The design and implementation of a multimedia storage server tosupport video-on-demand applications

In this paper we present the design and implementation of a client/server based multimedia architecture for supporting video-on-demand applications. We describe in detail the software architecture of the implementation along with the adopted buffering mechanism. The proposed multithreaded architecture obtains, on one hand, a high degree of parallelism at the server side, allowing both the disk controller and the network card controller work in parallel. On the other hand; at the client side, it achieves the synchronized playback of the video stream at its precise rate, decoupling this process from the reception of data through the network. Additionally, we have derived, under an engineering perspective, some services that a real-time operating system should offer to satisfy the requirements found in video-on-demand applications.This research has been supported by the Regional Research Plan of the Autonomus Community of Madrid under an F.P.I. research grant.Publicad

A comprehensive approach in performance evaluation for modernreal-time operating systems

In real-time computing the accurate characterization of the performance and determinism that a particular real-time operating system/hardware combination can provide for real-time applications is essential. This issue is not properly addressed by existing performance metrics mainly due to the lack of completeness and generalization. In this paper we present a set of comprehensive, easy-to-implement and useful metrics covering three basic real-time operating system features: response to external events, intertask synchronization and resource sharing, and intertask data transferring. The evaluation of real-time operating systems using a set of fine-grained metrics is fundamental to guarantee that we can reach the required determinism in real-world applications.Publicad

Efficient memory management in VOD disk array servers usingPer-Storage-Device buffering

We present a buffering technique that reduces video-on-demand server memory requirements in more than one order of magnitude. This technique, Per-Storage-Device Buffering (PSDB), is based on the allocation of a fixed number of buffers per storage device, as opposed to existing solutions based on per-stream buffering allocation. The combination of this technique with disk array servers is studied in detail, as well as the influence of Variable Bit Streams. We also present an interleaved data placement strategy, Constant Time Length Declustering, that results in optimal performance in the service of VBR streams. PSDB is evaluated by extensive simulation of a disk array server model that incorporates a simulation based admission test.This research was supported in part by the National R&D Program of Spain, Project Number TIC97-0438.Publicad

Efficient memory management in video on demand servers

In this article we present, analyse and evaluate a new memory management technique for video-on-demand servers. Our proposal, Memory Reservation Per Storage Device (MRPSD), relies on the allocation of a fixed, small number of memory buffers per storage device. Selecting adequate scheduling algorithms, information storage strategies and admission control mechanisms, we demonstrate that MRPSD is suited for the deterministic service of variable bit rate streams to intolerant clients. MRPSD allows large memory savings compared to traditional memory management techniques, based on the allocation of a certain amount of memory per client served, without a significant performance penaltyPublicad

Implementation of a Hardware/Software Platform for Real-Timedata-Intensive Applications in Hazardous Environments

Real-Time Technology and Applications Symposium. Brookline, MA, USA, 10-12 Oct. 1996In real-time data-intensive applications, the simultaneous achievement of the required performance and determinism is a difficult issue to address, mainly due to the time needed to perform I/O operations, which is more significant than the CPU processing time. Additional features need to be considered if these applications are intended to perform in hostile environments. In this paper, we address the implementation of a hardware/software platform designed to acquire, transfer, process and store massive amounts of information at sustained rates of several MBytes/sec, capable of supporting real-time applications with stringent throughput requirements under hazardous environmental conditions. A real-world system devoted to the inspection of nuclear power plants is presented as an illustrative examplePublicad

Minimizing buffer requirements in video-on-demand servers

23rd Euromicro Conference EUROMICRO 97: 'New Frontiers of Information Technology', Budapest, Hungary, 1-4 Sept 1997Memory management is a key issue when designing cost effective video on demand servers. State of the art techniques, like double buffering, allocate buffers in a per stream basis and require huge amounts of memory. We propose a buffering policy, namely Single Pair of Buffers, that dramatically reduces server memory requirements by reserving a pair of buffers per storage device. By considering in detail disk and network interaction, we have also identified the particular conditions under which this policy can be successfully applied to engineer video on demand servers. Reduction factors of two orders of magnitude compared to the double buffering approach can be obtained. Current disk and network parameters make this technique feasible.Publicad

