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Old 07-10-2014, 05:54 PM
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Originally Posted by zoreo View Post
So you can choose to show a lot of miscellaneous stuff on the sides with a very wide picture or focus on what's really important- making it big and easy to see with a more narrow format.
I think for the size of picture most people watch at home 16x9 strikes a pretty good balance between these objectives.
That's not surprising, since 1.78:1 is much closer to the supposedly aesthetically pleasing "golden ratio" of ~1.62:1 than the 2.39:1 ratio used for many films.
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Old 07-10-2014, 05:58 PM
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Uh, of course 1280x720 has more pixels than widescreen SD. 720p is HD. SD is SD.

Here's a partial explanation of the crazy world of digital SD video:

...

An anamorphic video is stored in the FAR (720x480) and flagged with a SAR. When you multiply the horizontal resolution of the FAR by the SAR, you get the final horizontal resolution used during playback, which when divided by the vertical resolution, gives you the DAR.

...

Are you still reading? Isn't digital video fun? If you really want the nitty-gritty on digital video, try reading this article and see if your head explodes.
Yes, I read it. Understood only about a third of it.
If video technicians (engineers?) ever disagree about how to handle FAR, DAR, and SAR, that could lead to WAR.

A lot of what you wrote dealt with "storage" on a disc or a computer. What I was wondering about is all of the different resolutions listed as "16:9 SD" or "widescreen SD" in the rabbitears.info link that I included in post15. Some of the subchannels of WGCU are listed as being widescreen but have a rather low resolution of 480x480. I was wondering whether that was a typo or what it really meant.
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Old 07-10-2014, 06:12 PM
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Originally Posted by zoreo View Post
Well I'm not a believer that wider is always better. The wider a screen is, the relatively smaller it is vertically, and vertical size is very important. .
I tend to agree with you. That's one of the reasons that I often use the 16:9 setting on my TV even when I am watching a channel that shows mostly 480i programming. It's not so much that I would mind having the pillar bars at the left and the right. What grieves me is that when I choose any setting other than 16:9, then when the station goes to a commercial, I often wind up with a letterboxed image (bars at top and bottom) or, even worse, the dreaded postage stamp effect ("window boxing") where there are bars top, bottom, left and right. More bars in more places might be a good thing for cell phones, but it is very annoying when it comes to watching TV.

I will say, though, that for some movies letterboxing is essential. The big dance number "June is Bustin' Out All Over" in "Carousel" would not look right when zoomed and cropped to 4:3 or shown in pan-and-scan.
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Old 07-11-2014, 12:40 AM
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Originally Posted by veedon View Post
Some of the subchannels of WGCU are listed as being widescreen but have a rather low resolution of 480x480. I was wondering whether that was a typo or what it really meant.
To my knowledge, 480x480 is not a valid resolution under the ATSC specifications, but it wouldn't surprise me if stations use invalid resolutions anyway, since they will probably work. If a 480x480 video frame contains a widescreen image, there are two likely ways for it to be stored. Either:

  1. All 480 horizontal pixels contain image, and only 360 vertical pixels contain image, i.e. 60 pixels at the top of the video frame and 60 pixels at the bottom of the video frame are black. The stream would be flagged with a SAR of 4:3, so that 480 * 4 = 1920, then 1920 / 3 = 640, so the stream gets stretched to 640x480 with only 360 vertical pixels used, thus giving you 640x360 pixels of image area, which is 16:9 (and shown windowboxed on a widescreen TV).
  2. All 480 horizontal pixels contain image, and all 480 vertical pixels contain image, and the stream is flagged with a SAR of 16:9, so that 480 * 16 = 7680, then 7680 / 9 = 853.333 (rounded to 854). The stream therefore gets stretched to 854x480 and enlarged to fill your screen, thus giving you a 16:9 image with no black bars on a widescreen TV. The image quality would just be lower than that of a 720x480 DVD, since the horizontal resolution of a 480x480 stream is lower and thus contains less detail. The technique for turning it into widescreen, however, is the same.
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Old 07-11-2014, 01:11 AM
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Originally Posted by Aleron Ives View Post
To my knowledge, 480x480 is not a valid resolution under the ATSC specifications, but it wouldn't surprise me if stations use invalid resolutions anyway, since they will probably work. If a 480x480 video frame contains a widescreen image, there are two likely ways for it to be stored. Either:
As I previously posted, the FCC is not enforcing the two SD formats. As long as the values are within the MPEG-2 Main@High profile, it will be allowed. MPEG-2 decoder chips will pretty much handle anything thrown at it. Doing 480x480 is a bit saving tactic. Allows them to have more bits for the HD stream.

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  1. All 480 horizontal pixels contain image, and only 360 vertical pixels contain image, i.e. 60 pixels at the top of the video frame and 60 pixels at the bottom of the video frame are black. The stream would be flagged with a SAR of 4:3, so that 480 * 4 = 1920, then 1920 / 3 = 640, so the stream gets stretched to 640x480 with only 360 vertical pixels used, thus giving you 640x360 pixels of image area, which is 16:9 (and shown windowboxed on a widescreen TV).
  2. All 480 horizontal pixels contain image, and all 480 vertical pixels contain image, and the stream is flagged with a SAR of 16:9, so that 480 * 16 = 7680, then 7680 / 9 = 853.333 (rounded to 854). The stream therefore gets stretched to 854x480 and enlarged to fill your screen, thus giving you a 16:9 image with no black bars on a widescreen TV. The image quality would just be lower than that of a 720x480 DVD, since the horizontal resolution of a 480x480 stream is lower and thus contains less detail. The technique for turning it into widescreen, however, is the same.
#1 : The TV would not know that the image was letterboxed with black bars. That info is not transmitted. So, this guess is moot.

