Technical Description 3-5

Video Processing

Video Processing is a complex process to reduce the amount of image data that must be processed on any given picture frame. If processing is not used, videoconference performance is reduced by conditions such as complex picture backgrounds, poor camera lighting conditions, and object movement. This ensures a H.320 system processes image objects in the picture that actually move. This lowers significantly the amount of picture information that must be transmitted to the far end (for each frame) and provides a higher quality picture.

Audio

Three options for H.320 define the audio requirements used for a videoconference:

•G.711 - for narrowband transmission (at 48-56 Kbps)

•G.722 - for wideband transmission (at 48-56 Kbps)

•G.728 - for narrowband transmission (at 16 Kbps)

G.711 is telephone quality audio (narrow band - 3 KHz), while G.722 is used for stereo quality audio (wideband - 7 KHz). G.728 offers the highest quality audio providing a narrow band 16 Kbps rate. This is necessary for low bit rate transmissions.

A manufacturer’s videoconferencing system that supports all three audio requirements has the greatest capability and flexibility to provide the highest quality video at all data rates.

for Example:

In a 128 Kbps videoconference connection (typically BRI), the G.722 (48-56 Kbps rate) or G.728 (16 Kbps rate) options would be employed. If audio quality is more important than video quality (48 Kbps for the audio and 80 Kbps for video), the system could use G.722.

If video quality is more important than audio quality, the system employs G.728. The audio uses 16 Kbps leaving 112 Kbps for the video.

Data Transmission Rate

Data Transmission Rates impact the perceived quality of the video picture. The higher the data rate the better the video quality. At T1 speeds (1,536 Kbps) the video quality will be best. However, many connections will not use this rate because of cost. In today’s systems, some users connect at the 768 Kbps rate as a trade-off between high quality video and cost. Most use the 384 Kbps rate. The 128 Kbps rate is becoming more widely used with the increased availability of ISDN service.

VisuaLink 128/384 General Description

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NEC 128 manual Video Processing, Audio, Data Transmission Rate, For Example
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128 specifications

The NEC 128 is a remarkable microprocessor that represents a significant leap in technological innovation during its time. Introduced in the early 1980s, this processor was designed to meet the demands of increasingly sophisticated computing tasks, primarily aimed at the burgeoning field of personal computing and embedded systems.

One of the standout features of the NEC 128 is its 16-bit architecture, which was quite advanced for its era. This architecture allows for a greater data throughput, enabling the handling of larger data sets and providing improved performance over its predecessors. The NEC 128 operates on a clock speed that typically ranges from 4 to 8 MHz, making it capable of executing instructions efficiently and swiftly, which was crucial for running more complex applications.

The processor is built using CMOS technology, which offers significant advantages in terms of power consumption compared to earlier bipolar technology. This characteristic made the NEC 128 not only suitable for desktop computing but also an appealing choice for battery-operated devices, enhancing its versatility. The use of CMOS allowed for a reduced heat output, contributing to the reliability and longevity of devices powered by this microprocessor.

Another noteworthy aspect of the NEC 128 is its support for a variety of addressing modes. This flexibility enables programmers to write more efficient and compact code, optimizing the use of memory resources. By supporting both immediate and indirect addressing, the NEC 128 allows for more dynamic programming, which is essential for developing applications that require real-time processing.

The processor's architecture also includes a robust instruction set that facilitates arithmetic operations, logical operations, and control flow management. This comprehensive instruction set is instrumental for developers, as it provides the necessary tools for creating a wide range of applications, from simple utilities to more complex software systems.

In summary, the NEC 128 microprocessor is characterized by its 16-bit architecture, efficient CMOS technology, and a versatile instruction set, making it a compelling choice for its era. Its combination of performance, power efficiency, and flexibility positioned it as a formidable player in the personal computing market and laid the groundwork for future advancements in microprocessor technology. With its various applications and features, the NEC 128 remains a noteworthy chapter in the history of computing.
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