University of Bristol NDT Laboratory Multi-Frame Matrix Capture Common File Format (MFMC- CFF) Requirements Capture Martin Mienczakowski, September 2014 OVERVIEW A project has been launched at the University of Bristol to improve the uptake of Full Matrix Capture (FMC) by researchers, equipment manufacturers and industrial end-users. FMC is the recording of coherent signals from distributed transmit / receive combinations with appropriate phase information that allows reconstruction and signal processing post acquisition. It has been proposed that the impact of FMC would be enhanced if there were a Multi-Frame Matrix Capture Common File Format (MFMC-CFF) allowing the transfer of experimental data between organisations. MFMC is taken to mean the capture of multiple matrices of data, this could include full matrix capture but does not exclude, half matrix capture or the capturing of other part matrix methods. This file format will consist of a framework / specification with a library which allows fundamental important parameters to be stored alongside experimental data and user defined parameters. In the project a number of existing file formats will be considered alongside developing a completely new file format. Participation will be required from project participants in evaluating the various file formats (in particular where a participant has a propriety format or great experience with a generic format). A down selection will be made from these options before development / documentation of a technical specification. From this a demonstration library will be constructed. The aim of this document is to capture the requirements from the stakeholders associated with this project. This is achieved by completion of a survey by participants and review of this document. STAKEHOLDERS The following stakeholders have been identified during the requirements capture exercise and were consulted with the questionnaire: End Users (Rolls-Royce Marine, Rolls- Royce Aeropace, EDF, Ontario Power Group, CEA CEVA) Equipment Manufacturers (Applus RTD, Diagnostic Sonar Limited, GE, UTEX, M2M, Olympus NDT, Peak NDT, ZETEC,) University Researchers (University of Bristol, Imperial College, University of Strathclyde, University of Warwick, University of Manchester, University of Nottingham) Other Research Organisations (Electric Power Research Institute, TWI) UK RCNDE Members / Associate Members The following have responded to the questionnaire: Diagnostic Sonar EDF Electric Power Research Institute GE Measurement & Control Imperial College Olympus NDT Ontario Power Group Rolls-Royce Aerospace Rolls-Royce Marine TWI University of Bristol University of Strathclyde 1
REQUIREMENTS The following general requirements will be necessary in any file format developed: Requirement Category Storage of multiple frames of data (i.e. a scan of data) in a single file All mandatory attributes stored within each file Ability to store data from 1D, 1.5D, 2D and flexible arrays Ability to store data and appropriate decoding information from multiple arrays The ability to store part of the matrix of data (e.g. half matrix capture) Storage of custom parameters File fully describes acquisition scenario to allow reconstruction of an image from the data Data is viewable without specialist software for example a standard movie / image format Files may be expandable during acquisition Inclusion of data compression techniques Inclusion of compatibility with perceived future developments in the field, e.g. increased dynamic range (greater bits per sample), novel algorithms, Ability to extract a specific frame of data without reading in all previous frames Without reference to user-defined information (eg when it is not accessible to some file readers), it shall be possible to reconstruct an image from the data using just the Essential Parameters. There should be enough information about any pre-processing prior to storage (analogue / digital) to reconstruct the raw waveforms. This can include user-defined attributes. / ATTRIBUTES The following Essential Parameters will be included in the file format: means even if the parameter is not expected to be used it has to be set to a correct value. E.g. Y element coordinates on a 1D array. means that a flag will be provided to indicate whether the parameter is valid or not, not essential for the majority of reconstruction algorithms. Probe Geometry (Probe Coordinate System, PCS) Element dimensions (shape, length, width) Focal length in water due to element curvature (0 if planar) 3D Element location relative to origin of PCS (All elements) Element orientation relative to PCS (two angles, elevation and azimuthal, of normal to element) All above for multiple arrays e.g. different transmit and receivers Per Frame Scanning Location (Global Coordinate System, GCS) Probe location (origin of PCS but in global, GCS, coordinates) Probe orientation (three angles relative to x, y and z axes in GCS), relationship between two coordinate systems Expected location of the specimen surface All above for multiple arrays different transmit and receivers Probe Setup Probe centre frequency Probe bandwidth 2
