IS 480p acutally twice the data of 480i?

[flagmaster]

Ok, this might be a silly question, but Id like to see what you all think about this subject.

First, what I know is this...

480i (internlace)- Normal TV, that is NTSC, and has been this way forever. There are 525 lines, and 480 of them are make up the acutal video we see. The rest are used for sync, and closed captition, and some other odd-ball stuff.
Lines of video are drawn onto your screen starting at line 1, then 3, then 5, then 7 and so on till it gets to the bottom of the screen. This will draw 1/2 of the full frame of video, and then very quickly, it "flybacks" to draw line 2 4 6 8 and so on. When it finishis this, all of the line 1 2 3 4 5 6 7 8 up to 480 have been drawn. Due to the "human preisistance of vision" it looks to us like a nice solid picutre.

480p (progressive) - I understand that the vidoe frame is drawn starting at line 1, then 2, then 3 and so on. This way, the entire frame of video is put onto the screen in the same amont of time it would nomrmally take to draw it twice, one for the even lines, and one for the odd lines.

Now most of use will get to see 480p from our DVD's using a progressive scan player. (about $30 bucks at radio shack will get you a decent entry level one).

To me, all 480p really does is prevent "flicker", giving you a rock solid frame of video, but not really at any higher resolution (no more pixels) then 480i.

Now HDTV increases the number of lines to 720p or 1080i, and also increases the number of horizoinal pixels.....ALOT MORE, and thus both 720p and 1080i will looks amazing comparied to 480p.

Only just in the last few months has Fox gone HD. They have been digital for a while, and they where sending TV shows in 480p. And they did look really good. (They look even better now!!).

I guess to sum up....my question is...

"is 480p really any better then 480i, other then less flicker"?

Also, what about non-scaned (non CRT) devices like projectors, lcd, and plasma? They dont scan and draw pixels a line at a time, they just turn them all on and off "instantly". Dose 480i even apply to these?

Carey

[chachi]

Ok, this might be a silly question, but Id like to see what you all think about this subject.

First, what I know is this...

480i (internlace)- Normal TV, that is NTSC, and has been this way forever. There are 525 lines, and 480 of them are make up the acutal video we see. The rest are used for sync, and closed captition, and some other odd-ball stuff.
Lines of video are drawn onto your screen starting at line 1, then 3, then 5, then 7 and so on till it gets to the bottom of the screen. This will draw 1/2 of the full frame of video, and then very quickly, it "flybacks" to draw line 2 4 6 8 and so on. When it finishis this, all of the line 1 2 3 4 5 6 7 8 up to 480 have been drawn. Due to the "human preisistance of vision" it looks to us like a nice solid picutre.

480p (progressive) - I understand that the vidoe frame is drawn starting at line 1, then 2, then 3 and so on. This way, the entire frame of video is put onto the screen in the same amont of time it would nomrmally take to draw it twice, one for the even lines, and one for the odd lines.

Now most of use will get to see 480p from our DVD's using a progressive scan player. (about $30 bucks at radio shack will get you a decent entry level one).

To me, all 480p really does is prevent "flicker", giving you a rock solid frame of video, but not really at any higher resolution (no more pixels) then 480i.

Now HDTV increases the number of lines to 720p or 1080i, and also increases the number of horizoinal pixels.....ALOT MORE, and thus both 720p and 1080i will looks amazing comparied to 480p.

Only just in the last few months has Fox gone HD. They have been digital for a while, and they where sending TV shows in 480p. And they did look really good. (They look even better now!!).

I guess to sum up....my question is...

"is 480p really any better then 480i, other then less flicker"?

Also, what about non-scaned (non CRT) devices like projectors, lcd, and plasma? They dont scan and draw pixels a line at a time, they just turn them all on and off "instantly". Dose 480i even apply to these?

Carey

The difference between interlaced video and progressive video lies solely in the way the video data is delivered and displayed. While one passes odds then evens whereas the other passes them all, after 480 lines are passed via either method you get one video frame.

