iscan plus problems- is this normal? - AVS Forum
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post #1 of 5 Old 08-28-2000, 02:39 PM - Thread Starter
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I just got a new DVDO Iscan Plus for less than $500 shipped from winegenius@yahoo.com. Overall, I'm impressed with it, but I noticed some glitches that I wasn't expecting. These problems seem to occur whether I use composite or S-Video connections. My signal chain is:
Panasonic SVHS 7670 VCR or Pioneer 704 LD
Harmon Kardon AVR80 receiver
DVDO Iscan Plus
Linksys KVM switcher
Sony 1272Q front projector

Here are the problems I've seen:

1. When surfing CATV channels from the VCR, the image jitters very severely vertically (like 10% of screen height) for about a second or two, each time I change channels. Then it locks on and is fine. The video is almost unwatchable during the jitter period, and would probably give an epilectic person seizures. This happens every time I change to any channel.

2. Some highlights (almost-white areas) are "blasted out" and lose details. I think that this is because the internal non-adjustable white level inside the unit is cranked too high, so it causes the video DACs to clip.

3. The shadows also seem to have lost slight details, although not as much as the highlights.

4. Two VHS rental tapes (Girl on a Bike, Passion of Ayn Rand) that play fine without the Iscan exhibit extreme distortion, which causes the normally vertical sides of the image to bend in a curve, especially towards the top, by about 10% of the screen's width. I verified that this occurs both on the projector and on a computer 17" monitor, so it's definitely the Iscan that's causing it. And a herringbone pattern appears over the whole image. It's almost unwatchable, definitely much worse than without the Iscan. I'm wondering if this is caused by Macrovision on the tape. I never have this problem on SVHS tapes that I recorded. Another rental tape (the Story of Us) didn't have this problem.

5. When visual fast forwarding, rewinding, or pausing a VCR tape, the Iscan seems to lose sync and the image gets very distorted, sometimes only filling only about the top half or quarter of the screen. It's almost bad enough that when fastforwarding through commercials you have a hard time telling when the program has started up again.

6. During the credits at the end of a movie, the credits wave back and forth, as if rather than going straight down the screen they slalom down. They only deviate by maybe 2% of screen width, but it's enough that you notice it and say "that's not right". This waving back and forth is also slightly noticeable on parts of the movie where the camera pans up or down.

As an experiment I removed the Linksys KVM and the receiver from the signal chain, and these problems still occurred.

Overall, when a movie is playing on LD or VCR I am very impressed with this unit's deinterlacing quality. It even does a decent job of deinterlacing video (TV) sources.

Does anyone else experience these same problems? I'm wondering if I got a bad unit or if there are workarounds.

Thanks!

-Tom

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[This message has been edited by Tom Morrow (edited 08-29-2000).]
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post #2 of 5 Old 08-28-2000, 03:31 PM
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I have the iscna hooked to a sony 1252. The jitter between channel changes happens to me as well, I think the iscan just loses sync with the source. I have heard a TBC in the chain may solve this.

As far as the wavy lines, I sometimes get a shift in credits at the very top, and it only happens on certain discs. i was told this was a macrovison issue.

EJ

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post #3 of 5 Old 08-29-2000, 05:25 PM - Thread Starter
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I just ordered the Sima SCC device which looks like it may kill two birdes with one stone: allowing me to control brightness and contrast, and defeating Macrovision.
http://www.simacorp.com/scc.html

We'll see how that works.

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post #4 of 5 Old 09-03-2000, 09:38 PM
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Quote:
Originally posted by Tom Morrow:
I just ordered the Sima SCC device which looks like it may kill two birdes with one stone: allowing me to control brightness and contrast, and defeating Macrovision.
http://www.simacorp.com/scc.html

We'll see how that works.

I have the Iscan and also bought the Sima SCC device in hopes it would correct the white blooming and the macrovision problem. Good news and bad news. The good news is it does do those things. The bad news is the severe loss of frequency response when viewing DirecTV or DVD. The sharpness of the picture was degraded enough that I didn't want to watch it that way. With video tape it works ok but I seldom watch anything on tape nowadays.

