Re: HDF data types on UNIX and windows

[hcp(at)newsread.ed.ac.uk (H C Pumphrey)]

Hmmm. It's HDF day in this group, clearly......

In article <8t6s4p$13n$1@naxos.belnet.be>, "Henk" <deckard_007@deja.com> writes:

|> I have this HDF file with vgroups and vdata.  I can open and view the
|> contents via scispy (although it crashes a lot!), but not via IDL.  I first
|> used my own program (didn't work) and afterwards the HDF_BROWSER.  They both
|> complain about 'Unsupported or unknown HDF data type (16389)'.  I'm using
|> IDL5.3 on HP-UX 10.20 .

The HDF User manual says 

HDF Data Type | HDF Data type flag and value | Description
float32       | DFNT_LFLOAT32 (16389)        | 32-bit little-endian float 

So it is not unknown, it is unsupported.

|> Also the java hdf-viewer from ncsa does not work.
|> Has anyone encountered this kind of problem ?  Any tips ?  Scispy says the
|> datatype is 'Little Endian 32-bit floating point type'.

And that therefore tallies with the message you got from IDL. Maybe
only a small fraction of HDF files have this data type in and support for
it is therefore unreliable in many packages.

I have tried a few HDF viewers and readers and found that most are flaky. 
They tend to support the subset of HDF files that the writer uses them on, 
and fail on others. (I had assumed that IDL's HDF support was better than 
this, maybe I was not quite right in that assumtion.)
This in turn suggests to me that HDF is too big and 
complex. I get the impression that HDF5 is intended to cut exactly
this Gordian[1] knot.

Hugh


[1] I have proably spelt that wrong, but you know what I mean. 
    Alexander the Great, blah, blah


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