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HDTV
is short for High-Definition Television, a new type of television that provides much better resolution than current televisions based on the NTSC (National Television System Committee) standard. There are a number of competing HDTV standards, which is one reason that the new technology has not been widely implemented. All of the standards support a wider screen than NTSC and roughly twice the resolution. To pump this additional data through the narrow TV channels, images are digitized and then compressed before they are transmitted and then decompressed when they reach the TV.
See the charts below to learn more about HD Formats and Format Conversions.
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HD Formats
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HD formats have not been standardized. Some names indicate frame rate but not resolution;
some indicate resolution but not frame rate. The most common formats are:
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Common Name
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Pixels X Lines = Resolution
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Frame Rate
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Aspect Ratio
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p or i
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{p} = Progressive Imaging:
Every digital field or frame is unique and contains a complete image.
The fields progressively advance without overlapping or blending.
Progressive imaging better imitates the way film progresses. Because there
are no flicker frames, this format is a better digital intermediate when going
to film.
{i} = Interlaced Imaging:
The image is comprised of half of the lines being alternately overlaid at
a time, forming a complete image every half a frame (field). Some say
the interlacing captures motion better. Because of flicker frames and
artifacting when blending fields to frames, this format is not recommended
when going to film.
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24p
(1080)
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1920 X 1080
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23.98fps
aka 24 fps
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16:9
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p
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1080i
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1920 X 1080
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29.97fps
aka 59i
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16:9
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i
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720p
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1280 X 720
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59.97fps
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16:9
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p
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720p Varicam*
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1280 X 720
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59.97fps w/3:2 pulldown
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16:9
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p
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25p
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1920 X 1080
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25fps
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16:9
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p
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All of these are un-squeezed images and fill their 16:9 frames.
These formats must be down-converted for offline purposes.
*Varicam is a Panasonic 24fps format recorded at 60fps w/3:2 pulldown added.
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Format Conversions
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Common HD to HD Cross-Conversions
Same format clones, from 24p to 24p for example, require no special treatment or machines
and lose none of their original formatting or quality. For all of the conversions listed below, a
cross-converter called a Universal Format Converter or a Teranex must be used. (Some HD
decks have an internal converter.) Not all labs have a UFC or a Teranex and most will charge
more for this cross-conversion.
24p to 1080i
Resolution of the image remains the same but there is some altering of the motion when going
from the 24fps progressive to 30fps interlaced.
1080i to 24p
Resolution of the image remains the same but if there is a lot of motion in the shot, some
quality may be lost when going from 30fps interlaced to 24fps progressive. Judder, motion
and temporal artifacts may result as well.
720p to 24p
This is an up-conversion to a higher resolution. The quality of the original image would not
be compromised. If the 720p material is 60fps, then judder, motion and temporal artifacts may result
from the up-conversion. If the 720p is "Varicam" type (60fps w/3:2 pulldown), then a flawless 24p
up-conversion can be achieved.
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HD to Standard DEF Conversions
HD can be easily down-converted to Standard Definition with a 4:3 aspect
ratio (the traditional size of video). It does not cost any more than a normal
tape to tape transfer. However, you will want to specify what you would like
to do about the 16:9 frame size. Your choices are:
Edge Crop
4:3 Center Cut: crop the image on the right and left side of the frame so that it fills your 4:3 frame.
Anamorphic
Squeeze the image so that you can un-squeeze it and crop it yourself or perhaps deliver it on a non-HD 16:9 format.
Letterbox
Frame the image with black on the top and bottom of the frame so that the full width of the picture is visible.
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