Since the real world / natural light and eyesight does not entail interlaced video, our eyes 'prefer' progressive video displays to interlaced since after all that's what retinas are designed for ;)

100hz sets worked well for many people as doubling the refresh rate functionally equated to progressive scan unless one's eyes were sensitive to that sort of frame rate issue.

Interlaced/progressive video signals for lcd/plasma screens really only influence the path in the circuitry the signal takes before it is mapped and displayed and can vary from one manufacturer & model to another.

Some screens process I signals and pass P signals untouched to the pixel mapping (last process before actual display) but some process all incoming signals prior to the mapping phase.

YMMV

[RavenStL]

well 480 = 480. no difference there. Definatley only reduces the "flicker" you see with Action, camera movement, etc.

All depends on your set. I have a 720P only HDTV LCD. So all my 1080I gets downconverted and sent to the lcd as 720P. And all my 480I and 480P gets unconverted to 720P.

If I send out 480I on my DVD (selectable with a switch) I see flickering on my LCD. If I send 480P, it looks fabulous compared to 480I. Not better resolution, but the loss of flickering of the picture when the camera is moving. (NOTE! I Only see a difference WHEN the camera or actors are MOVING quickly!...)

My question has always been, is raw 720P better then 1080I???
Would I enjoy 720P with less flicker, and less resolution, OR 1080I with MORE resolution and MORE flicker. When I was comparing 1080I on a Mitsubishi CRT RP (Rear Projection) and my 720P LCD RP, I couldnt see the difference. So I spent MORE money for LESS resolution cause I prefer seeing a FULL 60 frames a second. Now if the signal is native 1080I, it may still stagger like 480I. OMG I am just as confusing sounding as when I was on the Sales floor.
I also wanted the smaller cabinet where I can put ALL my A/V equipment UNDER the TV. very nice.

DId I even answer the post, I cant remember, hope so.

RAW 720P has more bandwidth then 1080I, yadda yadda yadda...... Cant derive 720P from a RAW 1080I do the the lack of bandwidth so the flicker will remain..... blah blah blah...... OMG I hate HDTV!!!! LOL

Lets get 1080P and stick a fork in it...... :)

EDIT::
OMG, I didnt answer the question I first read.

Is 480P twice the data? Yes and No. Hows that for an answer???

Movies are already ONLY 50 FPS.... go figure.....
480I only does 30 full FPS.
Now, 480P does 60 !!
Sheesh, I hate the world somedays....
So its twice the data if you were counting how many pixels got refreshed on your CRT.
BUT, the source REMAINS the SAME 50 FPS (movies) and they do crazy reverse 3:2 pulldown or whatever. My head is hurting, hope this helps//

[flagmaster]

Wow, I think you may need more help with this then I do. :)

Thanks for the input guys.

[Jeff D]

Movies are already ONLY 50 FPS.... go figure.....
480I only does 30 full FPS.
Now, 480P does 60 !!
Sheesh, I hate the world somedays....
So its twice the data if you were counting how many pixels got refreshed on your CRT.
BUT, the source REMAINS the SAME 50 FPS (movies) and they do crazy reverse 3:2 pulldown or whatever. My head is hurting, hope this helps//

Well. maybe if you are in PAL land where things run at 50Hz this may be true, but not in St Louis... Film is 24 fps and only changed to be used when not projected from a projector. 3:2 pulldown and the like. There are other methods used for 50Hz areas, but I won't bother with that. DVDs that are movies are (or should be) encoded at 24fps with the flags to correctly display them at 60fps/30fps. 30 and 60 fps are the exact same thing exept for the way they are delivered and because of that they are different.

So to the real question of twice the data... that's like impossible to say as you are talking TV and 480i is analog and 480p would be digital. Apples and oranges. If you were talking 480i digital and 480p digital still not really the same thing because the source format does a lot to change the encoding. MPEG picture is a full frame of data that is split to be displayed correctly. Regardless of 480i or 480p it's still a full frame. In TV land maybe it contains a progressive image or maybe it contains an interlaced image. Regardless it's still a full frame. If you are trying to display a 480i sourced stream in 480p world what you get is a frame doubled 480i signal displayed in 480p. No 3:2 pulldown or anything fancy just the full 480i 30fps images displayed twice at 60fps.

