The Clicker -- Why are there 18 standards for HDTV?

Remember how a few weeks ago we said we were looking for new feature columnists? Well, we're happy to introduce The Clicker, a new weekly column from Stephen Speicher about something we all can relate to: television.

Hello and welcome to "The Clicker," Engadget's weekly wandering into the granddaddy of all gadgets – the television.

Have a seat on the couch. Kick back, relax. Just remember the rules: keep your shoes off the coffee table and keep your grubby little hands off my remote. Hold on; that sounded a bit hostile. You'll have to forgive me. I get a little possessive of my remote. Don't worry – I am currently seeing a therapist about this. Well… this and my fits of blind rage upon discovering that CSI has been deleted from the TiVo in order to make room for Emeril Lagasse!

Besides, I%uFFFDm sure that you, as Engadget readers, can understand the Zen-like relationship that a man has with both his remote control and his TiVo. If you%uFFFDre anything like me, you%uFFFDve learned to scan through the channels with the best of them. You too have developed a Jedi-like ability to quickly skip over Lifetime, Oxygen, and The Hallmark Channel while spending a little more time on ESPN and the Sci-Fi Channel. Basically, your hand feels naked without the remote.

But I digress.

Having spent some time in the cable TV world, I%uFFFDm often asked questions about television, HDTV, cable, etc. %uFFFDThe Clicker%uFFFD is my weekly opportunity to answer these questions. If you too have a question, email me at [e-mail].

This week%uFFFDs question comes from Bill Jordon. He asks, %uFFFDWhy are there 18 different standards for HDTV? Why do some stations (like ESPN-HD) use 720p and other stations (like HBOHD) use 1080i?%uFFFD

First, to be technical, there are eighteen different %uFFFDATSC DTV (digital television) formats%uFFFD of which only six are actually High-Definition. Of the six HDTV formats only two are used frequently, 720p and 1080i. That doesn%uFFFDt really answer the question, but it narrows the field down a bit and gives us something to work with.

The answer comes down to what type of content the broadcaster is looking to optimize. We all know that 1080i has the higher resolution, so why bother offering another format like 720p? While it%uFFFDs true that 1080i has a greater number of pixels (1920 x 1080 vs. 1280 x 720), 720 has two things working to its advantage. First, 720p is a progressive signal. Second, 720p is 60 fps (frames per second). 1080i, on the other hand, is interlaced and 30 fps (60 fields per second).

Where does this matter? It matters for fast movement (e.g. sports). Let%uFFFDs look at an example using both 720p and 1080i:

Suppose that we have a tennis ball moving across the screen for 1 second. A broadcast in 720p is going to show 60 complete images of the tennis ball. Think of it like an old-fashioned flipbook that has 60 pages. Each page will have a complete image and when you quickly flip through the entire book it will give you movement. This is much like how traditional film works (albeit with 24 fps).

If we were to do the same experiment with 1080i, it would be quite different. Unlike progressive formats, which show the whole picture, interlaced material relies on the fact that two half-pictures will generally combine to make one whole picture. As such, 1080i will display the even lines for 1/60th of a second followed by the odd lines for 1/60th of second. If we return to the flipbook example, we can see that the book will still have 60 pages but each page will look a little like we%uFFFDre looking through mini-blinds. Of course, when it%uFFFDs sped up it doesn%uFFFDt look like this. A combination of the display (afterglow) and the mind combine to complete the picture.

%uFFFDBut can%uFFFDt you de-interlace a 1080i signal and have the best of both worlds?%uFFFD (De-interlacing is the process of converting an interlaced signal into a progressive signal by combining the even lines and the odd lines to form one solid picture) Yes, but even in the best case you are only getting 30 fps (half the frames of 720p). In the worst case, the even lines and the odd lines don%uFFFDt quite match up. For instance, assume that the camera is capturing half the picture every 1/60th of a second. In that case, it%uFFFDs possible that the ball has moved enough in that short amount of time that the odd lines don%uFFFDt align with the even lines.

In either case, 720p has the potential to deliver a smoother, more stable picture when dealing with fast motion.

It%uFFFDs easy to see why ESPN-HD chose 720p as its standard. Likewise, as ABC and ESPN are owned by the same parent company, one can see why ABC wanted to be inline with its sister network.

