Using XENA with LCD’s

[David Mack]

Thanks Tim,

Regards LCD’s being progressive – yes, that’s why I was somewhat surprised to find that the Black Magic system drove it in interlaced. In Europe, being 25P Fps, the best solution would be to deliver 25 Frames per second but refresh the screen twice per image, to give you a rock solid 50Hz refresh. I’m going to be trying it out when my reseller has it sorted.

Thanks again.

[Tim Kolb]

It drives it in interlaced?

I don’t think you can even do that via DVI. I think progressive is all you’ve got.

When you put interlaced in it and display it progressive, that starts to look a little chopped, but it’s the footage, not the pipeline. Computer displays and display drivers are progressive.

TimK,
Director,
Kolb Productions,

Creative Cow Host,
Author/Trainer
http://www.focalpress.com
http://www.classondemand.net

[Jeff Brown]

A while back I had asked Black Magic tech about the HD-Link and interlaced display. It does not display interlaced. It converts interlaced to progressive display.

The only interface for LCD display I know of that will show you if you have field reversal, or interlace artifacts, i.e., a true interlace display, is the eCinema Systems EDP100, and it’s standard-def. I _hope_ there are others! But that’s the only one to date that I’ve been told by the manufacturer that “yes, you will see interlace twitter if it’s there”.

Wish I knew more about the new crop of HD monitors (Like the JVC).

-jeff

[David Mack]

Hmmmm. OK, maybe it’s not interlacing in the true sense (LCD’s just can’t as there’s no bleed I’m guessing) but it doesn’t seem to draw it from top to bottom line by line in the true progressive way either. It does seem to draw every other line and then do a second scan to fill in the others. You can see this on horizontal movement – you see a feathering where every odd line is ahead of every even line (or visa versa).

[Tim Kolb]

[David Mack] “You can see this on horizontal movement – you see a feathering where every odd line is ahead of every even line (or visa versa).”

That’s what we’re attempting to tell you…

What you have is a progressive scan display SHOWING you interlaced content. The display can’t reformat your video. If it was on an interlaced display, you wouldn’t see the sawtoothed edges on playback because it would display as interlaced. On a progressive display, interlaced shows exactly what you refer to…

Re-render all your content (or shoot it) as progressive, then it will look progressive…of course then it will look just a touch stuttery on an interlaced television.

TimK,
Director,
Kolb Productions,

Creative Cow Host,
Author/Trainer
http://www.focalpress.com
http://www.classondemand.net

[David Mack]

No, no, no. It’s not that. I can spot interlaced footage! I do animation and always render progressive. So the images are progressive, however you CAN see the feathered edges – this can only mean that the odd and even lines of the image are being drawn separately doesn’t it? On the blackmagic settings, the screen refresh is described as 25Hz Interlaced. That’s where I see the issue arrising. If that could be 50Hz Progressive (but showing 25Fps) then I think it would give rock solid playback.

[Tim Kolb]

[David Mack] “On the blackmagic settings, the screen refresh is described as 25Hz Interlaced.”

…if the card is set to output interlaced, it’s outputting interlaced, even if you animation clip is progressive.

TimK,
Director,
Kolb Productions,

Creative Cow Host,
Author/Trainer
http://www.focalpress.com
http://www.classondemand.net