Motion and gesture file formats
With the development of gesture controllers, haptic systems, motion capture systems, etc, on the one hand, and with the need of allowing virtual reality systems to inter-communicate through control data, the question of gesture and motion takes more and more importance. Motion and gesture file formats are widely used today in many applications that deal with motion and gesture signal. It is the case in domains like motion capture, character animation, gesture analysis, biomechanics, musical gesture interfaces, virtual surgery. Those formats are low-level formats, i.e. formats close to the signal produced by the capture system. One should distinguish low-level format from higher-level formats that encode events and actions. High-level formats do not encode motion or gesture signals themselves but a description of those motions and those gestures.
Existing format that encode gesture and motion
BVA and BVH file formats
BVH means Biovision Hierarchical Data. This format is one of the most currently used today. At the basis, Biovision, a motion capture company, has developed it. The BVA format, also developed by Biovision is the BVH primal form. This format is mainly used for the animation of humanoid structures and gives a standardised definition of them. The format is largely and successfully spread in animation community certainly because of its simple specifications.
MNM file format
This file format allows renaming the segments of a BVH file: a name defined by the user is associated to the predefined label in the BVH file.
ASK/SDL file format
The format is a variant of the BVH file format developed by Biovision. The ASK file (Alias Skeleton) only contain information concerning the skeleton and, as a result, does not contain any information about the channels or the movement. The offset coordinates are absolute unlike the BVH in which they are relative. The SDL file associated to the ASK file contain the data of the movement but it can contain many other information concerning the scene than the very samples of the movement.
AOA file format
Adaptative Optics is a company dedicated to the creation of hardware support for the motion capture. This ASCII file format simply describes the captors and their position at each sampling period.
ASF/AMC file formats
This format was developed by Acclaim, a video game company. Once entered in the public domain it has been used by Oxford Metrics (Vicon Motion Capture Systems). The Acclaim format is composed of two different files, one for the skeleton and the other one for the movement. The separation between these two types has been done because the same skeleton is often used for numerous distinct movements. The file containing the skeleton description in the ASF file (Acclaim Skeleton File) and the file containing the movement data is the AMC file (Acclaim Motion Capture data).
BRD file format
The format is uniquely used by the motion capture system Ascension Technology “Flock of Birds” developed by LambSoft. It allowed stocking the data coming from a magnetic motion capture system.
HTR and GTR file formats
The HTR format (Hierarchical Translation Rotation) has been developed as a native format for the skeleton of the Motion Analysis software. It has been created as an alternative to the BVH format to make up for its main drawbacks. A HTR variant exist which is called the GTR format (Global Translation Rotation) and is the same format less the structural information.
TRC file format
The TRC file format is another file format from Motion Analysis. It contains not only the raw data from the full body motion capture system they developed but also the output data coming from their face tracker.
CSM file format
The CSM format is an optical tracking format that is used by Character Studio (an animation and skinning plug-in for 3ds Max) for importing marker data.
The National Institute of Health C3D file format
Many of the motion capture companies are often linked to the biomechanics research. The systems are then used to assess the performances of an athlete or the needs of a physically handicapped person. The needs of researchers, often supplied by more than one society, lead to the definition of a common format, the C3D format. This format has been built following this philosophy, so it has tried to carry the most complete amount of information useful for the biomechanics research. The features below was considered as necessities:
- The possibility to stock analogical data (i.e. directly coming from the measure instrument) and three-dimensional data (obtained by the information processing).
- The possibility to stock information on the material, which have been used (position marker, force captors), on the recording process (sampling rate, date, type of examination…), on the subject itself (name, age, physical parameters…).
- The possibility to add new data to the ones already recorded.
- The file was a binary file unlike most of motion capture file format, which often are ASCII files.
The GMS file format
The GMS format is a low-level, binary, minimal, but generic, format for storing Gesture and Motion Signals in a flexible, organized, optimized way. The GMS format takes into account the minimal features a format carrying movement/gesture information needs: flexible dimensionality for the signals, versatile structuration, flexible types of the encoded variables, and spatial and temporal properties of gesture and motion signals. GMS received the support of the the FP6 Network of Excellence IST-2002-002114 – "Enactive Interfaces".