%uFFFDSo, if 720p delivers a smoother picture, why not just use it?%uFFFD The answer is resolution. 1080i has many more pixels and often you don%uFFFDt need the extra frames. The majority of the content being shown today was first shot on film. Most TV dramas and nearly all movies start their lives as film. Since film is 24fps, 1080i%uFFFDs 30 fps is more than enough to capture all the frames. The result is that broadcasters who feel that film-based material is their bread and butter will often choose 1080i.

There are, of course, other arguments for each of the technologies (e.g. bandwidth, remote cameras, matching digital TVs, etc.), and, like any good format war, proponents on each side view their side as the only side.

Until next week, save my seat!

[dreampc @ Dec 19th 2005 12:10AM]

Welcome aboard... Why are there so many standards... and specifically when tv stations broadcast SD, and then at 720p or 1080i....

[Walter @ Dec 19th 2005 12:10AM]

Good stuff... explained clearly.

Thanks.

[Balzac2m @ Dec 19th 2005 12:10AM]

Hell, I don't understand why there is no 1080p in use.
Interlaced has obviusly no advantages, but 720p is just... not enough resolution.
Is it just a bandwidth problem? It turns this whole HDTV-Stuff into a joke, i want 1080p (for home use, I know that you get it as a pro, but this is something that doensn't help as its broadcasted in low-res).

Hopefully some day they will make up their mind and give us something useful

[illdefined @ Dec 19th 2005 12:10AM]

good analogies and straight info.

what happens with conversions? do 1080i signals converted down to 720p still play at 30fps? whattabout 720p signals converted up, does their framerate half?

thanks.

[Chris Heinonen @ Dec 19th 2005 12:10AM]

Problems with 1080p are, I believe, that it takes a ton of bandwidth, and that when the HDTV standards were drawn up, there was really nothing out there that could support 1080p. Only this year are we starting to get incredibly expensive LCD and DLP screens that can do 1080p, but no tube or plasma based sets that can do it. I think 1080p would be the better standard for things like HD-DVD, but they are going to go with 1080i as well it seems.

[RyTec @ Dec 19th 2005 12:10AM]

Welcome. Good work..

[edward @ Dec 19th 2005 12:10AM]

Actually, just get one of these guys (http://www.crutchfield.com/S-sNpNDH6uAi4/cgi-bin/ProdView.asp?g=153650&I=284LC45GD6) and you'll have a 1080p LCD. For whenever people get their act together and start broadcasting at that level...

For the record, you can find one as low as 5 grand on the internets if you look hard enough.

[Catmull Rom @ Dec 19th 2005 12:10AM]

Yes, 720P can run at 60fps, but no broadcaster actually sends out 60fps progressive signals, and I've yet to see even a ridiculously high-end consumer TV be able to display 60P either. It always ends up at 720P 30fps, and I doubt they interpolate in the lost 30fps either.

Ideally 1080P running at 24fps is best IMHO, but it would still need to be bumped up to 30fps via your TV or tuner in the end to deal with the 60hz power cycling of North America. (With lights running at 60Hz a 24P TV shows terrible flicker.)

It took us 50 years to update our TV system, HD was originally supposed to be 1080 (based on NHK specs who invented it) so why are we crapping it back down to 720?

[edward @ Dec 19th 2005 12:10AM]

That 5 grand will get you 46"...which is more than enough for most people.

[Joseph Holmes @ Dec 19th 2005 12:10AM]

Good clear writing. I'm looking forward to future installments (especially as I shop for a HD TV)...

[[sinz] @ Dec 19th 2005 12:10AM]

"Yes, 720P can run at 60fps, but no broadcaster actually sends out 60fps progressive signals, and I've yet to see even a ridiculously high-end consumer TV be able to display 60P either."

This is nonsense. Several broadcasters (i.e. Fox and ESPN) do indeed broadcast 720p at 60fps and if you haven't seen a TV that can display 60P then where the hell do you shop? Quite simply, you've no idea what you're talking about. If you don't believe it, I highly suggest you browse over to www.avsforum.com or www.doom9.org and do some reading.