#2 : The MPEG-2 chips do not scale to an intermediate size. When flagged as 16:9, it will directly scale the two values directly to the monitor's resolution (1920x1080 or 1280x720). If flagged as 4:3, it will scale the vertical to the display's vertical and the horizontal to 75% of the display's horizontal, adding black to the remaining pixels (unless the monitor has an option to display something else in the pillar bars).

Now, here comes the but part of #2 . The user normally has display setting options. Things like taking 4:3 and filling the screen. Or keeping the aspect ration, where the top and bottom are sliced off when zoomed. Or taking 4:3 and stretching the horizontal to fill the screen, not stretching the vertical. And for those 4:3 windowboxed images, stretch vertically and horizontally to crop all of the black bars. That is just a few of the options.

In the case of the posted image, I put it into photoshop and did a perspective correction and scaled to 1280x720. From what I can tell, the original image is 4:3 letterboxed, but the monitor is stretching the horizontal. That can be caused by either of two reasons: 1) the station screwed up and has the image flagged as 16:9 (anamorphic widescreen), or 2) the monitor is set to stretch 4:3 to 16:9. This setting might, might I say, be channel selectable. That means on other channels it gets 4:3 right, but on this channel the internal setting is wrong.

Check the setting in the monitor for aspect ratio. If it is exactly the same as other channels that do work correctly, then the engineering staff at the TV station has it flagged wrong and all you can do is contact the chief engineer and tell him/her that.

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Old 07-11-2014, 03:32 AM
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The TV would not know that the image was letterboxed with black bars. That info is not transmitted.
The TV doesn't need to "know" about the bars, nor did I say it would. The fact that it doesn't know about them is part of the problem with letterboxed widescreen, as I mentioned in my earlier post. Letterboxed widescreen is a main cause of windowboxing on 16:9 TVs.

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The MPEG-2 chips do not scale to an intermediate size. When flagged as 16:9, it will directly scale the two values directly to the monitor's resolution (1920x1080 or 1280x720).
I didn't mean to suggest that it would. I stated those values to make the aspect ratio of the source material (hopefully) clearer to veedon by stating the target image dimenions at the original resolution. If you weren't scaling to fit your screen, e.g. playing the video on your PC in a window, then you'd actually get those resolutions. If you were scaling the video to fit your screen, then it would automatically get upscaled and resized simultaneously.
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Old 07-11-2014, 06:01 AM
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Originally Posted by Aleron Ives View Post
The TV doesn't need to "know" about the bars, nor did I say it would. The fact that it doesn't know about them is part of the problem with letterboxed widescreen, as I mentioned in my earlier post. Letterboxed widescreen is a main cause of windowboxing on 16:9 TVs.
Ya, windowboxing sucks. It is a result of old 4:3 videos containing letterboxed material. Having to zoom those 360 vertical lines to 720, or 1080, really results in horrible looking video.

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I didn't mean to suggest that it would. I stated those values to make the aspect ratio of the source material (hopefully) clearer to veedon by stating the target image dimenions at the original resolution.
Sorry, misunderstood your intentions.

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Old 07-11-2014, 09:24 AM
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When I look at my PBS World channel, OTA, It is windowboxed. Black on all four sides. The OP sees only top and bottom black lines. The OP's PBS station is sending it out that way provided he has his TV set to Normal as he stated...

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Old 07-11-2014, 06:25 PM
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If it was a HD channel getting messed up I can understand getting upset but a SD channel is not worth being bothered over.

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When I look at my PBS World channel, OTA, It is windowboxed. Black on all four sides. The OP sees only top and bottom black lines. The OP's PBS station is sending it out that way provided he has his TV set to Normal as he stated...
By default my HDTV stretches SD channels to fill the screen which for 4:3 looks bad but when it is Widescreen SD it looks fine as far as SD goes and of course I can change SD to 4:3 with the display option if I choose.
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Old 07-11-2014, 06:49 PM
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Well I was confused too- why was what was suppose to be a 4:3 SD picture filling the width of a 16x9 HD screen?

Yeah, when I first started learning about digital TV and aspect ratios, I had the impression that a SD image was always 4:3 (and that a 4:3 image was always SD) and that a HD image was always 16:9 (and that a 16:9 image was always HD).

But later I learned that aspect ratio and the definition of an image are different concepts, although oftentimes the situation described above is what happens.
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Old 07-11-2014, 06:58 PM
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Originally Posted by Aleron Ives View Post
To my knowledge, 480x480 is not a valid resolution under the ATSC specifications, but it wouldn't surprise me if stations use invalid resolutions anyway, since they will probably work. If a 480x480 video frame contains a widescreen image, there are two likely ways for it to be stored.
Well, please forgive a non-techie for not completely understanding. I understand what an aspect ratio is, and I understand that a video file that is stored on a computer can have information encoded that says that it has a certain natural or native resolution. I also understand that video processing can be done to display something in a resolution that is not the native resolution, and that this video processing can also involve changing the aspect ratio.

