svhs question
12 messages in this thread
QUESTION:
I have a SuperGen genlock and an Amiga 3000.
Is there any value to using a SVHS vcr when editing output from my Amiga
when the SuperGen is not producing a SVHS signal…..
…..or am I simply wasting money on an overqualified vcr?
Steven,
Yes, editing to VHS even without Y/C output is better than VHS. In fact,
since we've installed the toaster (which doesn't offer Y/C) we've been
doing everything in composite.
The real advantage of S-VHS is the separation of signals on the tape.
Keeping the signals always separate does help but is not always feasable.
For a while I was shooting in VHS and editing up to S-VHS (BR-S810U) with
much better results than an all VHS production.
Bill.
>> The real advantage of S-VHS is the separation of signals on the tape.
Sorry if it seems like I'm picking on you, but this is such a popular
misconception that it should be addressed so everyone understands it. The
truth of the matter is that VHS and SVHS both record the signal on the tape
in exactly the same way. In both cases, the chroma portion of the signal
is downconverted recorded along with the luminance (which is recorded at a
much higher frequency). No, they're not recorded on separate tracks, as
the vendors wanted everyone to think.
The only difference between the two recording modes is that in SVHS the
center frequency of the luminance portion of the signal was raised
somewhat, so that there would be greater bandwidth (and hence a higher
resolution). There is absolutely no diference in the recording of the
chroma signal.
As to the design of the deck, vis a vis the use of Y/C connectors, it would
help to understand the signal path in regular VHS. Composite video comes
in the input jack and is split into two components — the luminance (B&W
detail) and the 3.58MHz chrominance (color). The chroma signal is then
downconverted to a much lower frequency (621KHz) because there's no way you
can record a 3.58MHz signal on VHS tape — it would be too much information
on too little tape. Of course, this is done at the expense of much of the
detail in the color portion of the image. The two signals are then
recombined and recorded on the tape. On playback, the signal comes off the
tape, the chroma is converted back up to 3.58MHz, it's combined with the
luma signal and output as composite video. On an SVHS machine, all the Y/C
connectors do is tap the signal while it's still in the separated
luma/3.58MHz chroma state. This helps reduce the artifacts encountered
when the luma and chroma signals are combined into a composite signal, and
since there is some degradation every time this is done, keeping the
signals separate through the signal path can result in a significantly
better finished image.
Pete
Pete,
Yes, you've caught me on that–both VHS and S-VHS are color under with the
only difference being recording bandwith and frequencies.
However your statement that keeping the signal always separate makes
a "significant" difference really depends on your perception of
"significant". This was one question I had to seriously consider
before installing a Video Toaster in to my configuration as the Video
Toaster does not support Y/C input. I edited some footage that was
Y/C separated from the camera to the edit deck, then I switched to
composite and re-edited. Yes, there was a difference. Yes, it was
noticable. No, I would not classify it as significant. I must assume
many S-VHS users agree otherwise so many of them would not be using
the Video Toaster.
If we were having an engineering discussion I _might_ agree that it's
significant. But when it comes down to it and the finished program is
dubbed onto VHS, I don't think it really makes a significant
difference. I won a contract over a competitor who shoots in beta and
my price was higher! Why? because a) the client couldn't perceive a
quality difference and b) (most importantly) my demo and overall
presentation were better.
When discussing the business side, rather than the technical side, of
video–"significance" takes on a new meaning. Heck–there are plently
of people out there that think a EP VHS recording made on a machine
with dirty heads, played back on a machine with maladjusted tracking
looks "just fine".
Bill.
I hope this reply doesn't come across as hostile, it wasn't intended to.
No — it doesn't come across as hostile at all.
And you're right — the definition of "significant" is quite
subjective. I'm the technical supervisor in a Beta-SP post facility,
and am thus quite picky. By the time you can see a difference on the
screen, you've passed my definition of "significant" already. As you
pass each generation, the degree of degradation is significantly
(there's that word again!) affected by the care taken in the creation
of the previous one. And I must admit that I don't agree with the
view that "it's going to VHS anyway, so…", simply because the
quality of the original footage is so critical. Have you noticed the
difference in image quality between a movie that you purchase on VHS
(okay — that's film — how about something like "Dorf on Golf" with
Tim Conway, which is direct-to-video) and something shot with a
camcorder? Even when the camcorder footage is first generation?
They're both on VHS, and the professionally-produced material is at
least one generation (probably several) older than the camcorder
footage; yet it still looks better. Why? Because VHS can look good
as long as the original material you're feeding it is exceptionally
good. And only then. It's not as though VHS drags everything you
feed it down to a certain level, no matter what. It's more as if it
applies the same amount of degradation to any applied signal. So if
the original is exceptional, the VHS copy will look OK. If the
original is anything less, the VHS will look horrific. IMHO.
As to the quality difference, it has to do with how much processing the
signal is subjected to in each generation. Encoding and decoding from
composite to Y/C clobbers the heck out of the signal (up and downconverting
it is even worse, but you need a format change to fix that), and every
processing step you can save will yield measureable (and visible) signal
improvement.
Hi Guys, I know exactly what you mean by starting with the best possible
signal no matter what the end product winds up to be.
