High Definition Television
by Dawn McGatney
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Kaluza Solving Einstein In 5-D (16:9, 1080p) And Watching "Maxwell's Wonderful Equations" Fall Out. |
And your sons and your daughters shall prophecy,
Your old men shall dream dreams,
Your young men shall see visions;- JOEL 3:1
There are more things in Heaven and Earth, Horatio,
Than are dreamt of in your philosophy.- HAMLET 1:5
This film has been modified from its original version.
It has been formatted to fit your screen.- ANALOG TV: Hollywood Movie
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Hi-
I'm DAwn's dog Wolf... A gift to DAwn from some jilleroo I was... way,
way back... that year when she spent the whole summer out on the sheep
station, back when I was just a magical pup, racing along with higher-dimensional
roos.
SO... Why am I writing these pages on what's "really up" with High Definition
TV?
First, as always, because DAwn asked me to... And sometimes, it's VERY
difficult to say "NO" to this woman. And so this article will be your dog Wolf's
"Opus #5".
Second, because it seems to me that the better folks understand just how HD
and an HDTV receiver REALLY work, the better they can make a decision on
selecting one, the better their long-term home networking solutions will be (as in
FiOS, for example), and the better to learn about networking. (You will definitely
understand why color TV looks better on digital TV, and why even non-HD digital
programs look better on many flat panel HDTV sets.)
Third... because there is SOOO much MIS-INFORMATION on HD floating around,
especially on the Web, but even in reputable magazines and well regarded newspapers.
Right. So what makes your dog Wolf the ultimate authority on HD?
In all modesty (oh yeah), I have been explaining things to folks on the Net
for ten years now, beginning with the Internet itself; and your dog Wolf has a fairly
good idea of how to separate the data packets from the digital background noise. And
whenever we come to a fork in the road, we'll simply ring up the HDTV set manufacturer
or the cable or satellite or FiOS engineers... even TV broadcast engineers who are
actually doing this high definition broadcasting (even if one or two might insist that
we sign a non-disclosure agreement or some such).
But fifth (there is no fourth), and foremost, because Precise Networking Solutions
(aka "The Boss") in Maryland and DC has been getting so many questions from its own
clients asking about HD and HDTV sets, and what they have to do to prepare for the end
of analog TV broadcasts.
"Wolf..." PNS demanded of us, "Wolf, what are you here for today, Wolf?"
"To sing opera", we replied. (No, sorry, wrong script, writers' strike and such.)
"Wolf, write one of your Dog Wolf© articles for us, write about
High Definition Television (HD), as it exists in the early months of 2008, and
write so that everyone who reads it can understand it... but don't talk down to
folks; our clients are not dodos; write for us something that we can refer our
own clients to... Oh,and be certain that it's 100% accurate."
So when we're done, perhaps "The Boss" will say to your dog Wolf, "So you work at Car
Phone Warehouse, chasing higher-dimensional roos... and you wrote THAT... we weren't
expecting THAT... your Opus #5 is a complete breath of fresh air... we thought you were
absolutely fantastic." Ah, we'll see, we'll see.
(Wolf? What's a bilbie? "Bilbies are marsupial omnivores," we reply; "they are
members of the Peramelemorphia biological order and the largest of the bandicoots."
(Just doing some mental calisthenics to loosen the muscles of our mind a bit before
we REALLY get down to business.) )
And to be honest, I now am curious myself to see exactly what is inside that
Magical Mystery Tour named High Definition TV, the things that are taking up so
much space (and so many dollars) in the Big Box Stores... the devices that connect
us to the magic of digital HD... this thing that folks love to debate and argue over
at dinner parties... and so this is a tour we'll all be taking together... Dr. Steve
will translate things like "Discrete Cosine Transforms" for us; and DAwn will translate
my Aussie mutterings into simple, mainly English text.)
At the outset (before Halloween of 2008 arrives)... let me state
that, like some fine wine, all my dog Wolf pages improve with age and with
your feedback and help and advice... from all the knowledgeable gurus out there
in cyberspace. Cool. Very cool... The sharing ethic of the Net, yet once again
at work.
And also at the outset, let me state for the record... anyone who tells
you that you'll easily pass your FCC first-class radiotelephone exam after
reading your dog Wolf's article here is simply pulling your leg. This page
is NOT intended to be a guide for folks planning on a first-class radiotelephone
exam at the FCC (though you should make it into the FCC's "Digital TV Deputy Program"
without any trouble).
BUT... A thorough dicussion of digital television broadcast theory is
beyond the scope of this article. Yes, I WILL discuss the fundamentals of
digital television broadcasting. And yes, the information that I'll be giving
you WILL cover digital television transmission principles in greater detail
than is required for passing the FCC's first-class radiotelephone licensing
examination. But, er, hmmm... well, we'll see.
(We started this article in July of 2007, it's now December 2007; we're
waiting for a call from XXXX (name of TV Station) to clear up some esoterica;
and with luck and a favourable wind, we should be finished with "Opus #5" on
or about 23 January 2008.)
So, this having been said, let the adventure begin. And as always, I refuse
to talk down to folks... these pages are NOT "HD For Dodos". No, they're
HD for YOU, our intelligent readers out there. ¿Está claro? (The remainder of
this article is nonessential reading. You should skip it, unless you are curious
about High Definition TV and Analog TV and Digital TV and...)
And Happy Halloween. (It comes on October 31st, you know.)
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Especially worth noting--> In the opinion of Precise Networking Solutions, much of the public is not aware that
things are happening in February 2009 that could affect their TV reception; others are aware that something is happening,
but are relying on the saleman at a Big Box Store for information ("information" generally of the Some electronics stores, especially upscale stores like Tweeters, will not be carrying government subsidized ($40 coupon) boxes. (Every converter box sold is a potential HDTV set not sold; some converter boxes are selling as low as $39.99, which means that you pay, with the coupon, the state sales tax only (except in Delaware and Oregon, where you get the box for free... no state tax.) ) THE NEXT TO BOTTOM LINE---> HDTV manufacturers don't want TV viewers to buy a government-subsidized converter box; they want folks to buy a new HDTV set. THE BOTTOM LINE---> The FCC has not done a great job yet of educating folks in the
US about what is going to happen and when, and what they can do about it. A lot of viewers who receive
According to the 30 January 2008 edition of TVWeek, a study in January 2008 by The Consumers Union found that 36% of people surveyed in December 2007 didn’t know about the transition from analog to digital TV that’s set to take place February 17, 2009. Of those who did know about it, 74% had major misunderstandings concerning what is going to take place. 58% believed that ALL TVs would need a digital converter box to function, and 48% believed that ONLY digital TVs would work after 2009. It's surely time for the FCC to begin running full-page advertisements in popular magazines and newspapers, along with frequent 60 second TV spots explaining in simple English what the options are for each category of viewer... especially the fact that cable and satellite and FiOS customers need do nothing. Congress has allocated a whopping $5 million to the NTIA (an agency of the Dept of Commerce) for efforts to educate consumers on the conversion to digital. Compare this to Britain... when the UK made a switch similar to the US digital conversion, it spent $400 million in education efforts... on a much smaller population, according to Chris Murray, senior counsel at the Consumer's Union, a consumer advocacy organization that publishes the excellent Consumer Reports magazine. However, the TV broadcast industry does have two traveling "road shows" (giant vans) going about the country, visiting county fairs and air shows and such, not to mention over 200 volunteers in a "speakers bureau", explaining to groups (especially the elderly) about the digital conversion and converter boxes. There you go. (Oh, the NTIA is also responsible for keeping cable TV rates "reasonable"; so what... me worry?) (Ok now... raise your hand if you like the idea of a "government certified box" installed in tens of millions of US households. Sorry, just being paranoid.) See now why all of this occurs after the presidential and congressional elections in 2008, and after the new president is inaugurated in 2009, and most importantly, after the Superbowl of 2009? As "Big Brother" says... "Expect The Unexpected."