What I don't understand is where all of this happens. When a site such as rabbitears speaks of 480x480, if that is not the actual resolution and 1:1 aspect ratio that the program gets displayed as on a TV set that is set to "Normal", then is 480x480 just a characteristic of some video file that gets "transmitted" to the viewer. What all is actually transmitted? People speak of "fllags" being encoded in a stream to give instructions about how to process the image at the final destination.
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Old 07-11-2014, 07:14 PM
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On the whole matter of letter boxing and whether it is a good thing or not, I think one source of confusion is that viewers don't always know whether the letter boxing is sort of "built into" the program that is being received or whether the letter box appearance is caused by a setting choice on the viewer's TV set.

The other lamentable thing is that if the letter boxing is "built into" the image that the TV receives, but the TV does not recognize that the top and bottom bars exist, then for some reason the TV set may think that it has to also add bars at the left and right.
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Old 07-11-2014, 08:15 PM
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What I don't understand is where all of this happens. When a site such as rabbitears speaks of 480x480, if that is not the actual resolution and 1:1 aspect ratio that the program gets displayed as on a TV set that is set to "Normal", then is 480x480 just a characteristic of some video file that gets "transmitted" to the viewer. What all is actually transmitted? People speak of "fllags" being encoded in a stream to give instructions about how to process the image at the final destination.
Ah, I see your confusion. When a station is said to transmit 480x480, that does define the resolution of the digital image that the station sends. There are 480 pixels of horizontal information and 480 pixels of vertical information, and the aspect ratio of these two dimensions is 480 / 480 = 1.0. If you displayed this image on your TV as 1:1, though, it wouldn't look very good, because your TV has either 1280x720 or 1920x1080 pixels, and 480x480 would not cover much of your screen. You'd have a tiny 480x480 square in the very center of your screen, while the rest of your screen "real estate" would be wasted and empty.

As such, this 480x480 image needs to be enlarged to fill your screen, and your TV does this automatically when it displays the image. If your TV were to enlarge the image in a 1:1 fashion, then 480x480 would become 720x720 or 1080x1080, depending on whether you have a 720p or 1080p TV.

The problem with this is that movies, TV shows, and other videos pretty much never have a 1:1 aspect ratio, so the 480x480 stream sent by the station also contains metadata that says, "This channel has a resolution of 480x480, but the aspect ratio of the image contained in those 480x480 pixels should really be 4:3, not 1:1." Your TV notices this information and then distorts the 480x480 image during playback. Instead of getting a 720x720 or 1080x1080 image, which would be 1:1, you get a 960x720 or 1440x1080 image, which is 4:3 (960 / 720 = 1.333, and 1440 / 1080 = 1.333, too).

The extra pixels are being generated in real time by your TV when it resizes the image, just as you can take an image from your camera and "blow it up" by enlarging it with MS Paint, Photoshop, or any number of other programs. The difference is that your TV is doing this in realtime. Does that make more sense?

If you're wondering why a 4:3 program would be transmitted as 1:1 in the first place (instead of sending a 4:3 program as a 4:3 image, which would probably seem like a more sensible approach), the goal is to save bandwidth. If the station sends a 640x480 (4:3) transmission, that image has a total of 307 200 pixels (if you multiply 640 by 480), and the station will need to dedicate a certain amount of bandwidth to make the image look good and not have artifacts.

On the other hand, if the station squishes the same picture into 480x480 pixels and transmits that (squishing the horizontal resolution and making people appear taller and skinnier), the image has only 230 400 pixels now, instead of 307 200 pixels the way it did before. Sending a smaller image means that the station can get away with using a lower bitrate, which saves more bandwidth for the other sub-channels the station has. The aspect ratio metadata is able to correct the distorted image when your TV plays it back, which reverses the "squishing" effect when the image gets stretched back out, and thus people will have the correct proportions again (instead of being too tall and skinny).

The downside of this is that the image will have less detail, because it lost 160 horizontal pixels in every frame (640 - 480 = 160).

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On the whole matter of letter boxing and whether it is a good thing or not, I think one source of confusion is that viewers don't always know whether the letter boxing is sort of "built into" the program that is being received or whether the letter box appearance is caused by a setting choice on the viewer's TV set.
Yes, that's a constant problem.

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The other lamentable thing is that if the letter boxing is "built into" the image that the TV receives, but the TV does not recognize that the top and bottom bars exist, then for some reason the TV set may think that it has to also add bars at the left and right.
It's actually sort of the opposite. The TV will enlarge the image until either the horizontal or the vertical sides of the picture reach the edge of your screen, and then if the other sides of the picture don't extend to the edge of the screen, then those parts of the screen are unused and thus appear black.
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Old 07-11-2014, 09:05 PM
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Ah, I see your confusion. When a station is said to transmit 480x480, that does define the resolution of the digital image that the station sends. There are 480 pixels of horizontal information and 480 pixels of vertical information, and the aspect ratio of these two dimensions is 480 / 480 = 1.0. If you displayed this image on your TV as 1:1, though, it wouldn't look very good, because your TV has either 1280x720 or 1920x1080 pixels, and 480x480 would not cover much of your screen. ... this 480x480 image needs to be enlarged to fill your screen, and your TV does this automatically when it displays the image... the 480x480 stream sent by the station also contains metadata that says, "This channel has a resolution of 480x480, but the aspect ratio of the image contained in those 480x480 pixels should really be 4:3, not 1:1." Your TV notices this information and then distorts the 480x480 image during playback. Instead of getting a 720x720 or 1080x1080 image, which would be 1:1, you get a 960x720 or 1440x1080 image, which is 4:3 (960 / 720 = 1.333, and 1440 / 1080 = 1.333, too).

The extra pixels are being generated in real time by your TV when it resizes the image... Does that make more sense?

