[rrd-users] RRD and Respironics Smart Card
chris at montfordhouse.com
Tue Apr 22 21:34:55 CEST 2008
Thanks for your replies.
I originally replied to Simon alone by mistake but
am resending this re-edited to the group instead.
You are right, it may be proprietary.
To that end, I've emailed Respironics
directly asking for a linux dump tool.
Surely their software techs have just such
a tool for diagnostics already made.
I can't be faulted for asking, eh?
I looked at the data in Hackman Hex Editor
and did an ASCII search on my name.
It found that and my phone number within the
data, so you're probably right - it's
likely not encrypted or compressed.
I compared the files. Areas of interest
included the top of the file, the used area
and the unused area.
The top of the .rrd starts 'RRD' and general
information about the rrd setup.
The .bin file starts with 'RA' and my general
patient data plus other info I cannot decipher.
The middle (recorded) areas seem dissimilar,
as do the ends (unrecorded). Empty content for
the .bin file is a wall of FF. Not so in the .rrd.
However, I have only compared two files.
I tried rrdtool dump - the simplest
way I could think of to access the file.
This doesn't work.
The .bin file contains some general data about me,
a high resolution data set for about a week,
depending on the number of events recorded.
The higher the number of events per day,
the fewer days of hi-res recording are overwritten.
There is also a lo-res data set that includes daily records
about 20 fields for up to six plus months, maybe longer.
The fact that I can tell where data ends, where
the two content types begin and end,
and empty content begins again seems to indicate
some sort of rrd.
Both sets of data are graphed as images rather
than line-art like excel. I wouldn't exactly call
the graphs fancy, but they are informative.
Distinctive features of rrdtool that might indicate whether your
Respironics card is using rrdtool include
1. Consolidating data over a variety of time periods. Does the card simply
return data for the last 30 hours, for example, or does it return data by
hour, day, and week?
2. Does it generate cool, and very distinctive, graphs like rrdtool?
On Tuesday 22 April 2008 02:06:41 pm Simon Hobson wrote:
> Chris wrote:
> >Granted, there is the possibility that the .bin file is
> >not using Tobias Oetiker's algorithms.
> >But why would Respironics reinvent the wheel?
> Why wouldn't they ? There are many reasons : having a proprietary
> format that isn't readable with other tools might be a design goal;
> not using anything 'tainted' with an open licence might also be a
> requirement; just plain "we know better" attitude; not knowing about
> rrdtool; not running a system suitable for running rrdtool - so
> there's a few options for you, the list is by no means complete.
> >Respironics' smart card system is younger than RRDTool.
> So ? rrdtool does not have a monopoly on fixed size circular buffer
> >Others on my preferred list about cpap machines have suggested
> >the likelihood that the file is some form of rrd.
> >I suspect its encrypted and/or compressed.
> >I'm looking for suggestions or pointers about how to unlock and
> >dump such a file. Any help will be greatly appreciated.
> Detective work is needed.
> I'd be surprised if it was encrypted as this would make updates
> unneccessarily complex and processor intensive.
> So, hexdump the file and take a peek - try and figure out what format
> it's in. You can do the same with an rrd file and compare - the
> difference being that you can make custom rrd files, and experiment
> with inserting known data into them (and I imagine that Tobi probably
> has a file spec somewhere).
> That's probably as much help as anyone on this list can give you.
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