h5toh4 performs a basic conversion designed to meet common requirements; it does not attempt to convert every HDF5 object that a file might contain. The following describes some of the tool’s limitations: 1. Limited datatypes conversions h5toh4 does not convert datasets of the following datatypes: Array Multi-dimensional strings Bitfield Time The tool issues a warning message and skips the dataset, but continues to process the file. 2. Unrecognized datatypes h5toh4 issues an error and exits upon encountering a dataset of the following datatypes: Object reference Region reference ENUM Any variable-length datatype 3. Compound datatype When h5toh4 encounters a dataset of the following datatype, it causes a segmentation fault: Compound datatype with a field of array datatype and 5 or more dimensions The tool successfully processes compound datatypes with fields of array datatype and 4 or fewer dimensions. 4. Dimension scales h5toh4 does not support dimension scale datasets; they are treated as regular datasets in HDF5 and SDSs in the conversion to HDF4. 5. Unlimited dimensions HDF4 allows only one unlimited dimension, so h5toh4 is limited in its ability to convert HDF5 datasets with unlimited dimensions. If the first dimension of an HDF5 dataset is unlimited, that is: If dim[0]=H5S_UNLIMITED, then h5toh4 will set that dimension to unlimited in the resulting HDF4 dataset. Other dimensions will be set in the HDF4 file to their current size in the HDF5 file. 6. Number of objects An HDF4 file is limited to 20,000 objects. h5toh4 cannot support file conversions that would exceed that limit (and its behavior in such situations is not tested). 7. File size h5toh4 can convert files up to 2 GB in size; it will exit with code 1 if the source HDF5 file is larger than 2 GB.