....
You are very good at explaining things. That was an excellent explanation.

I guess I would only quibble a bit about terminology because I still speak "layman's language" rather than techie talk. (But I'm learning). So, as a layman, I don't really even think of anything other than the final picture that is displayed on the screen as being an "image". I guess there are good reasons to think about the thing that is in the pipeline, before it reaches the TV set, but I tend to think of that as being more of a data stream than an image. And saying that the TV set "distorts" a 480x480 image to produce a displayed image in 4:3 aspect ratio, seems a bit backward. I would argue that the 480x480 thing that is coming through the pipeline is itself a distorted thing, and the TV set actually undistorts (albeit with an accompanying loss of resolution).

I wonder if this process of sending a lower resolution through the pipeline is a form of OTA data compression, and, if so, how does that compare to the compression that cable companies use. I had read somewhere that one advantage of OTA is that it often uses less compression than cable TV does. Is that true or is it a myth?

Regarding the horrible "postage stamp" effect, I think we may be saying the same thing, just in slightly different ways. I was imagining a situation where a station decided to (for whatever reason) do a "widescreen SD" approach where basically the image is SD and is intended to be regarded as 16:9, but black bars are intended to be built in at the top and bottom (not added by the TV set), with the bars themselves being regarded as an actual part of the 16:9 image rather than an add-on. The TV set would not actually "see" the bars, but in effect the TV set would regard the bottom of the lower bar as the bottom of the image, and the top of the top bar as the top of the image and thus think that there was no room to do any vertical stretching. There might be room to do horizontal stretching, but I am not sure whether a TV set's settings would ever allow stretching in only one direction. (I understand that distortion can occur when more stretching is done in one direction than another, but I don't know if it is even possible to have the stretching be entirely in one direction.) In any case, if the TV set saw a "480i" flag on the program or knew it was basically SD, wouldn't some settings cause the pillar bars to be added at the left and right, and then you would wind up with the postage stamp effect?
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Old 07-11-2014, 09:47 PM
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Yeah, when I first started learning about digital TV and aspect ratios, I had the impression that a SD image was always 4:3 (and that a 4:3 image was always SD) and that a HD image was always 16:9 (and that a 16:9 image was always HD).
This is splitting hairs, but an HD video is always 16:9. Even if the image that is being displayed in the 1920x1080 video is really only using the middle 1440 (4:3), the black pillar bars are part of the HD video that is transmitted. They are not instered by the TV/monitor. With SD video, 4:3 or 16:9 anamorphic, there are never pillar bars as part of the image.

Technically, the 4:3 image that is part of the 16:9 HD video can be positioned anywhere horizontally. In theory, they could have the 4;3 all the way to the left and have something else in the remaining area on the right.

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Old 07-11-2014, 10:04 PM
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Originally Posted by veedon View Post
I guess I would only quibble a bit about terminology because I still speak "layman's language" rather than techie talk. (But I'm learning). So, as a layman, I don't really even think of anything other than the final picture that is displayed on the screen as being an "image". I guess there are good reasons to think about the thing that is in the pipeline, before it reaches the TV set, but I tend to think of that as being more of a data stream than an image. And saying that the TV set "distorts" a 480x480 image to produce a displayed image in 4:3 aspect ratio, seems a bit backward. I would argue that the 480x480 thing that is coming through the pipeline is itself a distorted thing, and the TV set actually undistorts (albeit with an accompanying loss of resolution).
You are right. The 480x480 is a distorted 4:3 image and the TV/monitor undistorts it in order to display it correctly on the screen. Keep in mind that 720x480 video is also distorted, but in a better way because more resolution is added horizontally.

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I wonder if this process of sending a lower resolution through the pipeline is a form of OTA data compression, and, if so, how does that compare to the compression that cable companies use. I had read somewhere that one advantage of OTA is that it often uses less compression than cable TV does. Is that true or is it a myth?
Apples and oranges. While it may appear to be a form of data compression, it isn't in the context you are getting at. You are talking about MPEG-2 data compression of the video. Cable has been known for using more compression (less bitrate) in order to get three HD streams into a single QAM channel, vs two HD streams in the same channel. But, OTA has been just as bad when adding SD streams to their transmission, in that the bitrate for the HD stream is lowered in order to has bits for the SD streams. So, in reality, both are guilty.

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Regarding the horrible "postage stamp" effect, I think we may be saying the same thing, just in slightly different ways. I was imagining a situation where a station decided to (for whatever reason) do a "widescreen SD" approach where basically the image is SD and is intended to be regarded as 16:9, but black bars are intended to be built in at the top and bottom (not added by the TV set), with the bars themselves being regarded as an actual part of the 16:9 image rather than an add-on. The TV set would not actually "see" the bars, but in effect the TV set would regard the bottom of the lower bar as the bottom of the image, and the top of the top bar as the top of the image and thus think that there was no room to do any vertical stretching.
Widescreen SD does not contain letterbox bars if the image image is 16:9. By definition, widescreen 16:9 SD will never have letterboxed bars. That said, if the video is a 2:35:1 movie, it will contain letterbox bars, but the video itself is 16:9 anamorphic. What you are describing with the letterbox bars is when the original video is 16:9 and it is shrunk to fit into the 4:3, non anamorphic, image area. So, yes, no stretching other than to take the 480 vertical resolution and stretch it to fill 720, or 1080. The black bars would stay intact and result in the windowboxing effect.

