how-to block ads
|
|
Uniqs:
271 |
Share Topic
 |
 |
|
|
 intellerSociopaths always win.
join:2003-12-08
Tulsa, OK | great for locals....useless for everything else. sorry, I'll stick to cable. I cant exactly get ESPNHD, MHD, and National Geographic over the air. | |
Time4aNAPPremium
join:2007-04-09
Des Plaines, IL | said by inteller:sorry, I'll stick to cable. I cant exactly get ESPNHD, MHD, and National Geographic over the air. I don't think that's quite the point here. Cable does have its uses. But when it comes to HD, cable and satellite implementations can be difficult and expensive for the subscriber. In contrast, over-the-air local broadcasts in HD offer a cheap and easy alternative when it comes to local and traditional network programming. For a lot of us, that's enough.
For example, I have two TV sets and two TiVo boxes. I hope to add two PC-based PVRs to that soon. In order to get HD service of any kind over cable, I'd have to sign up for a substantially more expensive tier of service, and rent converter boxes. The rental fees for six converters is bad enough, but the complexity that it adds to recording, or just watching TV makes it unattractive to me. I've tried digital cable, and went back to extended basic after I noticed that I never used the box.
The "infotainment" channels (Discovery, History etc.) and old movies that I need cable for are just fine in NTSC. Everything else that I watch tends to be from local TV stations. For that it is much easier to slap ATSC/NTSC cards in my computers and record my shows off-the-air. Others who want an appliance can buy a PVR to do the same thing.
When it comes to the level of HD, if 1080p doesn't come to ATSC channels, I'm fine with that. 720p is just fine for now, and I really doubt that broadcasters are going to drop below that margin. Whenever 1080p becomes widespread enough for me to make that my default, I'll buy new equipment then. But for now I'll enjoy "the best things in life" that are free.  | | |
|
 koolman2Premium
join:2002-10-01
Anchorage, AK | All they have to do to bring 1080p to ATSC is go from 1080i 60fps and sample the same frame for both fields, bringing 1080p 30fps. The converters would see it as a 1080i 60fps signal, but it would show on your screen as 1080p 60fps, and look best if your TV weaves to deinterlace.
More than 1080p 30fps isn't possible with the standard, and probably never will be.
--
There's no place like ::1. | |
Time4aNAPPremium
join:2007-04-09
Des Plaines, IL | Deinterlaced 1080i still falls short of true 1080p. I do my HD viewing on computer LCD screens, so I've run the gamut of deinterlacing algorithms. Some are better than others, but a progressive scan source makes life easier. | |
koolman2Premium
join:2002-10-01
Anchorage, AK | If you sample the same frame for both fields and your screen weaves to de-interlace, it is the same as progressive scan.
--
There's no place like ::1. | |
Time4aNAPPremium
join:2007-04-09
Des Plaines, IL | If only it was that easy!
The problem with all scanning schemes is that none of the pixels occur at precisely the same time. For scenes with little or no motion, this isn't much of a problem. But what's TV without motion?
The reason why interlacing is used has to do with more motion information being sent per frame at no extra cost. The problem with taking one field, and superimposing it on top of the next field (which starts 1/29.97" later) and then displaying it as a progressive scan field is that every next line jumps back and forth in time, compared to the source. This tends to make the picture quality suck.
To have any success at all in producing a non-interlaced replica of an interlaced stream, interpolation must be done in time as well as space. This is what has made Yves Faroudja's patented process so good, and so expensive. 4-D signal processing is not cheap. There are a number of algorithms, both proprietary and open, which do a pretty good job, especially as CPU/GPU performance increases. But none, not even the Faroudja algorithm can make something out of nothing. So there will always be artifacts.
Another thing to note is that progressive scan isn't always best. For sports and other high-motion programming, interlaced still has the edge.
What I don't understand is why there's still scanning in television at all. CCD sensors replaced electron beam sensors a long time ago. LCD and other digitally-controlled display technologies are doing the same for the CRT. Frame buffers have been used in broadcasting for decades, and today RAM is so cheap that it's not a limiting factor for consumer electronics. So why aren't there any digital video formats out there that combine the benefits of film with those of TV? | |
koolman2Premium
join:2002-10-01
Anchorage, AK | You're not understanding... You are seeing the word de-interlace and assuming that I'm talking about a line doubler.
When interlaced images are made, they are sampled from a progressive image. Each field is sampled from different progressive images. Instead of doing this, use the same progressive image and scan the other half of the image and send it down the pipe. The result is a progressive picture being sent down the signal without any neat hacks or a revamp of the standard. The only downside is that the highest frame rate you can get is the field rate of the interlaced signal divided by two. The best part, however, is that the signal will work flawlessly on any systems that can receive a 1080i signal, while letting 1080p monitors display it without flicker, as long as they de-interlace using the weave method only.
--
There's no place like ::1. | |
Time4aNAPPremium
join:2007-04-09
Des Plaines, IL | said by koolman2:You're not understanding... You are seeing the word de-interlace and assuming that I'm talking about a line doubler. Not at all. If you're confused by my Faroudja reference, you should know that Faroudja's products do more than line doubling. Faroudja technology was in use by broadcasters before the consumer line doublers appeared.