When a movie encoded at 24fps it's displayed in a different patter to get 60 fps. I believe it's another 3 2 pattern with one frame showing for three draws, the next two, then three then two. So 12 of the pictures show for 24 frames and the other 12 show for 36.

How's that for not answering the question?

[FredThompson]

Geez. Will we ever get over the challenge of multiple definitions for the word "frame"?

Interlaced video has twice the temporal information of progressive video at the same display rate. NTSC progressive is ~30 fps. NTSC interlaced is two interleaved video streams of ~30 fps but with different timings. NTSC interlaced yields an effective frame rate of ~60 fps.

Film is 24 fps unless it's old or an experimental format. BRoadcasting film via video requires creating some additional "frames" to pad the rate to ~30 fps.

If you are trying to display a 480i sourced stream in 480p world what you get is a frame doubled 480i signal displayed in 480p. No 3:2 pulldown or anything fancy just the full 480i 30fps images displayed twice at 60fps.What?!?! 2 fields of 480i is not equal to 1 "frame" of 480p. You should be seeing a deinterlaced interpolation of 480i converted to ~60 fps 480p.

[SR712]

When TV was invented, it was designed to operate at 60 frames/sec (standard power frequency). Due to bandwidth limitations, it was not practical to broadcast 60 complete frames each second. So, television pioneers borrowed an idea from film. Instead of projecting each frame twice, like film projection does, the video engineers decided to divide each frame into two fields, each field having half the resolution of the complete frame. Instead of 60 complete frames making up one second of video, there are 30 discrete frames, and each frame is divided into two fields. Because the video frame is made up of 525 horizontal lines, displaying 262.5 lines twice each 30th of a second results in only slightly diminished picture resolution and greatly increased temporal resolution. The result is a flickerless 60 fields per second. (Actually, 40 lines are used for the vertical blanking interval, but that's another subject) First, all the odd numbered lines are scanned (making up field 1) and then all the even-numbered lines are scanned (field 2).This process is repeated for each new frame. The beam drawing the video begins with line 1, left to right. Once it reaches the end of line 1, it shuts off, and drops down to scan line 3. This process continues until it has completed all of the odd-numbered lines. Then it shuts down, retraces to the top of the raster to begin scanning line number 2. When all of the even-numbered lines have been scanned, it starts all over again with the information of the second frame. Timing is controlled by syncronizing pulses called horizontal and vertical sync and blanking.

All this to say, its 30 frames a second, 60 fields a second for NTSC Interlaced. There shouldn't be a question about that.

[FredThompson]

It is monstrously misleading, though common, to describe interlaced video by "frames." NTSC interlaced is 2 nearly-parallel video streams which alternate in time and location. There is no guarantee that the recorded image comes from the same point of view or time in any 2 fields. Additionally, field dominance is not locked. Sometimes the odd field is first, sometimes the even field is first.

Yes, data organization is 30 "frames" but NOT 30 images. Well, 29.97 or thereabouts, actually. That's where people get confused. Most simpllle explanations of how TV works state both fields make up a complete picture. That not accurate.

[rsvader]

Man, SR712 and Fred you guys are really showing your ages. You know what the deal is there are too many video pups that don't understand the history of TV and have no basis for where we have come. Additionally, the new HDTV formats were influenced by Computer guys more than Television engineers. Thanks for the history lesson SR only an old dog would know that much. But with that said the new ATV formats look great. I, however, am an advocate for 1080i as the resolution is superb, especially with sports. But wait, I also like Fox's 720p, when I really need to see if the ball made it over the line or if the receiver came down inbounds. 720p also works great with the new Mpeg4 coders (hardware and software) where Mpeg4 really has a problem with the new mixed mode movies (24fps and 30fps CGI, sometimes 60fps CGI, special effects). They don't do well with the changing fps during a presentation, they drop frames and add new ones.