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There might be room to do horizontal stretching, but I am not sure whether a TV set's settings would ever allow stretching in only one direction. (I understand that distortion can occur when more stretching is done in one direction than another, but I don't know if it is even possible to have the stretching be entirely in one direction.) In any case, if the TV set saw a "480i" flag on the program or knew it was basically SD, wouldn't some settings cause the pillar bars to be added at the left and right, and then you would wind up with the postage stamp effect?
Yes, horizontal only stretching is an everyday thing and is what was happening with the image that was posted. Many people set their TVs to stretch 4:3 to fill their screen, causing short fat people. I hate it. I've convinced many people to stop doing that.

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Old 07-11-2014, 11:10 PM
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Good conversations!

Maybe I wasn't clear enough when I mentioned "built-in" letter boxing. What I meant is that I think sometimes TV stations have a program that they think really should be shown with letter boxing, but they know that many people will set their TV to just make the program fill the whole 16:9 screen. So, to get around this and force the viewer to take deliberate steps to alter the image (if they wish to), what some stations will do is create an "image" that has built-in bars at the top and the bottom. The "picture plus top and bottom bars" is a single 16:9 image that fully fills the screen as far as the TV set itself can tell. The viewer might think that what he sees is an image with bars added, but from all that the TV set can tell, it's a single 16:9 image. So if the TV set is set to automatically stretch to 16:9, the TV set would do nothing and the letter boxing bars would still be visible. The only way to make the bars disappear would be to zoom the image.

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Old 07-12-2014, 12:03 AM
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And saying that the TV set "distorts" a 480x480 image to produce a displayed image in 4:3 aspect ratio, seems a bit backward. I would argue that the 480x480 thing that is coming through the pipeline is itself a distorted thing, and the TV set actually undistorts (albeit with an accompanying loss of resolution).
As mrvideo said, it's a two-way distortion. The 4:3 image gets distorted to 1:1 when it's "stored" in the 480x480 video frame, and then that 1:1 image gets distorted again back to its original 4:3 shape. The second distortion counteracts the first distortion and restores the original aspect ratio.

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*snip*
The only way to make the bars disappear would be to zoom the image.
Your line of thinking is correct, but it's not so much that the station is taking steps to "create an image with built-in bars". It's much more likely that the source always had built-in bars, because it was created as letterboxed 4:3 in the first place. Some videos are, unfortunately, made and released that way, which forces you to zoom the image to make it fill your screen. Such videos are intended for watching on a 4:3 TV, where the bars aren't a problem (as described in my first post). On a 16:9 TV, the bars are a nuisance.
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Old 07-12-2014, 12:07 AM
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Your line of thinking is correct, but it's not so much that the station is taking steps to "create an image with built-in bars". It's much more likely that the source always had built-in bars, because it was created as letterboxed 4:3 in the first place.
You beat me to it. Pretty much think/words exactly.

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Old 07-12-2014, 02:02 PM
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...

Your line of thinking is correct, but it's not so much that the station is taking steps to "create an image with built-in bars". It's much more likely that the source always had built-in bars, because it was created as letterboxed 4:3 in the first place. Some videos are, unfortunately, made and released that way, which forces you to zoom the image to make it fill your screen. Such videos are intended for watching on a 4:3 TV, where the bars aren't a problem (as described in my first post). On a 16:9 TV, the bars are a nuisance.
Yes, I. know that stations often just send along to the viewer whatever is sent to the station. I wasn't getting into the details of what the original "source" might be. I actually don't know much about how programming gets delivered to a station and prepared for broadcasting. I would guess that broadcast engineers have some role in that, but that some things may arrive set up in a way that limits what the station can do.

Maybe some of the issues regarding letter boxing or the really horrible window boxing (postage stamp effect) will go away as old CRT sets are phased out of use and nearly all sets have screens with a 16:9 aspect ratio.

I was pretty sure that in some cases the black bars were "built in", because quite often I find black bars even when I have the TV set in the 16:9 setting. In fact, I recently watched a program on a SD subchannel that displayed as a postage stamp when I chose the "4:3" setting or the "set by program setting". When I chose the "16:9" setting, then I got the letter box effect. The only way to completely fill the 16:9 screen was to do a zoom.

When watching some kinds of programming (such as documentaries and travelogues), the amount of screen space used will even change within the broadcast of a single program. Perhaps the program consists of footage shot in a variety of resolutions and aspect ratios.
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Old 07-12-2014, 10:34 PM
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Yes, I. know that stations often just send along to the viewer whatever is sent to the station. I wasn't getting into the details of what the original "source" might be. I actually don't know much about how programming gets delivered to a station and prepared for broadcasting. I would guess that broadcast engineers have some role in that, but that some things may arrive set up in a way that limits what the station can do.
Stations receive programming via satellite. What is received is directly recorded onto their media server and played out to air at the appropriate time. Engineering only gets involved if something is broken. For network programming (ABC, CBS, CW, FOX, NBC) during primetime, the satellite feed goes directly to air.

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Maybe some of the issues regarding letter boxing or the really horrible window boxing (postage stamp effect) will go away as old CRT sets are phased out of use and nearly all sets have screens with a 16:9 aspect ratio.
CRT 4:3 sets, do not have windowboxing issues. The issue will not go away when SD 4:3 programs are viewed on 16:9 monitors.

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I was pretty sure that in some cases the black bars were "built in",
Letterbox black is always part of the original source. HD monitors will only add pillar bars.

