Beginning Video for AV

• Video components – voltage circuit– Luminance– Color– Timing

• Scan rates– Video 525 lines interlaced – Computer pixels, Lines vs. Pixels– How may Pixels are in the frame

• Refresh Rates– Traditional Video 15.75 khz = 525 lives x 30 frames per sec– Computer graphics 640 x 480 up to 1390 x 1024 up to 110 Khz.

BNC

RCA

RCA to BNC

BNC to RCA“Bullet”

BNC to BNC

RF

Computer connections

• 15pin

Computer connections

• DVI connectors

Single vs Dual DVI

• Cables come in two classes. Single link cables support bandwidth of 165 MHz or 165 million pixels per second. Dual link can support a bandwidth of 330 MHz. To calculate your bandwidth multiply your horizontal resolution by your vertical resolution by your refresh rate. For example, a standard XGA (1024x768) display would have a refresh rate of 60 Hz. 1024 x 768 x 60 = about 47 MHz. A standard XGA display would easily transmit over a single digital link. A single link cable could support standard HDTV (1920x1080)! Dual link can support QXGA (2048x1536) without any problems.

What is the Distance Limitations of DVI?

• The standard spec for DVI is up to 5M. However, high quality copper cables and fiber optic cables are available that allow for the DVI signal to transmit at much greater distances. Fiber cables can easily transmit a DVI signal 100M and beyond! A Repeater can also be used to boost the signal and send it further distances. Distance will be affected by the amount of bandwidth that is passing through the cable.

• What is the difference between DVI-I vs. DVI-D?

• These are the two most confusing digital connectors available. DVI-D allows for digital only signal transmission. However, DVI-I allows for digital or analog signals to pass over this cable/connector. You could have a VGA connector on one end of a cable and a DVI-I connector on the other and transmit an analog signal to the display. You could also have a DVI-I or DVI-D connector on one end and transmit a digital signal. The DVI-D male connector will connect/transmit with a DVI-I female. The DVI-D female connector will not connect/transmit with the DVI-I male.

DVI to VGA Adaptor

Video Formats

• Composite video:• The most common and basic type of video signal used in AV

presentations is composite video. Composite video is carried to its destination by a single coaxial video cable that carries all the picture color, brightness or luminance, and signal timing information. What this amounts to is a case of the proverbial 10 pounds of potatoes in a 5 pound bag. To squeeze all of this signal information into one cable, all of this seperate information is compressed or encoded into a single 1-volt electrical signal that is decoded at the display device resulting in a degraded image quality. This signal is different from the coaxial RF (radio frequency), video signal or cable video that you might use in home video systems. Encoding audio with the video signal degrades RF transmissions even further but they can be transmitted through the air to your home.

Component Video:Component video signals are used to maintain the quality of the picture by keeping the color, luminance or brightness information, and signal timing information separated on different cables. These cables must be of equal length so that they deliver the information to the display device at the same time. Types of Component:Y, R-y, B-yY/CR,G,B, SyncR,G,B, Horizontal, Vertical sync15 pin VGA Cables

Computer video files

• AVI files

• Mpeg2

• WMV (windows media)

• Quicktime

SDI – Serial Digital Interface

• Transfers 10 bit data “words” over composite or component cables.

• (~200 meter limit depending on cable quality)

• Hum eliminated

RGBHV – BNC Cables

VGA pin configuration is usually as follows

VGA Breakout CablesExtracts the color and signal timing information from a 15 pin “VGA” cable to 5 independent BNC cables

Sync cables color usually goes from horizontal to vertical light to dark i.e. White is horizontal, Yellow is vertical. Or grey horizontal, black is vertical

Video Scan rates:On a NTSC (National Television Standards Committee) system an interlacing of the horizontal scans is used to overcome several problems that arise when trying to transmit and display complex television signals. The beam first scans the odd numbered horizontal lines then returns to the top to scan the even lines. The odd and even scans of the video image are referred to as fields, and they combine totaling 525 total lines to create one frame of video. This scan technique completes a reasonably sharp picture that is displayed fast enough (~30 frames per second) to fool your eye into seeing a smooth persistent image. The interlacing of the video image helps to smooth out motion artifacts and flicker that would be more apparent if the image were displayed one line at a time. This display format also enables the transmission of video signals with a relatively low signal bandwidth requirement. The downside to this interlacing technique is that there is a loss of resolution in the picture information because only half of the total picture information is displayed at a time. 

