[McIDAS #ZBT-584576]: OpenADDE support for BZip2-ed products?

Hi Robert,

I apologize for the slow reply; it is training workshop time here in Unidata,
and my time has been consumed by it lately.

re:
> It's my understanding that OpenADDE supports reading zlib zipped Nexrad data 
> products.
> However, a change was made (a few years back?) when new data products became 
> available
> (like N0Q, a higher resolution version of N0R base reflectivity) from zlib 
> compressed
> products to bzip2. And from my quick look through your code, it looks like it 
> hasn't
> been updated in a long time and doesn't reflect that change.

The Unidata of Wisconsin (UW) Space Science and Engineering Center (SSEC) is
the group that put together and maintains the OpenADDE package.  I guess that
the lack of interest in the package has made updating the code a much lower
priority for them.

re:
> My interest isn't in actually using OpenADDE. I'm just trying to learn as 
> much as I can
> about the NIDS data format and this seems to be the best example of a NIDS 
> file decoder.
> The best information I can find is what you wrote 13+ years ago:
> 
> http://www.unidata.ucar.edu/support/help/MailArchives/datastream/msg00508.html
> http://www.unidata.ucar.edu/support/help/MailArchives/datastream/msg00552.html

All of the visualization packages that we support support (GEMPAK (written in C
and Fortran), IDV (written in Java) and McIDAS-X written in C and Fortran)
support use of the NEXRAD Level III products including the newer ones created
from dual polarization data.

re:
> Also, my files (from NOAAPORT) seem to have a 161 byte header, followed by a 
> bzip2 magic
> word (BZh2). I only understand the first 41 bytes, which is the same as you 
> said it would be:
> 
> CTRL-A              \r\r\n
> 570                 \r\r\n
> SDUS54 KLIX 010731  \r\r\n
> N0QLIX              \r\r\n
> 
> I can bzip2 uncompress the rest of the file, but the result is nonsense. My 
> only other
> reference is this Interface Control Document:
> 
> http://www.roc.noaa.gov/wsr88d/PublicDocs/ICDS/2620001U.pdf

The ICD is the reference we use to guide our software development efforts for
support of the Level III data products.  In particular, APPENDIX D. PRODUCT DATA
COMPRESSION USING BZIP2 contains the information needed to uncompress the
portion of the products that are compressed using bzip2 algorithms. Ultimately
the code in GEMPAK and McIDAS-X call the BZ2_bzBuffToBuffDecompress function
that is referenced in Appendix D.  The buffer passed to this function contains
the portion of the image that has been compressed using bzip2 (i.e., without
the header portion), and a named auxiliary buffer is populated with the
uncompressed image.

re:
> I appreciate any insights you might have, and understand if you are unable to 
> help.

Please let us know if the above helps...


Cheers,

Tom
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Ticket Details
===================
Ticket ID: ZBT-584576
Department: Support McIDAS
Priority: Normal
Status: Closed