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Old 2007-12-13, 02:08 PM   #1
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Default FAQ - Widescreen TV Stretch Modes.

Updated 2013.11.11. 10,135 Previous views:

This FAQ was first written when most HDTVs were Plasmas or CRTs, there was mostly 4:3 programming and people were concerned with burn in. Now that many HDTVs don't have burn in issues (LCD, DLP, LCoS) and since there's a lot more HD programming, one doesn't need to stretch 4:3 images which provides for the best picture quality and no distortion. I now recommend watching 4:3 as 4:3 and 16:9 as 16:9


Most HDTVs have a variety of stretch modes (So do some AVRs & STBs). Four of the basic modes are described below. Different sets will be slightly different and have slightly different names for these modes, but you'll get the idea from this discussion. Please also read the companion FAQ on "Black Bars".

Many TVs will remember the stretch modes for incoming HD and SD signals separately, so it's possible to stretch the SD channels and leave the HD channels alone, provided the STB sends the SD channels as 480i/p and the HD as 720P/1080i. Many cable and Sat STBs no longer allow for separate output formats due to HD IPGs.

1. Normal - no "stretching" of an image in either direction. The signal that came in, is what's shown on the TV. If the signal is 4:3, you will have "bars" on the sides of the image. If the signal is High Definition (16:9), the image will completely fill the screen and often "overrule" any stretch mode in place. (note standard DVDs are not high def and are explained later). Note also that any upconverted 4:3 programming on HD channels will still be 4:3 and the bars on the side will now be black and are also part of the HD image, which many HDTVs cannot stretch - although some STBs can.

2. Horizontal Stretch (often called Full*) - this mode stretches the image in a horizontal direction only. This is intended to stretch an "Enhanced for Widescreen" or "anamorphic" DVD so that the image is what was originally intended. If the original aspect ratio was 1.66:1 - 1.85:1, this will typically perfectly fill your screen. If it was 2:35:1, there will still be "black bars" on the top and bottom of the image, but this is normal. If you apply this mode to "standard" (4:3) programming, everyone will look "fat", however the amount of stretch will exactly fill the widescreen TV. (it takes a 4:3 image and stretches it to 16:9 or a 33% stretch) Many TVs also default to this mode for HD programming (the image is not stretched on most TVs)

3. Vertical and horizontal stretch (often called Fill or Zoom) - this mode stretches the image in both directions (zooms in). This is intended for DVDs that have not been "enhanced/anamorphic". If the original aspect ratio was 1.66:1 - 1.85:1, this will typically perfectly fill your screen. If it was 2:35:1, there will still be "black bars" on the top and bottom of the image, but this is normal. This mode can also be used for "widescreen" images on an SD channel. If you use this stretch mode on such a programme, the "widescreen image" will typically fill the screen.. If the aspect ratio was 2.35:1, there will still be bars at the top and bottom as described before and this is normal. Using this mode on "standard widescreen" images, will exacerbate any poor image quality, so a poor signal will look really bad in this mode. You have to have a really good original "standard widescreen" image to use this mode.

4. Non-linear stretch - this mode stretches the edges of a 4:3 image more than the center of the image. It also typically does a small amount of vertical stretch, but usually not enough to remove "tickers" or tops of heads. This mode is intended to be used on 4:3 images to prevent "burn in" from the "bars" that would normally be left on the sides of the image. This does not make the people look as "fat" as the horizontal stretch, but it can sometimes be a little disconcerting because the edges of the picture may make one side of an person "fatter" than the other side. (There is less "distortion" in the centre of the image, than at the edges) Once you get used to this image for a week or so, you don't even notice and it's not a bad way to watch 4:3 images on a widescreen TV. When I have people over, they often don't even notice the "irregularities" of this image and I've stopped noticing too, until something at the edge of the screen draws my attention to it.

5. Some TV's have even more options and there are scalers that will provide you with infinite choices, however, this should be good enough to explain the basics.

6. Some people do not like the black bars at the top of a 2.35:1 DVD. You can make these "disappear" by using the TV's or DVD player's zoom mode, however, you will lose some of the sides of the movie.


The following question also comes up a lot:
Quote:
I would appreciate any input on which widescreen HDTVs which are best at "stretching" a 4:3 picture onto the widescreen.
The "best" stretch mode for you is going to depend on you, and your brain, let me explain.

1. Your eyes are only the connection to the outside world. It is your brain that does the "seeing". If your eyes did the actual "seeing" everything would be upside down.

2. As anyone who has worn glasses knows, it takes a while to get used to the chromatic aberration and barrel distortion that glasses inflict on us.

What am I leading to?

1. The brain quickly learns to live with these "distortions" and they "fade into the background."

2 No one can tell you what is "best", only you can decide.

3. All of the stretch modes have some form of "distortion" or "cut-off", much like glasses (fat people, people's heads cut off, fat people at the sides of the screen, etc.)

4. After looking at a stretched image for a few days, your brain will "get used to" the image and you won't even notice.

So, go out and sample a few, remembering that after a few days viewing, you'll likely forget you're even looking at a stretch mode.