Computer scan Rates

• Computer displays need to carry much more detailed text and picture resolution than a NTSC Television system can deliver. To achieve the display of this fine resolution the rate, or speed, of the scanning beam “refresh rate” is increased. The total number of lines or picture elements, “pixels”displayed is also increased. The faster beam now can scan in a progressive mode, one line at a time, instead of the interlace mode of a TV system to eliminate the blurring of the image that is inherent in the interlaced scan.

Common Scan Rates

• VGA = 640 x 480

• SVGA = 800 x 600

• XGA = 1024 x 768

• SXGA = 1280 x 1024

• 1080i = 1920 x 1080 interlaced

• 720p = 1280 x 720 progressive

HDTV formats

• 1080i and 720p• How do 1080i and 720p compare? 1080i actually has higher resolution than

720p, but doesn't render motion quite as well. 720p-with its progressive scanning-delivers smoother motion (especially important for fast-moving action, such as in sports) but has lower resolution than 1080i. Still great, but lower. (Don't worry; any HDTV receiver can receive both formats, and a true HDTV television can display both formats.)

• Pixels• Another way to compare the two is by looking at their pixel count (pixel is

short for "picture elements", the individually addressable areas of light and shadow on your screen). The 720p format creates an image with 720 lines, each with 1280 pixels, so it has a resolution of 1280 x 720. The 1080i format creates an image with 1080 lines, each with 1920 pixels, so its resolution is a higher 1920 x 1080. Denser pixels = a better picture.

• HDTV Resolutions

To take full advantage of HDTV's ability to render spectacular clarity and detail, you must find an LCD, plasma, or DLP device that has a native resolution of either 1,280 x 720 pixels (720 lines progressively scanned with a widescreen 16:9 aspect ratio) or "1080i" (1920 x 1080), which represents a 16:9 widescreen image with 1920 pixels across each of 1080 interlaced scan lines. These are the only two High Definition formats defined by the HDTV standard. All network broadcasters use one or the other for their HD programs. For instance, ABC and Fox broadcast in 720p, while CBS, NBC, and PBS use 1080i. Likewise, cable and satellite networks will use one or the other: HBO, HDNet, DiscoveryHD, and Showtime use 1080i, whereas ESPN uses 720p. Broadcasters choose one or the other for different reasons. Progressive scanning (720p) produces a smoother, more film-like look, but a 1080i image actually contains greater detail. Though it has fewer lines, the native progressive scan format (720p) eliminates motion artifacts that originate in interlacing. For subject matter that contains a lot of rapid motion--Monday Night Football, basketball or hockey games, for example--720p will produce a clearer, more stable picture than 1080i. Alternatively, for subject matter that has very little motion, 1080i is capable of rendering more picture detail. And because 720p has the highest data bandwidth and horizontal scan rate, it usually means that 720p programming is converted or “scaled” to 1080i for transmission (it occupies less digital "space" than 720p).

Aspect Ratio of Video an computer signals

• Ratio of the width of an object to the height,4 x 3 ratio Common NTSC video16 x 9 common in HDTV5 x 4 in some computer displays (1280x1024)

Aspect ratio calculation

• 640 x 480 video or 640/480 =1.333 4 3

• 1024 x 768 xga or 1024/768 =1.333 4 3

• 1280 x 1024 sxga or 1280/1024 =1.25 5 4

• 1280 x 720 hdtv or 1280/720 = 1.777 16 9

• 1920 x 1080 hdtv or 1920/1080 = 1.777 16 9

Screen aspect ratio

• 10.5 x 14 3 4

• 15 x 20 3 4

• Some plasma or led displays will scale image to fill the display.

