CDV/DVD problems?
Joseph Preza
There's your answer...plain and simple. That's why a combi-player (LD/DVD)
can read CDVs.
JP
Bruce Tomlin
<film...@hotmail.com> wrote:
> One post mentioned that only LD machines have the circuitry to process
> the analog signal....this is a start but doesn't explain what the
> problem is.
The problem has nothing to do with the optical pickup, and everything to
do with laserdisc being an encoded analog RF signal. To decode it
requires radio frequency demodulation circuitry that is not used with any
equipment other than laserdisc. The only thing that comes close is video
tape players, and they use different frequency bands in different ways.
You might think that the pits are "just ones and zeros", but they aren't.
They are of a variable analog length, which is completely different from
the techniques used to record digital data. Yes, the disc can produce
digital audio, but only through a similar means as would be done with a
digital radio or television signal, by modulating it onto a specific band
of the RF spectrum.
filmbear
I've done a little bit of digging into the CDV format and I cannot
find any compelling reason that a DVD drive (on a PC) or even a
standard CD-ROM drive can't read the format.
The only reason I've seen is that CDV is an analog format and all
other CD based formats are digital...SO WHAT! Why is that such a big
deal? It's still read by a laser isn't it?
One post mentioned that only LD machines have the circuitry to process
the analog signal....this is a start but doesn't explain what the
problem is.
Let's start with the basics....at this point forget viewing the image,
can a PC based DVD drive access the signal? Is it physically
possible? Then how? Is it a laser wavelength issue or what?
Then...is is even possible for that "analog circuitry" to be emulated
through software? What does that circuitry do?
Anyone got a clue?
Thad Floryan
| Ok...
| I've done a little bit of digging into the CDV format and I cannot
| find any compelling reason that a DVD drive (on a PC) or even a
| standard CD-ROM drive can't read the format.
|
| The only reason I've seen is that CDV is an analog format and all
| other CD based formats are digital...SO WHAT! Why is that such a big
| deal? It's still read by a laser isn't it?
So are supermarket product bar codes [read by a laser].
The primary difference is that the pits and lands on a laserdisc (and
the video portion of a CDV disc) are varying length contrasted with the
fixed-positions/-lengths found on CDs, VCDs, and DVDs.
| One post mentioned that only LD machines have the circuitry to process
| the analog signal....this is a start but doesn't explain what the
| problem is.
|
| Let's start with the basics....at this point forget viewing the image,
| can a PC based DVD drive access the signal? Is it physically
| possible? Then how? Is it a laser wavelength issue or what?
Nope; in fact, the laser diode wavelength in a MUSE/HiVision HDTV laserdisc
player is almost identical to that used for DVDs -- around 650nm.
| Then...is is even possible for that "analog circuitry" to be emulated
| through software? What does that circuitry do?
It's a completely different scheme from MPEG-1 or MPEG-2.
| Anyone got a clue?
For the technical nitty-gritty on laserdiscs and CDVs, visit Bob Niland's
site at URL:
If you're interested in MUSE/HiVision HDTV broadcasts and/or laserdiscs, I've
collected some articles and a partial listing of available titles at URL:
http://www.thadlabs.com/LD_info/
Thad
Thad Floryan
Nope; in fact, the laser diode wavelength in a MUSE/HiVision HDTV laserdisc
player is almost identical to that used for DVDs -- around 650nm.
For the technical nitty-gritty on laserdiscs and CDVs, visit Bob Niland's
Thad Floryan
| In article <9pgq7s4c9nfv7qg3v...@4ax.com>, filmbear
| <film...@hotmail.com> wrote:
|
| > the analog signal....this is a start but doesn't explain what the
| > problem is.
|
| do with laserdisc being an encoded analog RF signal. To decode it
| requires radio frequency demodulation circuitry that is not used with any
| equipment other than laserdisc. The only thing that comes close is video
| tape players, and they use different frequency bands in different ways.
|
| You might think that the pits are "just ones and zeros", but they aren't.
| They are of a variable analog length, which is completely different from
| the techniques used to record digital data. Yes, the disc can produce
| digital audio, but only through a similar means as would be done with a
| digital radio or television signal, by modulating it onto a specific band
| of the RF spectrum.
And the other fact worth mentioning is that laserdiscs preceded CDs: LDs were
introduced to the marketplace in 1978, CDs didn't appear on the scene until
circa 1983 IIRC, and DVDs were introduced into a few test markets April 1997
with its world-wide rollout about 6-9 months later depending on the country.
CDVs appeared around 1985 and were manufactured until (at least) 1991; it was
about that same time (1991-1992) I saw the first VCD during a trade show at
Moscone Center in San Francisco -- it was THE HUNT FOR RED OCTOBER
Thad
Joseph Preza
the Pioneer 909 that there are two laser pick ups: one for LD and the other
for DVD. Or did I just dream this up?
Joe
Thad Floryan
There's no need for 2 pickups since a 650nm wavelength (for DVD reading)
will work just fine for laserdiscs, too (as has been proven with players
such as the HLD-X9).
As to whether it actually has 2 laser pickups -- I dunno.
Some DVD players have 2 pickups, but that's so they can also read CD-R
material which, due to organic dyes used for their reflective layer, need
a longer wavelength than that used for DVD-Video reading.
Thad
Jeremy Bond Shepherd
> It's still read by a laser isn't it?
>
So's the UPC code on my box of Rice Crispies. Wanna put THAT in your CD-ROM
drive?
- Jeremy
Alan Smithee
: "Joseph Preza" <joseph...@litronic.com> wrote:
: | Thad, is it not my understanding though that in LD/DVD combi-players such as
: | the Pioneer 909 that there are two laser pick ups: one for LD and the other
: | for DVD. Or did I just dream this up?
: |
: | Joe
: There's no need for 2 pickups since a 650nm wavelength (for DVD reading)
: will work just fine for laserdiscs, too (as has been proven with players
: such as the HLD-X9).
: As to whether it actually has 2 laser pickups -- I dunno.
It does- I've looked inside mine several times. They get traded in the
back of the machine with the side-flipping mechanism. With a little more
work they could've given it auto-flip DVD capability. I love this
machine, I feel like Dr. Evil in "Austin Powers" saying "Fire the giant
'laser'!"