h a l f b a k e r yRenovating the wheel
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For years I've been buying widescreen DVDs, because I've been preparing for the day when I could watch them on an actual widescreen TV.
A quick web search indicates, however, that most DVD players aren't as sophisticated as I was hoping. Let me go into SOME of the details.
For a long long time
the number of "scan lines" of broadcast TV, in the old-fashioned 4:3 aspect ratio, was 540 or so. In order to display the full width of a 16:9 wide-screen movie on such a TV, two different techniques have been used. One is to simply squish the image horizontally, leaving everything looking somewhat skinnier than normal.
The other technique is to use only part of the screen area for the image, with the result that big black bars stretch across the top and bottom of the TV screen.
Now think about what this means for a DVD. It was designed to hold data for 540 scan lines, to be sent to a TV, but not all of that storage space for scan lines are actually being used for DATA. Some is being wasted, holding the black bars.
Thus, when the DVD is played and the player is connected to an actual wide-screen TV, the black bars are still there.
As it happens, I own a DVD player that has an HDMI output and it claims to be able to "upconvert" an ordinary TV signal to high-definition. This could mean a couple of different things.
It might merely mean that it can create a satisfactory signal for a high-definition TV that might accommodate 1080 scan lines. For all I know, only the middle half of the screen, 540 scan lines, that is, will actually be used, and be given the data from the DVD.
The other possibility is that it might be able to "interpolate" scan lines, to create data to fill space in-between them, so that more than the normal 540 lines of data can be sent to a high-def TV.
HOWEVER! That's not necessarily good enough! Because, what if the DVD holds a widescreen movie? Then the black-bar scan lines get interpolated right along with the movie-data scan lines!
WHAT WE NEED is a DVD player sophisticated enough to identify the black-bar data on the DVD and ignore it, and upconvert the actual movie data.
As an example, let us suppose that only 340 scan lines hold movie data, while 100 above and 100 below are wasted with black-bar data. Those 340 lines need to be interpolated and even re-interpolated until they become 1080 scan lines, and THAT is the signal we want to send to a modern wide-screen TV.
And now, something of an alternative. Suppose our widescreen DVD actually has 540 scan lines of movie data, and it is the PLAYER that creates the black bars for an ordinary TV. In this case the player has to throw away some of the data in order to present the movie in the correct aspect ratio on an older 4:3 TV.
This movie would LOOK no different from the current situation, where much of the DVD actually holds black-bar data.
But, when the DVD player is hooked to a widescreen TV, it can start with 540 lines of data, instead of the roughly 340 lines previously described. The upconverted image will look better, in this case.
(The best case, of course, is to switch to Blu-Ray. But there are so many older DVDs already out there, waiting to be displayed as best as can be, that that is why I've posted this Idea.)
Auto screen shape
Auto_20screen-shape...6_3a9_20televisions
An older Idea with some similarities to this one. But I think this one has a different focus than that one. [Vernon, Oct 17 2012]
Black Bars
http://images.googl...1t:429,r:7,s:0,i:92
[normzone, Oct 19 2012]
[link]
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//For a long long time the number of "scan lines" of
broadcast TV, in the old-
fashioned 4:3 aspect ratio, was 540 or so.// |
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525 actually (for NTSC), of which roughly 480 are
visible. |
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//Now think about what this means for a DVD. It was
designed to hold data for
540 scan lines, to be sent to a TV, but not all of that
storage space for scan lines
are actually being used for DATA. Some is being
wasted, holding the black bars.// |
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Actually, that's not correct. The aspect ratio of a
DVD is set by a flag indicating
that it's either 4:3 or 16:9. Both video streams have
exactly the same resolution
for the actual video (i.e. 720x480), but the 16:9
picture is “squished”
horizontally. When the DVD detects that it's playing
a 16:9 movie, it stretches it
back to the correct aspect ratio, and then adds the
bars at the top and bottom if
necessary. |
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/And now, something of an alternative. Suppose our
widescreen DVD actually has
540 scan lines of movie data, and it is the PLAYER
that creates the black bars for
an ordinary TV. In this case the player has to throw
away some of the data in
order to present the movie in the correct aspect
ratio on an older 4:3 TV.… |
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…But, when the DVD player is hooked to a widescreen
TV, it can start with 540
lines of data, instead of the roughly 340 lines
previously described. The
upconverted image will look better, in this case.// |
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That's how it works currently. |
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For what it's worth, 16:9 video can be encoded in the
manner you describe (a 4:3 stream with the bars
baked in), but the DVD player will detect it as a 4:3
video stream, not 16:9. On a 4:3 TV, you won't see