(What About Canada?---> As of January 2008, 18 Canadian TV stations were broadcasting TV in both analog and digital on pairs of channels; most of these stations were in Ontario. The Canadian Radio-television and Telecommunications Commission (CRTC) has announced that it will force conversion to digital TV by the end of August 2011 (except in remote Canadian areas). )
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In fact, ATSC digital broadcasts (the system of digital TV used in the US) don't even have to be TV programs. They can
be audio only... just sound, no picture. In fact, they can be data only... no picture and no sound. Or
a digital broadcast can be some combination of these three types of elementary streams, all multicast together and
broadcast together on the same transport stream. ATSC Digital TV is broadcast as a stream of MPEG-2 bits called a
"transport stream". We'll dig more deeply into "streams" when we go fishing for MPEG-2... no, sorry, when we talk about
(CAREFUL---> HDTV sets almost always have a 16:9 width to height ratio (called "aspect ratio"). Although HD is ALWAYS displayed on HDTV sets as WIDE (16:9), having a wide 16:9 picture ABSOLUTELY DOES NOT mean that you are watching HD; maybe you are, and maybe you are not. Kan Ya Makan.)
There is a 1967 vintage color TV that had a little red light on it; when tuned to a color broadcast, the red light would
come on (though color is pretty obvious). It might be nice to have the same little red light on HDTV sets when they are
really receiving a High Definition broadcast. But after you actually see a few HD broadcasts on an HDTV set, you will
know when you're watching High Definition (HD) and when you're watching Standard Definition (SD).
If we pause here for a minute to examine "pixels" and "rows" (or "lines") in just slightly more detail, then many of the sections that follow will make a LOT more sense. So we will.
Just like the display on our computer monitors, the picture on an HDTV set is made up of very small squares. Look at the screen of an HDTV set very closely, especially a 50" set or bigger, and you'll see them. They're called pixels (short for "picture elements"). The brightness and color of each tiny square pixel often varies rapidly (30 times per second OR 60 time per second OR whatever), tricking our minds into seeing a MOVING picture.
NOW... usually, ALL of the pixels on the screen DON'T vary from frame to frame (picture to picture). Maybe a cowboy is riding through the scene, under the blue sky; all the bright blue pixels that represent the sky will probably stay bright blue for many, many frames. The sky pixels won't change at all. Hold that thought.
(WHAT'S A FRAME?---> A "FRAME" is a complete picture. The number of pictures captured by the TV camera (or displayed on your digital TV receiver) in ONE SECOND is called the "FRAME RATE". Like... in a movie theatre, there are 24 complete pictures on the screen each second, so the frame rate is 24. Frame rate is the number of complete pictures displayed on your TV set each second. (Yes, we know, there are actually 48 complete pictures on a movie screen every second, but each pair of pictures is identical; this helps reduces flicker and migraines. But the picture on the screen changes at most 24 times per second.)
WHAT IS FLICKER?---> Flicker is a biological thing, not an engineering thing; it's in the eye of the beholder. If the frame rate is too slow, a reasonable percentage of folks will see an annoying flickering. But the TV is not flickering. It's simply that the illusion of motion, conjured up in your visual system, is not being totally fooled into thinking you see true motion. At 10 frames/ second, almost everyone would see horrible flicker. At 100 frames/ second, virtually no one would see flicker. At various frame rates between these two (e.g., 30/ sec), varying percentages of folks would see annoying flicker. Again, it's not a bug in the broadcast or your TV set.)
NOW...
On an HDTV set, there will be anywhere from just under ONE MILLION pixels to just over TWO MILLION very tiny square pixels. (Analog TVs have rectangular "pixels", not square, and technically not even pixels in the digital sense.)
(Don't jump to ANY conclusions from these pixel counts... yet. 1080p (called "Full HD") does have the potential of displaying more of the detail in high definition signals than does 720p. NOTE--> The difference in the ability to display detail is most noticeable 1.) If your set is 50" or bigger; or 2.) if you like to watch TV within a few feet of the screen; otherwise, the difference is subtle. The "p" in 720p means "progressive scanning". Progressive scanning reduces the need to prevent flicker by filtering out fine details, as 1080i must; so the spatial (sharpness) resolution of 720p is much closer to 1080i than the number of scan lines (and pixels) would suggest.)
NOTE--> The old NTSC analog video screens have no true "pixels" that we can use to assign a number to horizontal resolution. (Mainly because pixels on an HDTV are square, and pixels on an NTSC analog set are rectangular.) The analog NTSC sets have a moving "splat" that creates 262½ lines on the screen's phosphors (some are invisible) every 1/60th of a second. Those folks who give you a number for pixels on an analog TV screen are comparing tiny square apples and rectangular oranges. But in the old black and white NTSC analog TVs, horizontal scan lines simply are NOT divided into pixels.
Each pixel on an HDTV receiver is really made up of three "sub-pixels", one red, one green, and one blue. By combining these three "primary additive" colors in various proportions, a single pixel can take on as many as several billion different colors.
IMPORTANT--> The pixels on the screen of an HDTV set are more closely spaced and are smaller compared to
an ordinary, non-HDTV set's screen; and again, HDTV pixels are square, not rectangular..
[A BRIEF JOURNEY INTO VISIOLOGY---> Ever wonder why every color that we can see is some additive combination of red, green, and blue light? DAwn asked her art teacher in K-12 why red, green, and blue just happened to be the primary colors; DAwn was suspended from school, after a few go-rounds. (Nothing new and exciting for DAwn.)
DAwn later asked an undergrad math prof the same question, and he muttered something about Fourier series. (Wrong.) An undergrad physics prof said that it was "the basic nature of light". (Wrong... plus a suspension from his class after DAwn let loose with uncontrollable laughter.) A few years later, the true answer arrived at the graduate level, where DAwn was required to take several classes in human physiology. The correct answer on why red and green and blue are the primary colors for HUMANS has nothing on Earth to do with those particular colors, nor with Fourier series, nor with the nature of light, nor with the color of bandicoot fur.)
The Correct Answer-->
There are two types of receptors in the human eye, rods and cones. Rods are great for low light, and they're most sensitive in the blue-green area; sadly, at night, the sky does not turn blue-green. So anyway, rods are light sensitive (and motion sensitive too), but rods are not great for resolution in low light. Rods are missing from the fovea (the center of our visual field), but they are scattered here and there about the retina... and so they're responsible for peripheral vision and night vision. But if all we had were rods... we'd have NO need for High Definition TV.
At night, the fovea is not sensitive; most of our visual information at night is carried by the rods, especially those in the periphery of our eyes. (When black bear attacks, we want to see him peripherally; we're not especially concerned about receiving a high definition image of his fur.) But it is the cones that carry color information and provide higher resolution. But cones are not very sensitive to light. They're concentrated in the fovea, providing high resolution central daytime vision. Cool. So what about red, green, and blue?
OK... Cones contain three pigments, a blue-sensitive pigment called cyanolabe, a green sensitive pigment called chlorolabe, and a red sensitive pigment (actually most sensitive in the yellow area) called erythrolabe. These three pigments are responsible for our three "primary colors". Folks missing one of these pigments (as well as dogs and most other mammals) are said to have dichromacy... they can match any color they see with a mixture of no more than two pure spectral lights. Normal humans, trichromats, require three pure spectral lights to match all colors in their visual spectrum... called the "three primary colors".
(Three pigments is by no means a maximum across all lifeforms. There is a shrimp species that has 20 different
photoreceptor pigments... and thus has TWENTY primary colors. It is left as an exercise for the student to design
a compatible color TV system suitable for this species of shrimp... that is, compatible between humans and shrimp.)]
