You do run the risk of expanding your data if you back it up with
compression... but that depends on the drive technology.
For example, the AIT algo for compression checks to see if the data is
compressible before writing it. If the data is compressible, it writes a
compressed block. If the data is not compressible (.gif, .jpg, etc), then
it writes an uncompressed block. It's able to do that on-the-fly and still
meet the rated transfer speed.
By using this method, you do not run the risk of expanding your data when it
is pre-compressed. That's why I encourage all of our AIT customers to keep
hardware compression activated. With other technologies that we distribute,
I advise that they turn compression off when dealing with non-linear video,
audio or pre-compressed graphics, otherwise they will not store the full
capacity.
Steve
www.cybernetics.com
[EMAIL PROTECTED]
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf
Of Daniel O'Donnell
Sent: Thursday, March 01, 2001 2:12 PM
To: retro-talk
Subject: Re: Ecrix VXA 33/66 tapes with Retrospect
I was puzzled by the statement as well. The biggest files these days
tend to be motion graphics or animations such as QuickTime or MPEG.
QT and MPEG are already compressed and will show very little if any
subsequent compression.
At 10:23 AM -0800 on 3/1/01, Jon Stevens wrote:
>on 3/1/01 8:04 AM, "Garret J. Cleversley" <[EMAIL PROTECTED]> wrote:
>
>> I am very happy with this as graphics files are very compressible (sp?).
>>
>> Garret
>
>Eh? It really depends on the type of file you are compressing.
>
>If the image (or any data for that matter) is already stored in a
compressed
>format (for example, .gif images are stored compressed), then there is
>absolutely no gain and in fact, you might have a negative effect.
>
>For example, a quick and dirty test:
>
>I have a .gif file on disk that is:
>
>12,461 bytes
>
>Compressed with Stuffit, the image becomes:
>
>12,677 bytes
>
>It is actually LARGER in compressed format!
>
>Just wanted to clarify that statement lest anyone become enamored with the
>idea that all graphic files compress well.
>
>thanks,
>
>-jon
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