All-Zero Noise Feedback Filter Approximating Pole-Zero Response

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Solution Overview

Problem

Conventional noise feedback coding (NFC) implementations offer limited flexibility in controlling the shape of coding noise due to their structural complexity and cost, despite providing better perceptual quality in speech coding.

Innovation Solution

An all-zero noise feedback filter is configured to approximate the response of a pole-zero noise feedback filter, allowing for flexible noise shaping while maintaining a simple and cost-effective configuration, by using a truncated finite impulse response of a pole-zero filter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional NFC implementations use pole-zero noise feedback filters, then noise shaping flexibility and perceptual quality are improved, but device complexity and implementation cost increase

Engineering Contradiction:

Improvenoise shaping flexibilityVSAvoidfilter structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces complex pole-zero filters with simpler all-zero filters, using a computationally inexpensive FIR approximation that achieves sufficient noise shaping performance without the complexity of IIR pole-zero structures. This substitutes a cheap, simple filter type for the more complex original filter.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the fundamental parameters of the noise feedback filter by using all-zero (FIR) structures instead of pole-zero (IIR) structures. This parameter change in filter architecture maintains noise shaping capability while significantly reducing computational complexity and implementation cost.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If white coding noise is used in conventional DPCM, then implementation is simple, but perceptual quality deteriorates due to high-frequency noise dominance

Engineering Contradiction:

Improvecoding structure simplicityVSAvoidperceptual noise quality

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces noise feedback mechanisms where quantization error is filtered and fed back to the quantizer input. This feedback loop shapes the spectral distribution of coding noise to match the speech spectrum, reducing perceptible high-frequency noise while maintaining overall system simplicity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Instead of directly shaping the noise spectrum through complex filtering of the output, the patent inverts the approach by shaping noise at the quantizer input through feedback. This indirect approach achieves noise spectral shaping with simpler structures by working backwards from the noise source.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8473286B2Noise feedback coding system and method for providing generalized noise shaping within a simple filter structure

Publication Date: 2013.06.25 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

A noise feedback coding (NFC) system and method that utilizes a simple and relatively inexpensive general structural configuration, but achieves improved flexibility with respect to controlling the shape of coding noise. The NFC system and method utilizes an all-zero noise feedback filter that is configured to approximate the response of a pole-zero noise feedback filter.