[Seth @ Dec 19th 2005 12:10AM]

1080p is the holy grail, but right now no one even produces a camera capable of capturing this kind of feed. Most of the broadcasters currently betting on 720p (ABC, Disney Channel, ESPN, Fox) will have to upgrade all of their equipment when 1080p rolls out, while other broadcasters have the assurances of Sony (who sells most of the 1080i gear) that their upgrade will be relatively painless.

[samu @ Dec 19th 2005 12:10AM]

nice. this is a good addition to engadget!

i don't actually know anyone who personally owns a DTV able to receive HDTV. Not true, i know 1 but they still don't use HDTV. mmmm. When these sets get to be 300 dollars then we'll talk.

[erik @ Dec 19th 2005 12:10AM]

I forget their name, but the major DBS netwrork in europe is making the HD move-right to 1080p!

[Botond @ Dec 19th 2005 12:10AM]

I have a question about ESPN.. when i watch it on my friends plasma, why does it have the black vertical bars on both sides? ESPN made them nicer with a logo saying HD, but is 720p a 4:3 AR?I didnt think so.. its a 16:9 plasma HDTV, and im really confused about the vertical bars. CBS HD is the same way, while TNT HD is the full 16:9 without stretch. Lemme know..

[[sinz] @ Dec 19th 2005 12:10AM]

Botond: That is because they do not film all events in wide screen formats or with HD cameras so they simply broadcast the same programming on their HD stations as they would on their normal DTV or Analog stations but in order to make the programming suitable for HD broadcast it must be in an HD resolution. The only options then are to crop off part of the bottom and top of the picture, or add the side borders you speak of. As cropping might cut out important parts of the picture the addition of borders is the accepted method.

[Richard @ Dec 19th 2005 12:10AM]

Whoever chose interlaced was braindead.

To display on anything but a CRT it needs to be deinterlaced, which results in artfacts. Interlacing has no place outside of 1930s era broadcasting technology.

As noone is buying CRTs these days, they would be better off sending 1080P at 24fps - LCDs and plasmas dont have refresh issues, and scanning an image multiple times via interlacing is not dificult for the remaining CRT users, it happens inside every DVD player that has to playback film onto a ntsc or pal TV

[Stuart @ Dec 19th 2005 12:10AM]

#12 wrote "1080p is the holy grail, but right now no one even produces a camera capable of capturing this kind of feed"

really? I disagree.

Stuart

[sm @ Dec 19th 2005 12:10AM]

"The result is that broadcasters who feel that film-based material is their bread and butter will often choose 1080i."

Actually it's quite the opposite. Film-based material, because it is acquired in a progressive fashion, is most often kept in a progressive-frame format: 1920x1080, 24p. The REAL reason there are so many formats is because HD was invented to be the replacement of both film AND standard defintion video as an ACQUISTION format. You can shoot HD, get close to the resolution of 35mm film (nominally 2K); still get the nice, progressive frame rate, and, with a good DP, get close to the same contrast and feeling of film.

The reason there are so many 'standards' is so that the people who are used to shooting film have an easier transition to HD, and the people who are used to shooting video have an easier transition to HD.

HD and its specs are fairly confusing, even to video professionals. And with the advent of 'HD-ready' sets and various cable outlets offering 25Mbps-encoded MPEG2 "HD" streams - what is true 'HD' often gets lost. Not to mention the fact that every Best Buy and 'video' website now has a "HD guru" who read a few articles and now thinks he knows more than he does.

[Michael @ Dec 19th 2005 12:10AM]

I'm a professional TV engineer.

Let me clear up about 1080p.

The idea behind 1080 line progressive, 24 frames per second is for post-production, not viewing at home.

If a show is made at 1080p 24f, it makes it much easier to convert to the various formats that you might distribute your show in.

The world is split into PAL (50 frames/s) and NTSC (60 frames/s). If you post in one format and convert to the other, it invariably looks crappy, mainly due to the frame interpolation (50 60). If you start at 24 frames, as we have done for years with films, the conversions are much cleaner.

In the HD world, the broadcasters are split between 720p and 1080i. If you are a content producer you want to make your stuff look as good as possible in either format, 'cause you don't always know who your customer will be. Being at 1080p makes the best downconvert to both HD formats.

