Freddy Roberto Acosta Buenaño

Several images are used as a part of the interactive data in the Nipo-Brazilian digital TV system that require good subjective quality while using the lowest possible bandwidth but the well-known traditional compression systems are already applied by default to these images. The concept of a mosaic image (several images forming one) has been formerly used in the steganography application field. The mosaic image is obtained by reordering the image-blocks of a secret image disguised as another image, the so-called target image, and then feeding both to a near reversible color-transformation algorithm. Its use is a possible solution to this need in digital interactive television, for which the main challenge is to achieve this by using less bandwidth for transmission. We propose here a procedure to reduce the amount of data needed to recover the secret image from the mosaic image, as well as a criterion to select the target image and therefore improve the quality of the recovered secret image in interactive data applications. The main objective is to efficiently transmit two images as one using a lower bandwidth. On the one hand, the number of bits needed to recover a given secret image is highly reduced by modeling the image-block standard deviation statistical distribution. On the other hand, the entropy of the image-block means and standard deviations per color component are used to identify the most convenient target image among the images set present in the interactive application of interest. A series of experiments with a set of 20 mostly natural images showed a reduction in the number of bits close to 3-to-1 with respect to techniques of reference. The proposed method allows us to improve the bandwidth use by reducing the number of bits needed to recover the secret image, it preserves the subjective quality of recovered secret images, and it gives the possibility to determine the best target images available in several multimedia and digital terrestrial television applications.

La esteganografía es un proceso que consiste en ocultar información dentro de un objeto (contenedor). Es un desafío mejorar las técnicas actuales de esteganografía con el fin de que proporcionen seguridad contra ataques de estegoanálisis estadístico. Este artículo propone una nueva técnica de transmisión segura de imágenes mediante la combinación de dos métodos: el primero basado en transformaciones reversibles de color, el cual transforma una imagen secreta en una imagen mosaico que luce similar a una imagen portadora seleccionada previamente; y el segundo busca las áreas más adecuadas (texturas y bordes) en la imagen mosaico creada para ocultar la información relevante requerida y posteriormente recuperar la imagen secreta. Estas zonas son de naturaleza ruidosa, por lo que representan un reto para el estegoanálisis al momento de extraer características encargadas de determinar si una imagen tiene información embebida. La efectividad del método propuesto se evaluó mediante el análisis de histogramas y utilizando la herramienta de estegoanálisis StegExpose.

El presente artículo muestra una solución al desarrollo automático de aplicaciones interactivas Ginga-NCL para la Televisión Digital Terrestre, a partir de plantillas prediseñadas. Productores de televisión y gente relacionada con este medio de comunicación masivo, no conocen o simplemente no tienen las herramientas necesarias para la creación de aplicaciones interactivas, en muchos casos ni siquiera se conoce la existencia de una plataforma para el desarrollo de las mismas. Es por esta razón que se propone una metodología totalmente nueva y amigable para el usuario, la cual permita generar aplicaciones interactivas sin tener el conocimiento técnico ni las habilidades de programación que implica su creación. La reducción del tiempo en la generación de aplicaciones, disminución de capital de inversión en la preparación y adiestramiento del personal, cambios on-air en la programación interactiva del canal de televisión, son algunos de los resultados que trae consigo este sistema.

In this paper we present a performance analysis about the capabilities of Alix board for handling VoIP over WiFi based systems with an embedded Asterisk server. First, we study the characteristics of all components of the Alix board to determine the possible options for operating systems that can run within this board using an Asterisk server. In addition we analyse the performance of SIP and IAX protocols combined with GSM, G.711 U/A, Speex, and G.726 codecs in WiFi based systems in conformance with IEEE 802.11b and IEEE 802.11g standards. Results were obtained using a SIPP's tool which determines the boundaries reached by the board respect SIP protocol. Performance analysis was tested on metrics related to CPU percentage of use and RAM memory consumption depending on which protocols and codecs were used. The main results show the feasibility of implementing VoIP over small processors with low consumption of RAM memory. Finally, regarding CPU use percentage the best performance in a real environment was achieved when we used IEEE 8011.b standard, with IAX protocol and GSM codec, reaching up to 110 simultaneous phone calls with 29% CPU resources and 9,4% Memory to process simultaneous calls were achieved considering that phone calls have coexisted with other type of internet services.

This article describes the analysis of return channel for digital terrestrial television (DTT), through the development of interactive application called Shopping Car buying and selling. Using the middleware Ginga-NCL, Lua and MySQL, to get evidence of the return path for the interactive application and determines the capacity of server performance.