Video Technology- stands for?

[tb582]

What does the P and the I stand for when you talk about the capibilities of a camera ie... 60i, 30p, and 24p.

[gadgetguy]

P= Progressive
I = Interlaced

[tb582]

So how does shooting in 24p give you that motion picture feel vs. just shooting in regular 29.97 MiniDV?

[gadgetguy]

Don't know. Sounds like marketing crap to me. Motion pictures (film) is shot at 24 fps and of course film is progressive, so you would start with similar sources, but at the end of the process, assuming it was all done correctly, the results are indistinguishable.

[lordsmurf]

Film is progressive. Progressive is one image displayed after another, in progression.

Interlaced is how a tv set operates. It's sort of hard to explain. Images are shown in a comb pattern. It's sort of like two images partially sharing the same space at any given time. Because of how well tv sets work, and how human eyes work, you think it's no different than progressive.

Look here for some sample images:
http://www.digitalfaq.com/dvdguides/capture/understandsource.htm#interlace

Be careful of "progressive" DV cameras. Many of them are known to be BS, and what you really has is a deinterlaced image, which is NOT the same as progressive. Or you have a progression done at half framerate, and the camera duplicates frames to get it up to spec.

[tb582]

http://www.digitalfaq.com/dvdguides/capture/understandsource.htm#interlace

Be careful of "progressive" DV cameras. Many of them are known to be BS, and what you really has is a deinterlaced image, which is NOT the same as progressive. Or you have a progression done at half framerate, and the camera duplicates frames to get it up to spec.

Thanks, I haven't got a chance to read the info yet but I will, supposedly the Sony VX2000 has a progressive scan setting, is that true progressive scan?

Say I were to shoot something with the vx2000 using the progressive scan, if the tv is going to interlace it anyway whats the difference?

[lordsmurf]

if the tv is going to interlace it anyway whats the difference?

Exactly.

Progressive is needed for a progressive display. If you're just using a normal tv, who cares? In the future, all display devices will be progressive, but by then, most of them will come equipped with excellent hardware deinterlace algorithms. Some have the ability to play both. The best ones can even crop or mask overscan.

[tb582]

if the tv is going to interlace it anyway whats the difference?

Exactly.

Progressive is needed for a progressive display. If you're just using a normal tv, who cares? In the future, all display devices will be progressive, but by then, most of them will come equipped with excellent hardware deinterlace algorithms. Some have the ability to play both. The best ones can even crop or mask overscan.

So are most of the new HD tv's out there considered progressive displays?

[Cornucopia]

Yes, depending on the technology behind the display...

(I could be wrong on this,but..)
CRT=Interlaced (Usually, but Progressive is possible)
LCD, LCOS=Progressive Only
Plasma=Either
DLP=Progressive (Usually, but Interlace is possible)

CRT and DLP can be configured to be able to switch back and forth between Progressive & Interlaced, but the others can't.

Re: Camera Frame Rates...

The most common are--

• 24P (Equal to International Film Rate/Motion), usually encoded on DV tape as 60i in 2:3:2:3 or 2:3:3:2 pattern (should be correctly reconstructed in computer).
  
  30P (Actually, 29.97P), encoded on DV tape as NTSC 60i (Actually 59.97I), where the ORIGINALLY TIME-SYNCHRONOUS odd + even fields are split apart (and should be reunited in computer). Has choppier feel than standard video because of the loss of inter-field motion.
  
  30I (Misnamed, should be 60I or 59.97I), normal NTSC DV (and analog) recording.
  
  25I (Misnamed, should be 50I), normal PAL DV (and analog) recording.
  
  25P Like 30P is from same time-synchronous frames, but field-split to fill 50I tape recording, for PAL DV.
  
  60P For 1280x720 HiDef recording in NTSC-common areas
  
  50P For 1280x720 HiDef recording in PAL-common areas.

There are a few other odd ones (15P, 12P).

Scott

[edDV]

Re: HDTV issues.

HDTV sets accept a variety of formats and internally convert to the "native display resolution" particular to the internal technology of that particular HDTV.

All HDTV sets will accept analog NTSC/PAL, interlaced analog components YPbPr, digital 480i and digital 1080i and convert them for display.

Many also accept progressive analog components YPbPr, digital progressive 480p, 720p and sometimes 1080p and convert them for display. 24, 30 and 60 frame rates are handled in expensive sets.

A limited subset of combinations is accepted by cheap HDTV sets (starting with 480i, 480p and 1080i)

Usually, you aren't doing the HDTV any favor by deinterlacing an interlaced signal upstream. Let the HDTV handle it.

If you want to produce a progressive 24p video project for some reason, the issues are covered well in this article. And no, the VX-2000* is not intended to compete with the AG-DVX100 for true 24p production. Stay with normal interlaced DV.
http://www.adamwilt.com/24p/


*The PD-150/170 and presumably the VX-2000/2100 have a progressive 29.97 frame per second mode that can be used for certain production purposes, but this isn't considered a distribution format.

[Cornucopia]

I concur about that AdamWilt article, VERY GOOD.

The 30P from PD150 is useful if you know that you are specifically going to output only for progressive use (such as web, compressed), as there are less artifact issues.

Shooting at any frame rate requires that the cameraperson know what kind of motion is happening (and will happen), both by the camera and by the subjects, and accommodates them differently. Mainly because there is a different "feel" to different framerates--up to the "Zone of Fluidity" (I just made that term up!), where the frame rate is fast enough that any motion looks fluid<<<edit: NATURAL>> (probably ~72fps and up).
So "Film rates" have a certain feel (which we are all used to by now) than "Video rates". Silent movie rates have a different (and noticeable) feel as well.

Scott

[edDV]

Normal 480i has an effective 59.94 motion rate* which is very forgiving. Some HDTV camcorders can shoot 720p at 59.94 frames per second which is great for hand holding and high motion sports (as promoted by ABC, ESPN and FOX).

At the other end of the spectrum you have 24 frame per second film and 29.97/23.976/25 fps progressive video acquisition. If you want to "go there" you are locked to a heavy tripod or gyro stabilized steadicam and are very limited in how you pan or zoom.

24p is jerky city and you need technique to make it look smooth. 24 fps also produces high flicker at native rate. For this reason, film projectors us a gate to repeat frames to 48 or higher "refresh". 25 fps video is frame rate doubled to 50hz (adequate) or 100hz (the new Euro retail hype). 23.976 fps progressive video is 3:2 frame repeated to match 59.94 refresh.

The main 24p "cinema" advantages come down to creative blurring of motion. Film does this naturally, video wants to take a series of high resolution snapshots that just doesn't look the same. Some are trying to alter CCD technology to respond more like film. If they accomplish this, your camcorder will likely only be good at this one effect.


* 576i has a 50fps effective refresh rate that falls a bit more in the jerky and flickery direction compared to 59.94 refresh. When I go to Europe, it takes me about 4 days to fully adjust to those flickering PAL TV sets.