There will be no change to Table 3, 1080p will not become a broadcast standard, so TV facilities will only consider changing the post areas, not the on-air playback systems.

On another note, here is the history of HDTV from my point of view: http://www.pusateri.org/cruft/docs/hdtvhistory.html

[The Jeremy @ Dec 19th 2005 12:10AM]

PAL is not 50fps, it is 24fps at the supposed 625 lines of resolution. NTSC is 30fps, not 60fps and a top of 525 lines (although 480p is the best one can truly get out of it). Take all that into account, and that is why British television programs often look washed out on American sets. I want 1080p. I hope Blu-Ray supports and masters its content in 1080p because by the time Blu-Ray hits the market at a reasonable consumer price, most of the LCD, tube, and Plasma screens will support it. Then the satellite companies could use 1080p as yet another way to compete with the HD cable offerings. In reality, 1080i and 1080p both fall short of what Zenith and AT&T Bell Labs had been working on in the mid-nineties in terms of HDTV. They had a 2000x2000 standard they were working on. 1080i and 1080p still falls flat in comparison with a virgin 35mm print. HD would have to be at 4,000 lines of resolution to match a good 35mm stock. Just imagine the resolution needed to equal 70mm. It will be a long time before you can have a definitive copy of "The Abyss" for home consumption.

[Gabriel @ Dec 19th 2005 12:10AM]

Screw you guys, in my little fantasy world I come home at night and turn on my JVC 4K2K 4096x2160 projector ( http://translate.google.com/translate?u=http%3A%2F%2Fwww.jvc-victor.co.jp%2Fpress%2F2004%2F4k2k_d-ila.html&langpair=ja%7Cen&hl=en&newwindow=1&safe=off&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools ) and watch movies encoded in MPEG-4 on a Blu-ray disc.

[Nkp @ Dec 19th 2005 12:10AM]

"PAL is not 50fps, it is 24fps at the supposed 625 lines of resolution."
No, PAL is 50 fields per second, or 25 interlaced frames per second, with the resolution of 625 split between 576 lines of visible picture, and the rest for stuff like TV-Text.

[Adam @ Dec 19th 2005 12:10AM]

I, too, am a professional TV Engineer/Producer. #20 is almost perfectly bang on. I disagree with the idea that 1080p will NEVER become a distribution format. I also have exposure to North America's most advanced digital cable network (Rogers Cable, Canada - at least last i heard) as I do some work for the local cable station.

I can tell you that service providers, and content producers, who have converted to HD have a LOT of capital invested. Visit http://bssc.sel.sony.com/ and see for yourself. Keep in mind that's a small look at the equipment required to run a station. Its also a damn fat data pig. Mind you, no one could have imagined what we do now, 10 years ago. Add cable headend encoders and digital terminals... If change happens its going to take long time.

As for #8:
Ideally 1080P running at 24fps is best IMHO, but it would still need to be bumped up to 30fps via your TV or tuner in the end to deal with the 60hz power cycling of North America. (With lights running at 60Hz a 24P TV shows terrible flicker.)

Umm... Convert to DC (required for the electronics anyway) and invert back locked to onboard clock to drive gun/lamp? We're not in 1945 anymore. Don't be a wuss.

I was watching various types of content on one of our new Sony Professional monitors that scans hidef Tuesday... Sexiest video I've ever seen, period. Long live the tube!

[Infinite @ Dec 19th 2005 12:10AM]

Be careful when you are saying "I want 1080p", if you get 1080 24/30p, it would be awful for displaying watchable video from a HD computer source since it would be outputting at 1920 X 1080/60 fps.

When you say "I want 1080p", you should really be saying "I want 1080/60p" to be able to use it with a computer at full resolution/frame rate.

[Dan @ Dec 19th 2005 12:10AM]

A PC with a $175 ATI HDTV video card - interesting...
http://www.ati.com/products/hdtvwonder/index.html
Supported HDTV Resolutions are:
480i and 480p:
640x480 > 4:3
720x480 > 4:3
848x480 > 16:9
720p:
960x720 > 4:3
1280x720 > 16:9
1080i:
1920x1080 > 16:9
http://www.ati.com/support/infobase/4050.html#virtual

[popeye @ Dec 19th 2005 12:10AM]

#24 is spot on, long live the tube!!! Plasma/LCD/ETC is for the visually impared.