NOW... our eyes will not discriminate between one or two million individual pixels. When you pull back a few inches from an HDTV set's screen, all the pixels combine in our visual system to form one crystal clear (moving) picture. (It's exactly the same as using tiny dots of many different colors to create the color comics in the Sunday newspaper. But... the pixels on an HDTV set also give the illusion of movement.)
Two illusions of pixels on an HDTV screen-->
The pixels on an HDTV set's screen are arranged in horizontal lines... HDTV screens display horizontal lines (or rows) of pixels... hundreds and hundreds of lines... and each line is just chock full of pixels. Each horizontal line will have anywhere from about one thousand (720p) to about two thousand (1080i or 1080p) tiny SQUARE pixels of light... points of brightness and color.
How many rows of pixels are there on an HDTV set's screen? 720p tells us there are about 720 rows of pixels; 1080i or 1080p tells us there are about 1080 lines of pixels. The "BEST" HDTV sets mass produced today are the 1080p sets. The "p" tells us that each row of pixels is energized (lit up) PROGRESSIVELY. In other words, progressive means that the display of the the lines progresses from the top to the bottom of the screen in sequential order (far faster than we can see).
In the US, HD programs are transmitted over-the-air in one of two video formats--> 720p or 1080i. Yes, 720p has fewer scanning lines than 1080i, but it has the advantages of "p"... the advantage of progressive scanning--> It is better able to display motion; e.g., football games. Because in a "p" (progressive) system, the WHOLE picture is captured completely at one time. Every line is captured sequentially in the TV camera, from top to bottom. Line 1, line 2, line 3... until the bottom of the picture is reached. And 60 complete pictures are captured every second.
(Actually, some NBC stations during prime-time use a video format of 1080p24 or 1080p30. Your HDTV set gets a message from "metadata" broadcast with these frames to convert them to 1080i30 in the decoding process. Some sets listen, some don't.)
THE BOTTOM LINE---> 1080i must blur its picture slightly to prevent "twitter", where
something appears on one horizontal line in only one of the two fields making up a frame. Still, 1080i has better
spatial resolution than 720p... it produces a sharper picture when the image is stationary or barely moving, because
it uses more scanning lines. 720p has better temporal resolution... it excels at reproducing rapidly moving objects
without blurring, because of its full-frame progressive scanning, which never chops up a frame. (Of course, all of this
may be meaningless if the broadcaster or cable provider over-compresses the video data stream.)
RESOLUTION CONFUSION---> Nothing (and we mean NOTHING) appears so often in HDTV articles and advertisements, and is used incorrectly by so many folks, as "video formats". More people are confused by format codes than by their cholesterol HDL and LDL scores. Your dog Wolf has learned that when something seems this confusing, it's almost always very simple... so don't let the salesman in the Big Box Store work with all his might to confuse you on the subject of formats... just to make a sale.
FIRST---> Video formats (720p, 1080i, 1080p, etc) are used in two different ways when one is chatting about HD and non-HD broadcasts-->
The two are often different. Format Codes apply to both analog and digital broadcasts and to analog and digital TV sets.
We specify the Format Code with which a TV PICTURE is transmitted, and the way that a TV PICTURE is displayed on our TV receivers, by answering THREE questions-->
As an example, let's see what the Format Code is for the good old NTSC analog broadcast system. This is a good example because, unlike the new digital formats, the old analog TV signal is transmitted in only one way; and the picture is transmitted with the same resolution that it is displayed by the TV set.
FIRST--> We know that 480 lines or rows of video are broadcast for each picture (or "frame"); so our format code begins with the number 480 (the resolution).
SECOND--> To answer the question of interlaced or progressive, we simply ask if all 480 lines are transmitted at one time from the TV camera, top to bottom... 1, 2, 3, ..., 479, 480. Because that IS one way to do it, send all of the 480 lines progressively from the top to bottom... send them all at once. If that's how our 480 lines are sent, progressively, then our second value is a "p". "p" stands for "progressive"... and we'd now have "480p" for our Format Code.
BUT... there is also another way that we can send these 480 lines that eventually will make up the picture on our TV set; we also can send them interlaced. Interlaced means that half the lines (240 lines), every other line, the odd lines, are sent from the TV camera first... 1, 3, 5, 7, ..., 477, 479. And then, 1/60th of a second later in this example, the even lines scanning the image in the TV camera are transmitted... 2, 4, 6, 8, ..., 478, 480. If this were the case, we'd now have 480i for our format code.
It turns out that, to reduce flicker in the old NTSC TV sets when NTSC standards were being developed, the old analog NTSC system sends those 480 lines interlaced... first the odd scanning lines trace across the image in the analog TV cameras; then "black" is transmitted for an instant; and then the even scanning lines from the TV camera trace across the image in an "interlaced" fashion... so we DO put an "i" after the 480... meaning that frames (complete pictures) are broadcast with 480 lines, but first the odd lines are sent, and then the even lines are sent. We specify 480 rows with "interlaced" transmission as 480i.
And THIRD-->, we want to indicate how many frames (complete pictures) are sent per second...
It's important that we understand that 480i can be a "family" of resolutions. Each family "member" refreshes the whole picture on the screen (the frame) a different number of times per second. In the US, under the old NTSC analog 480i standard, 30 complete pictures are sent from the TV station to our TV sets each second; i.e., 30 frames/sec. And so we specify our complete Format Code as 480i30. If we are sure there is no room for ambiguity, and that everyone will know that 30 complete frames are being sent each second, we can take a short-cut and specify our Format Code as 480i.
Let's go over this for a moment, because it is very important. A Format Code written as 480i can mean TWO different things-->
Fast forward now to the present and to HD broadcasts. There are two formats used for HD broadcasts in the US under the new digital ATSC standards. The first is 720p60. (720 lines (rows) are in each complete picture; p = progressive (not interlaced), the whole picture is sent from top to bottom at once; and 60 complete frames (pictures) are sent each second to our HDTV sets.) Because this Format Code 720p60 is so common today, it is often simply written as 720p, and we assume that 60 complete frames will be sent from the TV transmitter to our HDTV set every second.
The second format that is used for HD broadcasts in the US is 1080i30. 1080 rows in each picture;
i = interlaced, the 1080 lines are sent as 540 odd lines and then 540 even lines; and 30 complete frames
are broadcast every second. Because this resolution is also so common today, it is often simply written as 1080i,
and we assume that 30 complete pictures will be sent from the TV transmitter every second. ¿Está claro? Great.
| Short-Cuts |
Families |
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| Digital Transmission Formats |
720p--> 720p60 1080i--> 1080i30 |
No Transmission Families |
| Display Formats |
Example 480i--> 480i30 |
Example 1080p--> 1080p60, 1080p120, 1080p30, 1080p24 |
NOW... currently, there are SIX picture (video) formats that ATSC digital has labeled "HD"; but only two of these six formats are used in the US for over-the-air or cable or FiOS or satellite broadcasts)--> 1080i30 and 720p60.
All HDTV sets will work fine with either of these two HD formats, 720p or 1080i. ABC sends out its HD programming in 720p (720p60), NBC sends out its broadcasts in 1080i (1080i30), no problems. They both look GREAT on good HDTV sets. (Ok, granted, one of the two formats may look slightly better on a given HDTV set; try to get the Big Box Store to show you more than one HD broadcast input on the HDTV set you are thinking of purchasing.)