One other benifit to the SCC though is it does remove the macrovision from DVD's also which then allows copying to a video tape (If you were so inclined to do and which I don't ever seem to do).

FWIW, I have a Toshiba 3109 connected through the Iscan to a Sony VPH-1251. The white blooming through the Iscan is what bothers me the most and I wish there was a way to correct it.

John Richmond
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post #5 of 5 Old 09-04-2000, 04:09 AM - Thread Starter
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Summary:
Use a VCR with built in timebase correction, like the JVC 7X00 and 9X00 series, hook it up with the SVideo connection, and things will work much better with the iScan.

Details:
After talking with the DVDO tech guy, I learned that problems 4 & 5 (image that bends horizontally) are caused by the fact that normal VCRs put out an unsteady timebase, and the DVDO uses that timebase (doubling the scan frequency) to produce the image. My understanding is that the DVDO basically spits out 2 progressive lines of video whenever the incoming video signal gives it one line of interlaced. The problem is that the timing of the DVDO's output is hitched to the timing of the incoming signal, which isn't steady.

He said that they were working on perhaps incorporating timebase correction into future generations of the iScan. I think he means that the iScan would only be hitched to the incoming signal at the start of the field, and then after that the iScan would output a whole frame of data on its own clock.

Until then, he said using a timebase corrector is the only way to solve the problem. A timebase corrector digitally stores up a whole field of data at a time and then reclocks it and blits it out. I looked around for external timebase correctors, and didn't like that option. They start at $300 for the cheapest (the datavideo), and quickly go up to thousands for high quality.

I found out that there are VCRs available that have built in timebase correctors. The only consumer models are the JVC 7600, 7800, 9600, and 9800. I found a JVC 7800 which lists for $350 on the open-box section of the Good Guys store for $225, so I decided to give that a shot. It turns out that it solves problems 4 and 5 (the horizontal bending) perfectly. It is so much nicer being able to see whats going on in fast forward! It also improved problem 6 (the wavering titles) a lot so now they are rarely noticed. And it has discrete remote IR codes available on www.remotecentral.com, so this seems to be the perfect VCR for me.

And lo and behold, it fixed the blasted-out highlight problem (#2). I found that there were two factors affecting the highlights:

A. The composite input on the iScan blasts the highlights more than the S-Video terminal, probably because it has slightly more amplification. Or else my receiver is amplifying the composite more than the SVideo. I found that with either my old VCR or the new, switching from composite to SVideo improved (lowered) the highlights.

B. The JVC 7800 VCR outputs a lower signal level than my Panasonic 7670 VCR. This also helps the highlight problem.

The combination of switching VCRs and using SVideo rather than composite has gotten the highlights into the mostly unclipped range. And the shadows (problem #3) seem fine now too.

The only problem that hasn't been solved by switching VCRs is the vertical jitter for a second or so when switching channels (#1). The iScan guy said that most people experience a blank screen for a little while when switching channels. And I verified that on my computer monitor I got a blank screen rather than the vertical jitter. So I guess I should count my blessings that at least I can see something on my projector. BTW, the jitter is somehow less objectionable on the JVC versus the panasonic VCR, although still very annoying. But I'm learning to live with it and it doesn't phase me too much now. The iScan guy said they are aware of the problem and trying to find a fix for the next generation.

It looks like I'll probably be sending the Sima SCC that I ordered back. Now I'm really happy with the iScan, and I think I could probably never go back to interlaced video on the projector. The film mode deinterlacing is perfect, except when the iScan occaisionally gets confused about what mode it's in, on static images.

John-

I'm really not sure which problems are related to Macrovision and which aren't, but I'm sure that Macrovision can't be helping, and if there are problems at the top of the image it's likely to be related to Macrovision (which operates in the VBI above the image). At any rate, I think a TBC VCR might be a better solution than the Sima.

-Tom


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