Twisted Pair Audio Video Transmission Common Mode Multiplexing
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Solution Overview
Problem
Existing solutions for transmitting analogue video and digital audio signals over twisted pair cables require complex and costly multiplexing circuitry, making them unsuitable for cost-sensitive applications like retail displays and KVM switch systems.
Innovation Solution
The method involves transmitting digital audio signals as common mode signals on the same twisted pairs carrying red, green, and blue video signals, allowing other slower speed data like keyboard and mouse data to be sent on a separate pair, using a simple microprocessor and Intersil EL4543/EL9111 chip for encoding and decoding, thereby eliminating the need for FPGA-based multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital audio signals are transmitted over twisted pair cable using conventional multiplexing methods, then audio and video signals can be transmitted together, but the device complexity and manufacturing cost increase significantly due to required multiplexing circuitry
Solution Approach 1:
The patent combines digital audio signal transmission with existing video transmission over the same twisted pair cable by utilizing the common mode signal path. The audio data is transmitted as a common mode signal between the differential video signal pairs, merging audio and video transmission into a single cable infrastructure without requiring separate audio cables or complex multiplexing hardware.
Solution Approach 2:
The twisted pair cable is made multi-functional by enabling it to carry both differential video signals and common mode audio data simultaneously. The same physical medium (twisted pair cable) performs multiple functions: transmitting high-speed video data differentially and audio data as common mode signals, eliminating the need for separate transmission paths.
2Reliability
If FPGA or programmable logic device is used to provide high speed signalling for digital audio, then audio quality improves, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent replaces expensive FPGA or programmable logic devices with simpler, cheaper integrated circuits designed specifically for audio data transmission in common mode. The solution uses dedicated audio transmission circuitry that is more cost-effective and easier to manufacture than general-purpose high-speed logic devices, while still achieving reliable digital audio transmission.
Solution Approach 2:
The patent changes the signaling parameter by transmitting audio data as a common mode signal rather than using high-speed differential signaling that would require FPGA. This parameter change allows the use of simpler, lower-cost circuitry while maintaining adequate transmission quality for digital audio over the twisted pair cable.
3Device complexity
If analogue audio signals are transmitted over twisted pair cable, then simplicity is maintained, but noise interference occurs causing hisses and crackles
Solution Approach 1:
The patent substitutes analogue audio signal transmission with digital audio signal transmission. By converting audio to digital form and transmitting as common mode data signals, the system replaces the vulnerable analogue signal path with a more robust digital communication method that is less susceptible to noise interference, hisses, and crackles.
Solution Approach 2:
The patent introduces digital sampling and common mode signaling as an intermediary between the audio source and the twisted pair cable. The audio signal is converted to digital form, encoded as common mode data, transmitted over the cable, and then converted back to analogue at the receiving end. This intermediary digital representation protects the audio signal from noise interference during transmission.
4Productivity
If digital audio data is multiplexed with other data on the data pair, then cable utilization improves, but signalling speed requirements exceed what simple microprocessors can achieve
Solution Approach 1:
The patent segments the cable utilization by creating separate transmission paths: video signals use the differential mode of the twisted pairs while audio data uses the common mode path. This segmentation allows simple microprocessors to handle audio data transmission without needing to multiplex high-speed audio data with other signals, as the common mode path provides a dedicated channel for audio.
Solution Approach 2:
The patent adds another dimension to cable utilization by using both differential mode and common mode signaling on the same twisted pair cable. Instead of multiplexing all data through a single differential path requiring high-speed switching, the solution exploits the additional common mode dimension, allowing simultaneous video and audio transmission without complex multiplexing.
Data Source
AI summary
A system, apparatus and methods for transmitting video and audio data over twisted pairs are described. A differential signal that contains video color information is transmitted over each twisted pair. Data representing digital samples of at least one audio signal is transmitted on two or more of the twisted pairs as a common mode signal.