The newer and rather expensive HDTV sets can display what is called the "full high definition" format in
advertisements--> 1080p60. 1080p60 is NOT one of the ATSC 18 digital video formats, and it cannot be
broadcast
A CRITICAL POINT---> While HD is only transmitted (at present) at 720p and 1080i,
your HDTV set will convert the transmission format to the set's native format. Thus if you are watching HD at 720p on
ESPN or ABC on a 1080p HDTV set, your HDTV set will convert
But currently (2008), 1080p60 HD video signals are available only from the new generation of Blu-ray Disc DVD
players. Broadcasting 1080p60
| FORMAT CODE (SHORT-CUT) |
LINES PER FRAME |
INTERLACED OR PROGRESSIVE |
FRAMES PER SECOND |
BROADCAST OVER-THE- AIR |
| 480i | 480 | Interlaced | 30 | Yes (Analog/ Digital) |
| 720p | 720 | Progressive | 60 | Yes (Digital) |
| 1080i | 1080 | Interlaced | 30 | Yes (Digital) |
| 1080p | 1080 | Progressive | 60 | No |
FIRST... THE CARDINAL RULE---> No matter WHAT the display format of your HDTV set... 1080i or 720p or 1080p, etc... your HDTV set will convert any format that it can receive... 480i30 or 480p30 or 720p60 or 1080i30 or 1080p60, and so on, TO ITS NATIVE DISPLAY FORMAT.
For example--> a 720p60 Panasonic HDTV set will convert 480i30 and 480p30 and 720p60 and 1080i30 and 1080p60 ALL to--> 720p60, the native resolution of the HDTV set. How well the HDTV set does this conversion is a major factor in how good the picture on the HDTV set looks; better, more expensive sets, do the conversion better. Some lower price "off-brand" HDTV sets can do an AWFUL job of conversion; they look awful. (See "No Free Lunch" theorem.)
Some HDTV sets do the conversion so well that an analog 480i30 broadcast looks better on them than on an analog set (and the wide screen and better optical qualities of LCD and plasma flat-screen sets don't hurt either). OK... Now 1080p60/120.
Next, the interest in 120 Hz also has to do with movies.
The problem is that 1080i30 runs at... right... 30 frames per second, and squeezing 24 frames/ second film into 30 frame/ second HD presents problems... because you can't divide 24 into 30 without filling in the gaps with "something". And that "something" causes the film to "judder" in 1080i30 with a jerky-looking phenomenon that's really noticeable when the camera pans. The conversion from 24 frames (film) to 30 frames/ second (TV) is often called 3:2 pulldown.
Your dog Wolf is betting that you are now really curious as to what 3:2 pulldown might be, since the term arises so often in HD. It's the process used to convert 24 frames per second from film into 29.97 frames per second interlaced TV video. (The term "pulldown" refers to the mechanical action of the "pulldown gate" in a telecine (device to convert film frames into video frames) that "pulls down" each film frame into the imaging area.
A little more info--> Movies are shot at 24 frames per second. Why? When full-length commercial sound movies ("talkies") were introduced in October 1927, some constant speed was required for the "sound head". 24 frames per second was chosen because it was the slowest (and thus cheapest) speed which allowed for minimally acceptable sound quality.
Moving on to the FCC's approval of NTSC TV standards, since May 1941, NTSC TV pictures have been displayed at 30 frames per second (for a complete 480 line frame). Is 24 = 30? Nope, not in any number base. SO... Since these numbers are different, a convoluted conversion is needed to make movies viewable on TV.
The "convoluted conversion" process is what we call "3:2 pulldown"; it shows one movie frame three times and then the next movie frame two times. Although the arithmetic is interesting, it all boils down to repeating some movie frames the right number of times so that they synchronize with the television's pictures.
YES... 3:2 pulldown works, but it's kind of wasteful. Every time you repeat a movie frame, you are needlessly transmitting data, and data takes up space. Would it not be better if we sent the data for a movie just once? This is why the new ATSC digital standard allows the transmission of 24 frames per second, as well as NTSC TV's 30 frames per second. (However, there are no digital 24 frame/ second transmissions in the US.)
NOW... The 3:2 pulldown process has two parts-->
- The slowing of the film frame rate by a factor of 1000/1001, from 24.000 fps to 23.976 fps (color TV made us think that this was necessary; it was not).
- AND the creation of a "3:2" field cadence. The 3:2 cadence is created by taking one frame from the 24 frame film source and filling 3 of the 59.94 TV fields. The next frame of the 24 frame film source fills two of the 59.94 fields, the next frame 3 fields, the next frame 2 fields, etc. Bump, de bump, de bump, de doodle wap de doo.
This sequence causes 2 frames of the 24 frame per second film to fit into 5 frames of the destination 59.94 frame per second TV video. (The term "pulldown" has been broadened to describe any combination of a 1000/1001 speed change and 3:2 cadence creation.) See how film was broadcast by television? See what a pain the old NTSC color was with the 1000/1001 thing? (See how it was really not necessary? OK, we will.)
Enter the new and rather expensive 120 frame/ second HDTV sets. 120 is a very "flexible" number, as DAwn's 7th grade (8th grade? DAwn isn't certain.) arithmetic teacher would have phrased it... it is an even multiple of 24 (hint--> 5x24=120). And so, these new HDTV sets can avoid "3:2 pulldown" by changing their frame rate to something that's an even multiple of 24. And that's another reason that 120 Hz refresh rates are starting to show up.
If movies look "jittery" on a 1080p60 ("Full High Definition" say the advertisements) or on a 720p60, look
into a 1080p120. Some viewers will notice jerky motion when "3:2 pulldown" is used, especially on full scene panning,
because the various film frames did not all get equal screen time. Nuff said about 120 Hz for now.
CABLE AND SATELLITE TOO?---> If your TV programs come to you by cable or by FiOS or by satellite (or if you watch closed-circuit TV, like a security system uses); or if you hate TV and never watch it, you may not notice any major changes come 18 February 2009. (Then again, you definitely may, when everyone in the neighborhood opens her upstairs window, leans out, and screams, "My TV is crawling across the floor shouting in digital 'Feed Me, I'm Hungry', and I'm not going to take it anymore." (Sorry, think we mixed one too many metaphors there.) )
That having been said, let's first dig a little deeper into cable TV. And then we may even dig a little deeper into FiOS TV and satellite TV. Ok, first cable...
As of December 2007, 64 million American homes subscribed to cable television. And cable has more bandwidth, more channels, than over-the-air TV... cable has been assigned about 125 channels by the FCC, and in digital cable systems, we can compress bandwidth anywhere from two High Definition sub-channels in one physical cable channel to maybe a dozen Standard Definition subchannels in one physical cable channel... which works out to about 500-700 sub-channels (or "virtual" channels) in a cable system.
Over-the air, we'll have 50 physical digital channels, with 2-5 programs per physical channel... which comes to about
100-150 programs over-the-air (but NOT in one region). Thus cable wins the battle of the "channels",
especially when you consider that only a fraction of over-the-air channels are transmitting in any area; but the
compression employed by cable comes at a price... some cable channels look awful, usually due to excessive compression...
over-the-air broadcasts and FiOS tend to have better picture quality, especially if the station is broadcasting, say, just
two programs on its channel... one in High Definition, the other with minimal changes (like
But from these numbers, we can safely assume that the vast majority of TV viewers in the US are getting (and will be getting) their HD programming via cable; cable usually carries local network affiliates, plus bazoodles of cable-only programs... ESPN-HD, HD HBO, A&E HD, etc. (As of early 2008, there are perhaps 25+ HD cable channels in this area (Baltimore County Comcast), vs 85+ HD channels on satellite (DirecTV). You may want to add VIDEO ON DEMAND to cable's total HD programming; or not.)
According to the National Cable & Telecommunications Association (NCTA), as of March 2007, consumers in 209 (out of 210) local TV markets were served by (at least) one cable provider that offered High Definition programming. So what? So this seems to be saying that many cable providers are a reasonably decent source of HD; that is, at least they are offering some HD channels.
(Since the FCC in September 2007 stated that there are 40 million households using cable systems that are still analog, and since HD is only sent over digital cable, the NCTA's 209/210 numbers should be taken cum grano salis (with a grain of salt).)
