Vaddio UXHD CrossPoint - Manual (Page 6)

UXHD CrossPoint
UXHD CrossPoint Installation and User Guide 341-929 Rev. A Page 6 of 12
Really Important Stuff:
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Finding the “Sweet Spots”:
In any video signal chain, there can be many scalers. For example, in a standard PTZ camera system, pretty much
every product (camera, mixer/switcher, format converter, monitor, projector and PC) have scalers and they all have
“certain” capabilities. Try to stay as close to native resolutions as possible, minimize the amount of your scaling and
keep the in and out aspect ratios fairly close (See Figure 6) throughout the signal chain and design. It will not only look
better, it will be better. The UXHD CrossPoint is a great tool, but it can’t fix a flawed or antiquated design.
•
Good Example HD-SDI to RGBHV - The French Anchor:
If you would be connecting an HD-SDI signal at 720p/60 (16:9 aspect ratio) to Input 2, and wish to take a RGBHV out of
Output 1, pick a similar resolution with a similar aspect ratio. At least for now, wide screen computer resolutions using
RGBHV are at a 16:10 - not a big jump. So, logical outputs for wide screen computer is 1280 x 768@60 Hz/15:9, 1280 x
800@60 Hz/16:10 or 1360 x 768@60 Hz 16:9. The example below shows a 720p to 1280x768 format conversion
without severe image distortion. Granted the RGBHV image is about 6% taller than the HD-SDI, but still very useable.
•
Bad Example HD-SDI to RGBHV - The Zebra Accordion:
If you are connecting an HD-SDI signal at 720p/60 (16:9 aspect ratio) to INPUT 2, and wish to take a RGBHV out of
OUTPUT 1, an illogical choice for an RGBHV output is (1024 x 768@60Hz with 4:3 ratio). There are other ways to ruin
the image too; we just can’t recommend this one. We could have used circles in different quadrants, but we chose this
more rather interesting approach.
1
•
In the above example:
Converting an HD format into any other than 16:9 or close is a tricky proposition. Your display device may take the
above 1024 x 768 conversion and stretch the picture back out with its own scaler to fill the screen so the image looks
mostly normal. However, that scaler would be the 4
th in the chain (Camera → Mixer → Crosspoint → Displays) and the
more scalers you use, the further away from the original image quality and image clarity you get. A conversion like
Figure 9 may be unavoidable and it is done every day with mixed format displays (i.e. 16:9 TV and a XGA Projector
having to display the same signal). The trick, the secret sauce, of all scalers is knowing how to use them, knowing how
the scalers in a chain may interact and knowing how not to use scalers in a radical way. And remember, HD video
information can only be retained or lost in each successive conversion or scaling step, but it is not created.
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In General: For HD-SDI or YPbPr (16:9 HD formats) to RGBHV Scaling/Conversion, using the old 4:3 or 5:4 aspect
ratios of the RGBHV just isn’t a great idea (sound familiar yet). There are many WXGA formats to pick from and
recommend that you do. The UXHD CrossPoint was really not intended to patch up an existing system using really
old equipment. When used as intended, the UXHD CrossPoint is one of the most flexible digital to analog and back,
format converters and scalers available today, and did we mention that it is 3Gb/s HD-SDI Single link capable?
•
Silver Lining: With all that said, please look into the reference material provided by InfoComm and NAB regarding
the future and direction of the A/V and Broadcast industries and the digital formats that will be prominent in the next
few years (i.e. HD-SDI, HDMI, DVI, etc). There will be ample opportunity for refreshing the technology used in
today’s presentation environments and videoconferencing applications worldwide, which is an exciting proposition.
The UXHD CrossPoint will be part of that excitement.
Figure 8:
Simulated
Video Feeds
Good Example,
Slight Scaling
(one axis) and
Conversion
HD-SDI Digital Video 720p/59.94
[email protected], 16:9 ratio
RGBHV Analog Video
1280x768@60Hz, 15:9 ratio
Figure 9:
Simulated
Video Feeds
Bad Example
Scaling (both
axes and
Conversion)
HD-SDI Digital Video 720p/59.94
[email protected] - 16:9 ratio
RGBHV:
16:9 HD format incorrectly
configured to 1024x768
@60Hz with a 4:3 aspect
ratio. Stretching 720 to
768 and squeezing 1280
to 1024, this image is the
result.
Converted to RGBHV
1024x768 - 4:3 ratio
RGBHV
Same width at 1280
pixels, but a bit taller
by 48 pixels to 768 in
height - if the height of
both images were
adjusted to be equal
then the 15:9 picture
would appear to be
squeezed by 6% or so.