any difference, but on a 16:9 TV, the video will
appear in a small box in the middle of the screen. |
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I'm not sure I follow this. The last two DVD player's
I've owned have both played 16:9 movies in 16:9
format on a 16:9 screen. Don't most of them do
this, or have I just been lucky? |
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As I mentioned above, they all do that (at least,
they're supposed to). If they don't, either the DVD is
encoded improperly or your TV/player settings are
wrong. This entire idea is based on a fundamental
misunderstanding of how DVD video works. |
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//It was designed to hold data for 540 scan lines, to be sent to a TV, but not all of that storage space for scan lines are actually being used for DATA. Some is being wasted, holding the black bars// - I don't think this is true - i.e. the DVD isn't storing the "black bars" as video data. Anyway, all televisions and all DVD players (that I've ever seen) have display options that let you choose whether the picture should be shown stretched, cropped or letterboxed. |
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[V] is this a problem you're having ? or a problem you're anticipating. |
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// The best case, of course, is to switch to Blu-Ray. But
there are so many older DVDs already out there, waiting to
be displayed as best as can be, // |
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Even the very oldest DVDs in my collection look fantastic
on Blu-Ray. The only issue (and it's a very minor issue) is
that a DVD in a Blu-Ray player occasionally halts for a split
second. I assume the newer format runs at a slightly
different rpm and the player must therefore correct this. |
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My Philips Blu-Ray player also automatically
compensates for various pre-formatted widescreen discs.
Your argument is invalid. |
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//The only issue (and it's a very minor issue) is that a DVD
in a Blu-Ray player occasionally halts for a split second. I
assume the newer format runs at a slightly different rpm
and the player must therefore correct this.// |
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DVD and Blu-Ray are both constant linear velocity formats,
so the rotation speed of the disc varies as the optical head
moves towards the outside of the disc. The rotation speed
has to be tightly controlled for both formats, otherwise the
disc simply wouldn't play. |
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If you're getting the occasional pause or skipping, the most
likely reason is simply a scratched disc. It's possible it's a
defect with the player itself, but what you're describing
shouldn't be happening under normal circumstances. |
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interestingly, you can make a dirt cheap centrifuges
out of CD players by taking advantage of the
constant linear speed. Simply wodge a pipette tip in
the safety hole of the nasty boom-box cdplayer
someone left, snap off the lid and epoxy a couple of
tube holders to the top of the CD. Then, simply
select track 1 for 500RPM and track 11 for 200RPM. |
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[ytk], the only reason I assumed it had something to do
with the different formats was because it happens with
_every_ DVD we put in the player, and it always happens in
the same place in each movie. It isn't a skip, just a split-
second pause that coincides with a certain scene break. If
it is a defect in the player it certainly isn't bothersome
enough to warrant repair or replacement. |
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Ah, that's probably the layer change on a dual layer disc, then. |
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Commercially produced DVDs are generally recorded with two
layers of data stacked on top of each other, and when the
player reaches the edge of the disc on the first layer it has to
jump back to the center to start reading the second layer.
The layer change is usually designed to coincide with a scene
break so as to be less noticeable, and it often happens fast
enough that you can't even see it, but it sounds like your
particular player just stumbles over it a bit more than most. |
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That makes sense. It only happens with DVDs, so I imagine
that it might simply spring from an oversight in the design,
like the people at Philips creating a Blu-Ray player to play
Blu-Ray discs with maximum quality (which it does;
ironically, noticably better than my Dad's Sony), but not
putting
a great deal of effort into backwards compatibility. Or
maybe I'm wrong and it's something else entirely. |
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As of this writing I still haven't had the chance to see the output of a widescreen movie, stored on DVD, sent to a widescreen TV. So, this Idea was written partly because of THIS: |
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"A quick web search indicates, however, that most DVD players aren't as sophisticated as I was hoping." |
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In other words, there are a lot of people out there seeing black bars on their widescreen TVs. |
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In the very near future (perhaps as soon as tomorrow), I will be able to see how my new wide TV and new Blu-Ray player handle an old DVD with a widescreen movie on it.