Cable programming begins at what's called the HEAD END. The HEAD END is the location where the cable system accumulates ITS programming... from satellites, through microwave towers, from local broadcasts, from its own studios, from Neptune, you name it. (There are roughly 5,000 HEAD ENDs in the US; but it's estimated that perhaps as many as 40% of these don't output ANY High Definition (HD) programming (as of July 2007).)
The HEAD END assigns a ("virtual") cable channel number to each program that it intends to make available to the community. The HEAD END then shoves that programming onto fiber optic "trunk cables", which carry the programming into each neighborhood that is serviced by that cable provider.
Today's digital cable programming is largely ENCRYPTED at the HEAD END, especially the "premium" channels like Showtime. (You have to pay to play. And to play, you have to have the proper "key" to decode the encryption.)
Cable systems can be divided into two types-->
Another interesting thing about analog cable is that one program (like the TV Guide Channel) totally fills one
Digital cable is often touted as being able to offer a higher quality picture than analog cable. This is often true, with a dramatic improvement in chroma (color) resolution. Since we can't see color details, we throw away a lot of color data, both in NTSC analog and in ATSC digital. Analog NTSC shows about 120 lines of an image with color; but up to 270 lines with digital. However, digital compression often will "soften" the quality of the picture, particularly on channels that are compressed most severely. (See "No Free Lunch" Theorem.) We'll dig into the whole subject of color in just a bit.
A CRITICAL POINT---> If your cable provider does not offer digital cable, you WILL NOT receive HD programs via cable TV. So if the FCC has counted correctly, and there are 40 million households which have analog cable, these 40 million households will never receive High Definition broadcasts over cable (at least not until their cable system converts to digital). And if your cable provider DOES offer digital, but you have not subscribed to digital cable, you will not receive any HD programs which the cable company has encoded; with a QAM tuner on your HDTV set, you WILL be able to receive SOME HD at no cost, usually HD programming which is locally broadcast from network affiliates.
HUH?
OK... Some HDTV sets also have QAM tuners. Back when all TVs were analog, the "Cable Ready" TVs had QAM tuners; that's why you just plugged the cable into the back of the TV... no set-top box required. Same for the current HDTV sets with QAM tuners... just plug your cable into the back.
Now... TV manufacturers don't often discuss it, and they rarely print anything in their instruction manuals about it... but it's really true... cable providers relay to any customer with a QAM tuner all digital (including HD) transmissions that are unencrypted. And if your QAM tuner is on an HDTV set, you get HD. Free. No set-top boxes are required. How?
The cable channel numbers seen on your set-top box and in your program guide are VIRTUAL numbers. In the old days of 2-digit analog channels, the channel you were viewing actually corresponded to an "RF channel". When you went to channel 75, your cable-ready TV or set-top box was actually tuning to the radio frequency for channel number 75, and displaying the one "service" that lived there.
But with the advent of digital cable, and hundreds of three digit channels, that all went out the window. Now the cable company can stuff a dozen or more "services" into one cable RF channel. These services basically pile up in that channel, and now your set-top box and/or new HDTV set pulls them apart.
The virtual numbering plan in the cable system is proprietary, and requires the set-top box to decode. So they have one or more services at RF channel 11, but it's actually virtual service number 211. But HDTVs with QAM tuners don't know about virtual service numbers, they just knows that they found it at RF channel 11. So it gives it service number "11-0", and if it finds any others piled up there at RF channel 11, it'll call those 11-1, 11-2, etc. After all, HDTVs are expecting to find digital multicasting within a 6 MHz RF channel anyway; they are trained to sniff around, looking for multiple programs (services).
Many cable companies shift their line-ups frequently, so that QAM-sters must rescan to find the new arrangement. But it's not uncommon to find 9 or 10 free HD channels, though you may find one on channel 81-11 (the 12th "service" on major cable channel 81, for example). Again, you are not required to pay extra. But if you want a non-broadcast HD channel (like Discovery HD) which are almost always encoded, then you will need a set-top box (or a CableCARD) for that.
(In Other Words--> A QAM tuner integrated into your HDTV set will allows the free reception of unscrambled digital programming sent out by cable providers, usually local broadcast stations; however most digital channels are scrambled because the providers consider them to be extra-cost options and not part of the "basic cable" package.)
The CableCARD---> As of 1 July 2007, the FCC has required cable providers to separate security hardware (and software) in their set-top boxes from the hardware (and software) that does the receiving and tuning and recording. All of the security issues (the part that makes you pay $$$ each month or you get nada) are now on a card that slips into the box (or into the back of your TV)... the "CableCARD". (Comcast requires that their technician install the CableCARD in your TV.)
The FCC is working on the premise that you can buy the box (or buy a TV that incorporates the box), take it with you if you move, and just get a new card from your new cable company; the card is about the size of a credit card (but a bit more hefty). Comcast currently does not charge for the first CableCARD in most markets.
BE CAREFUL WITH "DIGITAL" AS APPLIED TO CABLE---> "Digital" as applied to cable systems can be slightly confusing; so your dog Wolf is now going to make it simple and non-confusing. We'll follow a TV transmission from the TV tower, to the cable provider, to your home...
OK... cable often carries stuff that is not broadcast over-the-air, like HBO and CNN and the Sci-Fi channel.
Cable also carries programming that IS broadcast over-the-air in your local or regional area.
NOW... during the present transition from analog to digital TV, most (but not all) over-the-air TV stations have TWO TV transmitters; each is broadcasting on its own channel, one is transmitting in the old NTSC analog format, and the other is transmitting in the new ATSC digital format (which is the standard for digital in the US). In theory, this will work out some of the bugs in the new ATSC digital transmission.
Your local cable company receives both transmissions, the old NTSC analog (until
Example in our area--> Virtual channel 211 (WBAL-DT) and virtual channel 208 (WBAL InstaWeather) are stuffed on top of the TV Guide channel, all in physical RF cable channel 11.
This answers the question of why Comcast bothers to convert everything to "Cable Digital" before sending it out on its cable network. Answer--> Digital technology enables Comcast to "compress" its signals. Because programs take up less space in "cable digital", many more programs can fit through the existing infrastructure using "Cable Digital" compression.
HD guru Bill Husted of the Atlantic Journal Constitution points out that the HD picture is superior (sharper) when it
is received over-the-air by an antenna at your home. Cable and satellite providers compress the HD picture so that they can
offer more channels; hence while over-the-air broadcasts can fit a maximum of
Yes, TV stations also compress digital broadcasts before transmission
Important To Note--> Cable providers compress different channels carrying HD by different degrees, for reasons that change with the phase of the moon. Just bear in mind that the more an HD broadcast is compressed, the worse it will look. In some situations, the compression becomes so severe that the cable channel shows no image (black) or digital static ("pixelation").
(FOR THE TECHNICIAN---> Using 8-VSB modulation for digital TV, as the ATSC digital standards require for US over-the-air broadcasts, we can broadcast 19.39 MBits/sec of video and sound and miscellaneous data. But if we feed 19.39 MBits/sec into the "exciter" (error correction, modulator, and associated functions), then as a result of the overhead added because of forward error correction coding and pilot and sync insertion, the actual data rate goes from 19.39 Mbits/sec at the input of the exciter to over 32 Mbits/sec at the output of the trellis coder (a component of the exciter that provides additional forward error correction using a convolutional code). 8-VSB modulation, using Nyquist filtering, can transmit this 32+ MBits/sec stream in a channel width slightly less than 6 MHz. Mirable dictu.)
