interlace help

[nymph4444]

525 Lines go left to right and they are Laying down not upright?

[jagabo]

The TV scans horizontally, 525 times a second. 485 of the scan lines constitute the visible picture. Because of overscan only about 440 of them are visible on the screen. Vertical resolution is measured with horizontal lines. Horizontal resolution is measured with vertical lines.

http://en.wikipedia.org/wiki/Analog_television

[nymph4444]

Sorry what I ment was I know the Horizontal Line that that go top to bottum are 525

What is the number of the Vertical Lines left to right or how do they masure width?

[edDV]

Sorry what I ment was I know the Horizontal Line that that go top to bottum are 525

What is the number of the Vertical Lines left to right or how do they masure width?

DVD VOBs were sampled by the DVD maker usually from film. Like Jagabo said DVD allows 720 or 704 pixels across the line (sampled 13.5 Ms/s) or 352 (half sampled at 6.75 Ms/s). Most DVDs you will be dealing with are 720x480. In order to convert to square pixel 640x480 as you desire, 720 pixels must be resampled to 640.

[jagabo]

What is the number of the Vertical Lines left to right or how do they masure width?

I already answered that:
https://forum.videohelp.com/threads/334839-interlace-help?p=2083307&viewfull=1#post2083307

But in the analog signal it's not pixels, it's the bandwidth of the circuit limiting the frequencies that can pass through:
http://en.wikipedia.org/wiki/Low-pass_filter
https://forum.videohelp.com/threads/319420-Who-uses-a-DVD-recorder-as-a-line-TBC-and-wh...=1#post1980652
https://forum.videohelp.com/threads/319420-Who-uses-a-DVD-recorder-as-a-line-TBC-and-wh...=1#post1981589

[nymph4444]

Sorry what I ment is
640x480 meens 640 is the Herizontal.

But when they talk about the Herizontal they say 525 I get that and then they say out of that only 480 can be seen.
But 480 is not the Herizontal lines are they?

[jagabo]

640x480 means 640 pixels wide, 480 pixels tall.

In a 640x480 digital frame the frame consists of 480 horizontal scan lines. Each scan line is 640 pixels wide.

[edDV]

and 525 is the total number of analog lines including the vertical interval. 480 lines make up the active raster. The other 45 lines are in the vertical interval.



When analog is referred to as 525/60 or 625/50, the first number is total scan lines, the second is field rate.

[nymph4444]

I think I get it now please tell me if I am right/?

If I say a video is 640x480 I am right 640 is width and 480 is hight?

But when you talk about Analog CRT screens and you say 525 Lines are the Hight and out off that only 480 can be seen that number 480 is not the same as my 480 for my Video Hight?

[edDV]

I think I get it now please tell me if I am right/?

If I say a video is 640x480 I am right 640 is width and 480 is hight?

yes

But when you talk about Analog CRT screens and you say 525 Lines are the Hight and out off that only 480 can be seen that number 480 is not the same as my 480 for my Video Hight?

Same number of lines, but analog vs. digital technology.

Analog NTSC sends 525 scan lines per frame sent as odd and even fields. Forty five of those lines are sent during the vertical retrace for the CRT so normally can't be seen. The remaining 480 lines make up the active picture area. An older CRT TV will have a "vertical hold" knob. If you unlock vertical sync, you will see the vertical interval lines become visible on the screen.



Because the NTSC picture is sent as 480 lines, one can say NTSC is vertically sampled. In that sense NTSC is analog in the horizontal direction but digitally sampled vertically. To make the picture fully digital, one must sample the horizontal lines. If one wants square pixels (same pixel width as line height) then one would sample each line to 640 pixels wide for 4:3 aspect ratio or 853 pixels for a 16:9 aspect ratio.

For reasons explained in other threads, video engineers decided against sending digital video as square pixels but instead settled on 13.5 Ms/s (mega samples per second) for sampling both NTSC and PAL to 704 pixels for the active picture area or 720 pixels (extending into blanking pulses).

SD digital video such as MPeg2 or h.264 captured from digital cameras, DVD or Blu-Ray will have active picture out to 720x480. Broacast SD digital video (ATSC or DVB) is sent with 704 active pixels. If you capture as 720, there will be 8 black pixels left and right as shown below.



NTSC, 4:3 video will show wide stretched at 704/720x480 so video players resample to 640x480 square pixels for display on a square pixel display. The above pixture is resampled from a 720x480 capture.

[nymph4444]

What I ment was out of the 525 Lines only 480 can be seen and this is Herizontal Lines am I right?

[edDV]

Yes the NTSC CRT scans like this


http://www.davidstringer.info/training/how_television_works.htm <---- This is an excellent video course.

Blue -- horizontal retrace happens during the horizontal blanking interval

Red -- vertical retrace happens during the vertical blanking interval. The TV CRT doesn't show these retrace lines. The CRT beam is turned off during retrace. They can send other types of data like closed captions or TV Guide during retrace.


Progressive scan CRT TV displays scan all the lines top to bottom with one vertical retrace per frame.

480 visible lines

[nymph4444]

I did not know how the scan line ware drawn am I righ?

The Od Lines start at the top left hand side and go left to right down the screen.
But when it get to the bottum of the screen it at the bottum middle of the screen?

And the even Lines when it gets to the bottum of the screen it keeps going till it gets to the far Right side?

Do I have this right?

[edDV]

I did not know how the scan line ware drawn am I righ?

The Od Lines start at the top left hand side and go left to right down the screen.
But when it get to the bottum of the screen it at the bottum middle of the screen?

And the even Lines when it gets to the bottum of the screen it keeps going till it gets to the far Right side?

Do I have this right?