Interfaces: from Extron

• What are Interfaces? An interface is a signal amplifier that includes signal processing capabilities to drive a signal over various lengths of cable. This is useful for ensuring signal format compatibility between various sources and destinations, and to compensate for the effects of marginal quality or long lengths of RGB cable. There are several functions of an interface: to buffer (or convert) the computer's output signal to the appropriate level and format of the local monitor to prevent loading (double termination) and impedance mismatch from the projector; to maintain the video resolution and frequency of the original source; to provide sharpness (peaking) and gain to compensate for cable loss; to act as a sync processor; and to convert unbalanced audio to balanced audio (active PC audio interfacing).

Questions to ask

• What type of computer(s) or graphics card(s) will be used?

• Will several inputs be used at once? • Where will the interface be located and will it

need to be moved? • What is the technical level of the user, and who is

going to have access to the interface? • What features are needed in this interface?

What are Scalers & Scan Converters?

Scalers take one video resolution and convert it to another resolution by using techniques such as de-interlacing, line duplication, line averaging, and motion interpolation. Some of these techniques produce a better image than others.When selecting a scaler, look for these features:•Aspect ratio control: Ability to horizontally and vertically resize the video image to match a specified aspect ratio, filling the display, and improving the overall perception of the displayed image. •Preprogrammed for plasma displays: The scaler is designed to output video that will best match the native resolution of the most common plasma displays. •Autoscanning: Allows the scaler to automatically recognize a range of input frequencies. The scaler is not limited to defined resolutions. •Memory presets: Saves size, centering, and filter settings for a given input source so that when the same signal is later selected again, those settings will be recalled. •Horizontal and vertical filtering: These adjustments allow the user to reduce image jitter, improve image stability, and prevent detail loss. Scan converters convert computer-video signals into signals that are compatible with NTSC or PAL display devices such as televisions. Sometimes a scan converter is referred to as a "PC to TV" converter or a "PC to video" converter. While the concept seems simple, scan converters use complex technology to achieve signal conversion because computer signals and television signals are very different.

There are several factors to consider when selecting a scan converter:

What is the scan converter's computer input compatibility? What is the maximum output resolution of the computer? Does the application require genlocking? What is the scan converter's color bit sampling? What is the quality of the scan converter's encoder? Which video output formats does the application require? Will an SDI output be used now or in the future? Is a test pattern generator required? Is downloadable firmware required/preferred?

    Step 1: What are Switchers?

 

Switchers enable multiple video and audio signals to be selected and sent to one or more display devices. For example, to view two computers with separate presentations, a switcher would be used to physically connect both of the inputs to the display device. The switcher would then be used to select or "switch" between the two computer presentations, allowing the user to alternate back and forth.To select the right switcher for a specific environment, begin by identifying the following things: 1.What are the signal types (e.g., computer, composite video, RGB, stereo audio)? 2.What are the connector types (e.g., BNC, S-video, 15-pin HD)? 3.How many inputs and outputs are needed? 4.Will there be switching between both video and audio sources?

Folsom presentation pro

Folsom Presentation Pro Back

MonMon

Termination of Video and computer signals

On at the end, off at the loop through

VHS

Term. Off

Term. Off

Mon

Term. On

75 ohm

Hi - Z

Hi - Z

75 ohm

Termination on

Termination off

Videoinput

Videoinput

Loop out

Loop out

Videoinput

Loop out

Auto Termination

Basic Video Setup

vhs

DVD

Computerlaptop

Sony 10243 inputs

projector

Composite video

Component video to 15

pin “breakout cable”

VGA 15 pin Male to Male

VGA 15 pinMale to Male

Sources Destinationswitcher

What are the problems with this setup?

Monitor for VHS and DVD

composite

component

15 pin

2 channel composite

monitorWith loop Through.

How is the termination

set?