Here in Baltimore County, Maryland, if you pay your cable bill (and if Comcast posts your monthly check to the correct
account), you get local station WJZ's analog broadcast on Comcast cable channel 23. And you can also get WJZ's digital
broadcast, which is sometimes an HD program, (if you pay $6.50/month extra to Comcast for HD) on Comcast cable virtual
channel 212. (Folks in this area refer to those channels broadcasting SD and HD digital as "the 200's", since these Comcast
channels are all in the lower 200's. On
A BRIEF ANECDOTE---> We recently visited our aunt and uncle, who had plunked down $7,000+ for two large, beautiful Samsung HDTVs plus installation. "Look at our HD" our aunt said on our arrival, pointing to what was perhaps the worst picture we have ever seen on a flat screen. First, she was tuned to cable channel 21 (analog) instead of 211 (digital). Next, the installers had forced the picture to fill the width of the HDTVs, resulting in "fat round-face syndrome". Next, we noticed that Comcast was renting our relatives two DVRs (Digital Recorders) with NO HDMI outputs (more on HDMI coming up). The installation (by either Best Buy or Comcast, we were afraid to ask) featured a single low quality coaxial cable, barely suitable for analog, connecting the Samsung HDTV sets to the Comcast DVRs.
We removed the single, cheap coax (which was causing "ghosting" and which CANNOT carry HD), replacing it with three "component" cables (one for each of the elements of an ANALOG TV picture), and we tuned one HDTV set to "HD Discovery Theatre". Voilà, HD. The difference, including the proper aspect ratio (16:9), the elimination of weird static and ghosting, etc, was beyond striking. Our aunt could not believe the beautiful colors and sharp resolution (pictures of bison from Yellowstone). End of anecdote.
Just A Note--> The Comcast DVR is digital; the three cables are analog; the HDTV is of course digital. So we
went from digital to analog to digital. Had we had a DVR with HDMI outputs, we could have stayed digital the whole time;
no conversions. (The scene when our aunt confronts Comcast demanding a DVR with HDMI outputs will not be a pleasant one.)
Component Video Jacks On HDTV
 |
Back to Comcast--> Since the signals that we get from Comcast are sent to our homes in "cable digital", they must first go through a "set-top box" or a DVR, which are rented from Comcast, for decoding any scrambled channels.
If you have a newer, more expensive TV, you may only have to insert a CableCARD from Comcast in a slot in your TV, eliminating the need to rent a set-top box or DVR (and also eliminating VIDEO ON DEMAND, at least for now).
Anyway, when we tune the set-top box from Comcast to some cable channel, it converts "CABLE DIGITAL" into either 1.) Analog, for our older TV sets, or 2.) Into ATSC digital for our newer HDTV sets (assuming we are subscribing to HD for a monthly fee). (Hint #1--> As we said, that set-top box can alternatively be a "Digital Video Recorder" also rented from Comcast for a few more dollars each month, but it can do some neat tricks; like record, or pause a live broadcast, or backspace a live broadcast.)
SO... If you have an OLD ANALOG TV, the set-top box will convert "CABLE DIGITAL" to ANALOG, and you can then watch most cable channels on your analog TV. You can even watch some broadcasts on your old analog TV that were originally broadcast from the ATSC digital TV transmitter. (Yep.) ¿Está claro?
Example--> In this area, station WBAL transmits the local and national weather 24/7 from its ATSC digital transmitter. With a "set-top box" tuned to Comcast channel 208, you can watch this ATSC digital broadcast 24/7 (if sanity is no issue) on your old analog NTSC TV set. The set-top box modifies the ATSC digital broadcasts so that you can watch them on your old NTSC analog TV set. Many of them.
What you CANNOT WATCH on your analog set are HD programs (obviously... your TV will display garbage); and Comcast will usually give you a black screen (or some message) on virtual cable channels that are intended to carry HD programming; thus we get a black screen for local station WJZ ATSC DIGITAL on our analog TV (recall... channel 212?).
BUT... if you have an HDTV set, you can connect the set-top box directly to your HDTV set... if the set-top box has an HDMI output; otherwise, you can use component video; otherwise... nope, that was your last chance. You can watch analog broadcasts (the HDTV set converts analog to digital) and non-HD digital broadcasts; and if you have told your cable provider that you want "HD capabilty" (usually for a few $ extra each month), then your HDTV set will display these HD DIGITAL programs in living high definition.
Just keep the "DIGITALS" straight in your mind-->
(For The Technician--> "Cable Digital Format" is simply TV signals that have been modulated by the digital QAM technique. More on QAM coming up.)
NOW... On 11 September 2007, the FCC ruled that analog cable systems (generally smaller providers) should not penalize customers who still have analog TVs and who have not purchased a digital set when analog broadcasting ceases. And so, analog cable systems must convert ATSC digital broadcasts from local and regional TV stations to analog... at least until 2012. Only one digital broadcast per station need be carried by the cable company in analog; i.e., multicasts are not required to be carried in analog (or carried at all, for that matter).
100% digital cable providers ("The Big Guys") can continue providing set-top boxes to allow OLD ANALOG TV sets to receive ATSC digital broadcasts from local and regional stations. In general, the broadcast station gets to decide which multicast (if it's multicasting) the local cable provider must carry.
Worth Noting--> A LOT of stuff on cable (and satellite) doesn't even come from broadcast TV stations... HBO, A&E, the Weather Channel, the Golf Channel, The Aardvark Channel, etc, are never even broadcast over-the-air. These are not required to be provided in analog format.
Also worth noting--> In September 2007, the FCC mandated that cable operators may not degrade broadcasters'
over-the-air High Definition TV signals when they are transmitted over cable systems in "CABLE DIGITAL" format so that they
look any worse than the rest of the cable system's HD. (All HD is created equal, hopefully, and transmitted to your home
equally, we hope.)
Some cable providers are beginning to use "Switched Digital Video" (SDV). SDV sends programming to neighborhood nodes, but these programs don't go to your individual home unless you request them. (Very cool, ay?) So if a subscriber on the node wants to watch Spider Man in HD, the cable channel carrying that movie gets the bandwidth it needs to deliver Spider Man to THAT ONE HOME. In other words, not every home gets every available cable program; instead, homes get only the channels they request. No one in the neighborhood requesting the Aardvark Channel in HD? Great, we'll use that bandwidth for the Weather Channel HD, which IS being requested.
This actually makes a great deal of sense; imagine the density of phone lines and equipment that would be required if we designed the public switched telephone system so that every phone could be in use at once. Comcast said that it planned to spend $150 million on SDV technology in 2007.
Now the question becomes... what happens when the dozen HBO's and the dozen Showtime's and the dozen Starz... you get the idea... what happens when they all provide programming in HD (1080i30)? Currently there is ONE HBO HD... ONE. If we spent $1,800 on an HDTV set on Black Friday this year (the day after Thanksgiving when stores cut prices to or below the bone, and buyers go beserk), we'd definitely want to see ALL twelve HBO's in HD, if we subscribed to HBO; especially if satellite offered it and cable didn't... just a hypothetical there.
BUT... The reality is that cable providers may need to actually increase the capacity of their physical networks,
before they will be able to offer many more channels live (not ON DEMAND) in HD. This becomes critical for cable
providers, because FiOS DOES have the capacity to carry the premium channels in HD without resorting to grotesque
compression or SDV or ON DEMAND.
ANOTHER VIEWPOINT ON CABLE TV---> The adverts on cable TV have been telling folks that as of mid-February 2009, there's no need to worry about the transition to digital. But the actual facts about how the conversion will affect cable subscribers have been been scant. And what hasn't been publicized is that the conversion to digital also will affect some cable subscribers.
As of mid-April 2008, there are about 65 million US "basic cable" subscribers, according to the National Cable and Telecommunications Association. About 37 million of these are digital subscribers, which means they most likely have a set-top box for each of their TV sets, a box for which they pay a monthly rental fee. Those customers actually will not be affected by the digital transition, regardless of the kinds of televisions they own.
But the 28 million cable subscribers who receive analog service, meaning that they probably plug their cable wire directly from the wall to their "cable-ready" TV... and not into a set-top box that they rent from the cable provider... may have a good reason for concern.
