hughes@mother.DEC (Gary Hughes - CSSE uVAX & AI Systems Group) (04/11/84)
Psuvm%iks asked whether it is possible to convert a PAL cassette to NTSC or
to play a PAL cassette on something that also works with NTSC.
The answer in both cases is yes.
There are a number of professional video service companies that will
convert from one format to another for a fee. I'm not sure how they do it
but my guess is they decode the signal to RGB and the re-encode into the
format you require. I don't know whether this introduces a timing problem
due to PAL using a 50Hz synch pulse and NTSC using a 60Hz synch.
I would expect that to do this officially you would have to own the
copyright or prove that the material is not copyright. Getting someone to
convert Dr Who tapes sent from the UK by a friend may be difficult.
As to playing PAL tapes; I'm glad you asked! I have just purchased the
necessary components to do just that (since I have a lot of PAL tapes from
Australia etc).
SONY make a number of receivers that are multisystem. The one I have is a
20" trinitron 5 system receiver (2072ME5, I think) that understands PAL,
SECAM 1 & 2, NTSC 3.38 and NTSC 4.43 (I may have the NTSC numbers slightly
wrong). It is also fairly insensitive to power supply - 110-240 volts, 50
or 60 Hz, self adjusting. It will receive broadcast signals in any of the
above systems using US or European channel standards. One the tuner locks
in a signal, the color decoders decide what colour system is present and
decode accordingly. It is about as automatic as you can get, with the
ability for manual override.
SONY also make three VCRs that are multisystem. The SLT50 is a 5 system VCR
that can receive and record all but the NTSC 4.x and play recorded tapes in
all 5 formats (beta II and III on NTSC). The other multisystem VCRs in
SONY's range do not have all 5 systems and I think the SLT50 is the only
one that can handle PAL tapes and record NTSC. It also has a self adjusting
universal power supply.
In reference to some news items about the noise (audible) made by some SONY
VCRs, the SLT50 also has a fairly noisy transport mechanism.
The cost of these two items together is about $2600 (about $1300 ea) here
in MA. They are not in SONY's consumer product range, so I had to find a
professional video supply house. This basically means that the units are
hard to find and discounting is rare. SONY restrict the range that their
regular dealers can handle to 'consumer' products and not 'professional' or
'industrial' products (SONY categories). I am told that in some states this
is illegal so you may be able to get discounts.
Panasonic have a smaller receiver for about $750, but the picture quality
is not as good. SONY have a 12" monitor that handles all five systems and
has two sets of RGB input and output that also sells for about $750. It is
a bit small for normal viewing but makes a great monitor and is designed to
be used as a terminal monitor (making it tax deductible for some?).
If anyone wants more details, mail me. If there is enough interest I will
send more info to the net.
Gary
UUCP: ...{ decvax | allegra | ucbvax }!decwrl!rhea!mother!hughes
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reality?: DEC, ZKO1-2/C07, 110 Spit Brook Rd, Nashua NH 03062msc@qubix.UUCP (Mark Callow) (04/13/84)
> From: hughes@mother.DEC (Gary Hughes - CSSE uVAX & AI Systems Group) > > Psuvm%iks asked whether it is possible to convert a PAL > cassette to NTSC or to play a PAL cassette on something that > also works with NTSC. > > The answer in both cases is yes. > > There are a number of professional video service companies that > will convert from one format to another for a fee. I'm not sure > how they do it but my guess is they decode the signal to RGB > and the re-encode into the format you require. I don't know > whether this introduces a timing problem due to PAL using a > 50Hz synch pulse and NTSC using a 60Hz synch. I replied privately to the original question but I just want to clear up how the conversion is done. The suggestion given above would not work due, among many things, to the different number of scan lines in the pictures. The actual black box used is called a field store standards converter. It digitizes one field and stores it. From the digitized image it reconstructs the field in the new format. It does all this in real time and is *expensive*. BTW thanks for the information about the multi-standard tv's and vtr's. -- From the Tardis of Mark Callow msc@qubix.UUCP, decwrl!qubix!msc@Berkeley.ARPA ...{decvax,ucbvax,ihnp4}!decwrl!qubix!msc, ...{ittvax,amd70}!qubix!msc "I'm a citizen of the Universe, and a gentleman to boot."
stekas@hou2g.UUCP (J.STEKAS) (04/13/84)
A similar conversion must be done to convert movies to NTSC
to be shown on TV. Anybody know how it's done? Since movies
have been shown on TV for a LONG time, there are certainly
non-digital solutions to the problem. My guess would be that
early conversions were done by training a TV camera on a
persistant screen which could blend the frames together.
Anyone know for sure?
Jimmsc@qubix.UUCP (Mark Callow) (04/15/84)
Conversion of films to TV is nothing like as hard as converting NTSC signals
to PAL signals or vice-versa. A flying-spot telecine machine is used.
This has a "projector" half and a "camera" half. The light source is
a CRT (hence the name flying-spot.) scanning just like the TV set.
The "camera" used to be a photo-multiplier tube. I don't know what
they use these days. By varying the geometry of the image on the
scanning CRT all kinds of tricks can be pulled such as showing
a cinemascope film without an anamorphic lense. I can't remember
exact details of this right now but I once saw it done at the CBC
studios in Montreal.
Since the film was shot at 24 frames/s and the TV is scanning at either
25 or 30 frames a second, depending on country, various tricks must be
played to synchronize the two otherwise you get horizontal black bars moving
down the picture.
Where TV is 25 frames/s they simply speed up the film. This results in
a 100 minute film only lasting 96 minutes. Other than that the speedup
is imperceptible.
Where TV is 30 frames/s the projector is gimmicked to show every fourth
frame twice so that 30 pictures are presented to the TV every second but
the film moves at an effective speed of 24 frames/s.
Also frame shifting is synchronized with the vertical blanking interval.
I have seen "telecine adaptors" advertised in Video magazine. These consist
of a box with a hole at one side through which you point your projector.
Inside there is a mirror that projects the image onto a ground glass screen
at which you have your TV camera aimed. These are a crock for anything
but slides. Without the proper synchronization you will get a flickering
image with large horizontal lines running up the picture just like you
get when you film a TV screen with a movie camera.
Seeing an ad for junk like that in what I thought was a reputable magazine
makes me wonder about the objectivity of said magazine's test reports.
--
From the Tardis of Mark Callow
msc@qubix.UUCP, decwrl!qubix!msc@Berkeley.ARPA
...{decvax,ucbvax,ihnp4}!decwrl!qubix!msc, ...{ittvax,amd70}!qubix!msc
"I'm a citizen of the Universe, and a gentleman to boot."