3. Technical Terms
Degrees of Freedom (DOF)
3DOF
Typically refers to a single sensor (accelerometer or gyroscope) 3 axis output values
Synonyms :
Related Terms : 3DOF (Movement)
6DOF
Typically refers to the usage of two sensors (accelerometer and/or gyroscope and/or magnometer) 6 axis output values
Synonyms :
Related Terms : 6DOF (Movement)
9DOF
Typically refers to the usage of three sensors (accelerometer, gyroscope and magnometer) 9 axis output values
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10DOF (and greater)
Typically refers to the usage and combination of sensors for 10 or more axis data output values
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Inputs & Outputs
Source
Typically referring to a sound source or a single mono or stereo input sound/track
Synonyms : Input
Related Terms :
Listener
Typically referring to the listening object representing your first person perspective ears or the virtual microphone object or location for stereo capture and playback
Synonyms : Decode, Monitor, Monitoring, Listening, Stereo Playback, Binauralized
Related Terms :
Encode
Having audio content input into a spatial or multichannel soundfield.
Synonyms : Pan, Panning, Input to Spatial Soundfield
Related Terms :
Decode
Having spatial or multichannel soundfield content output for an intended two ear or two channel playback.
Synonyms : Monitor, Monitoring, Listening, Stereo Playback, Binauralized, Listener
Related Terms : Binaural
Describing Rotations
Azimuth
Refers to the horizontal angle or direction or rotation. Typically when discussing spatial audio a common example of usage of azimuth would be the azimuth of a sound source panned around you as the listener.
Synonyms : Yaw
Related Terms : Heading
Elevation
Refers to the angular distance of the source above or below the horizon.
Synonyms : Height, Pitch
Related Terms : Heading
Heading
A direction or bearing, combining the above terms of Azimuth and Elevation.
Synonyms :
Related Terms : Azimuth, Elevation
Euler
Description of rotations comprised of 3 angles. Commonly using:
- Yaw
- Pitch
- Roll / Tilt
but sometimes referred to as X, Y, Z in some 3D systems (be mindful of the order in which X, Y, Z can refer to Yaw, Pitch, Roll)
Synonyms :
Related Terms : Degrees, Radians, Gimbal Lock
Quaternion
Mathematical notation for representing spatial orientations and rotations of elements in three dimensional space. Useful for avoiding common issues when describing 3D rotations in Euler such as Gimbal Lock
Synonyms : Quat
Related Terms :
Degrees
Used to describe rotation angles in which a full rotation is 360 degree units.
Synonyms :
Related Terms : Euler
Radians
Used to describe rotation angles in which a full rotation is 2π or 6.28318530718.
Synonyms :
Related Terms : Euler
Spatial Audio: Common Issues
Gimbal Lock
Gimbal lock is a loss of a degree of freedom when two axes rotate in parralel, the output rotation becomes one less degree of freedom.
To explain this more simply; two or more axes line up in a way so that the applied Euler rotation cannot distiguish which of the two axes are rotating because they yield the same results.
Example: If you add 90 pitch upward in degrees to an object, rotating yaw or roll would yield the same result.
Synonyms :
Related Terms : Euler
Latency
Describes when something has a latent or delayed reaction. Typically in spatial audio world we can describe headtracking or 3D rotations as being latent when you can percieve a time delay from your real world motion to the interacted virtual motion. This can be a very destructive issue for any hardware that has motion based sensors in them when applied to audio for spatial audio perception.
When discussing latency in the audio world in general it can refer to the actual audio signal itself having a perceived delay.
Synonyms :
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Additional Technologies
IMU
Stands for Inertial Motion Unit, a series of sensors usually within a silicon chip that can typically include any number of the following sensor types:
- Accelerometer
- Gyroscope
- Magnometer
Each of these sensor outputs can have typically 3 data outputs so the IMU typically includes a process called Sensor Fusion to combine the datasets of all sensors into one dataset for orientation and/or position.
Synonyms :
Related Terms : Sensor Fusion
Sensor Fusion
Sensor Fusion is a a mathematics for combining multiple datasets relating to motion or force into one dataset for predicting orientation, heading and/or position. The output data can be collected into different types such as Radians or Degrees or Quaternion.
Synonyms :
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Technical Descriptions
Realtime
Refers to a process or effect that can be applied in realtime, usually during playback but in general any process that can be computed faster than actual time.
Synonyms :
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Runtime
Refers to all processes that happen during the playback of the sound content.
Spatial audio processes that are limited to runtime processes have to compensate for what processing power is available on that device, this limitation means that these processes have to be able to run faster than realtime and can sometimes be limited in quality.
Synonyms :
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Render
Refers to a process of pre-determining all intended processes and effects to an output file usually to be faithfully replayed or reused without change.
Spatial audio content that has been pre-rendered or rendered has the added benefit of using more time expensive and higher quality processing effects that might not normally be too expensive to be processed in realtime, especially from device to device.
Synonyms :
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A-Format
A often misused term describing multichannel soundfields or multi-mic arrays that Is not ambisonics but is sometimes used as to create a multichannel source that later can be encoded into ambisonics.
Synonyms :
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B-Format
A synonym for an ambisonic encoded soundfield.
Synonyms : Ambisonics
Related Terms :
T-Format
A often misused term describing multichannel soundfields or multi-mic arrays that Is not ambisonics but is sometimes used as to create a multichannel source that later can be encoded into ambisonics.
Synonyms :
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P-Format
A often misused term describing multichannel soundfields or multi-mic arrays that Is not ambisonics but is sometimes used as to create a multichannel source that later can be encoded into ambisonics.
Synonyms :
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C-Format
Describes a partially ambisonics multichannel file where 2 of the channels are decoded from ambisonics the rest of the channels replicate ambisonic domain concepts to replicate the source ambisonic material. Was suggested as a temporary means of distribution to ensure that the first two channels can be played back safely on all systems as they are decoded from ambisonics into traditional stereo.
Synonyms :
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D-Format
Is not ambisonics: multichannel decoding from an ambisonic source
Synonyms :
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E-Format
Is not ambisonics: multichannel decoding from an ambisonic source
Synonyms :
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G-Format
Is not ambisonics: 5.1 multichannel decoding from an ambisonic source