When to interlace

ClipMan wrote on 10/22/2003, 7:17 AM

John,

...Edison invented the lightbulb out of necessity.....he drove a Tesla staple through his finger and needed some light to see where to put the bandaid...

readw wrote on 10/25/2003, 3:30 AM

Thanks to everyone who replied and although I have learned a lot about the history of TV and video I don't feel that I'am any the wiser as to my orginal question.

So to recap, I have a CGI graphics file produced using a program called Lightwave. Lightwave can output the file as an interlaced or non interlaced file which I want to import into Vegas 4. The file itself is a 3D motion graphic file of a logo, This file is similiar to a TV station identifier that I am sure you all have seen on from time to time. Is it best to render the file in Lightwave as a non interlaced or interlaced file, keeping in mind that this is a motion graphic and not a static image?

Thanks

Warren

farss wrote on 10/25/2003, 5:17 AM

I'd render it in interlaced, everything the same as whetever the rest of your project is going to be.

As I'm not familiar with your particular app I cannot comment much more except to suggest you try both, surely that will not take much time.

Don't let the interlace artifacts you'll see in the preview window if you're previewing on your PC spook you. They will not be there when viewed on a video monitor.

If you were planning on this thing being viewed on a PC then having it progressive might avoid this issue. The problem is most PC video cards and monitors only work in progresive. The downside to keeping it progressive is lower temporal resolution so you'll need to watch how fast it moves or else add some motion blur to make it look more realistic. All this also is affected by whether your in PAL or NTSC land.

Hope some of this help.

RBartlett wrote on 10/25/2003, 5:39 AM

Rendering interlaced or progressive with LightWave isn't a must decision. It should suit what your intended look is first, and what the target display device is capable of 2nd.

If you want it to be smooth, with the viewers brain making up for the lack of resolution as it runs through, and your viewer is watching it on TV, then interlace.

If you want it to be show more than a "venetian blinds worth" of each point in time but on an interlaced screen you can expect some noticable interframe flicker (you can blur the render etc to help the brain deal with this). Where the target could be a progressive display - either directly or through its de-interlacing circuit (which might effectively go into passthrough), then you'll see it exactly as you did in your proofing stage after rendering in LW.

For a motion logo, with volumetrics etc, I'd tend towards interlaced rendering. If I was building cells for film, or just very likely to be using a PC or progressive display/player, I might be swayed into progressive if the look was what I wanted.

When it comes down to it, the persistence of the human eye makes progressive footage on interleaved displays quite OK in many cases. Quite why a broadcast TV program currently goes into progressive/slow-shutter whenever a live music act starts, I'm not entirely convinced on this.

Jumping from progressive to interlaced and back also is a bit cruel on the brain - especially on interlaced viewing equipment.

Happy rendering.

PS - I don't think you'll see an awfully large amount of difference in rendering times. Progressive has the edge where light and other interdependencies are being calculated. In my experience. Some folk like to do 24p animations even if the rest of the programme they are putting together is some other setting. Then I'd say they are looking both a saving in rendering time and disc space, and also being suckered in by the pulldown activity (in NTSC targets).