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When watching some kinds of programming (such as documentaries and travelogues), the amount of screen space used will even change within the broadcast of a single program. Perhaps the program consists of footage shot in a variety of resolutions and aspect ratios.
When those programs dig into the past, the sources will end up being SD 4:3. When correctly displayed within the HD show, they will add the pillar bars.

I'm really pissed at the producers of the CNN series The Sixties. They've taken all of the old 4:3 videotape and film and chopped the top and bottom in order to fill the screen. That results in 25% of the image being thrown away. Stupid, really stupid.

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Old 07-13-2014, 12:58 AM
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I've noticed that a lot of 4:3 footage gets shown with blurry clones of the left and right sides of the image now, presumably because station managers are tired of people calling to complain that the station is broken when they see pillarboxing on their TVs.
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Old 07-13-2014, 04:13 AM
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Originally Posted by Aleron Ives View Post
I've noticed that a lot of 4:3 footage gets shown with blurry clones of the left and right sides of the image now, presumably because station managers are tired of people calling to complain that the station is broken when they see pillarboxing on their TVs.
I'm also seeing this a lot lately and don't quite know how I feel about it. I guess unlike cropping it doesn't lose anything and yet it manages to fill the screen and truthfully at a quick glance it does really seem to be 16:9'ish, but does it really add anything......
The first few times I saw it I couldn't figure out how or what they were doing but it seems they are taking the left and right side of the screen, flipping it over and blurring it out, kind of interesting.
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Old 07-13-2014, 04:15 AM
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When those programs dig into the past, the sources will end up being SD 4:3. When correctly displayed within the HD show, they will add the pillar bars. I'm really pissed at the producers of the CNN series The Sixties. They've taken all of the old 4:3 videotape and film and chopped the top and bottom in order to fill the screen. That results in 25% of the image being thrown away. Stupid, really stupid.
There are concerns by producers and TV programming execs that square pictures with blanking on the sides will repel "ordinary" viewers who don't understand what they're seeing. And there's another side that says that all 4x3 programming annoys viewers because it looks "old." One can also make a good argument in a documentary that the constant cutting back and forth between new 16x9 footage and 4x3 material is too distracting. I think you could make an argument that some kind of decorative border might work better than black, at least for short segments, but it's a judgement call.

The problem as I see it with PBS stations is that they have no money, and their technical staffs have been cut down to the nub. There's nobody there in the control room to say, "oh, wait! The aspect ratio is wrong! Let me flip this switch and fix it!" One of the local LA stations constantly shows their stuff in what I call "fattenized" 16x9, widening out 4x3 material to fill the HD frame, which looks like crap. The main PBS station, KOCE, generally gets it right. But across the dial on other channels, it's a crap shoot.

It's very frustrating when you get uncaring, non-technical people in a position of power. They tend to make very bad decisions that are completely wrong, particularly with technical issues, but unfortunately they're the ones running the stations.

You think 16x9 and 4x3 are screwed up now. Wait until we have 4K, HDR, and different frame-rates. In five years, they'll have 150 additional ways to show movies & TV shows incorrectly.
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Old 07-13-2014, 04:28 AM
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Very good explanation.

What kinda sucks is that ATSC allows for a couple of SD image sizes. While 720x480 is the ideal for old NTSC material converted to digital, the ATSC spec actually calls for 704x480 (4:3 or anamorphic 16:9) or 640x480 (4:3 only). The problem is that the FCC does not require stations to only use those two SD formats. 720x480 is allowed because it is within the limits of Main Profile @ High Level. Stations have been known to use 352x480 in order to save bandwidth. The image will probably look like crap, but who cares, as long as it brings in the $$$. Many stations don't care about HD quality, so why care about SD quality.
Horizontal resolution for SD is still based on the SD analogue standards which don't neatly fit into the modern digital formats. When digitising a 52us active line of a 625/50 (aka 576i25 or 576/50i) signal at 13.5MHz (standard SD luminance sampling rate) the actual active 4:3 or 16:9 picture area is 702x576. Digital studio systems allowed a little extra latitude either side to cope with small timing errors and to avoid introducing ringing by cropping the extreme left and right of an image, so are 720x576.

I believe NTSC lines are a a little longer, with a 52.2us line time but a 4:3 or 16:9 NTSC image is still narrower than 720x480, at somewhere between 704 and 705x480, so there is a good argument for using 704x480 at the final link in the chain, as it is the closest MPEG2 multiple to the actual 4:3 or 16:9 active area.

However the 720x576 (and 720x480) is a little wider than 4:3 or 16:9. If you are up converting you take the central 702x576 frame and scale to 1920x1080 or 1280x720 NOT the full 720x576 (as you will introduce geometric distortion). In the UK many broadcasters use the 704x576 (nearest MPEG multiple to 702x576) variant. I'm not sure what the NTSC precise widths are (things get a bit confusing as 60Hz SD formats lost lines when digital TV was introduced, unlike 50Hz formats which just padded their two half-lines to full lines going from 575 active (287.5 x 2) to 576 active (288x2)

720 is a good common width for both 50 and 60Hz standards that don't share a single line length when sampled at the same sampling rate, but should never be treated as the full active area of the format, as if it is you will introduce geometric distortion. (I've seen this happen in broadcast chains with an incorrectly designed downconverter that scaled 1920x1080 to 720x576 not 702x576)