That is how a classic NTSC CRT scans. When NTSC changed from 486 visible lines to 480, the half lines were absorbed into the vertical interval retrace area so you don't have to worry about that. The remaining 480 lines are all full width left to right. Digital video assumes 480 full width lines.

[nymph4444]

OK so the Od Lines start at top far left and stop at bottum middle.

I get this part.

Now when the even Line start it starts at top Middle and ends at bottum far right?

Am I right?

[edDV]

OK so the Od Lines start at top far left and stop at bottum middle.

I get this part.

Now when the even Line start it starts at top Middle and ends at bottum far right?

Am I right?

For the 480 line area, all lines start left and finish right.

The analog half line stuff happens off screen in most modern video. Only an issue for classic analog video capture.

Consider digital video all full line width.

[jagabo]

The scan order image edDV posted in post #192 is a little inaccurate. This image shows it a little more accurately:



I've left out the horizontal and vertical retrace lines to reduce confusion. The top field (green) starts at the top center of the frame, ie, it is only half a line. Similarly, the bottom field (white) ends at the bottom center of the frame, only half a line. Yes, the scan lines are drawn at a slight diagonal. The effect is accentuated a lot here because we are only using a 7 scanline tall image. In a 485 line tall NTSC image the angle is very very slight.

If you could watch my seven scan line image being drawn on the face of an interlaced CRT it would look something like this:



Notice how the bottom field is fading away as the top field is being drawn, and vice versa. Also, the scan lines are drawn very thin in this image. On a real television screen the scan lines are nearly two lines thick so that each field nearly fills the screen.

[nymph4444]

I think I get it more now.

The Top Field Od Lines start at the Top middle of the screen and go to the Right to Left all the way down the screen and end in the at the Bottum middle of the screen.

I get this.

But just tell me one thing about the Even Lines when they start I know they start right under the First Od Line.

But do the Even Lines start at the top middle as well and end at the Bottum middle as well?

So but I could not see it to good I just want to know about the Even Lines now?

[jagabo]

No, the top field starts with a half scanline at the top and ends with a full line near the bottom. The bottom field starts with a full line near the top of the frame and ends with half a scan line at the bottom of the frame, just like I pictured it.

[edDV]

I think I get it more now.

The Top Field Od Lines start at the Top middle of the screen and go to the Right to Left all the way down the screen and end in the at the Bottum middle of the screen.

I get this.

But just tell me one thing about the Even Lines when they start I know they start right under the First Od Line.

But do the Even Lines start at the top middle as well and end at the Bottum middle as well?

So but I could not see it to good I just want to know about the Even Lines now?

After 199 posts I still can't understand what you want to know or why this is a problem for you. For digital video there are no half lines. Is your interest in analog capture? You never indicated anything other than DVD VOB. DVD VOBs are 480 lines high.

[nymph4444]

Sorry everyhing is ok I am just wanting to know about Analog NTSC?

All I ment was in the photo it shows the First Field starting at top middle and ending at bottum biddle.

So if I get you right the when the even Lines start the start near the top but in the Middle as well and end at bottum middle as well?

[Gavino]

Yay! 200 posts now and I still can't decide whether nymph4444 is a troll or just a slow learner with an insatiable curiosity. Anyway, I'll give him the benefit of the doubt for now, but I must commend edDV and jagabo for their seemingly infinite patience.

Sorry everyhing is ok I am just wanting to know about Analog NTSC?

All I ment was in the photo it shows the First Field starting at top middle and ending at bottum biddle.

So if I get you right the when the even Lines start the start near the top but in the Middle as well and end at bottum middle as well?

Read again what jagabo said:

No, the top field starts with a half scanline at the top and ends with a full line near the bottom. The bottom field starts with a full line near the top of the frame and ends with half a scan line at the bottom of the frame, just like I pictured it.

See also his diagram at post #197.

[nymph4444]

Thank you for all your help I can't see to good this is why some photos you showed me I did not see to good.
I was not playing around or trying to make fun of anyone.

Now I think I get it so far and I am useing Handbrake but need help with something.
I whent to there forums but they can not help me.

I am converting an Interlaced VOB file to mp4 H264 and I would like it to stay Interlaced.

So In Handbrake when I com to the De Interlace dropdown box I set it to OFF.
I thought this will keep my Interlaace video as Interlace and not ad a De Interlace.

They tell me it will still output as Prograsive but it will keep Artifacts Interlaced.

Please explane???

[jagabo]

I think you have to manually add the tff or bff flags on the Advanced tab, at the bottom.

[nymph4444]

So if I set De Interlace to OFF in the dropdown list it will take my Interlaced VOB file and just pass it thought so my output will be Interlaced?

Does anyone know for sure?

[jagabo]

Why don't you just try it and see what happens?

[nymph4444]

Do you meen try it and then check it in Media Info?

Does it sound right what they told me that if I take an interlaced VOB file and convert it but set De Interlace to OFF that it will still make it prograsive but have Interlace Artifacts in it??

[jagabo]

Does it sound right what they told me that if I take an interlaced VOB file and convert it but set De Interlace to OFF that it will still make it prograsive but have Interlace Artifacts in it??

Yes. I don't really use Handbrake but a quick perusal of the UI doesn't show any way of telling x264 to encode interlaced. So it will take the interlaced frame, encode it as if it's progressive, and flag the video progressive. When a player plays the video it will play it as if it is progressive -- ie, it will show both fields at the same time.

Maybe someone who knows the program better knows a way around that.

[nymph4444]

Well what do they mean it will have interlaced Artifacts in it but it will output the file as Prograsive?

What is Artifacts?

[jagabo]

It means you'll see interlace comb artifacts when there is motion. Like this: