Can you tell if it is compressed or not?

Hi all

Is it possible to tell if data saved to a floppy is compressed or not?

I work with a piece of equipment that allows set-up configs to be
saved to a floppy. I am trying to decypher the content of the floppy
but it makes little sense at the moment. A few minor changes to the
equipment appears as totaly different data on the floppy. The
manufacturer offers no help. Any advice?

Thanks in anticipation.

Aluk

"AlUK" <alanhenery@hotmail.com> wrote in message
news:4f721faa.0409181613.7752af67@posting.google.com...
> Hi all
>
> Is it possible to tell if data saved to a floppy is compressed or not?
>
maybe with experience and a hex dump.

> I work with a piece of equipment that allows set-up configs to be
> saved to a floppy. I am trying to decypher the content of the floppy
> but it makes little sense at the moment. A few minor changes to the
> equipment appears as totaly different data on the floppy. The
> manufacturer offers no help. Any advice?
>
possibly it is a binary format or is using some form of
compression/encryption.

one can't tell what is going on from this description...

"cr88192" <cr88192@remove.hotmail.com> wrote in message news:<TJ53d.4650$nc6.536@news.flash
newsgroups.com>...
> "AlUK" <alanhenery@hotmail.com> wrote in message
> news:4f721faa.0409181613.7752af67@posting.google.com... 
> maybe with experience and a hex dump.
> 
> possibly it is a binary format or is using some form of
> compression/encryption.
>
> one can't tell what is going on from this description...

Thanks for your reply. Can you tell me what information is required.

Al

"cr88192" <cr88192@remove.hotmail.com> wrote in message news:<TJ53d.4650$nc6.536@news.flash
newsgroups.com>...
> "AlUK" <alanhenery@hotmail.com> wrote in message
> news:4f721faa.0409181613.7752af67@posting.google.com... 
> maybe with experience and a hex dump.
> 
> possibly it is a binary format or is using some form of
> compression/encryption.
>
> one can't tell what is going on from this description...

Further info. The file is small (570 bytes). Various configs show
similar or same data at the start of the file then the data changes
greatly. (some kind of header?)

Thanks

Al

"AlUK" <alanhenery@hotmail.com> wrote in message
news:4f721faa.0409190347.612c7532@posting.google.com...
> "cr88192" <cr88192@remove.hotmail.com> wrote in message
> news:<TJ53d.4650$nc6.536@news.flashnewsgroups.com>... 
>
> Thanks for your reply. Can you tell me what information is required.
>
better descriptions would help.
maybe a hexdump of a few files.
...

"AlUK" <alanhenery@hotmail.com> wrote in message
news:4f721faa.0409190352.4245823b@posting.google.com...
> "cr88192" <cr88192@remove.hotmail.com> wrote in message
> news:<TJ53d.4650$nc6.536@news.flashnewsgroups.com>... 
>
> Further info. The file is small (570 bytes). Various configs show
> similar or same data at the start of the file then the data changes
> greatly. (some kind of header?)
>
hell, at least this implies you are probably looking at it in a hex editor
or such...

dunno, this is still pretty vague.

alanhenery@hotmail.com (AlUK) wrote in
news:4f721faa.0409181613.7752af67@posting.google.com:

>
> Hi all
>
> Is it possible to tell if data saved to a floppy is compressed or not?
>
>

Sometimes.  Since many compressors leave headers you can often
assume if you see these headers in the file it is compressed.
However there are zip files that compress to themselves so some files
can be safely thought of as both. Then again if the file was compressed
by one of my bijective compressors. They map to every possible files so
any file can be thought of as a compressed file or an uncompressed file.
You need more than the information in the file to know for sure. You need
to know what the file is for.



David A. Scott
--
My Crypto code
http://bijective.dogma.net/crypto/scott19u.zip
http://www.jim.com/jamesd/Kong/scott19u.zip old version
My Compression code http://bijective.dogma.net/
**TO EMAIL ME drop the roman "five" **
Disclaimer:I am in no way responsible for any of the statements
made in the above text. For all I know I might be drugged.
As a famous person once said "any cryptograhic
system is only as strong as its weakest link"

"AlUK" <alanhenery@hotmail.com> wrote in message
news:4f721faa.0409181613.7752af67@posting.google.com...
> Hi all
>
> Is it possible to tell if data saved to a floppy is compressed or not?
>
> I work with a piece of equipment that allows set-up configs to be
> saved to a floppy. I am trying to decypher the content of the floppy
> but it makes little sense at the moment. A few minor changes to the
> equipment appears as totaly different data on the floppy. The
> manufacturer offers no help. Any advice?

Here is a simple test: try to compress the data with an off the shelf
program (gzip, rar, etc.).  If it compresses, then it was not compressed.
If it does not compress, then either it was already compressed, or it's
encrypted, or it's random data.  However you can't tell which without more
work.

-- Matt Mahoney

"David A. Scott" <daVvid_a_scott@email.com> wrote in message news:<Xns95695918F9805H110W296
LC45WIN3030R@130.133.1.4>...
> alanhenery@hotmail.com (AlUK) wrote in
> news:4f721faa.0409181613.7752af67@posting.google.com:
> 
>
>     Sometimes.  Since many compressors leave headers you can often
> assume if you see these headers in the file it is compressed.
> However there are zip files that compress to themselves so some files
> can be safely thought of as both. Then again if the file was compressed
> by one of my bijective compressors. They map to every possible files so
> any file can be thought of as a compressed file or an uncompressed file.
> You need more than the information in the file to know for sure. You need
> to know what the file is for.
>
>
>
> David A. Scott

The file is used to store the setup of a video switcher.(TV studio)
The switcher is a multiple input (cameras, VT's HDD's etc) and
multiple output. The file is used to quickly restore the desk to any
saved configuration. The Hexdump prog I am using does not allow me to
copy the output to paste here. Is there any way of attaching a file to
these messages?

Thanks again for any info

Al

"Matt Mahoney" <matmahoney@yahoo.com> wrote in message
news:ePi3d.6571$n16.1611@newsread2.news.atl.earthlink.net...
>
> "AlUK" <alanhenery@hotmail.com> wrote in message
> news:4f721faa.0409181613.7752af67@posting.google.com... 
>
> Here is a simple test: try to compress the data with an off the shelf
> program (gzip, rar, etc.).  If it compresses, then it was not compressed.
> If it does not compress, then either it was already compressed, or it's
> encrypted, or it's random data.  However you can't tell which without more
> work.
>
this is not very accurate imo. some really simple compression teqniques, eg,
using bitfields and only including sone items, rle, ... will still result in
some additional compression, making it seem like it was "uncompressed" under
this test.

of course, this may not matter much.