When interlaced images are made, they are sampled from a progressive image. Each field is sampled from different progressive images. For my edification, could you direct me to a broadcast TV camera that does 1080p60? Ikegami if possible.
Instead of doing this, use the same progressive image and scan the other half of the image and send it down the pipe. The result is a progressive picture being sent down the signal without any neat hacks or a revamp of the standard. The only downside is that the highest frame rate you can get is the field rate of the interlaced signal divided by two. I know that an interlaced frame consists of two fields. The rest I don't understand. With 1080i, each field has only 540 lines. So it's not possible to send (or recover) more than half of the data in a 1080p60 frame to/from a 1080i ATSC signal. What am I missing?
The best part, however, is that the signal will work flawlessly on any systems that can receive a 1080i signal, while letting 1080p monitors display it without flicker, as long as they de-interlace using the weave method only. OK. Now I understand that you're talking about weave as in "bob and weave". But weave de-interlacing is only good for stills and stuff shot on film. When it comes to video sources that scan (as opposed to a film exposure), the bob method is best. And both are the most primitive forms of de-interlacing around! I've got much better than that at my disposal.
It's looking to me like you're talking about 24fps movies sent over 1080i ATSC. I'm not. Most of my ATSC programming was shot at 1080i or 720p. Can you clarify, please? | |
koolman2Premium
join:2002-10-01
Anchorage, AK
1 edit | In a 1080i picture, you can have, say, 60 fields per second. Each field represents a different temporal period, 1/60 s from the previous field. Take a 1080i signal, and sample every two fields from the same temporal period, and you end up with a full 1080p signal at 30 frames per second. Granted, most sets that de-interlace basically average the fields out so this wouldn't work well, but it is very much possible.
Oh, and by weave, I mean that the set takes both fields and displays them at the same time, creating what is commonly referred to as the comb artifact.
--
There's no place like ::1. | |
Time4aNAPPremium
join:2007-04-09
Des Plaines, IL | said by koolman2:In a 1080i picture, you can have, say, 60 fields per second. Each field represents a different temporal period, 1/60 s from the previous field. Take a 1080i signal, and sample every two fields from the same temporal period, and you end up with a full 1080p signal at 30 frames per second. If each field has a different time period ("temporal period" is redundant), then precisely how do you propose getting two different ones from the same time period of time? Quite a paradox, that. And if you use the same field twice, that's line doubling, which you have already expressed your disdain for. I don't see a way out of this one.
Oh, and by weave, I mean that the set takes both fields and displays them at the same time, creating what is commonly referred to as the comb artifact. Well...I might be just some dumb broadcast TV engineer in the #3 market, but I do believe that my leg is being pulled. I'll admit that it has been some time since I got my 1st Class R/T license (since merged into General Class), but I do remember a thing or two about artifacts, comb filters and raster images. I was among the first users of the very first color-under decks. I've seen literally years worth of dot crawl. I remember when 8-bit time base correctors were the best available. I don't even want to think about how many times I've sat at a CCU, registering 3-tube color cameras. Yes, I know a few things about artifacts, namely that they are not a Good Thing.
Dude, you're just getting around to material that I discussed several hours ago. Apparently you didn't notice that.
A bit of advice: If you don't know what you're talking about, don't advertise it.  | |
koolman2Premium
join:2002-10-01
Anchorage, AK
1 edit | No, you're just not getting it. I'll try to make it as simple as I can, but after this I give up.
You have six samples of time, or frames. Each frame represents 1/60 s of time. Resolution is 1920x1080
Each frame is a non-interlaced (progressive) image.
When encoded and sent as MPEG2 over an ATSC signal, which only supports up to 1080i at 60 fields per second, the picture must (obviously) be stripped of some information to get down to the 540 lines per field. Since each field represents 1/60 s, half of the information is lost.
As you are well aware, most of the time, the information from one full frame to the next doesn't differ often, except in motion (duh).
If we delete every other (original) frame so that we now only have three, but we still broadcast at 60 fields per second, we can sample the same frame twice (odd lines first, even second) and encode them and transmit as ATSC. The signal now contains a full frame every 1/30 s, and therefore is now a progressive signal. Basically, instead of deleting half of the lines in the image, delete half of the images.
I know what I'm talking about, but it's quite difficult to explain. Please refrain from insulting my intelligence. Thanks.
--
There's no place like ::1. | |
intellerSociopaths always win.
join:2003-12-08
Tulsa, OK Reviews:
 ·Cingular Wireless
| reply to Time4aNAP
i'm sorry, but National Geographic HD looks like a billion times better in HD than the regular channel. And I guess you've never seen Planet Earth in HD. Why would I want to take things shot in HD and watch them in SD? lame excuse.
Most local content isn't in HD, so the antenna is useless. And the national network stuff that is in HD does not look discernable on cable versus antenna.
The only thing here is you gain is some free channels. Worth about .10 cents each. | |
|