So what was the question which is better, it won't be figured out until the first day of 2007 when the Federal mandate for ATV occurs unless Congress relaxes the date until 2009 with a phased in plan, what a nightmare that will be. Fred and SR are both right on target, technically speaking. Common sense tells us the more information the better the picture and progressive scan is easier on the eye. But the FCC tells us everything will be solved on Jan. 1 2007.

[AlphaWolf]

Perhapse we should just have 1080p.

[jonbig]

Perhapse we should just have 1080p.

Unfortunately, 1080p can't fit in the over-the-air broadcast channel bandwidth.

[justmike]

Unfortunately, 1080p can't fit in the over-the-air broadcast channel bandwidth.

Well one thing I have learned is that as soon as somebody says something like that someone figures out a way to do it. Remember when modems would never go about 300 baud? :cool:

[FredThompson]

300 baud is less than the available ~4800 baud bandwidth of analog voice lines. Those modems which would claim to connect at greater than 4800 were using data compression. With cruddy lines, you'd frequently get faster true throughput at 4800 than with the compression. jonbig is stating OTA 180p isn't possible with the current bandwidth limits. Can't put a size 10 foot in a size 5 shoe, so to speak.

[AlphaWolf]

Unfortunately, 1080p can't fit in the over-the-air broadcast channel bandwidth.

Even in mpeg-4? I figure it should be able to with regular mpeg-2 though. I mean each channel can carry up to four 1080i feeds simultaneously IIRC.

300 baud is less than the available ~4800 baud bandwidth of analog voice lines. Those modems which would claim to connect at greater than 4800 were using data compression. With cruddy lines, you'd frequently get faster true throughput at 4800 than with the compression. jonbig is stating OTA 180p isn't possible with the current bandwidth limits. Can't put a size 10 foot in a size 5 shoe, so to speak.

AFAIK 28.8 is the theoretical max. IIRC it was extended to 56k by some technique of sending two bits per analog pulse.

That was the true bandwidth as well. Compression is only any good for text transfers (e.g. webpages.) Even files with heavy bit entropy that are impossible to compress can manage a 5Kbyte/sec transfer over a standard line.

Ku-band satellites use a comparable technique that doubles their bandwidth. They actually send double the data that is otherwise possible by sending two signals that overlap on the same frequency. These signals are distinguished by having different polarization (I am not sure how the physics works out, but one is called circular polarization and one is called linear.)

[jonbig]

Well one thing I have learned is that as soon as somebody says something like that someone figures out a way to do it. Remember when modems would never go about 300 baud? :cool:

Nope, can't do it. It's a mathematical and physical theoretical limit.

Google Shannon's Theorem.

Now if you want to degrade the quality of the picture, you can sqeeze something that turns into 1080p into the channel, but you'll have less fidelity compared to the original source. Better compression algorithms might produce something that is still pleasing to the eye, but that's beyond my expertise.

[jonbig]

Ku-band satellites use a comparable technique that doubles their bandwidth. They actually send double the data that is otherwise possible by sending two signals that overlap on the same frequency. These signals are distinguished by having different polarization (I am not sure how the physics works out, but one is called circular polarization and one is called linear.)

Actually, they are both circularly polarized, one clockwise, the other counter-clockwise.

[FredThompson]

Oh, yeah, that's right. 28.8 was the limit. The 56K stuff was data compression. Problem with that was so much bandwidth was consumed with retraining that throughput suffered.

I've been on broadband for about 5 years now. Frankly, I forgot the modem numbers. The analog voice range was something like 4k, wasn't it? 4 of those would be bundled together. Something like that.

From what I've seen, MPEG4 is able to give just about twice the effective bandwidth of MPEG2 IF the encoding is very good. In that regard, sure, you could fit more video data in the same space.

I'm not messing with HD, myself, until the disc wars are done. Been there, done that, with other video formats.

[AlphaWolf]

Nope, can't do it. It's a mathematical and physical theoretical limit.

They could always broaden the digital TV spectrum.

[FredThompson]

There's been talk about removing OTA "regular" TV bandwidth and reassigning it.

I still think a T1 to every house would solve a lot...

