Dictionary for RITMO Course on Motion Capture

Definitions of some of the core terminology used in the RITMO Course on Motion Capture. Please let us know if something is missing.

Accelerometer: A sensor that measures the change of motion. This is based on the gravitational pull. Accelerometers can measure in 1, 2, or 3 directions. They are often combined with gyroscopes and magnetometers into inertial measurement units (IMU).
Action: An action can be defined as a motion sequence with a beginning and an end. Actions are often (but not always) goal-directed.
BPM (Beats per minute): Measurement unit for musical tempo. A typical dance tempo is 120 BPM, which means that there are 2 beats per second.
Coarticulation: A grouping of two or more sequential elements into a larger “chunk”. This can be how a fast sequence of sound-producing actions in music may be perceived as one coherent segment or how phonemes in speech are coarticulated into words or phrases. We maytalk about coarticulated actions of a performer, but also to explain how sequential elements are experienced.
Cognition: Conscious mental activities, such as thinking, understanding, learning, and remembering.
Communicative movements: Movements intended for communication, such as how musicians give each other signs during a performance or communicate directly to the audience through body language or gestures.
Controlled environment: Used in research to control variables. For instance, in a lab setting.
Demographical data: Information about a person such as age, gender, cultural background, etc. Such information is often collected in experiments to have background information about participants.
Descriptive analysis: The analysis of a phenomenon like movement by describing how it is performed, for example, the kinematics of the body (velocity or acceleration of body parts) or spatial features (size and position in the room). Descriptive analysis may often be a useful “objective” starting point for further functional or aesthetic analysis.
Ecological setting: In research experiments, there is often a trade-off between controllability (being in control of all variables) and ecological validity where something is studied in its natural context. For example, studying a musician in a lab (controllable) or on stage during a concert (ecologically valid).
Effort: A subcategory of the Laban Movement Analysis (LMA) system. Contains four dimensions: space, time, weight, flow.
Embodied cognition: In the field of embodied cognition, cognitive processes are explained as being inseparable from the body. The perceiver is not only a passive receiver of information that is being processed and understood in the brain alone. Rather, the perceiver interacts with the environment. See also Internet Encyclopedia of Philosophy entry.
Entrainment: The synchronization of two (or more) independent processes. For example, moving one’s foot to the pulse of the music. Here the tapping of the foot entrains to the beats in the musical sound.
Excitation: The moment of energy transfer from sound-producing action to a sounding object. For instance, the moment when a guitar string is released or the time span in which a clarinet player blows into the clarinet.
Functional analysis: The analysis of a phenomenon through its functional properties, such as whether an action is sound-producing, sound-modifying, etc. This is as opposed to descriptive analysis.
Gesture: A movement of part of the body, often a hand or the head, to express an idea or meaning.
Gyroscopes: A motion sensor that measures rotation.
Impulsive action: A type of sound-producing action where a short, abrupt transfer of energy occurs between the sound-producing action and a sounding object. For instance, crashing two cymbals together.
Inertial measurement unit (IMU): A sensor unit that combines a 3D accelerometer, a 3D gyroscope, and a magnetometer. Together these sensors tell about the position and orientation of the sensor unit.
Iterative action: A type of sound-producing action where a rapid series of impulsive actions fuse into a continuous stream. For instance, dragging the fingers across all the strings of a harp.
Kinematics: The branch of physics that describes the motion of objects in space over time. Kinematics does not take into account the force and energy needed for the motion.
Kinesphere: The imaginary volume that one can reach around one’s body. The kinesphere is where we can perform actions.
Laban Movement Analysis (LMA): The movement analysis system developed by Rudolf Laban.
Labanotation: The movement notation system developed by Rudolf Laban. The notation is based on writing symbols of the different body parts along a vertical axis.
Magnetometer: A sensor that measures the direction, like a compass.
Modality: The term modality can be understood as a channel of sensory information. It includes, but is broader than, the five senses seeing, hearing, tactility, taste, and smell.
Motion: The displacement of an object in space over time. Often used interchangeably with movement, although motion is often the preferred term in physics and scientific research.
Motion capture: A technique for measuring and storing human body motion through various types of technological systems.
Motion image: An image created by calculating the difference between the current video frame and the previous video frame. Often used as the basis for other types of computer-based video analysis.
Motiongrams: A technique for visualising motion over time, based on motion images from ordinary video files.
Music-related body motion: A diverse category of movement, ranging from purely instrumental, such as hitting a piano key, to purely communicative, such as gesticulating in the air. Music-related movement may occur in any type of location, for example, a concert hall, at home, in the street, or a club setting.
NIME (New Interface for Musical Expression): A community of researchers and an annual conference focusing on developing new technologies for musical expression. See also nime.org.
Optical marker-based motion capture system: State-of-the-art technology for measuring movement using cameras and reflective markers.
Perceive/perception: To experience, be aware of, realize or understand something.
Qualitative analysis: Analysis based on verbal or categorical information and using interpretation and reasoning as methods. Qualitative analysis is often used in the humanities and parts of the social sciences.
Quantitative analysis: Analysis based on numerical data using mathematical and statistical methods. Quantitative analysis is often used in the natural sciences but increasingly also in other fields.
Quantity of motion (QoM): Measure used to describe the overall amount of movement in a recording. Quantity of motion may be calculated in different ways, for example by averaging the velocities of all recorded markers in a full-body motion capture recording.
Sampling frequency: The sampling frequency is the number of times per second a phenomenon is measured and stored as a number. For audio, a typical sampling frequency is 44.1 kHz, which means that 44 100 measurements are done per second. Sampling frequencies are typically much lower for movement data, between 50 and 1000 Hz (50 to 1000 measurements per second).
Sound-accompanying action: Actions that follow some features in the musical sound, but that are not involved in sound production. Example: playing “air-guitar” or “conduct” to music.
Sound-modifying action: An action that modifies the sound, such as changing the pitch with the left hand on a string instrument or the mute position on brass instruments.
Sound-producing action: An action that creates sound through excitation, such as hitting, stroking, and blowing.
Spectrogram: A visual display that shows the frequency content of the sound over time. Is often used in sound analysis.
Stimulus: A term used in psychology to describe what the subjects perceive in an experiment. The stimulus may refer to the musical sound being used, while the dance movement is the response.
Subject: A person taking part in an experiment.
Tempo: Musical tempo is the speed or pace of the music, often measured in beats per minute (BPM).
Time-varying descriptors: Descriptors that are calculated from short, sequential time-frames and then forming a sequence of numbers.
Waveform: A waveform representation of a sound signal shows how the amplitude varies over time.

Published Apr. 8, 2021 11:15 AM - Last modified Dec. 18, 2022 10:12 PM