All above for multiple arrays different transmit and receivers Ultrasonic Setup Receive amplifier gain Distance amplitude correction at acquisition (full description of DAC curve) Filter type (0 no filter, 1 low pass, 2 high pass, 3- band pass, 4 user specified) Filter centre frequency (0 no filter) Filter bandwidth (0 no filter) Level of time averaging (number of averages, default - 1) Transmit Aperture flag: 0 - Single element transmit receive, 1 user specified Transmit virtual elements. If user defined Transmit Apertures are used for transmit then a table of virtual element locations and relative phases per aperture must be provided to allow reconstruction of an image Number of arrays in use All above for multiple probes different transmit and receivers In the case of multiple probes, assignment of global element numbers to all elements in all probes. Waveform Encoding Bits resolution Bytes per sample (could be non-integer) Data Type Class: Signed integer / unsigned integer / two s-complement / floating-point / text Byte Ordering: Big Endian/Little Endian Level representing 0 Volts Vertical resolution (Volts per digitisation level) Data acquisition rate Time of first point in waveform Number of time points FMC Sequence Number of waveforms per frame Matrix relating each scan line to a transmitting element Matrix relating each scan line to a receiving element Number bytes per waveform General Setup Nominal coupling medium velocity (shear and compression) Nominal specimen medium velocity (shear and compression) Number of frames Nominal scan extent (X,Y,Z) (for creating arrays at analysis time) Dead Elements FMC Common File Format version Number There will be a structure provided for the storage of MFMC data, this structure will store the following information and MFMC data for each transmit-receive pair: Firing sequence number (required in multiplexing for example) Transmit number (element number for single element firing but becomes aperture number in the case of aperture firing) Receive number Actual waveform data. This must be meaningful RF style data that can be used to create an image. Thus, if excitation was a coded sequence or chirp, the decoding, pulse compression, or deconvolution must be performed prior to storage. In addition, the following information per frame, or field (collection of n firings) if less than a frame is captured continuously, will be stored to account for continuous motion during acquisition of a frame: 3
Location at time of first (i = 1) firing location Location at time of last (i = n) firing location There will be scope for user-defined parameters within the format, parameters that have been identified in the requirements capture process that fall into this category are as follows: Probe Probe serial number Probe manufacturer Wedge serial number Wedge dimensions Ultrasonic Setup Custom filter specification, if a filter is selected in essential data Transmit aperture details if Transmit Aperture flag is set to user specified Focal length of transmit aperture (or focal laws) Steering angle of transmit aperture (or focal laws) Pulse centre frequency Pulse bandwidth Pulse voltage Pulse duration Time base offset (may be, for example, a firing delay between voltage being applied and pulse) Amplifier linearity checks System sensitivity levels Unusual firing patterns arbitrary elements, arbitrary phases, different amplitudes Signal that is emitted (reference signal chirp, Gaussian pulse, etc) Waveform decoding data used to get to the RF waveforms stored. General Setup Operator details (i.e. name) Inspection procedure details Location details (plant location / name) Type and serial number of array controller Inspection volume dimensions Manipulator details (serial number etc.) Calibration block details (serial number) Calibration curve (raw data, scale of axes) General notes section Software version number Angle dependent velocity data for anisotropic materials Manipulator type (X,Y,Z or R,theta or ) Coupling medium velocity (shear and compression) for each frame CONSTRAINTS The following constraints have been identified in the requirements capture process: Constraint Compatibility with existing file formats If an existing format is chosen then freedom of use must exist for new adopters The format is chosen then should have a low / no cost for access A large part of the format already written / available A level of global acceptance exists for the format chosen The focus of the project will be the benefit of stakeholders with a UK presence due to funding restrictions / 4
No quality assurance of software will be provided No support of software guaranteed Recognition of the file format as a British or global standard is beyond the scope of this project If expandability of file is offered, a description of how that must be implemented should be included in the specification Examples and recommendations showing how to work within the essential framework when not all parameters required e.g y element location on a 1D array Examples to show how to work with moving probes and multiplexing EXISTING FILE FORMATS FOR COMPARISON The following file formats have been identified for consideration by the project: AVI / movie formats DICONDE HDF5 Multi-Page TIFF / BIG TIFF Ontario Power Group custom file format Rolls-Royce Marine custom file format University of Strathclyde custom file format XML type file format New file format 5