You see, cable providers have two options for dealing with their customers with old analog TVs when we convert to digital next February. They can either convert the new digital broadcast signals to analog at the source... the "head end"; OR they can make their cable systems all digital and rent customers a set-top box for every TV they use... a set-top box that will convert the cable signal back to analog for viewing on older analog TVs. (The $40 subsidized converter boxes will be of NO help in this situation.)
Now... the big cable companies like Comcast (the largest) are expected to take option #1... that is, they will pump both digital and analog signals through their systems. "There won't be changes in prices because the broadcast channels are going digital," said Comcast spokeswoman Sena Fitzmaurice. "But there may be changes in prices and services for other reasons."
Cable companies may convert some programming from cable analog to cable digital, as they have been doing; but FCC rules require that local broadcast channels remain viewable to analog customers. But over time, a complete migration from analog to digital service is inevitable. Why? An analog signal takes up more space on the cable network than a digital signal, and subscribers pay less for it. With cable digital, cable companies also can offer additional services, like "On Demand".
BUT... Smaller cable systems are expected to have a more difficult time. Jess King of Cablevision of Marion County LLC recently spoke to a gathering of residents at an "over-55" retirement community. "My decision was, whether I continued to try to muddle along here with all of my channel space being used up with a few analog channels, or whether I would go all digital," King said. "So I got an FCC variance to go all digital."
Now... King's company is small, he says, with fewer than 10,000 subscribers; and he is facing increasingly intense competition from satellite companies that offer large packages of HD channels, an option not available to him due to capacity limitations. Whether other cable companies like King's can pass on costs related to the digital transition to customers is a subject that both the cable industry and the FCC generally avoid.
The FCC's digital transition Web site says that if a cable company goes all digital and thus requires customers to start renting a set-top box for every analog TV they watch, "any costs related to it will be determined by the cable company." Yet FCC regulations that were approved last fall (2007) appear to contradict that point.
The FCC's rules require cable companies to provide local broadcast channels to customers with older analog TVs through
February of 2012. (Certain smaller cable systems can request a waiver.) The FCC's rules also note that a cable provider
who converts to all cable digital must supply analog customers with the equipment needed to view the local broadcast
channels; and
If that were the case, Jess King (of Marion County LLC) said it would bankrupt him. "I can't put that much money into these homes," he said. "How can anyone... I'm talking about the government or even an individual... think that a company could absorb that kind of a cost?"
BUT... Nothing in the FCC's rules would prevent operators from continuing to offer both analog and digital signals, however.
Brian Dietz, a spokesman for the National Cable and Telecommunications Association, said his organization interprets the rules to mean cable companies are prevented from recovering costs stemming from the head-end down-conversion, not the costs of set-top boxes required by the all-digital option. But fine print aside, analog cable customers just want to know if the digital transition is going to cost them more money. And that, according to Dietz, is "a decision that's left up to individual cable operators."
Uh Huh.
IMPORTANT INTERESTING INFORMATION---> If you already have an HDTV set (or any type of
set with a digital receiver), and if the set has both an ATSC digital tuner and a cable QAM tuner ("Cable-ready"), you should be able to receive those HD broadcasts that your cable provider is required (by the FCC) to
carry, without the need for renting a digital converter/decoder box or the need for a subscription; but you will not
be able to receive non-local-broadcast HD channels (which is most of the HD universe---> E.G., Discovery HD, HD HBO, A&E
HD, SciFi HD, etc). And without renting a digital cable box, some features like "On Demand" will not be there.
"Digital cable" or "digital satellite" does not mean a program necessarily is in high definition. It may be, or it may not be. On DirecTV (satellite), channel 231 (The Food Network) is digital satellite, but it's NOT HD. But DirecTV channel 231-1 (The Food Network In HD) is digital satellite and IS HD.
OK... And as for satellite... since the 1990's, satellite programming has been digitized (100% digital) and compressed, allowing more channels per satellite. Digital has also meant that satellite reception has better picture and sound, no more snow and crackle, as was common with analog satellite broadcasts.
Today (early 2008), satellite television, from outer space to the dishes that decorate more than 22 million US homes, is 100% digital (which, compared to cable, makes things simpler for us to follow). But like "cable digital", "Satellite Digital" is different from the ATSC digital that is broadcast from TV towers across the US (and will rule the Land after February of 2009).
Because HD broadcasts from satellites to our dishes require more "space" on the satellite broadcast spectrum than non-HD broadcasts, satellite providers are compressing their HD transmissions more and more, now using a newer technology than the MPEG-2 compression specified by ATSC for over-the-air broadcasts. The newer technology is called MPEG-4. And MPEG-4 must be decoded using new set-top boxes in your home, such as the "H-20". (No, not water... just thinking how the "Set-Top Box" Industry must be the remaining support for the world's shaky economy.)
In addition, to handle HD, DirecTV is employing a newer transmission protocol called "DVB-S2" from the SPACEWAY-1 and SPACEWAY-2 satellites. This allows DirecTV to squeeze more HD programming into its satellite signal than was previously feasible using the older DSS transmission protocol.
DVB-S2, the next generation of DVB-S, provides higher throughput and improved coding efficiency. Low-density parity check (LDPC) coding is improved in DVB-S2 and provides increased flexibility for satellite operators. The Adaptive Coding and Modulation (ACM) feature of DVB-S2 is useful in interactive data applications by allowing the satellite operator to dynamically adjust coding and modulation based on signal quality feedback from remote terminals under varying conditions, such as rain fade.
As of October 2007, DirecTV is still planning to offer as many as 100 national HD channels by the end of the year, all of which are expected to be MPEG-4 encoded (compressed). (They came close; as of January 2008, DirecTV has over 85 HD channels available.) In fact, as of September 2007, DirecTV was already rolling out MPEG-4 HD boxes, as are several cable operators, who are also anxious to switch to MPEG-4 to make more efficient use of currently available bandwidth.
DirecTV---> DirecTV Direct Broadcast Satellite (DBS) service transmits HD video in a format that is not quite one of the 18 ATSC video standards. It is most similar to the ATSC 1080i30 format, but while the ATSC standard specifies 1920 pixels per line for 1080i30, DirecTV reduces this number by 1/3 and broadcasts
1280 pixels per line. Thus, a few on the Internet have dubbed DirecTV's video format "HD Lite."However, the ATSC format standards were developed for over-the-air TV broadcasts; these standards do NOT apply to satellite broadcasts, especially since the vast majority of satellite programming comes from "non-broadcast" fare, such as HD HBO, The Sci-Fi Channel HD, etc.
Whether DirecTV is reducing the HD picture resolution to allow it to transmit more channels is a topic that has started more than one barroom brawl; this reduction in pixels per row also has been the subject of a class action suit filed by a DirecTV customer. We've seen just one HD broadcast from DirecTV (Discovery HD Theatre) on a large HDTV (about 50"), at the home of some friends, and it looked absolutely fine to us... sharp and crisp and detailed; but we did not do a comparison viewing, nor did we view any calibration videos.
The practice of reducing the original resolution of an HD signal between the broadcast facility and the home is often called "down-sampling". Thus far, customers have reported down-sampling only on 1080i30 HD video; 1920 pixels per row x 1080 rows, interlaced can be down-sampled to 1440 pixels per row x 1080 rows, interlaced; or it can be down-sampled further to 1280 pixels per row x 1080 rows, interlaced (as in the case of DirecTV), with a corresponding reduction in transmission bandwidth consumption. In contrast, over-the-air ATSC broadcasts of 1080i30 are fixed at 1920 pixels per row x 1080 rows, and no down-sampling is permitted by the ATSC standards (or by the FCC's rules).
