Interlace help

thebrain900 wrote on 4/23/2011, 7:30 PM

I think I know this one so I will tell you and you can tell me if I am right it is about Interlace Video.

Interlace Video is when every Frame is made up of Two Fields a Top Field and a Bottum Field.

So to display one frame the TV would draw all the Bottum Fields first then go back to the top of the screen and draw all the Top Fields.

This would make one Frame yes or no??

And when it whent back to start draw all the Bottum Fields the Bottum Fields would be the Start of the Next image Yes ore no?

Comments

musicvid10 wrote on 4/23/2011, 8:39 PM

"So to display one frame the TV would draw all the Bottum Fields first then go back to the top of the screen and draw all the Top Fields."

No.

Depending on the correct field order, it goes U_L_U_L_U_L . . . by drawing ONE FIELD at a time.
But if by sayiing "fields" you really mean "scan lines on a CRT screen" (be careful here), you are at least thinking correctly.
The human eye is not capable of detecting the jitter unless the fields are out of order.
The result is a temporally blended image.

Now, deinterlace in Vegas either blends the two fields, or drops one field and duplicates the other, so 60 fields become 30 progressive frames, for instance.

Former user wrote on 4/24/2011, 5:25 AM

Actually, the eye can detect the jitter. The only reason you don't is because CRTs (tube style TV screens) have a persistence of vision designed in. This causes the image to be retained on the screen a bit longer than the 1/60th of a second that the field is drawn (in NTSC).

It draws one field first. This might be what the OP is referrring to as "all the bottom fields". Then it draws the second field, while the first field slowly fades away. Each field is every other line of the full frame. So the Upper field might be the odd lines and Lower might be Even. This is perceived as a frame of video.

Upper and lower fields is really kind of a misnomer. It would make more sense to call it 1st and 2nd field. I guess the term Upper and Lower refers to one field being one line higher on the screen than the other field. Upper and Lower did not come into use until video was created on computers. Until that time it was called Field 1 and 2. But since non-video people created computer video, they made their own terminology.

Dave T2

thebrain900 wrote on 4/24/2011, 9:13 AM

Yes that is what I ment thanks for all the help I new I understood it.

Now here is the thing and this is a Video Editing problem so it does not go into Movie Studio. So if you can't help me I undertand I am just having a lot of Prablems with my little project.

I am taking NTSC DVDs that I have of the 1970's TV show Buck Rogers and I want to convert just a fue show to MP4.

When I convert them if I set De Interlace to NO
and set Interlace to NO

My MP4s comeout good and play good on my computer and on my 5. inch media player.

But if I set Interlace to YE it will play in split screen. One image on top half of screen and the sdame image on bottum of screen.

I thought you sould Interlace video if it is comeing off a DVD?

Former user wrote on 4/24/2011, 11:04 AM

If your final goal is to view only on a computer, then you want to de-interlace. A computer by design is a progressive (non-interlaced) display.

If your goal is to watch it on a TV from a DVD, then you want to leave it interlaced, but since you already have the DVDs I assume you aren't making more. Also, if you are going to leave it interlaced and you are ripping from a DVD (not just copying as in an DVD to tape copy), then you need to make sure that you interlace the same as the orignal, that is UF First or LF first.

Dave T2

thebrain900 wrote on 4/24/2011, 7:54 PM

Thanks I think I am geting it now but what did you meen the Field Order is
ULULUL

Do you meen CRT TVs draw upper field then lower field?

Former user wrote on 4/24/2011, 8:03 PM

A CRT will draw the field order as it is on the DVD or videotape. If your field order is Upper Field First, then it will draw that first, and vice versa for Lower Field. The video capture/render determines the field order.

Dave T2

thebrain900 wrote on 4/24/2011, 8:14 PM

I thought in the USA the Field Odr was
All Lower Feild first then all Upper feild next?

Former user wrote on 4/25/2011, 5:34 AM

No. It can be eithe way.

The normal DV-AVI is lower field first. But most uncompressed formats and HD are upper field first. But there is no hard and fast rule. Many commercial DVDs are upper field first.

Dave T2