A few questions...

drummerboy678

drummerboy678

Well-known member
I have been trying to avoid posting something like this, as I feel it has been done to death. But after searching through old posts, I know I'm not the only one who is confused.

Interlaced
Deinterlaced
Native Progressive Scan
Progressive Timelines
Pulldowns (2-3-3-2, 2-3, etc)
Aspect Ratio
Flicker
Field Dominance
Thick and Thin

These terms confuse the crap out of me. Whenever someone tries to explain one, they end up using 5 others to explain it, and the message never gets through. If anyone could maybe make a sticky of FAQ about this, that would be great.

I understand that takes a lot of time however, so I'll just post my problem here as well...

Premiere Pro 1.5, footage shot in 24p (scene 5, not 6), squeeze mode, widescreen timeline, 1/120 shutter...

Every 4th frame is (I think) interlaced... As in, every fourth frame looks bad. I'm assuming this is an interlacing problem (because in photoshop, I hit 'deinterlace' and it cleans up fine). Why would this happen every 4th frame, and how do I prevent it?

(1-3) good frame: http://img149.exs.cx/img149/4566/test32wv.jpg
(4) bad frame: http://img149.exs.cx/img149/8688/test45zz.jpg



Thanks in advance for your help... Sorry for another question like this...
An article, FAQ, or Sticky Post on this topic would be incredibly helpful!
 
There at least 1 or 2 PDF files that cover this and I'm sure Barry's book does as well. For people doing real work on the DVX it's not a bad idea to pick up a book or two on video. A good site to check out that has specific answers on 2:3 and 2:3:3:2 issues is:
http://www.adamwilt.com/24p/index.html

24p (F5) is SUPPOSED to be interlaced just like standard video is supposed to be interlaced. It's not an accident and it's not bad frames.

NTSC video (U.S) operates on the concept of 60i. 60 fields of interlaced images. A field is all the odd lines displayed alternated with all the even lines displayed. A video frame is made up of both odd and even lines to fill a full frame but if there’s fast motion you will see the difference between odd and even lines. This is the 29.97 frame rate. There a whole history of technical issues why this was done but I won't cover that here.

Interlacing works when played as video. If you stop and look on a single frame, especially on a computer screen you'll see the line difference. It may not look good ass a single frame but this is all about making the moving image look good, which is the reason for the interlacing.

When you take a video frame grab into Photoshop it's showing both sets of lines. If there's fast motion you may find it produces 'cleaner' still image by deinterlacing the image. Deinterlacing can be done by duplicating one set of lines (1/2 vertical resolution) and blending the lines together.

Film runs at 24fps frames. There are no fields or lines. When film is transferred to video it needs to convert from 24fps to 29.97fps, otherwise it would all be sped up. To do this simply one frame in every 4 could be duplicated. 4 frames of film at 24fps = 5 frames of video. But this doesn't produce the smoothest action. So they actually convert 24fps to 60 fields per second. This allows smoother action but in some video frames you will have odd line from one film frame and even lines from another. Once again the whole point is to look good in motion, not as a still. The process of going from film to video is called Telecine and this type of speed conversion is know as adding pulldown or 2:3 (signifying frames to fields). This is exactly what happens to feature films when transferred to videotape or displayed on broadcast TV.

Since the original was captured at 24fps it still has the 'film look' but is now able to be displayed with regular video.

This is exactly what the DVX does when you shoot in 24p (F5) mode. It's converted on the fly so it can be displayed on regular video in the smoothest manner. If you wish to get back to true 24fps frames then you run a process of pulldown removal (since pulldown was added when it was saved to tape) in your editing or effects program.

Progressive means that you're capturing a full frame. There are no fields or odd/even line issues. This is naturally what happens to film and to create 24fps this is what happens with the DVX. It also produces a cleaner image for effects or to get still from. DVX NTSC allows for 24p and 30p. Since the capture rate is different it looks different when played in motion.
The main reason video looks 'live' is because of the 60 fields a second. If you see film shot and projected at faster speed it will have this 'live' look.

The 2:3:3:2 pulldown (24pa F6 mode) is on the DVX to allow faster and clean conversion of the standard video back into the internal 24fps. When using traditional pulldown (2:3) such as film telecine or DVX in 24p (f5) mode some of the frame images are broken into fields and mixed with the next frame. To convert back into 24fps frames requires separating these fields and recombining and resaving/recompressing these frames. This takes more computing power and causes some quality loss. By using a 2:3:3:2 mode (24pa F6) this just adds an extra frame (made of 2 fields) for every 4 frames. This makes it's easy for the editing software to just skip this added frame, no on the fly deinterlace/interlace process required and no need to convert and resave the image so you get better quality. What you give up with 2:3:3:2 is the smoothness of motion. If you observe fast action you may see a little more stutter than you would if it had been shot in 24p mode.

When using the 24pa mode you need to do the pulldown removal and edit at 23.98 (23.98 instead of 24fps because we're dealing with the true time rate of video) Now in order to play back this footage onto a real video monitor the editing software adds pulldown (2:3 speed conversion) in real time since NTSC still requires 29.97.

Bottom line is if you just need video with the film look then shoot 24p (F5). Capture and edit at 29.97 and don't worry about seeing the odd/even interlace lines.
If you're going to film or 24fps DVD then consider using 24pa (f6), do the pulldown removal and edit 23.98.

See http://squiresstudios.com/dvx100/dvx100fcp.html for more info.

Aspect ratio: 4:3 and the like reflect the ratio of horizontal to vertical. Imagine a rectangle 4 inches wide by 3 wide. That is 4:3. Standard video is 4:3.
HDTV and widescreen video is usually referred to as 16:9
Film is usually just given the fraction number. 1.33 was used for old movies. (The horizontal side is 1.33 times the vertical of the image) This is very close to 4:3 and the reason why video is the way it is.
Most films today are shot 1.85 or 2:35 widescreen. The latter is done using anamorphic lenses that squeeze the image in the camera and then a special projector lens is used to unsqueeze it.
Video can use anamorphic lenses as well to change from the 4:3 aspect ratio or use special chips or compressions to create wider images.

Field dominance- Different digital systems work with odd/even fields in different ways. Some start a sequence with the odd image and some start with the even field in terms of order.

Thick and thin- how the odd/even lines are dealt with. Normally there is a little blurring/blending of the lines. If you photograph a thin horizontal line on video it will flicker. By shooting with Thick line the image of that physical line is make to spread over more lines on video and avoid the flicker. But if you want to go to film then you want everything to be recorded cleanly since you don't need to worry about video lines.
 
Scottdvx100 - Wow, thank you so much... Thats exactly what I was looking for. I'm sure I'll be ordering Barry's book soon, my parents just dont like ordering off the internet.

Thanks again so much for the great post... hopefully this will help other people as much as it did me!
 
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