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Publicações

Publicações por CTM

2008

Automated rhythmic transformation of musical audio

Autores
Hockman, JA; Bello, JP; Davies, MEP; Plumbley, MD;

Publicação
Proceedings - 11th International Conference on Digital Audio Effects, DAFx 2008

Abstract
Time-scale transformations of audio signals have traditionally relied exclusively upon manipulations of tempo. We present a novel technique for automatic mixing and synchronization between two musical signals. In this transformation, the original signal assumes the tempo, meter, and rhythmic structure of the model signal, while the extracted downbeats and salient intra-measure infrastructure of the original are maintained.

2008

The effects of lossy audio encoding on onset detection tasks

Autores
Jacobson, K; Davies, M; Sandler, M;

Publicação
Audio Engineering Society - 125th Audio Engineering Society Convention 2008

Abstract
In large audio collections, it is common to store audio content with perceptual encoding. However, encoding parameters may vary from collection to collection or even within a collection - using different bit rates, sample rates, codecs, etc. We evaluate the effect of various audio encodings on the onset detection task. We show that audio-based onset detection methods are surprisingly robust in the presence of MP3 encoded audio. Statistically significant changes in onset detection accuracy only occur at bit-rates lower than 32kbps.

2008

Volumetric Object Reconstruction using Generalized Voxel Coloring

Autores
Azevedo, TCS; Tavares, JMRS; Vaz, MAP;

Publicação
Image Analysis - From Theory to Applications. Proceedings of IWCIA 2008 Special Track on Applications, Buffalo, NY, USA, April 7-9, 2008.

Abstract

2008

3D object reconstruction from uncalibrated images using a single off-the-shelf camera

Autores
Azevedo, TCS; Tavares, JMRS; Vaz, MAP;

Publicação
COMPUTATIONAL VISION AND MEDICAL IMAGING PROCESSING

Abstract
Three-dimensional (3 D) objects' reconstruction using just bi-dimensional (21)) images has been a major research topic in Computer Vision. However, it is still a hard problem to solve, when automation, speed and precision are required and/or the objects present complex shapes and visual properties. In this paper, we compare two Active Computer Vision methods commonly used for the 3D reconstruction of objects from image sequences, acquired with a single off-the-shelf CCD camera: Structure From Motion (SFM) and Generalized Voxel Coloring (GVC) SFM recovers the 3D shape of an object using the camera(s)'s or object's movement, while VC is a volumetric method that uses photoconsistency measures to build a 31) model for the object. Both methods considered do not impose any kind of restrictions to the relative motion involved.

2008

A scalable and efficient approach for obtaining measurements in CAN-based control systems

Autores
Andersson, B; Pereira, N; Elmenreich, W; Tovar, E; Pacheco, F; Cruz, N;

Publicação
IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS

Abstract
The availability of small inexpensive sensor elements enables the employment of large wired or wireless sensor networks for feeding control systems. Unfortunately, the need to transmit a large number of sensor measurements over a network negatively affects the timing parameters of the control loop. This paper presents a solution to this problem by representing sensor measurements with an approximate representation-an interpolation of sensor measurements as a function of space coordinates. A priority-based medium access control (MAC) protocol is used to select the sensor messages with high information content. Thus, the information from a large number of sensor measurements is conveyed within a few messages. This approach greatly reduces the time for obtaining a snapshot of the environment state and therefore supports the real-time requirements of feedback control loops.

2008

Analyzing TDMA With Slot Skipping

Autores
Andersson, B; Pereira, N; Tovar, E;

Publicação
IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS

Abstract
Distributed real-time system, such as factory automation systems, require that computer nodes communicate with a known and low hound on the communication delay. This can be achieved with traditional time division multiple access (TDMA). But improved flexibility and simpler upgrades are possible through the use of TDMA with slot-skipping (TDMA/SS), meaning that a slot is skipped whenever it is not used and consequently the slot after the skipped slot starts earlier. We propose a schedulahility analysis for TDMA/SS. We assume knowledge of all message streams in the system, and that each node schedules messages in its output queue according to deadline monotonic. Firstly, we present a non-exact (but fast) analysis and then, at the cost of computation time, we also present an algorithm that computes exact queuing times.

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