Dos fuentes para una etnohistoria de la música en Venezuela

En este artículo se revisan dos textos de la historiografía musical venezolana,por ser pioneros en la investigación arqueológica y antropológica como fuentes parael conocimiento de la historia de la música en Venezuela: Die guajiro indianer EineEthnographische Skizze (1870) de Adolfo Ernst y Contribución al estudio de la músicaen Venezuela (1939) de José Antonio Calcaño. Se realiza un ejercicio de revisión de laliteratura historiográfica musical desde una perspectiva analítica que los valoriza comofuentes para una etnohistoria, punto de partida para emprender otros trabajos similaresque ayuden a entender este universo; si bien no fueron concebidos con una expresa intencionalidadetnohistórica, se internan en áreas que son propias de lo que se considerahoy ámbito de la etnohistoria

Essays on Art in Venezuela (Ramón de la Plaza, 1883): an Ethnohistorical Musical Perspective

El General Ramón de la Plaza Manrique (1831-1886), distinguido personaje de la elite caraqueña, publicó en 1883 una colección de ensayos que ofrecían un amplio panorama de las artes en Venezuela incluida la música. Uno de los apartados más interesantes tiene que ver con el mundo indígena, donde abunda en detalles relacionados con los orígenes unívocos de la músicaprehispánica. El tratamiento dado a los temas, las referencias a sistemas sonoros antiguos, la comparación como método y en general el trasfondo de las ideas expuestas, revela un universo dematices susceptibles de ser abordados desde perspectivas novedosas. La interdisciplinaridad posibilita el cruce de miradas adaptadas a los tiempos que corren, permitiendo la comprensión enextenso de objetos de estudio como la música; es el caso de la etnohistoria cuyos objetivos alcanza gracias al despliegue paralelo de la metodología de la etnografía y las ciencias de la historia. Eneste artículo se analiza un texto canónico de la historiografía musical venezolana y latinoamericana para actualizar sus planteamientos a través de un sesgo etnohistórico musical.O General Ramón de la Plaza Manrique (1831-1886), distinguido personagem da elite de Caracas, publicou em 1883 uma coleção de ensaios que ofereciam um vasto panorama das artes na Venezuela, incluída a música. Uma das partes mais interessantes tem a ver com o mundo indígena, onde existem abundantes detalhes relacionados com as origens unívocas da música pré-hispânica. O tratamento que recebem os temas, as referências aos sistemas sonoros antigos, a comparação como método e, em geral, a substância das ideias apresentadas, revelam um universo de matizes susceptíveis para a abordagem desde inovadoras perspectivas. A interdisciplinaridade faz possível o intercâmbio de olhares adaptados aos tempos que passam, permitindo a compreensão extensa de objetos de estudo como a música; é o caso da etnografia e as ciências da historia. Neste artigo, analisa-se um texto canónico da historiografia musical venezuelana e da América Latina para atualizar seus enfoques, através de uma visão etno-histórica musical.General Ramon Plaza Manrique (1831-1886), distinguished character of the Caracas elite, published in 1883 a collection of essays which offered a wide panorama of the art in Venezuela, including music. One of the most interesting sections is about the indigenous world, abounding in details regarding the unequivocal origin of pre-Hispanic music. The treatment of topics, the references to old sound systems, the comparison as study method and, in general terms, the background of the ideas reveal a world of shades that can be approached from new perspectives. Interdisciplinarity enables the exchange of glances adapted to the times, allowing extensive understanding of objects of study such as music; in the case of ethno-history, whose objectives are achieved thanks to the parallel deployment of the methodology of ethnography and history sciences. In this paper a canonical text of the Venezuelan and Latin American musical historiography is analyzed in order to update its approaches through an ethno-historical musical bia

Reproductive biology of Polioptila lembeyei (Aves: Polioptilidae) in the Siboney-Juticí Ecological Reserve, Santiago de Cuba, Cuba

Se estudió la biología reproductiva de Polioptila lembeyei en la Reserva Ecológica Siboney-Juticí, Santiago de Cuba, Cuba durante los años 2006 y 2007 en seis formaciones vegetales. Se describieron aspectos de su reproducción en términos de cronología reproductiva, tamaño de puesta, duración del período de incubación, permanencia de los polluelos en el nido, morfometría de nidos y huevos, y caracterización del sitio de nidificación en cuanto a la altura de los nidos y especie y altura de las plantas utilizadas como sitio de nidificación. Se localizaron 89 nidos durante las dos temporadas reproductivas, 43 en el año 2006 y 46 en el 2007. El período reproductivo se extendió desde finales de marzo hasta julio, abarcando 129 días en el año 2006 y 122 días durante el año 2007. Las nidadas tuvieron una duración de 36–56 días (construcción 8,6 ± 2,8 días, puesta 8,6 ± 2,7 días, incubación de 14,0 ± 1,2 días y permanencia de los pichones en el nido 14,5 ± 1,0 días). De los 45 nidos examinados el tamaño de puesta modal fue de tres huevos (88,9 %), encontrándose también nidadas de dos (6,7 %) y cuatro huevos (4,4 %). De 38 nidos con huevos para ambas temporadas, 15 nidos produjeron pichones (32 pichones en el 2006 y 20 pichones en el 2007) y solo tres nidos durante el 2006 (37,5 %) lograron producir volantones, los cuales salieron con éxito del nido. La planta más utilizada como sitio de nidificación fue Acacia macracantha (80 % de los nidos detectados), aunque también se hallaron nidos en otras ocho especies de plantas. Las alturas de ubicación del nido fue de 2,7 ± 1,5 m (n = 82; rango 0,3–6,4 m) y la distancia del nido al dosel de la planta utilizada como sustrato fue de 1,1 ± 0,9 m (n = 80; rango 0,1–5,4 m).The reproductive biology of Polioptila lembeyei was studied in six vegetation types during the years 2006 and 2007 in the Siboney-Juticí Ecological Reserve, Santiago de Cuba, Cuba. Breeding aspects including reproductive chronology, clutch size, incubation length, nestling period, egg and nest morphometrics, and aspects of the nesting site (nest height, plant species, and plant height) were described. Eighty-nine nests were found during both reproductive seasons, 43 in 2006 and 46 in 2007. The reproductive period occurred from late March to July for 129 days in 2006 and 122 days in 2007. The length of the nesting period was 36–56 days (nest construction 8.6 ± 2.8 days, laying 8.6 ± 2.7 days, incubation 14.0 ± 1.2 days, and nestling period 14.5 ± 1.0 days). Of the 45 nests examined, modal clutch size was three eggs (88.9 %), although nests with two (6.7 %) and four eggs (4.4 %) also occurred. Of 38 clutches in both seasons, 15 of them produced chicks (32 chicks in the 2006 and 20 chicks in the 2007) and only three nests in the 2006 season (37.5 %) produced fledglings. Acacia macracantha was the plant species most used as nesting substrate (80 % of detected nests) although nests were also found in eight other plant species. Nest heights were 2,7 ± 1,5 m (n = 82; range 0.3–6.4 m) and the distance from nest to the canopy of the substrate plant was 1.1 ± 0.9 m (n = 80; range 0.1–5.4 m)

“El último aldabonazo”.: El drama político de Chibás y su representación en la prensa internacional.

Eduardo Chibás was one of the most important politicians of the fifties in Cuba. Insightful and aggressive in his speeches, the way of his death supposed a shock in the island. In this paper, we try to show the media impact of this decease outside of Cuba, in the rest of the world. The importance of Eduardo Chibás dead is not limited to the disappearance of an extraordinary politician, the suicide and the reasons behind this suicide are very important too.Eduardo Chibás fue uno de los políticos más importantes de la Cuba de la década de los cuarenta. Agudo y agresivo en sus discursos, su forma de morir supuso un shock dentro de la isla. En este artículo intentaremos mostrar la repercusión mediática que tiene ese fallecimiento fuera de Cuba, en el resto del mundo. La importancia de la muerte de Eduardo Chibás no se ciñe a la desaparición de un político capital, sino también por la ejecución en forma de suicidio y la implicación política que este quería tener