Most of my work is underwater. I think you can understand why I'm hasitant
taking a betacam whenever I don't have to. The reason is obvious as I like
to state in my underwater videography courses. "It's a crazy business.
Thousends of dollars worth the electronics, inside a PVC tube and trusting
a rubber band to keep the water out".
So I shoot with an AG-450 s-vhs whenever possible. I also have footage from
my early days, streight vhs. By the way, I started with film. Video is much
cheaper, I can shoot my brains out at little cost.
My point is this. I still use some of the footage from streight vhs. I also
use the s-vhs. When I bump up ot beta or even 1", I can see the differance
by the time I have the vhs copy. The better the starting signal, the better
it holds up. The differance is "significant", (boy, I learn fast). Also
when I run y/c to composite, back to y/c and wind up final on composite,
I'm better off to keep it vhs through once I'm there.
Within the next couple of days my Toaster is arriving. I will come out from
source y/c to tbc, out of tbc composite to toaster, out composite to
recorder and record in s-vhs format. I wonder how it will look. I will also
try running out of the toaster composite to another tbc and out y/c to the
recorder. If you interested i would let you know which is better, and how
"significant" the differance.
happy de and incoding, george
George,
Best of luck with your setup. I suspect that if you use transcoding TBC's
as you suggest, the results will be better (I don't know how much — but
better) than if you simply use the composite spigots on the SVHS decks.
This is due to the fact that most decent TBC's have better en/decoding
circuitry than most SVHS decks. This may not be the case with really
high-end machines (like Panasonic's AG7750), and I don't know what you're
using. I'd certainly be interested in hearing what you discover, and I'll
bet quite a few others here would like to hear as well.
Pete
Pete, I'm using ag-7500A's and my final tbc in to which I will be feeding
the toaster output is an Alta Cygnus 5.5 which is not a bad tbc. I'm hoping
for the best. will let you guys know which setup gives a cleaner final
output. Right now I'm planning to use the toaster for the bells and
whistles on the fly. when i get more comfortable with it, i might rendering
3D, then I will get a good single frame recorder. but i suspect it will be
some time since computers scare the hell out of me. I'm used to dedicated
black boxes. will keep you posted. I hope to have it all hoocked up by this
weekend. BUT I'M STILL LEAVING MY OLD BLACK BOXES CAPABILITY HOOKED UP,
JUST IN CASE. happy toasting, george
(reply to both messages)
Pete,
I agree with everything you say. I too can spot the difference between
programs originally shot in film and video. I've crewed on an HDTV
productions and have seen how good video can get. In fact (don't tell this
to any of my clients) I cringe every time I do a production in S-VHS. But
it's all I can currently afford so I'm stuck with it.
You're point about using the philosphoy "well, it's going down to VHS
anyway" as a panacea is well taken. In fact, I never actually use this as
my yardstick. My personal philosophy is "the best possible job with all
available rescources".
Another point I always like to make is that a video project starts when the
writer writes the first "FADE TO:" and ends when the record-tab is knocked
out of the edit master. Many things happen between those two points and
only part of that is technical. It's very important for people involved in
video, especially those starting out, to remember that you could make a
good training video with a camcoder and a good script, but the best
equipment in the world will do little to improve a bad script.
As to the frame servo/TBC question: I was basing much of my response based
on my early days when I started out with 2 Panicsonic AG-1950's–days I
would sooner forget. If I recall correctly I read that you had a pair of
1950's. You know–those machines that were fully functional insert and
assembly editors–sometimes–if you were lucky. Personally I think
Panicsonic pulled a real snow-job on alot of people with those
machines–even worse was the 1950/1820 combination they marketed. I got
suckered into that one–but that's another (very long) story (and part of
the reason I now purchase NOTHING made by Panicsonic!).
Bill.
Actually, a few millenia before the beginning of Time, I owned one (count
'em — one) 1950, and one portable deck whose model I don't even remember
(it was the standard VHS precursor to the AG7400 — before SVHS existed).
I had to modify both machines so the audio mute wouldn't kill the audio
during searching with the AG-A95 controller.
Lotsa fun. Yeah, I'd rather forget it, too. Now I can play with the
expensive toys and let someone else worry about paying for it 😉
Meanwhile, I still have an AG7400 for field acquisition for my own
low-budget productions; but now I edit up to Beta. Meanwhile, the AG1950
has become my home VCR, a role it fills quite admirably.
Pete
Pete,
I know what you mean. I'm using one 1950 for a home VCR and the other is in
my office hooked up to a JVC BP-5300, a dinosaur of a VHS deck, for when
friends ask me to make dubs of tapes I'd rather not put into my S decks. (I
also have an AG-2400… somewhere… maybe in a closet).
I hope (someday) to upgrade to MII or beta on the edit side–but these days
I'm lucky to make the rent! Oh well, I can always dream.
BTW, do you remember a fellow CIS'er and budding video entrepeneur by the
name of Bill Dwyer? He stopped by my place one day (back in my work at home
days) and was supposedly going to see you next. It was about 2 years ago
and I never found out if he ever got his ideas off the ground.
Bill.
Sure, I remember Bill. He never did stop in and see me, though. Haven't
heard from him in quite awhile.
Pete