Optical Video Signal Dithering for SMPTE Pathological Patterns
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Solution Overview
Problem
The transmission of SMPTE 259M signals over optical communications systems is affected by pathological signals, which cause distortion, increased bit error rates, and picture quality degradation due to their low frequency content and deviation from the assumed 50% duty cycle modulation.
Innovation Solution
Dithering is applied to the least significant bit of each data word in parallel form to break up the repeating patterns of pathological signals, which can be encoded and decoded according to the SMPTE 259M standard, allowing for reversible recovery of the original signal state, thereby reducing adverse effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pathological signals with low frequency content are transmitted over optical communications systems, then data communication can be established, but waveform distortion and increased bit error rates occur due to disruption of power control circuitry
Solution Approach 1:
The patent applies parameter changes by modifying the signal characteristics through dithering - adding controlled noise to change the frequency content and statistical properties of the signal. This transforms pathological signals with long runs of identical bits into signals with more balanced transitions, thereby reducing low frequency content and eliminating waveform distortion while maintaining data integrity
Solution Approach 2:
The patent introduces an intermediary processing stage between the data source and the optical transmitter. This intermediary applies dithering and scrambling operations to preprocess the data signal, breaking up pathological patterns before transmission. The intermediary acts as a buffer that prevents harmful signal characteristics from directly affecting the optical power control circuitry
2Object-affected harmful factors
If dithering is applied to break up pathological signal patterns, then waveform distortion is reduced, but additional signal processing complexity is introduced
Solution Approach 1:
The patent segments the signal processing function into distinct modular components: a dithering unit that adds noise, a scrambling unit that randomizes bit patterns, and an undo-dithering unit at the receiver. This segmentation allows each component to be optimized independently and simplifies the overall implementation by dividing the complex task of pathological signal elimination into manageable stages
Solution Approach 2:
The patent applies preliminary action by performing dithering and scrambling operations on the data signal before it is transmitted over the optical network. This preemptive processing breaks up pathological patterns in advance, preventing them from causing waveform distortion during transmission. The preliminary action ensures that even if pathological signals are present in the original data, their harmful effects are eliminated before reaching the optical transmitter
3Length of stationary object
If SMPTE 259M signals are extended for longer distance transmission over optical fibers, then communication range is improved, but signal compatibility with existing coaxial cable infrastructure is lost
Solution Approach 1:
The patent achieves universality by creating a signal processing system that can operate across multiple media types. The dithering and scrambling operations are designed to work with both traditional coaxial cable signals and optical fiber signals. This allows the same processed signal to be transmitted over different physical media, enabling SMPTE 259M signals to maintain compatibility with existing infrastructure while extending reach to optical networks
Data Source
AI summary
A method and apparatus is presented for reducing or eliminating pathological data patterns from signals for transmission over optical communications systems. One embodiment includes a decoder/deserializer configured to receive an encoded serial digital signal, a ditherer configured to dither a least significant bit of each digital data word, and a reserializer/encoder configured to serialize digital data and encode it, for example according to an applicable communication standard such as SMPTE 259M. The improvements may be provided in a single removable unit, such as a small form-factor pluggable (SFP) module compatible with existing optical communications equipment.