Update 20141 (Jan 2022)
Since the MRC2014 format was published (Cheng et al., 2015), there have been a number of minor extensions and clarifications. These do not change the structure of the file, but may affect how some fields are interpreted. These changes are now confirmed as version “20141” of the format. Following the convention of the NVERSION field, this is the first update of the 2014 format. The NVERSION field should be updated for new files.
New data modes
Mode 12
To represent floating point real numbers in half precision, i.e. 16 bit, often called float16. Proposed by Takanori Nakane to store summed micrographs and extracted particles, where the likely precision doesn’t require the use of float32, and space can be saved. The proposal refers to the IEEE754, binary16 representation (there are several alternative encodings).
Support for Mode 12 has been added to mrcfile 1.3.0.
Mode 101
To represent 4-bit data, packed two per byte. The initial usage will be an option in SerialEM for putting out frames from the K2 camera.
Proposed by David Agard and David Mastronarde, August 2015.
New EXTTYP types
- The FEI format has been split into FEI1 and FEI2. The latter is an update with more metadata.
- HDF5 has been added
Clarifications to existing format
- The format allows for the permutation of the map axes with respect to the original coordinate frame, as specified by MAPC,MAPR,MAPS. Clarified that NX,NY,NZ and NXSTART,NYSTART,NZSTART refer to the permutated axes in this case.
- A comment on handedness has been added.
Proposed extensions
None at present.