Audio Envelope Coding with Cumulative Distribution Quantization
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Solution Overview
Problem
Current audio signal envelope encoding and decoding methods, particularly those using linear predictive coding (LPC), face challenges in achieving a smooth and precise spectral envelope representation while maintaining low bit rates and reasonable computational complexity, often compromising on either precision or efficiency.
Innovation Solution
The proposed solution involves an apparatus and method for generating and decoding audio signal envelopes using distribution quantization, which includes an aggregation function with monotonically increasing points, allowing for precise encoding and decoding of audio signal envelopes by determining coding values based on aggregation points and applying interpolation to reconstruct the envelope, thereby achieving a smooth and precise spectral representation with low bit rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear predictive coding (LPC) is used for spectral envelope modeling, then the spectral envelope can be represented, but achieving both smooth representation and precise representation while maintaining low bit rates and reasonable computational complexity is difficult
Solution Approach 1:
The patent transforms the spectral envelope representation from direct LPC coefficients to a cumulative distribution function domain. By changing the parameter space and using a monotonically increasing aggregation function with controlled derivative properties, the system achieves smooth spectral envelopes with reduced computational complexity. The aggregation function's derivative control allows precise envelope shaping without complex operations.
Solution Approach 2:
The patent introduces an intermediate cumulative distribution representation between the raw spectral data and the final envelope. This intermediate domain uses aggregation points and monotonically increasing functions that serve as a mediator, simplifying the transformation process and enabling smooth envelope generation with lower computational requirements compared to direct LPC methods.
2Measurement precision
If more coding values are used to increase spectral envelope precision, then the representation quality improves, but the bit rate increases
Solution Approach 1:
The patent uses a limited number of aggregation points with controlled derivative properties to achieve smooth spectral envelopes. Rather than using many coding values, the method applies partial action by focusing computational effort on key aggregation points whose derivatives control the envelope shape, achieving good precision with fewer transmitted parameters.
Solution Approach 2:
By transforming to the cumulative distribution domain and using monotonically increasing aggregation functions, the patent changes the parameter representation efficiency. The aggregation values and their derivatives provide a compact way to describe the spectral envelope shape, reducing the number of bits needed compared to traditional methods while maintaining precision.
3Ease of manufacture
If traditional quantization methods are used, then the encoding process is simple, but the spectral envelope smoothness and precision are compromised
Solution Approach 1:
The patent changes the quantization approach by working in the cumulative distribution domain with monotonically increasing aggregation functions. This parameter transformation maintains encoding simplicity while improving spectral envelope smoothness, as the aggregation function's continuous derivative properties naturally produce smooth envelopes without complex post-processing.
Solution Approach 2:
The patent applies preliminary action by pre-defining the monotonically increasing aggregation function with controlled derivatives before the actual encoding process. This preliminary setup ensures that the subsequent quantization and encoding steps naturally produce smooth spectral envelopes, combining simplicity with precision.
Data Source
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AI summary
An apparatus for generating an audio signal envelope from one or more coding values is provided. The apparatus comprises an input interface (1610) for receiving the one or more coding values, and an envelope generator (1620) for generating the audio signal envelope depending on the one or more coding values. The envelope generator (1620) is configured to generate an aggregation function depending on the one or more coding values, wherein the aggregation function comprises a plurality of aggregation points, wherein each of the aggregation points comprises an argument value and an aggregation value, wherein the aggregation function monotonically increases, and wherein each of the one or more coding values indicates at least one of an argument value and an aggregation value of one of the aggregation points of the aggregation function. Moreover, the envelope generator (1620) is configured to generate the audio signal envelope such that the audio signal envelope comprises a plurality of envelope points, wherein each of the envelope points comprises an argument value and an envelope value, and wherein an envelope point of the audio signal envelope is assigned to each of the aggregation points of the aggregation function such that the argument value of said envelope point is equal to the argument value of said aggregation point. Furthermore, the envelope generator (1620) is configured to generate the audio signal envelope such that the envelope value of each of the envelope points of the audio signal envelope depends on the aggregation value of at least one aggregation point of the aggregation function.