Transform Audio Codec Sign Encoding for Low-Bitrate Residuals
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Solution Overview
Problem
Existing transform domain coding schemes are inefficient at low or moderate bit-rates, leading to unsatisfactory encoding results due to inadequate bit distribution in audio signal encoding.
Innovation Solution
A method that determines the position and structure of residual vectors in the frequency domain to selectively encode the amplitude and sign of coefficients, only encoding signs when changes would be audible, thereby optimizing bit usage and improving perceived quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the signs of all residual vector coefficients are encoded, then the audio quality is improved, but the number of bits required increases
Solution Approach 1:
The patent applies local quality by differentiating the encoding treatment of different residual vector coefficients based on their position in the frequency scale and their structural characteristics. Instead of uniformly encoding all coefficients, the method selectively encodes only those coefficients where sign changes would be perceptually significant, thereby optimizing bit allocation to where it matters most for audio quality
Solution Approach 2:
The patent implements partial action by encoding only a subset of residual vector coefficients rather than all coefficients. The criterion Φ(z) ≤ Θ determines which coefficients require sign encoding, allowing the system to perform partial encoding that suffices for maintaining perceived audio quality without the excessive bit consumption of full encoding
2Productivity
If fewer bits are used for encoding, then the bit rate is reduced, but the audio quality deteriorates
Solution Approach 1:
The patent changes the encoding parameters dynamically based on the characteristics of each residual vector. By evaluating the position indicator z and structure measure Φ for each vector, the system adapts the encoding parameters (whether to encode signs) to match the local signal characteristics, maintaining quality while reducing overall bit rate
Solution Approach 2:
The patent uses partial encoding action where only necessary coefficients are encoded with full precision. This selective approach allows the system to operate at lower bit rates by performing encoding actions only where perceptually required, rather than applying excessive encoding to all coefficients
Data Source
AI summary
Methods and devices for efficient encoding/decoding of a time segment of an audio signal. Methods comprise deriving an indicator, z, of the position in a frequency scale of a residual vector associated with the time segment of the audio signal, and deriving a measure, Φ, related to the amount of structure of the residual vector. The methods further comprise determining whether a predefined criterion involving the measure Φ, the indicator z and a predefined threshold Θ, is fulfilled, which corresponds to estimating whether a change of sign of at least some of the non-zero coefficients of the residual vector would be audible after reconstruction of the audio signal time segment. The amplitude of the coefficients of the residual vector is encoded, and the signs of the coefficients of the residual vector are encoded only when it is determined that the criterion is fulfilled, and thus that a change of sign would be audible.