[AlphaWolf]

Why? T1 is slow compared to what most people already have available (hell, I myself have had more than twice that bandwidth since 1997.) It also isn't capable of the bandwidth necessary for HDTV by a long shot.

[FredThompson]

I thought T1 was higher throughput than cable modem/ADSL. Geez, my second strike. Must be showing my age. Anyone seen my teeth? It's cold in here...

[jonbig]

I thought T1 was higher throughput than cable modem/ADSL. Geez, my second strike. Must be showing my age. Anyone seen my teeth? It's cold in here...

A T1 is only about 1.5Mbit/sec. That's only about 187kB/sec.

[jonbig]

They could always broaden the digital TV spectrum.

Well, sure, but do you *really* want to push back Digital TV another decade?

[FredThompson]

Heh, guess I remember a T1 as being "huge" when I was on dial-up. OK, a big, old, honkin' trunk of fiber optic cables. There, that ought to hold you whipper-snappers!

[AlphaWolf]

Well, sure, but do you *really* want to push back Digital TV another decade?

*shrug* I already have digital TV through directv :D

[RavenStL]

Verizon FIOS . Now thats the s**t! 15 Mb down and 2 Mb Up. :droooool:

I think Directv sells there programming through verizon........ Some special fiber to multiswitch thing-y-ma-jig.

Over the air seems "antiquated" to me. Hell, when will the first "tv station" (ABC, NBC, CBS, Fox, etc) go in some city and they decide not to build a tower. Seems like it should happen someday. send a feed to a satellite and let people watch on cable and satellite as they do now.

[Nanoic]

The post about there is not enough bandwidth for 1080p is not entirely correct. If the question was about 1080p60, then answer is correct. However, it should be noted there are some 1080p formats that can fit in OTA bandwidth are part of the ATSC spec. 1080p24, 1080p25, 1080p30 can be broadcast OTA but are woefully under utilized. My personal belief is that film movies should be broadcast at 1080p24 instead of 1080i60 which in theory should allow 720p60 and 1080i60 displays to scale better.

Listing of ATSC formats http://support.gateway.com/s/CsmrEltrncs/DigitalTV/Shared/2517984faq42.shtml

[mike_s]

AFAIK 28.8 is the theoretical max. IIRC it was extended to 56k by some technique of sending two bits per analog pulse.

The theoretical (practical is less) limit on standard analog phone lines is 8000 baud. Such lines are digitized to 8 bits, 8000 times per second (64Kbps channel).

Perhaps you're confusing "baud" with "bits per second," which is something completely different.

"Baud" is the number of quanta (or symbols) of information per second. In the case of a 28.8K bps modem, each symbol encodes 9 bits. 28.8K / 9 bits per quanta = 3200 baud.

The Shannon limit for an analog line is about 35Kbps due to noise. "56K" modems do better than that because they only offer 56K in one direction, and that direction is not subject to A/D conversion at the head end, and hence has a lower noise floor, increasing the Shannon limit. The same bearer channel, if end-to-end digital, can carry 64Kbps (or sometimes 56Kbps, due to inband signalling) bidirectionally.

[RavenStL]

This thread has finally made my ears start bleeding :)

Just finished putting new John Deere bearings in my mower deck. Sure, make a bearing with a standard 0.750 bore but have a 1.755 OD and what the heck, a 0.610 thickness, just to make you go spend $30. And then $15 for a belt that looks alot like a $4 4L600. Dang, Tivos sure are cheap in comparison. :)

(Sorry, had to add some Farmer-esque to this Engineering textbook thread :) )

[cheer]

A T1 is only about 1.5Mbit/sec. That's only about 187kB/sec.
Veering widely off topic...

Yes, true, a T1 is 1.544mb/sec (or effectively 1.536 depending on what you're doing at layer 2).

But a T1 is also a clear pipe (again depending on layer 2). Most of us that have broadband have some kind of shared medium -- cable, or fixed wireless, or whatnot. There's DSL, of course, but unless you live nice and close to your CO I doubt you're getting 1.5 up/down on DSL.

--chris