Multimedia scheduling for interactive multimedia systems

International audienceScheduling for real-time interactive multimedia systems (IMS) raises specific challenges that require particular attention. Examples are triggering and coordination of heterogeneous tasks, especially for IMS that use a physical time, but also a musical time that depends on a particular performance, and how tasks that deal with audio processing interact with control tasks. Moreover , IMS have to ensure a timed scenario, for instance specified in an augmented musical score, and current IMS do not deal with their reliability and predictability. We present how to formally interleave audio processing with control by using buffer types that represent audio buffers and the way of interrupting computations that occur on them, and how to check the property of time-safety of IMS timed scenarios, in particular augmented scores for the IMS Antescofo for automatic accompaniment developed at Ircam. Our approach is based on the extension of an intermediate representation similar to the E code of the real-time embedded programming language Giotto, and on static analysis procedures run on the graph of the intermediate representation

Ordonnancement adaptatif d'un graphe audio avec dégradation de qualité

National audienceLes systèmes interactifs musicaux sont des systèmes particulièrement dynamiques qui combinent du traitement du signal avec du contrôle en temps réel. Ils sont souvent utilisés sur des plateformes où il n'est pas possible d'avoir des garanties temps réel précises. Nous présentons ici un algorithme de dégradation temps réel en ligne pour obtenir un compromis entre la qualité audio et les retards par rapport aux échéances audio, dans un graphe audio dynamique. Nous évaluons expérimentalement les performances de l'algorithme

Synthèse, caractérisation et applications de polyesters dérivés d'oligothiophènes

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Approximate audio processing in an audio graph for interactive music systems

Interactive music systems are highly dynamic systems that combine audio processing and control in real-time, and they often have to work on soft real-time platforms, where no stringent real-time guarantees can be upheld. We present here an overhead-aware online degradation algorithm that find a tradeoff between quality and lateness for the processing nodes of a dynamic audio graph. We show that we can scale to thousands of nodes

On the Usability of Shortest Remaining Time First Policy in Shared Hadoop Clusters

International audienceHadoop has been recently used to process a diverse variety of applications, sharing the same execution infrastructure. A practical problem facing the Hadoop community is how to reduce job makespans by reducing job waiting times and ex- ecution times. Previous Hadoop schedulers have focused on improving job execution times, by improving data locality but not considering job waiting times. Even worse, enforcing data locality according to the job input sizes can be ineffi- cient: it can lead to long waiting times for small yet short jobs when sharing the cluster with jobs with smaller input sizes but higher execution complexity. This paper presents hSRTF, an adaption of the well-known Shortest Remaining Time First scheduler (i.e., SRTF) in shared Hadoop clus- ters. hSRTF embraces a simple model to estimate the re- maining time of a job and a preemption primitive (i.e., kill) to free the resources when needed. We have implemented hSRTF and performed extensive evaluations with Hadoop on the Grid’5000 testbed. The results show that hSRTF can significantly reduce the waiting times of small jobs and therefore improves their makespans, but at the cost of a rel- atively small increase in the makespans of large jobs. For instance, a time-based proportional share mode of hSRTF (i.e., hSRTF-Pr) speeds up small jobs by (on average) 45% and 26% while introducing a performance degradation for large jobs by (on average) 10% and 0.2% compared to Fifo and Fair schedulers, respectively

A Term Rewriting Based Structural Theory of Rhythm Notation

We present a tree-based symbolic representation of rhythm notation suitable for processing with purely syntactic theoretical tools such as term rewriting systems or tree automata. Then we propose an equational theory, defined as a set of rewrite rules for transforming these representations. This theory is complete in the sense that from a given rhythm notation the rules permit to generate all notations of equivalent durations. It can be used to explore the space of Using complementary tree automata formalisms, one can restrict the search space according to notations preferences regarding e.g. metre or other user defined syntactic constraints

Towards an Equational Theory of Rhythm Notation

International audienceTrees are classical representations of hierarchical structures in symbolic music, in particular for rhythm notations, where the durations are defined by a hierarchy of subdivisions. Structures called rhythm trees have been integrated since a long time into Computer Aided Composition environments such as Patchwork and OpenMusic , for programming rhythmic objects.Term rewriting and tree automata and transducers are well established formalisms for transforming and reasoning on trees. With solid theoretical foundations, they are used in a wide range of applications including automatic reasoning, natural language processing, and foundations of web data processing. In this work, we consider a tree structured representation of rhythm suitable for defining a set of rewrite rules (i.e. oriented equations) preserving rhythms, while enabling the simplification of notations. This set can be seen as an axiomatization of rhythm notation which can be applied to reasoning on equivalent notations in assisted composition

Compression-based Dependencies Among Rhythmic Motifs in a Score

Music similarity has been widely studied through melodic and harmonic matching, clustering, and using various metrics for measuring distance. Such analyses offer the musicologist a view of the ‘sameness’ of parts of a score. However, similarity alone does not necessarily allow exploitation of that sameness in reasoning about the music. In this paper, we present work in progress to investigate rhythm similarity at various scales, beginning at the smallest (single measures or groups of measures). We use normalised compression distance and variations thereof to derive similarity-based dependencies between parts of the music. Establishing such dependencies may allow software engineering dependence analysis techniques to be applied to music to, e.g. remove from focus aspects not relevant to a particular enquiry (‘slicing’), determine the sensitivity of later parts of the music on former parts (‘impact analysis’), and to find motivic processes and developments within the musical form. The analysis will thus draw on software engineering techniques, information theory, and data compression. Our results thus far show that text-based compressors introduce significant non-linear artefacts at small scales making similarity identification based on compressed lengths difficult. Future work will involve progressively larger scale music to determine the sensitivity of the results to the size of music being analysed in order to guide musicologists wanting to adopt similar approaches. We expect to find that at larger scales, the artefacts in text compression become less significant and identifying the threshold at which this happens is thus important. We discuss tree compression as having the potential to capture musically-important relationships lost by text compression and believe that this approach would be more successful at small scales

Embedding native audio-processing in a score following system with quasi sample accuracy

International audienceThis paper reports on the experimental native embedding of audio processing into the Antescofo system, to leverage timing precision both at the program and system level, to accommodate time-driven (audio processing) and event-driven (control) computations, and to preserve system behaviour on multiple hardware platforms. Here native embedding means that audio computations can be specified using dedicated DSLs (e.g., Faust) compiled on-the-fly and driven by the Antescofo scheduler. We showcase results through an example of an interactive piece by composer Pierre Boulez, Anthèmes 2 for violin and live electronics

Comparative Study of Alternating Low-band-Gap Benzothiadiazole Co-oligomers

The benzothiadiazole – arylene alternating conjugated oligomers have been designed and synthesized via Suzuki coupling reaction. The structures and properties of the conjugated oligomers were characterized by 1HNMR, 13CNMR, UV–vis absorption spectroscopy, photoluminescence (PL) spectroscopy. The luminescent measurements demonstrate that polybenzothiadiazoles are good chromophores able to form thin films by Langmuir-Blodgett (LB) technique, making them suitable for further applications. Also the electrical properties of obtained films confirm the good potential of these novel aryl-based π-conjugated polymers for the development of various electrical and electrochemical solid-state devices