Capturing computer content (animation)

F

Flintstone

Well-known member
I've long used a scan converter to capture computer content, such as real-time 3D simulation @ 60i (from real full-flight simulator image generators...the $15 million full motion kind).  I've tried various scan converters with different results.  The problem with scan converters is that they output interlaced video, as well as generates unwanted artifacts, however minimal they may be.

The target audiences are potential clients, and trade shows.  90% of clients them watch the DVDs on laptops or desktop computers.  And at trade shows, plasma screens are used to display the visuals.  As we all know, 60i is far from perfect on computer screens, and deinterlacing is basically crap!

Today, I decided to try another approach.  I rented a DVX100 (company expense... besides I don't have mine yet) and pointed it at a 50" Barco screen and set it at 30p, tweaked the gamma and chroma levels, then matched the synchroscan to the refresh rate of the screen.  This is just a preliminary test mind you.

The results were stunning.  No need to use filters to cut down on flicker, no aliasing (almost.. hey, it's still 4:1:1 DV after all), and no scaling artifacts.  Even though I synchroscanned the footage, I still have a minuscule little bluish line scrolling from top to bottom. I tried tweaking with the synchroscan, but to no avail.

Are there any other tricks to get rid of this minor scan line scrolling on the screen?

The alternative would be to hook up the system to a quality LCD monitor, and shoot it instead.  I'd certainly get rid of the scan line problem, but in past tests, when I shoot an LCD screen, you could see the pixel mask... granted it wasn't much, but it was perceivable nonetheless.  Are there any LCD (1600x1200) screens out there that are worthy, and can be used to shoot with to achieve great results?
 
Re: Capturing computer content (animation)

I'm pretty clueless about what you are asking and I'm sure you already thought of this, but... what about just taking whatever video output you have (prior to entering the 50" screen) and feeding it into the analog inputs on the DVX and copy it to tape that way? (I'm sure this is totally off - but what the heck.)

Oh - I don't think you can record progressive that way which is what you wanted.
 
Re: Capturing computer content (animation)

24Peter, the problem with computer generated video signal it that it isn't NTSC.  It typically runs at resolutions of 1280x1024p or 1600x1200p resolution, and poor old NTSC is 720x480i (486 for D1). Now, most computers graphic cards have video out on them, but it comes at a price; that price is over-filtering to compensate for flicker artifacts due to 1 (or so) pixel lines.  The problem with over-filtering is that it blurs the output.  That is why there are $6000 scan converters out there, but if you want perfect results, scan converters can go up to the $20000 range.  Also, I have yet to see a progressive scan converter.  This is why I am seriously contemplating the camera angle.

When HDV becomes a reality, then this might not be an issue. One could always set the resolution at 1280x720 on the computer and then take a converter that converts VGA to component video. But we are not there yet, and I suspect that a full line of HDV hardware and distributable media won't be fully available until 2005.
 
Re: Capturing computer content (animation)

When you shoot off the monitor you're losing resolution.

You should consider rescaling in the computer and dumping out direct through:
- a good video card with component or at least s-vhs output
- save in DV format and save through firewire (some loss in DV codec but same as DVX)

Best results would be to rescale on computer and directly burn to a DVD at the correct frame rate and interlace as you like. This avoids any loss other than a pure rescale.

If you have a fast machine for a tradeshow then you could consider playing it out directly to a high res monitor. I playback 1k+ res all the time on my PowerBook.
 
Re: Capturing computer content (animation)

Scott, I've been doing scan conversions for about 18 months now.  In actuality, and I am talking from experience, using a camera gave far better results then using a scan converter.  S-video outputs from video cards are just that, cheap scan converters.  Like I said, on-board video-out from graphic cards are over-filtered and appear slightly blurry, and you loose out on important details (details that I can now see when shot with the DVX).  Again, I speak from experience.  I trust my eyes, and not only mine, but the eyes of those involved in this endeavor. They all vouched that the quality is by far better then anything they've seen... aside from the real image generator, of course.

In any event, the image generator (or IG) I’m using does not support s-video or composite out, only VGA.  Just to put things in perspective, the image generator is no ordinary PC.  The video cards used in one IG are manufactured by the company I work for, CAE Inc.  The display system comprises of four PCI cards (soon to be PCI-X) with four R300 (ATI Radeon) chips, totaling 16 GPUs to process the imagery.  The minimum output is 1024x768, so we modified the driver settings to output 720x480 in order to get a one to one conversion.  Don't get me wrong; the resulting scan converted output was very good, and certainly much better then when the source resolution was higher.  But I can tell you right now; quality is way better when shot with the DVX.  

Why is it better?  I’m not entirely sure, but as far as I can figure, optical interpretation/interpolation is far superior to electronic methods.  This procedure translates sub-pixel information much better then anything I've seen.  An unexpected benefit I got with shooting with the DVX was a slight motion blur effect in high-speed scenes.  Something I never got with scan converted material.

Of course if I could load the whole database scenario and render the whole thing in Maya, then the quality would be perfect, but unfortunately, it's not possible.

***

Mad_Cow, I've tried Camtasia, and unfortunately, it can't keep up with the 24fps frame rate on a standard computer with intensive graphics activity.  I certainly don't dare installing it on a dedicated image generator where the resources are stretched to the limits in normal operation.  I'll be lucky if I'd get 1fps out of it.

But the thought did cross my mind to capture pure data from the VGA port using a special frame grabber.  I could in theory capture at 1600x1200 uncompressed (requiring a powerful system with extremely fast and large storage), and manipulate the data in After Effects or some other software that could efficiently and cleanly rescale the video to the format I wished.  But such a system would be very expensive, and the fact that there is some R&D involved did not sit well with my VP.

***

My original question still stands though, are there any other settings in camera to get rid of a slight scan line that scrolls from top to bottom when filming a CRT?  I’ve tried tweaking the synchroscan, but to no avail.  If not, then are there any clean and sharp LCD 1600x1200 monitors out there that could be shot with a DVX with no discernable pixel mask?

Wow this took a long time to write… sorry for the bore.  ::)
 
Re: Capturing computer content (animation)

This may be insulting but have you tried changing the refresh rate on the VGA monitor?

I've had the same problem for a different reason. We shoot corporate on the Panasonic Vericam and frequently need to show our client's website in the finished product. You can spend half your operating budget on a scan converter with dubious results or shoot a monitor - either VGA or LCD. LCD's are fine except when the pixel mask creates some kind of mosaic interference pattern with the CCD and you get concentric circles all over the screen...

With VGA you often get that refresh rate that is just left or right of your syncro-scan's ability to compensate. I often get so flustered that I forget...you can reset the scan rate of the computer/monitor. Usually one of the available settings will yield a perfect match to my syncro-scan. Let me know if this fixes that nasty little line.
 
Re: Capturing computer content (animation)

This may be insulting but have you tried changing the refresh rate on the VGA monitor?
Click to expand...

[tt](In a Homer Simpson Voice)[/tt] Doh! :eek:

It's always the simplest things that throw you off! Actually, no, I haven't tried! I really feel stupid for not trying. :-[

It did pass through my mind though. The one thing that stoped me from trying it is, and I say this without being sure, apparently the image generator is tied in to the clock of the refresh rate. Something to do with optimal redering?? Again, I'm not sure, and I'll ask one of the engineers tomorrow morning.

Thanks for reminding me WHunterC.
 
Re: Capturing computer content (animation)

It turns out that the refresh rate is locked by the custom drivers of the IG to 60Hz, so changing it is out of the question. Back to square one.

The LaCie Photon20Vision LCD screen seems to be an option! Anyone has any experience with that LCD model?
 
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