And if poster #8 did convert to DC his lights would last far longer as well...

[John Laur @ Dec 19th 2005 12:10AM]

For what it's worth (and excuse mixing some terminology for clarity), you don't have to deinterlace 30i video to 30p. A bob deinterlacer will deinterlace each field to a full frame so you deinterlace 1080i/30 into 1080p/60 if you want to. A good external scalar can do this for you if your TV does not (and if you have a monitor that will let you look at it). I'm suprised as technically correct as the author of this piece was that he did not mention that there's more than one way to skin the cat with deinterlacing.

In fact, if you had really good source (ie if it was shot at 1080p/60 and then interlaced for broadcast) you could deinterlace it to half the vertical resolution at 60p giving you 1920x540.

Good bob deinterlacers have to do a little more than just flip the fields, though.. There's actually more to it, but you get the idea...

[Klaus Grosser @ Dec 19th 2005 12:10AM]

Be realistic, I doubt we will see 1080 before long, simply because there are no displays largely and economically available for it yet. What's the use in having 1080p content if your display (Plasma, TFT you name it) is nailed down to 480, 600 or in best case 720/768 hardware lines, where does that plus in resolution go when the picture is interpolated?

[geoff pedder @ Dec 19th 2005 12:10AM]

I don't really get why standards are still so different across the world. My TV here in the UK can display NTSC just as easily as PAL so the reliance on AC power frequency for refresh speeds is no longer a problem. Why not use a standard frame rate such as 24p for movie content and 48p for sports etc, at 1080? It looks like PAL viewers will still have to watch movies sped up by 4% and NTSC viewers will still be watching 3/2 pulldown converted content.

[joel @ Dec 19th 2005 12:10AM]

"what happens with conversions? do 1080i signals converted down to 720p still play at 30fps? whattabout 720p signals converted up, does their framerate half?"

can someone answer this? I was wondering the same thing.

[Slippy @ Dec 19th 2005 12:10AM]

Nice. I never knew that, and according to GI Joe, "knowing is half the battle".

[Tom Taborda @ Dec 19th 2005 12:10AM]

Frankly: I don't care about broadcasting, for it is marring the development of a perfect Digital Home Cinema (DHC) system.

I want the best domestic Video+Audio combination. Something au pair with Digital Cinema (the one George Lucas used to shot 'Star Wars' that could be fully enjoyed on selected Digital Theaters around the world).

And so I want the BEST movie media (a 60GB HD-DVD; blue-ray, holographic? 12" LP sized disc? whatever). I want to watch movies at home.

Broadcasting, with it's bandwidth limitations is an aftertought. Once my DHC system is set, I could buy the HDTV-Tuner as a add-on (sattelite dish, fiber-optic cable). Since it's quality is inferior to my DHC, my system is able to cope with Broadcasting inferior quality. Perfect for the World Series, Jeopardy, Discovery Channel etc...

When Broadcasting standards change to a better one, just change the HDTV-Tuner.

[Viv @ Dec 19th 2005 12:10AM]

Major European broadcastors are launching HDTV this year, on satellite, cable, DSL and DTV probably in MPEG-4, 1080i format... 720p is not really an option... given that PAL is much better than NTSC, the gap between SD and HD is smaller in Europe than in the NTSC world...

[Viv @ Dec 19th 2005 12:10AM]

Major European broadcastors are launching HDTV this year, on satellite, cable, DSL and DTV probably in MPEG-4, 1080i format... 720p is not really an option... given that PAL is much better than NTSC, the gap between SD and HD is smaller in Europe than in the NTSC world...

[Bernard Hides @ Dec 19th 2005 12:10AM]

I need some advice. I'm relocating to Australia, I know there is a Difference in the normal TV systems NTSC and PAL, also I know the power supply is 220/240 compared to 110 here, I would need a power converter, but is there a difference between the HD systems, are they both 1080, and are they compatable? Has the NTSC and PAL systems in HD 1080 become one? Is it possible to take a CRT tv set that is HD compatable here, work in Australia on there HD cable network.