algorithms since the hypothetical reference decoder (HRD) requirement is only satisfied for the highest frame rate sub-stream of every dependency (spatial or coarse grain scalability) layer. In this paper we propose a novel RC approach that aims to deliver several HRD-compliant temporal resolutions within a particular dependency layer. Instead of using the common SVC encoder configuration consisting of a dependency layer per each temporal resolution, a compact configuration that does not require additional dependency layers for providing different HRD-compliant temporal resolutions is proposed. Specifically, the proposed framework for rate-controlled SVC uses a set of virtual buffers within a dependency layer so that their levels can be simultaneously controlled for overflow and underflow prevention while minimizing the reconstructed video distortion of the corresponding sub-streams. This in-layer multi-buffer approach has been built on top of a baseline H.264/SVC RC algorithm for variable bit rate applications. The experimental results show that our proposal achieves a good performance in terms of mean quality, quality consistency, and buffer control using a reduced number of layers.This work has been partially supported by the National Grant TEC2011-26807 of the Spanish Ministry of Science and Innovation.Publicad

Rate Control Initialization Algorithm for Scalable Video Coding

Proceeding of: 18th IEEE International Conference on Image Processing (ICIP), 2011.In this paper we propose a novel rate control initialization algorithm for real-time H.264/scalable video coding. In particular, a two-step approach is proposed. First, the initial quantization parameter (QP) for each layer is determined by means of a parametric rate-quantization (R-Q) modeling that depends on the layer identifier (base or enhancement) and on the type of scalability (spatial or quality). Second, an intra-frame QP refinement method that allows for adapting the initial QP value when needed is carried out over the three first coded frames in order to take into consideration both the buffer control and the spatio-temporal complexity of the scene. The experimental results show that the proposed R-Q modeling for initial QP estimation, in combination with the intra-frame QP refinement method, provide a good performance in terms of visual quality and buffer control, achieving remarkably similar results to those achieved by using ideal initial QP values.The Spanish National grant TSI-020110-2009-103 (AFICUS) and the Regional grant CCG10-UC3M/TIC-5570 (AMASSACA).Publicad

RBF-Based QP Estimation Model for VBR Control in H.264/SVC

In this paper we propose a novel variable bit rate (VBR) controller for real-time H.264/scalable video coding (SVC) applications. The proposed VBR controller relies on the fact that consecutive pictures within the same scene often exhibit similar degrees of complexity, and consequently should be encoded using similar quantization parameter (QP) values for the sake of quality consistency. In oder to prevent unnecessary QP fluctuations, the proposed VBR controller allows for just an incremental variation of QP with respect to that of the previous picture, focusing on the design of an effective method for estimating this QP variation. The implementation in H.264/SVC requires to locate a rate controller at each dependency layer (spatial or coarse grain scalability). In particular, the QP increment estimation at each layer is computed by means of a radial basis function (RBF) network that is specially designed for this purpose. Furthermore, the RBF network design process was conceived to provide an effective solution for a wide range of practical real-time VBR applications for scalable video content delivery. In order to assess the proposed VBR controller, two real-time application scenarios were simulated: mobile live streaming and IPTV broadcast. It was compared to constant QP encoding and a recently proposed constant bit rate (CBR) controller for H.264/SVC. The experimental results show that the proposed method achieves remarkably consistent quality, outperforming the reference CBR controller in the two scenarios for all the spatio-temporal resolutions considered.Proyecto CCG10-UC3M/TIC-5570 de la Comunidad Autónoma de Madrid y Universidad Carlos III de MadridPublicad

A Rate Control Algorthm for Low-Delay H.264 Video Coding with Stored-B Pictures

A rate control (RC) algorithm for H.264 video coding with stored-B (SB) pictures is proposed for low-delay applications. Different models for P and SB pictures are defined for a better QP and MAD estimation. Furthermore, a novel saw-tooth shaped model of target buffer level has also been introduced for a proper bit allocation in GOP structures with SB pictures. Our experimental results show that this proposal outperforms the reference software RC in terms of buffer occupancy and target bit rate adjustment at the expense of slight quality reduction.Publicad

Deployment of Digital Video and Audio Over Electrical SCADA Networks

With the arrival of new hardware and software technologies, supervisory control and data acquisition human-machine interfaces (SCADA/HMI), usually text-based, can now benefit from the advantages the inclusion of multimedia information brings. However, due to the special requirements imposed by such systems, integrating audio and video data into the SCADA interfaces is not a trivial task. In this document we analyze those special characteristics and propose solutions so this integration is possible in power systems communication.Ministerio de Ciencia y Tecnología TIC2000-0367-P4-0

Power Systems Monitoring and Control using Telecom Network Management Standards

Historically, different solutions have been developed for power systems control and telecommunications network management environments. The former was characterized by proprietary solutions, while the latter has been involved for years in a strong standardization process guided by criteria of openness. Today, power systems control standardization is in progress, but it is at an early stage compared to the telecommunications management area, especially in terms of information modeling. Today, control equipment tends to exhibit more computational power, and communication lines have increased their performance. These trends hint at some conceptual convergence between power systems and telecommunications networks from a management perspective. This convergence leads us to suggest the application of well-established telecommunications management standards for power systems control. This paper shows that this is a real medium-to-long term possibility