Hi there,
With netCDF-C now supporting HDF dynamic filters, the behaviour of
nccopy has slightly changed. In the past nccopy could be used to
uncompress files previously compressed with custom HDF dynamic
filters. Nccopy used to read <infile>, relying on HDF to invoke the
decompression using the filter, and then it would create a new netCDF
file, <outfile>, uncompressed. In version 4.6.0, nccopy also reads
<infile> relying on HDF as before, but then writes the new <outfile>
applying the filter options defined in <infile>. I guess this is the
new default behaviour when not passing the -F argument.
Is there any option that can be passed in the -F argument to tell
nccopy not to apply any compression algorithm?
Thanks! and keep up the good work! Dynamic filter write support is a
very hice feature!
Here an example, with a sample.nc file previously compressed with a
custom HDF filter.
jrgu@linux-ozpe:~/FiltersTest/Test> ncdump -h -s sample.nc
netcdf sample {
dimensions:
number_of_columns = 30 ;
number_of_rows = 60 ;
variables:
short effective_radiance(number_of_rows, number_of_columns) ;
effective_radiance:_Storage = "chunked" ;
effective_radiance:_ChunkSizes = 60, 30 ;
effective_radiance:_Endianness = "little" ;
effective_radiance:_Filter = "56782,2,1,60,30,16,1,0,0,0,0,0,0,0" ; //
filterID + filter options (cd values)
ubyte pixel_quality(number_of_rows, number_of_columns) ;
pixel_quality:_Storage = "chunked" ;
pixel_quality:_ChunkSizes = 60, 30 ;
pixel_quality:_Filter = "56782,1,1,60,30,8,1,0,0,0,0,0,0,0" ; //
filterID + filter options (cd values)
// global attributes:
:_SuperblockVersion = 2 ;
:_IsNetcdf4 = 1 ;
:_Format = "netCDF-4" ;
}
I have added some debugging messages to the custom HDF dynamic filter
and obtained the following when using nccopy:
* Nccopy in NetCDF-c 4.4 and 4.5: the decoding functionality in the
filter is invoked once for each variable when reading in_file:
jrgu@linux-ozpe:~/FiltersTest/Test>
../netcdf-c-4.5.0/ncdump/nccopy sample.nc sample_nccopy45.nc
/Deconding/
/CD VALUES 2, 1, 60, 30, 16, 1, 0, 0, 0, 0, ... /
/Components: 1, Lines: 60, Samples: 30/
/DataBytes: 2/
/Decompression successfull/
/Decode End: 3600/
/Deconding/
/CD VALUES 1, 1, 60, 30, 8, 1, 0, 0, 0, 0, ... /
/Components: 1, Lines: 60, Samples: 30/
/DataBytes: 1/
/Decompression successfull/
/Decode End: 1800/
* //Nccopy in NetCDF-c 4.6: the decoding functionality in the filter
is invoked once for each variable when reading in_file. The encoding
functionality in the filter is invoked once for each variable when
writing out_file
jrgu@linux-ozpe:~/FiltersTest/Test> nccopy sample.nc
sample_nccopy46.nc
/Deconding/
/CD VALUES 2, 1, 60, 30, 16, 1, 0, 0, 0, 0, ... /
/Components: 1, Lines: 60, Samples: 30/
/DataBytes: 2/
/Decompression successfull/
/Decode End: 3600/
/Deconding/
/CD VALUES 1, 1, 60, 30, 8, 1, 0, 0, 0, 0, .../
/Components: 1, Lines: 60, Samples: 30/
/DataBytes: 1/
/Decompression successfull/
/Decode End: 1800/
/Encoding/
/CD VALUES 2, 1, 60, 30, 2, 1, 60, 30, 16, 1, .../
/Components: 1, Lines: 60, Samples: 30/
/DataBytes: 2/
/Pixel: 1800/
/ERROR: Error in jpeglsCompress: Parameter values are not
supported by CharLS./
/Compression failed/
/ERROR: Error during the JPEG-LS compression of the dataset./
/Encode End -> Result: 0/
/Encoding/
/CD VALUES 1, 1, 60, 30, 1, 1, 60, 30, 8, 1 /
/Components: 1, Lines: 60, Samples: 30/
/DataBytes: 1/
/Pixel: 1800/
/ERROR: Error in jpeglsCompress: Parameter values are not
supported by CharLS./
/Compression failed/
/ERROR: Error during the JPEG-LS compression of the dataset./
/Encode End -> Result: 0/
Cheers,
Joaquín
Any email message from EUMETSAT is sent in good faith but shall
neither be binding nor construed as constituting a commitment by
EUMETSAT, except where provided for in a written agreement or contract
or if explicitly stated in the email. Please note that any views or
opinions presented in this email are solely those of the sender and do
not necessarily represent those of EUMETSAT. This message and any
attachments are intended for the sole use of the addressee(s) and may
contain confidential and privileged information. Any unauthorised use,
disclosure, dissemination or distribution (in whole or in part) of its
contents is not permitted. If you received this message in error,
please notify the sender and delete it from your system.
_______________________________________________
NOTE: All exchanges posted to Unidata maintained email lists are
recorded in the Unidata inquiry tracking system and made publicly
available through the web. Users who post to any of the lists we
maintain are reminded to remove any personal information that they
do not want to be made public.
netcdfgroup mailing list
netcdfgroup@xxxxxxxxxxxxxxxx
For list information or to unsubscribe, visit:
http://www.unidata.ucar.edu/mailing_lists/
