🚀 go-pugleaf

In article <830801963snz@cdsl.demon.co.uk>, Peter Hayward
<peter@cdsl.demon.co.uk> writes
>
>    I'm sorry if this is a duplicate but the original, posted on Sunday,
>    seems to be "one of the small number of news articles lost by
>    demon".
>
>In article <EziU5DAvAegxEwer@furfax.demon.co.uk>
>           derek@furfax.demon.co.uk "derek" writes:
>
>| Have been asked by a friend owning a standard AIWA audio DAT tape
>| recorder whether there might exist any interface devices/methods whereby
>| he might save much money and backup his PC *without* purchasing a
>| further dedicated DAT drive.
>|
>  No it hasen't been done and I don't believe it can be done for a
>  meaningful budget.  About the only thing a DDS (Digital Data Standard)
>  drive shares with an audio DAT drive is the transport mechanism and
>  head/drum.  Even the recording format is different in the sense that
>  the DDS drive stores additonal checksums (ECC level 3) not present in
>  the audio version. A short drop out in audio may go undetected by even
>  the best ear but a few zeros shoved in the middle of you favourite
>  .EXE file will not please you.

Hi Peter, thanks for the info. and for your trouble in replying. I had
guessed that the EC levels would not be adequate in themselves, but then
I hadn't expected anyone would rely on them either!
>
>| I haven't examined any DAT drives, intended for either straight audio or
>| PC digital work, and have no idea whether the 'domestic' variety have
>| any electronic control interface to accompany the buttons and (probably)
>| an inevitable datastream I/O.
>|
>| It doesn't take much effort to imagine that given such control I/F,
>| what's required (at the least!) is an I/O board to SCSI, ATAPI or what-
>| have-you, with an appropriate backup package plus driver. The trick has
>| been done with video recorders in the past with variable success I
>| gather.
>|
>   But think of the bandwidth difference. If you really mean to encode
>   you data onto an audio signal then you will be running at modem
>   speeds.  How long will a 1 GB take to backup at 28.8 KBPS!  The video
>   recoder gets away with it because you are modulating a much higher
>   frequency signal.
>
>   Sorry but I think this a total non starter.

Here I have to disagree.

With great respect I don't believe you're comparing like with like. I
would guess that VHS tape backup was (is?) probably achieved by
generating a bitstream with considerable redundancy (hamming codes or
the like) and using most of the useful video bandwith of, say, 3MHz. I
would have made a wild guess that perhaps 1.5Mbits/S might be usable
without consulting Mr. Shannon!

What I had envisaged for use of audio DAT tape recorders was that
someone would directly use the digital datastream available at least at
presumably some 44.1kHz * 16bits * 2 (stereo) or thereabouts, and no
data compression like the DCCs and Minidiscs of the world. This gives a
raw data rate of over 10Mb/min which beats the maximum *compressed* data
rate of my Jumbo tape drive.

So even given an extra software protocol layer with some sensible ECC,
or even 100% data redundancy with some form of timeshift to overcome
large drop-outs, I would have guessed this was anything BUT a non-
starter! Presuming, that is, that people are happy to press the
start/stop buttons when instructed by a hypothetical screen message!
-- 
derek                                   derek@furfax.demon.co.uk