> Peter Monta wrote:
>
> > Hm, 3 kbit/sec. Soundcard/tape has high SNR and is quite linear; one
> > could use some V.34-like QAM/TCM scheme but at a higher symbol rate.
> > If V.34 can get 30 kbit/sec from a phone line, surely a tape deck with
> > 15 kHz bandwidth would roughly quadruple this, giving around 80 MByte
> > per 90-min tape. Would want to interleave to control dropouts.
>
> YOU do the reference carrier tracking with anything but a tape costing
> more than your computer 8-)
A friend of mine here at work was intrigued by this idea and has done
some investigation, using the cheapest tape deck he had. Unfortunately,
most of these multi-MB storage calculations for audio tape are unfounded.
His cheapo tape recorder loses phase for mid-to-high frequencies. This
kills QAM/TCM coding really fast. The automatic volume control (AVC)
distorts amplitude in a totally nonlinear fashion. The stereo coding
in modern tape decks steals bandwidth. About the only thing reliably
preserved is the frequency distribution. At present, with a bit of work,
he estimates he can get at most a couple of megabytes on a 90 minute tape.
A better tape deck might have better qualities, but it'd probably take a
*lot* of manual tuning for each individual tape deck to handle the wide
variety of hardware quality out there.
A pity, but possibly sound-card networking might work a little better,
given decent cables. One limitation is that SoundBlaster hardware (the
most common type of sound card from what I can see) either isn't capable
of full-duplex, or can only do 16-bit one way and 8-bit the other. This
means you could have a two-way 8-bit channel, or a 16-bit downstream and
an 8-bit upstream.
Sincerely,
Ray Ingles (248) 377-7735 ray.ingles@fanucrobotics.com
"Monkeys would be harder on equipment than college students,
but only because they're stronger." - Jim Ingles
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/