Ensemble Designs 9455 3G Clean and Quiet Protection Switch - Manual (Page 58)

www.ensembledesigns.com 7435 and 9455 - page 58
Model 7435 and 9455 Clean and Quiet Protection Switches
Embedded Audio
Digital Audio can be carried along in the same bitstream as an SDI or HD-SDI signal by taking
advantage of the gaps in the transmission which correspond to the horizontal and vertical intervals
of the television waveform. This technique can be very cost effective in transmission and routing, but
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.
HDMI
The High Definition Multimedia Interface comes to us from the consumer marketplace where it is
becoming the de facto standard for the digital interconnect of display devices to audio and video