Noise Feedback Quantization for Audio Encoding
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Solution Overview
Problem
Temporal Noise Shaping (TNS) in MPEG-2/4 AAC audio coding systems is limited by increased bit rate consumption, lack of backward compatibility, and increased decoder complexity due to the need for transmitting filter coefficients and applying inverse filters.
Innovation Solution
Noise Feedback Quantization (NFQ) is employed in digital audio encoding, where the quantization error is filtered and fed back as a signal to shape the noise in the frequency domain, allowing for dynamic control of noise shaping without requiring filter coefficient transmission to the decoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Temporal Noise Shaping (TNS) is used to control quantization noise temporal envelope, then noise shaping performance is improved, but bit rate consumption increases due to filter coefficient transmission
Solution Approach 1:
The patent extracts the noise shaping function from the traditional TNS framework that requires filter coefficient transmission. By using a modified quantization process that inherently shapes noise without requiring separate filter parameters, the solution removes the problematic element (filter coefficient transmission) while preserving the beneficial effect (noise shaping performance).
Solution Approach 2:
The quantization process itself is made to perform the noise shaping function without requiring additional components or parameters. The quantizer is designed to automatically shape the temporal envelope of quantization noise through its internal operation, making the system self-sufficient and eliminating the need for external filter coefficient management.
2Manufacturing precision
If TNS filter coefficients are transmitted to the decoder, then noise shaping control is improved, but backward compatibility is lost
Solution Approach 1:
The patent removes the requirement for filter coefficient transmission that breaks backward compatibility. By redesigning the noise shaping mechanism to not depend on transmitted filter parameters, the solution maintains compatibility with legacy decoders that expect standard quantization formats while achieving improved noise shaping control through the modified quantization process.
Solution Approach 2:
The modified quantization process serves multiple functions simultaneously: it performs standard quantization for compatibility with existing decoders while also implementing noise shaping control. This multi-functionality allows the same encoding process to benefit both legacy and advanced systems without requiring separate processing paths.
3Manufacturing precision
If inverse filter is applied in the decoder, then noise shaping performance is improved, but decoder complexity increases
Solution Approach 1:
The patent extracts the noise shaping function from the decoder side operations. By moving the noise shaping control to the encoder's quantization process, the solution removes the need for complex inverse filtering operations in the decoder, thereby reducing decoder complexity while preserving noise shaping performance through the encoded signal characteristics.
Solution Approach 2:
The encoded signal itself carries the noise shaping information without requiring additional decoder processing. The quantization process embeds the temporal envelope control directly into the quantized coefficients, allowing the decoder to reconstruct the shaped noise characteristics through simple inverse transformation without requiring complex filtering operations.
4Manufacturing precision
If filter parameters are transmitted as side information, then temporal envelope control is improved, but bit rate efficiency decreases
Solution Approach 1:
The patent removes the side information transmission requirement for temporal envelope control. By integrating the noise shaping control directly into the quantization process parameters that are already transmitted for standard decoding, the solution achieves temporal envelope control without requiring additional bit rate allocation for filter parameters.
Solution Approach 2:
The existing quantization parameters serve dual purposes: they control both the standard quantization process and the temporal envelope of quantization noise. This multi-functionality allows the same parameter set to achieve both compression and noise shaping objectives, eliminating the need for separate side information channels and improving bit rate efficiency.
Data Source
AI summary
In a first aspect, arbitrary shaping of the temporal envelope of noise is provided in spectral domain coding systems without the need of side-information. In the encoding, a filtered measure of quantization error is applied as a feedback signal to the frequency-domain representation of a discrete time-domain signal prior to quantization, so that the filtering parameters of said filtering affect the shaping of quantization noise in the time domain of the quantized frequency-domain representation with unchanged quantization of the discrete time-domain signal when it is inversely transformed from the frequency domain back to the time domain in decoding. This may be accomplished with respect to each of a plurality of frequency bins or groups of bins. In another aspect, frequency-domain noise-feedback quantizing in digital audio encoding is provided.