Of course I'll let you-all know the results. |
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If people are seeing black bars on widescreen TVs
when watching 16:9 DVDs containing 16:9 video, it's almost
certainlybecause their equipment is misconfigured. It has
nothing to do with how the DVD video is stored on
the disc. |
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I'm afraid your premise is simply flawed here. You're
attempting to solve a problem that just doesn't exist. Having
made many a DVD myself, in both 4:3 and 16:9 aspect ratios, I
can assure you that the black bars are simply not stored as
part of the video stream on 16:9 DVDs. In the unlikely event
that they are actually stored in the video stream, the DVD
would be designated “4:3 letterbox” rather than 16:9. By
definition, then, 16:9 video /cannot/ have black bars in it. |
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The only exception to this would be if the video itself is a
wider aspect ratio than 16:9, such as 2.35:1 for example. In
this case, the video stream will have small black bars at the
top and bottom, because the DVD specification only allows for
4:3 and 16:9 aspect ratios. But even then your “solution” of
discarding the black bars before upconverting doesn't do
anything for you, because you can't recover information that
isn't there. It will make no difference whether you remove
the black bars before upconverting or not, since you have to
add the bars back in anyway when you display the picture on
a 16:9 TV. |
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There are no 16:10 TVs. Even monitors that have a
native 16:10 aspect ratio handle 16:9 video by either
adding bars at the top and bottom or stretching the
16:9 picture vertically. The only way to display a
true 16:10 picture on them is by connecting them to
a computer or some other device that supports a
resolution of 1920x1200. |
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Are we to play only on the white keys from now on? |
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<obligatory misreading>Disappointed - I thought this was "Remove the Black Bras"</om> |
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Well, my blu-ray player apparently is able to remove the black bars, without having to do any special configuration. My dvd player, connected via HDMI to a widescreen TV, is still displaying black bars. |
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When I have more time, I'll investigate the DVD-player's menu to see if there really is a configuration option to remove them. |
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If your source is a different viewing aspect ratio than your screen, there's usually only 2 (decent) options: |
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- stretch it uniformly until the sides of the source touch the perimeter of the screen, |
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- stretch it uniformly until the top & bottom of the source touch the perimeter of the screen. |
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which works for everything except when non-square pixels are used, then it (may) get messy however, since TV and movie studios have as many lawyers as TV and DVD player manufacturers, there's usually a way to play pretty well everything. |
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Wait - the US still has black bars? |
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Yes, but in keeping with the spirit of racial equality, they
allow white people to come in if we promise to sit quietly
in the corner and behave ourselves. |
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In my opinion, 'television', 'DVD', 'Blu-Ray', 'High Definition' etc., and the concept of requiring some specific piece of hardware to view some specific format (and vice versa), are all obsolete. It's just data. So, store or broadcast the video in whatever resolution and aspect ratio is deemed appropriate _for the content_ (without any black bars, interlacing, etc.), and let the software or the viewer decide how to render it on any given hardware. |
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So, you are asking for a piece of hardware to solve what is a software problem. |
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An immediate (but slightly tedious) solution is to reprocess your problem content (e.g. with VLC) to suit your system. |
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(Sorry for seeming to criticise your solution on the grounds that the problem should not have been created in the first place). |
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//In other words, there are a lot of people out there seeing black bars on their widescreen TVs.//
In other words, there are a lot of people who can't read the instructions for their TV or DVD player.
Recently, I was in a movie rental shop, and the movie they had playing behind the counter was all stretched and wrong. I nearly cried. It's often the same with "viewer" videos and photos on the TV news. All stretched to crap.
Surely it's not that hard to get the aspect ratio right? |
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Dealing with different aspect ratios and video
formats is part of my job. Once as I was driving
home after a fairly long day, I was stopped behind a
car that seemed unusually tall for its width. My first
thought was “Huh, the aspect ratio is set wrong.” |
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Maybe this is the solution to the obesity epidemic.
People are just living in the wrong format. |
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So yesterday I finally got a chance to take a widescreen DVD and put it into my old DVD player, hooked up to a widescreen TV, and twiddle with the control-menu options. The player had some "TV options" which included an option to select a 16:9 ratio screen. |
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After that, no black bars. Excellent! And thank you, [ytk]. I might mention that there was no indication that the type of video output depended on the type of connection; the 16:9 TV setting seemed possible even if the DVD player was hooked up via an old-fashioned composite-video cable. |
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By the way, the movie I chose was an old one, "Hatari!", which absolutely was MADE for widescreen. Beautiful scenery, and lots of it. |
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