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BTW, as a side note, in the digital world NTSC, or PAL, does not exist. NTSC and PAL are OTA analog transmission standards. NTSC has been used to describe analog tape based devices as well, even though most recorded the color in a different format.
Though NTSC and PAL colour-under recordings usually retained the NTSC-ness and PAL-ness so it was arguably a fair thing to do (usually they just heterodyned the subcarrier down and back up again - though one variant of SECAM VHS recording - there were two - used an alternative system ISTR)
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Plus, the video and audio are separate on tape and playback. That said, what was recorded on analog tape was damn close to what was transmitted.
And of course there were digital PAL and digital NTSC formats. D2 and D3 digital VTRs used 4fsc digital sampling of the composite signal to allow for digital composite recording. In the NTSC territories, NTSC composite vision switchers were also marketed - though few PAL models were made as Europe had already moving to digital component studios (France in particular as SECAM was never a good studio standard - and many were already using PAL analogue internally and transcoding)

And a number of broadcasters used digital composite distribution over fibre. The BBC used 140Mbs circuits for their PAL analogue distribution - and the signal remained in the PAL composite domain, no decoding to component. (Digital stereo audio was NICAM compressed and inserted into the blanking area using a system called Sound-In-Syncs - aka SIS, which was then modulated onto a NICAM 728 carrier for broadcast to home - as our analogue TV system included digital stereo audio from the late 80s)

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In the digital world, all of that is gone. No more vertical, or horizontal, sync pulses. No more color burst, hell no more separate luminance and color for that matter. SD video should not be labeled as NTSC or PAL. Hell, I've even seen 1080i29.97 labeled as NTSC. If it is 29.97/59.94, it is NTSC. If it is 25/50 it is PAL. Wrong, all wrong. For some idiotic reason, I've even seen 23.976 digital video labeled as NTSC.
In the main yes - but there are digital composite formats (we deal with them at work still) - and I think they retain a recording of the colour burst (just as analogue VTRs did - though I may be wrong) - and although digital component formats don't have colour bursts, there are still SAV and EAV signals (Start of Active Video) and (End of Active Video) in baseband digital component standards, and blanking still exists in baseband (and some data in blanking is also recorded on digital VTRs).

Once you get to compressed signals, then only active video is usually compressed, though some formats (IMX for instance) will also allow you to digitally preserve a portion of the VBI (to allow VITC, Closed Captions/Subtitle data etc. to be preserved). It's always initially confusing when you find an IMX50 (aka D10) file which will have a resolution of 720x512 (480 + 32 lines of blanking) or 720x608 (480 + 32 lines of blanking) I've seen those resolutions REALLY fox people ;-)

Totally agree with the sloppy use of PAL and NTSC to mean 25/50 and 29.97/59.94 (or 30/60) - particularly stupid as there is a PAL-M format which uses PAL encoding with a 525/60 (aka 480i29.97 aka 480/59.94i) source signal - so there are both 50 and 59.94 variants of PAL in the wild...

DVDs particularly annoy me in this regard...

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Old 07-13-2014, 04:47 AM
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There are concerns by producers and TV programming execs that square pictures with blanking on the sides will repel "ordinary" viewers who don't understand what they're seeing. And there's another side that says that all 4x3 programming annoys viewers because it looks "old." One can also make a good argument in a documentary that the constant cutting back and forth between new 16x9 footage and 4x3 material is too distracting. I think you could make an argument that some kind of decorative border might work better than black, at least for short segments, but it's a judgement call.

The problem as I see it with PBS stations is that they have no money, and their technical staffs have been cut down to the nub. There's nobody there in the control room to say, "oh, wait! The aspect ratio is wrong! Let me flip this switch and fix it!" One of the local LA stations constantly shows their stuff in what I call "fattenized" 16x9, widening out 4x3 material to fill the HD frame, which looks like crap. The main PBS station, KOCE, generally gets it right. But across the dial on other channels, it's a crap shoot.

It's very frustrating when you get uncaring, non-technical people in a position of power. They tend to make very bad decisions that are completely wrong, particularly with technical issues, but unfortunately they're the ones running the stations.

You think 16x9 and 4x3 are screwed up now. Wait until we have 4K, HDR, and different frame-rates. In five years, they'll have 150 additional ways to show movies & TV shows incorrectly.
What's annoying is that 4:3 / 16:9 header aspect switching is relatively straightforward to implement (even if you don't have AFDs). The key thing is to ensure that your playout system respects it. There are multiple ways of doing it - some of which will survive satellite distribution. But you have to do it right. What you don't want is to have to have a switch in master control that you have to manually use on each transition.

AIUI at the BBC all material is cached 16:9 to the transmission server - so it is pillar boxed on ingest to the playout servers. So a 12F12 source will be pillar boxed to 12P16. 16F16 sources will be ingested as 16F16. The 16F16 content will also have an active format descriptor assigned to it which will signal what format should be used when it is displayed on a 4:3 (aka 12F12) display - whether it should be 12F12 centre cut, 14L12 shallow letterbox or 16L12 deep letterbox. (This process also works in the HD domain, with 4:3 SD content unconverted to 12P16 HD) I know other broadcasters cache 4:3 as 12F12 and 16:9 as 16F16 and use metadata to drive ARCs on live transmission. This process is in some ways less robust, but it can mean you avoid the resolution loss of a 12F12->12P16->12F12 round trip (where horizontal resolution can be limited)

On transmission the 12P16 and 16F16 content is cut and mixed in the 16:9 domain. However the MPEG2 encoders used at the final link in the chain get signalling (sometimes from Line 23-style WSS, sometimes from GPIs) that will either trigger a 12F12 ARC (so that 12P16 content is ARCed to 12F12) and an MPEG2 header switch to flag that the stream is now 4:3 not 16:9 (used on satellite where AFDs are not supported), or the 12P16 video will be encoded, and the MPEG2 header retains the 16:9 flag, but the AFD will signal that the content is 12P16 and receivers can do what they need to do (based on user configuration) with it.
For those not familiar with 12F12, 12P16 etc. They are the normal descriptions used in the SD world to describe the active picture area and the underlying aspect ratio of the signal carrying the picture, scaled to XX:9 - so 16 for 16:9, 14 for 14:9, 12 for 4:3=12:9. F=Full Screen, P=Pillarbox - black bars left and right, L=Letterbox - black bars top and bottom. They are also used in AFD-land to signal what the output format should ideally be for a given input format.