Each manufacturer has his own name for these stretch modes, but the descriptions should allow you to understand which is which. Here are some "translations"

New Hitachis
NORMAL = 4:3 Standard
FULL = 16:9 Standard
FILL = 4:3 Zoom1
SMOOTHWIDE = 4:3 Expanded
Also, 4:3 Zoom 2 - Big Zoom.
Also 16:9 Zoom - Zoom (perhaps for 2.35:1 DVDs to eliminate black bars above and below, but lose sides???)

Toshiba (Note that the operating manuals for many Toshibas are incorrect - follow the following instead of what they say)
NORMAL = Natural
FULL = FULL
FILL = Theater Wide 2
SMOOTHWIDE = Theater Wide 1 and/or Theater Wide 3 may be used for watching 4:3 images. Your choice depending on preference, since these are not identical to the Hitachi "Smoothwide".

Zenith IQB64W10W: Provided by Zarlor
NORMAL = 4:3
FULL = 16:9
FILL = ZOOM
Only those 3 are available.

Sony
NORMAL = Standard
FULL = Stretch/Full
FILL = Zoom
SMOOTHWIDE = Wide-Zoom

Pannasonic
NORMAL = ???
FULL = Full
FILL = Zoom
SMOOTHWIDE = Just

RCA
NORMAL = Normal
FULL = Full
FILL = Fill

Mits
Standard - HDTV automatically uses this.
Full = Expand
Fill = Zoom
Smoothwide = Stretched - Non-linear stretch
Normal = Narrow

Bell HD STBs (use the * button to cycle)
Normal - Normal
Full - Stretch
Smoothwide - Partial Zoom
Fill - Zoom.

For the BTV receivers, the stretch mode for SD channels will be "remembered" separately from the mode for HD channels, so the TV's stretch mode will not come into play.

Rogers HD STBs (use the # button to cycle through the various stretch/zoom options)


If you're still not getting the right picture from your DVD player, please note the following:

DVD players have a menu for selecting "widescreen or 16:9" TVs. This should be set to 16:9 or widescreen when watching DVDs on a widescreen TV, or on a 4:3 TV with "vertical compression". Some DVD players have even more settings available. Make sure that you choose the right one depending on your TV and DVD player (read the manuals).

Some TVs have an "auto-stretch" mode, which attempts to properly stretch incoming signals, however, it doesn't always work properly and non-anamorphic DVDs will not be properly stretched on most "auto-stretch" TVs. You either need to turn off "auto-stretch" or override it.


Note regarding stretching of HD inputs.

Many HDTVs cannot properly stretch HD (720P, 1080i, 1080P) signals, or the number of stretch modes are limited

* when viewing an HD input, the TV may say "full" or "normal" but there is no actual stretch taking place - a true HD signal will fill a 16:9 screen.

This same issue comes up on DVI/HDMI connections - on several STBs and upconverting DVD players that output 720P or 1080i. You will need to "workaround" by using a different connection - component video or less, or set the device to output 480i/p.



Please PM 57 if you have any comments or suggestions for this post.
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Old 2008-09-10, 03:21 PM   #2
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Some newer TVs (1080P using HDMI) have a setting, either under the user setup, HDMI setup, or as part of the stretch modes, which allows for 0% overscan, or 1:1 pixel mapping - List provided by Michael_TLV.

Sony ... Full Pixel
Panasonic ... HD Size 2
Samsung ... Screen Fit
LG ... Just Scan
Pioneer ... Dot by Dot
Sharp ... Dot by Dot

This mode is designed to be used with computers so you can see the entire desktop. If you use it with regular TV, you end up seeing things that you should not be seeing. This includes white lines at the top of the screen (VBI-like Information), sometimes thin black bars, sometimes thin lines on the left or right edge of the screen ( black lines, coloured lines, etc).

This is due to the fact that the various affiliates don't always do a perfect job of upconverting, or centering the image on the screen, since TVs should be running with at least 2% overscan to avoid these issues.

You have a choice, you can either put up with this annoyance, or you can switch to the appropriate stretch mode (usually called wide, full or 16:9 on HD channels), or by changing the setting in the user setup menu to 1-2% overscan. instead of 0% / 1:1 pixel mapping, etc) - depends on the TV - usually outlined in the operating manual.

Sometimes the STB may be the cause of the issue and changing the STB may help, or the next firmware update may also help if you report the issue to your service provider.

See the following link for more on the topic:

http://www.digitalhome.ca/forum/show...879#post788879

Some TVs allow you to select/keep the stretch modes/overscan for each input. I would recommend that you use pixel/pixel for the DVD/BD input, where none of the annoyances mentioned above should occur and use Full/16:9 for the "TV" input. If you can put up with the annoyances above, then you can use the pixel/pixel mode, or change it when watching a programme where it bothers you. The pixel/pixel mode can provide a sharper image, depending on the input.

Another Tip: Some TVs have a user setting which allows you to move the picture up a few pixels - usually called vertical position or similar. In some cases this minor shift in picture may obscure the VBI information (or small black bars) at the top of the screen (not available on all TVs inputs or formats)

See the following post on Overscan:

http://www.digitalhome.ca/forum/showthread.php?t=93233

Yet another Tip:

Some STBs send varying amounts of overscan depending on the output setting. For example:

1080i on BTV STBs often gives more overscan.
1080i on Rogers STBs often gives less overscan.
Shaw Direct STBs have different amounts of overscan for 1080i/0000 (Native/passthrough)
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Old 2010-12-13, 04:12 PM   #3
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