HDF(4.x) and HDF5

Important Message Both HDF4 and HDF5 are supported by the NCSA HDF group. We will continue to maintain HDF4, as long as we are funded to do so. We do not plan to add any new features to HDF4, but we will fix bugs and build and test it on new operating system versions. We recommend using HDF5, especially if you are a new user and are not constrained to using HDF 4.x (HDF4). We also recommend that you consider migrating from HDF4 to HDF5 to take advantage of the improved features and performance of HDF5.

Versions 1, 2, 3, and 4 of HDF were backward compatible, and HDF4 can access files from earlier versions.  HDF5 is a completely new format and library; conceptually related to but incompatible with HDF4 files and libraries.

 This page provides pointers to information and software to help HDF4 users work with HDF5.

Software

• h4toh5 utility [Description] -- convert any HDF4 file to HDF5, using default mappings.

 
• h5toh4 utility [Description] -- convert HDF5 to HDF4.  (Not all objects can be converted, and is not an inverse of h4toh5.)
   
• H4toH5 Conversion Library (beta) -- library to convert individual HDF4 objects into HDF5 objects. Also includes the h4toh5 and h5toh4 utilities.

   User's Guide [pdf]
   Reference Manual [pdf]

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Documentation

Differences between HDF4 and HDF5

Introduction to HDF5 (Slides)

HDF4 vs HDF5

Backward/Forward Compatibility

HDF4 and HDF5 Performance Preliminary Results (Slides)

HDF5 Abstract Data Model (Slides)

HDF5 Tutorial

HDF4 and HDF5 Compatibility and Transition

Mapping HDF4 Objects to HDF5 Objects (Specification) [pdf]

Transition from HDF4 to HDF5: Notes about Compatibility, Conversion, and Interoperability of HDF and HDF-EOS  (White paper) [pdf]

Transition from HDF4 to HDF5: Issues  (Slides)

 

H4toH5 Conversion Library

User's Guide [pdf]

Reference Manual [pdf]

Technical Reports

Tests of the NCSA h4toh5 utility with NASA Datasets, August, 2001. [HTML]

This paper reports tests of the h4toh5 utility using real NASA data.  The utility converted files, usually in less than one second per file.  These results show that conversion of HDF4 files to HDF5 is feasible for large collections or on demand.

Conversion of from HDF4 to HDF5: "Hybrid" HDF-EOS Files, Feburary. 2002. [HTML]

In this experiment, the heconvert utility is augmented using the H4toH5 Library. In addition to the standard conversion of HDF-EOS objects, the experimental program identifies and converts non-EOS objects in an EOS dataset, creating a more complete HDFEOS5 file. In conclusion, this experiment shows that the H4toH5 Library provides a toolkit to more easily construct conversion utilities for NASA HDFEOS files.