KRAMER ELECTRONICS LTD. 2
1 INTRODUCTION
Congratulations on your purchase of this Kramer Electronics SDI / Analog converter. Since 1981,
Kramer has been dedicated to the development and manufacture of high quality video/audio equipment.
The Kramer line has become an integral part of many of the best production and presentation facilities
around the world. In recent years, Kramer has redesigned and upgraded most of the line, making the best
even better. Kramer’s line of professional video/audio electronics is one of the most versatile and
complete available, and is a true leader in terms of quality, workmanship, price/performance ratio and
innovation. In addition to the Kramer line of high quality distributors, such as the one you have just
purchased, Kramer also offers a full line of high quality switchers, processors, interfaces, controllers and
computer-related products.
This manual includes configuration, operation and option information for the
SD-7401
SDI to
Analog converter
1.1 Digital and Analog signals
An analog signal varies continuously. It may have any value (within its physical bounds) and can
change at any instant. A digital signal is made up of a finite number of discrete levels, usually – but not
always – changing only at discrete time periods. An example of a digitized waveform is shown below.
1.2 Several points to consider when working with digital signals
The minimum noise introduced by quantizing is 1 bit (1 level), so the higher the number of bits, the
lower the inherent noise, and the higher the resolution.
Since A/D and D/A conversions create artifacts, it is important not to convert back and forth. In a
“mixed” outfit, the video should be digitized, and
all
the digital processing done before converting back to
analog.
“Multi-media” systems usually quantize the video to 8 bits (i.e. 2
8
= 256) levels. Some “levels” are
dedicated to special codes (SAV, EAV – similar to syncs in analog video), leaving 220 quantization levels
(~3mV steps) for the luminance signals. Audio is usually quantized to 16 bits for multi-media systems.
Broadcast systems usually use 10-bit video, and 20- to 24- bit audio.
The advantages of working in a digital domain are obvious – a digital signal may be transported
very easily, and saved and retrieved reliably with no generation losses.
The transmission of a digital video signal is reliable up to a certain length of cable. Beyond this
length, the signal is destroyed. This phenomenon is known as the “cliff-effect”. To avoid the “crash” at
the cliff, an “equalizer and reclocker” should be inserted at a distance less than the “cliff” length. From
ANALOG SIGNAL
DIGITAL SIGNAL