Moral---> If you're an HD purist, you may want to view local HD broadcasts (including network affiliates where available) using a rooftop antenna; in this configuration, no down-sampling is permitted. Nor is the additional compression so severe that the picture is degraded, as is the case with some channels offered by cable providers. For the rest of us, down-sampled HD still looked great (so far); we suspect that the quality of the HDTV set, the quality of the cables carrying programming from the satellite box into the HDTV set, and the quality of the original broadcast are more relevant to the final picture quality of satellite transmissions than 1920 vs 1440 vs 1280 pixels per row.
ALERT--> Satellite subscribers may also have to upgrade their dishes; usually slightly larger dishes are required for receiving HD. You will almost certainly need to contact your satellite provider and ask for an HD set-top box... though your HDTV set may have built-in satellite HD reception capability; and while you're on the phone with them, you may want to sign up for an HD subscription plan as well, giving you extra goodies like CNN in HD. Buying an HDTV alone will NOT get you High Definition, though it is a necessary step to HD.
If you subscribe to satellite via DirecTV, you will need an HDTV set; an HD Subscription with DirecTV; a DirecTV HD Receiver—-> Model HR20 or H20; a 5-LNB Satellite Dish; and a B-Band Converter module.
Comcast cable, obviously a competitor of DirecTV, states in its advertising, "We put Comcast HD and satellite HD side by side, and even satellite customers agreed that HD looks better with Comcast." In a March 2007 study of 125 individuals who subscribed either to DirecTV or to the DISH DBS (satellite) service AND who also expressed a preference, Comcast states that 66% of this subset preferred the Comcast HD picture, while 34% preferred the DirecTV HD picture.
Our interpretation of the results, based on Comcast's data, is that, of roughly 155 subjects who had satellite service, 83 subjects preferred Comcast HD and 73 either preferred DirecTV OR had no preference. We suspect that Comcast's HD picture quality varies in different locales, and like the picture from DirecTV, varies among brands of HDTVs and the control settings on these TVs, etc. DirecTV's advertising also has claimed that it offers an HD picture "superior" to cable. The battle continues to rage. (We suspect that had DirecTV designed this study, the results might have been quite different.)
Now a representative from FiOS, Verizon's fiber-optic service, states--> "Our Standard Definition is better than their high definition." -Quoted in the W$J, 18 February 2008.
Interestingly, the Comcast study did not compare Comcast and DirecTV to over-the-air broadcasts. It would be informative for Consumer Reports to conduct a study in which all four were compared under a range of circumstances. So, anyway, who is best? Some points to bear in mind
--->
- First, your HDTV set is going to do one, possibly two things. If it is receiving an interlaced broadcast from ANY source, 480i30 or 1080i30, it is going to have to de-interlace these into 480p30 or 1080p30 for your flat screen HDTV set. Higher quality (more expensive) HDTV sets do de-interlacing better.
- Second, your HDTV set has to convert its input format to its native format. If you are watching an HD program on NBC (e.g., Leno), it is (generally) being broadcast in 1080i30. If your HDTV set is a 720p, it must convert 1080i30 to 720p60. Higher quality (more expensive) HDTV sets do this conversion better.
- As over-the-air broadcasts go, if you have a strong signal from a local station, logically neither cable nor satellite nor FiOS can be superior to a strong
over-the-air signal, since they all three get the sameover-the-air signal, though not necessarily via an antenna. In general, it is the additional compression that cable and satellite (and possibly FiOS) apply that degrades the HD picture (though there are other factors).
- From personal experience, the quality of a given cable channel changes with the phase of the moon. Two weeks ago, MSNBC (in SD from Comcast) was unwatchable; tonight, it is crystal clear (in SD) on a Panasonic 720p60 HDTV set.
In 2005, WiFi and Internet access suddenly became much faster, courtesy of Verizon, the "phone company" for millions in the US.
The secret word was FiOS, which stands for "Fiber-Optic Service" (and a little thought will reveal why Verizon didn't name it "FOS". Verizon has also pointed out that "fios" in Irish means knowledge.) In some parts of the US, Verizon's FiOS service was providing 15 million bit per second Internet download speed (and 2 million bits per second Internet upload speed), compared to 6 million bps and 0.384 million bps provided by large cable companies like Comcast. And the cost for FiOS was just a hair more. (You could also get FiOS at 5 mbps/ 2 mbps for a few dollars less, and 30 mbps/ 5 mbps for several $ more.)
FiOS was in 2005 available to about 3 million homes in the US. Says Verizon, "Verizon FiOS is the latest in fiber-optic technology. It delivers laser-generated pulses of light, riding on hair-thin strands of glass fiber, all the way to your front door. When FiOS meets your HDTV, you can get TV at blazing-fast speeds." (FiOS is a "fiber to the premises" (FTTP) service.)
Ok, so what? So this. Using FiOS, WiFi ran at about 8 (EIGHT) million bits per second, compared to about 1 (ONE) million bps with typical cable. EIGHT TIMES FASTER. And in 2005, Verizon also planned to be using FiOS to bring all-digital television, with lots of HD, into homes. UNCOMPRESSED.
In a nutshell, with FiOS, stuff is not just carried to and from our homes (and offices) via fiber. In the FiOS world, the fiber actually ENTERS our homes (and offices)... and this is the key to the speed of FiOS.
When you go with FiOS, you abandon cable, you abandon DSL. And FiOS is not compressed... no lossy compression. It's HD picture is superior to cable and satellite, in our opinion.
By late 2006, Verizon was predicting that, after it does its tweaking, you'll have 100,000,000 bits per second flowing in and out your home on fiber; and THAT IS FAST. It's three times the THEORETICAL limit of cable. And it's fast enough to let you download entire movies to your home IN A FEW SECONDS. As of late 2006, FiOS was running at 5-50 million bits per second.
OK... Bottom line--> FiOS runs much faster than cable or satellite. FiOS is fast enough to bring just about anything in or out of your home that you'll want for the Network of The Future. And the bandwidth of FiOS is such that compression is not needed. But read on...
Problem #1 with FiOS--> It's expensive. Verizon charges $35/month for a FiOS speed of 5 million bits/ sec (about the speed of Comcast cable). Want 50 million bits/second? Verizon charges $160/month. (BUT... in areas like NY City where competition is ferocious, you can get FiOS running at 50 million bits/second for as "little" as $90/month. Moral--> Even Rolex haggles.) But by early 2008, FiOS was offering Internet, phone, and TV, all for a starting price of $99/month... with an HDTV thrown in free (later it was a nice digital camera) if you signed up for two years or more.
Problem #2 with FiOS--> Verizon may have to dig up your lawn to get the fiber into your house; and the installation isn't trivial; it can take a few hours.
But FiOS allows Verizon to deliver hundreds of channels of TV (including HD), just like Comcast has been doing, but without the need for the compression that degrades the picture. FiOS IS FASTER than cable; "ON DEMAND" takes perhaps three seconds to kick in with FiOS; cable takes a bit longer than that. And the picture, when using FiOS, is clearer and brighter and more consistent than cable, according to folks who have tried FiOS for TV. (But some of these also claim that FiOS TV is subject to occasional "pixilation." (That's when the TV picture morphs into digital blocks for 1-2 seconds... Remember when there were rabbit-ears and "snow? This is simply digital noise.) Verizon is also in the process of introducing a digital video recorder (DVR) that can show its stuff on ALL the TVs in your home... not just the TV that the DVR box is sitting next to.
Fiber. Fiber. Fiber. Stay tuned... we'll add the nitty-gritty of FiOS as it becomes available to more and more folks.
Because we've just about reached the future of high definition TV delivery. (By early 2008, over one million Comcast customers have switched to FiOS; to appease stockholders, Comcast is again paying a dividend (something it hasn't done
since 1999), and it's doing a $7 billion stock buyback; these measures put a bottom under the price of Comcast stock.)
