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Recommendation:

Only compression filters that are officially supported by a default installation of the current netCDF4 software distribution should be used in Earth Science data products in netCDF4 or netCDF4-compatible HDF5 formats.  Currently, DEFLATE is the only such filter.


Recommendation Details:

NetCDF4 has recently (4.7.0) enabled access to non-default (i.e., non-DEFLATE) HDF5 compression filters.  However the filter identification and access are currently obscure (~five digit IDs) and non-portable (no guarantees client software will be able to decompress them).  DEFLATE is the only compression filter that is guaranteed to work with default (non-customized) netCDF4 installations, and so DEFLATE is the only compression filter that should be used in interoperable Earth Science data products in netCDF4 or netCDF4-compatible HDF5 formats.

This recommendation may evolve as netCDF4 extends its default compression filter support to other filters.

Here is a link regarding netCDF4 general filter support: https://www.unidata.ucar.edu/software/netcdf/docs/md__home_wfisher_Desktop_gitprojects_netcdf-c_docs_filters.html .

This recommendation does not exclude use of the shuffle filter, which is not a compression filter.

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