12F12 = Full height/width 4:3 in a 4:3 frame
12P16 = Full height/full height 4:3 in a 16:9 frame with thick pillar box bars left and right
16F16 = Full height/width 16:9 in a 16:9 frame
16L12 = Full width/full height 16:9 in a 4:3 frame with thick letterbox bars top and bottom

14L12 = Non full-width/full height 16:9 in a 4:3 frame with cropping left and right but shallower letterbox bars top and bottom. This is the UK preferred format for viewing 16:9 content on a 4:3 screen and was used by all broadcasters for airing most 16:9 content when 4:3 analogue SD transmissions still existed here. You may see UK shows air in this format still if a 4:3 master was purchased, or a commercial edit was done in the 4:3 domain.

16L12 = Full width/full height 16:9 in a 4:3 frame. This is mainly used for movies where cropping to 14:9 isn't ideal, as well as some arts shows (particularly opera and ballet where cropping left and right on wide shots isn't ideal)

14P16 = Full width/non-full height 4:3 in a 16:9 frame with light cropping top and bottom and narrow black bars left and right. This is the UK preferred format including 4:3 archive content in 16:9 news bulletins. It is deemed less distracting than cutting between 16F16 and 12P16, but doesn't compromise the original framing as much as a full 16F16 conversion of 12F12 content (i.e. a full 16:9 crop and zoom)

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Old 07-13-2014, 08:14 AM
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I'm not sure what the NTSC precise widths are (things get a bit confusing as 60Hz SD formats lost lines when digital TV was introduced
I'm confused by that statement. NTSC analog to MPEG-2 digital has been 480 from the beginning. What does our going to digital TV have to do with that?

BTW, when I recode 720x480 SD MPEG-2 video, I centercut the 704 pixels.

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Once you get to compressed signals, then only active video is usually compressed, though some formats (IMX for instance) will also allow you to digitally preserve a portion of the VBI (to allow VITC, Closed Captions/Subtitle data etc. to be preserved). It's always initially confusing when you find an IMX50 (aka D10) file which will have a resolution of 720x512 (480 + 32 lines of blanking) or 720x608 (480 + 32 lines of blanking) I've seen those resolutions REALLY fox people ;-)
When Fox first went digital, they put out 720x512. Here is an example sat feed frame.

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Totally agree with the sloppy use of PAL and NTSC to mean 25/50 and 29.97/59.94 (or 30/60) - particularly stupid as there is a PAL-M format which uses PAL encoding with a 525/60 (aka 480i29.97 aka 480/59.94i) source signal - so there are both 50 and 59.94 variants of PAL in the wild..
Add to the stupid list that NTSC/PAL are used to describe HD variations, when there weren't any analog HD variations. That is the one that gets me the most.

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Old 07-13-2014, 08:19 AM
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What's annoying is that 4:3 / 16:9 header aspect switching is relatively straightforward to implement (even if you don't have AFDs). The key thing is to ensure that your playout system respects it. There are multiple ways of doing it - some of which will survive satellite distribution. But you have to do it right. What you don't want is to have to have a switch in master control that you have to manually use on each transition.
That is something that is never going to happen here. Hell, AFD isn't even fully implemented.

My original complaint, to which Marc Wielage responded to, was that the CNN The Sixties documentary episodes were not original 4:3 with pillar bars. I do not see how your U.K. system could even be used with such a program.

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Old 07-13-2014, 12:21 PM
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Although I am sometimes critical of digital television because of some mild annoyances such as the postage stamp effect, I must say that overall I am pleased with the completed transition to digital broadcasting. Some of the SD subchannels are very nice to have. And I think that AntennaTV and Me-TV have both done a pretty good job of delivering good picture quality for the old shows that they specialize in.
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Old 07-13-2014, 03:40 PM
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I'm confused by that statement. NTSC analog to MPEG-2 digital has been 480 from the beginning. What does our going to digital TV have to do with that?
US analogue NTSC had more active lines than 480. The original D1 decks recorded 720x486 (not 480) to ensure that they met the FCC requirements, though I believe the formal NTSC spec was for 483 active lines. (Similarly D2 and D3 digital composite decks recorded more than 480 lines for the same reason)

When DV digital decks appeared, they only recorded 480 lines (the nearest Modulo 8 multiple), and technically didn't meet FCC specs, though I believe the specs were tweaked with the introduction of digital TV - which was based on 480 lines. I've never been fully clear on how this impacted on aspect ratio... I suspect it may have gone in to the "too difficult" box in many cases.

(When I was in a different line of work, I was an R&D engineer for a broadcast equipment manufacturer in the UK who made quite a lot of money selling DVEs to US TV stations to permanently apply a small amount of zoom on their picture in Master Control to ensure they never breached the FCC blanking specs!)
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