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Ensemble Designs BrightEye 83 HDMI to 3G / HD / SD SDI Converter User Manual

Page 20

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BrightEye 83 and 83-F - Page 20

83 and 83-F

HDMI to 3G/HD/SD SDI Converters

can also add complexity to signal handling issues because the audio content can no longer be treated

independently of the video.

Eye Pattern

To analyze a digital bitstream, the signal can be displayed visually on an oscilloscope by triggering the

horizontal timebase with a clock extracted from the stream. Since the bit positions in the stream form

a very regular cadence, the resulting display will look like an eye – an oval with slightly pointed left and

right ends. It is easy to see from this display if the eye is “open”, with a large central area that is free of

negative or positive transitions, or “closed” where those transitions are encroaching toward the center.

In the first case, the open eye indicates that recovery of data from the stream can be made reliably and

with few errors. But in the closed case data will be difficult to extract and bit errors will occur. Generally

it is jitter in the signal that is the enemy of the eye.

Frame Sync

A Frame Synchronizer is used to synchronize the timing of a video signal to coincide with a timing

reference (usually a color black signal that is distributed throughout a facility). The synchronizer

accomplishes this by writing the incoming video into a frame buffer memory under the timing

direction of the sync information contained in that video. Simultaneously the memory is being read

back by a timing system that is genlocked to a house reference. As a result, the timing or alignment of

the video frame can be adjusted so that the scan of the upper left corner of the image is happening

simultaneously on all sources. This is a requirement for both analog and digital systems in order to

perform video effects or switch glitch-free in a router. Frame synchronization can only be performed

within a single television line standard. A synchronizer will not convert an NTSC signal to a PAL signal,

it takes a standards converter to do that.

Frequency Response

A measurement of the accuracy of a system to carry or reproduce a range of signal frequencies. Similar

to Bandwidth.

H.264

The latest salvo in the compression wars is H.264 which is also known as MPEG-4 Part 10. MPEG-4

promises good results at just half the bit rate required by MPEG-2.

HD

High Definition. This two letter acronym has certainly become very popular. Here we thought it was all

about the pictures – and the radio industry stole it.

HDCP

HDCP (High-bandwidth Digital Content Protection) is a content encryption system for HDMI. It is

meant to prevent copyright content from being copied. Protected content, like a movie on a Blu-Ray

disc is encrypted by its creator. Devices that want to display the protected content, like a television,

must have an authorized key in order to decode the signal and display it. The entity that controls

the HDCP standard strictly limits the kinds of devices that are allowed decryption keys. Devices that

decrypt the content and provide an unencrypted copy are not allowed.

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