Audio Decoder Bit Allocation for Highly Tonal Signals
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Solution Overview
Problem
Modern audio encoders face challenges in efficiently encoding highly tonal signals due to underestimation of bit-consumption, leading to loss of important frequency components and sub-optimal audio quality, while overestimation results in excess bits and inefficient bit distribution between initial and residual coding stages.
Innovation Solution
A signal-dependent audio encoding method that adjusts the number of audio data items and bit distribution based on signal characteristics, using a two-stage coder processor with an entropy encoder for initial coding and a residual encoder for refinement, shifting bits from the initial to the residual stage for highly tonal signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If power spectrum based bit consumption estimation is used for highly tonal signals, then computational complexity is reduced, but bit consumption estimation accuracy deteriorates leading to underestimation
Solution Approach 1:
The patent applies different estimation strategies to different signal types: power spectrum based estimation for general signals, and enhanced estimation incorporating tonality detection for highly tonal signals. This local differentiation resolves the contradiction by matching the estimation method to the signal characteristics, maintaining low complexity for most signals while improving accuracy for problematic cases.
Solution Approach 2:
The patent changes the estimation parameters dynamically based on signal tonality. When high tonality is detected, the system adjusts the estimation approach to account for the specific bit consumption patterns of tonal signals, thereby improving accuracy without significantly increasing overall computational complexity.
2Reliability
If global gain is increased to prevent bit consumption underestimation, then important frequency components are preserved, but excess bits are generated for non-tonal signals
Solution Approach 1:
The patent dynamically adjusts the global gain based on detected signal tonality. For highly tonal signals, a higher global gain is applied to ensure accurate bit consumption estimation and preserve important components. For non-tonal signals, the standard gain is used to maintain bit efficiency. This dynamic adaptation resolves the contradiction by optimizing both reliability and efficiency based on signal characteristics.
3Manufacturing precision
If more bits are allocated to initial coding stage, then spectral coefficient precision is improved, but residual coding stage has insufficient bits for refinement
Solution Approach 1:
The patent performs preliminary tonality detection and bit consumption estimation before the coding stages. Based on this preliminary analysis, the system pre-calculates the optimal bit distribution between initial and residual coding stages. This preliminary action ensures that highly tonal signals receive sufficient bits in the initial stage for accurate coefficient encoding, while leaving adequate bits in the residual stage for refinement, resolving the contradiction through advance planning.
Data Source
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AI summary
An audio encoder for encoding audio input data (11) comprises: a preprocessor (10) for preprocessing the audio input data (11) to obtain audio data to be coded; a coder processor (15) for coding the audio data to be coded; and a controller (20) for controlling the coder processor (15) so that, depending on a first signal characteristic of a first frame of the audio data to be coded, a number of audio data items of the audio data to be coded by the coder processor (15) for the first frame is reduced compared to a second signal characteristic of a second frame, and a first number of information units used for coding the reduced number of audio data items for the first frame is stronger enhanced compared to a second number of information units for the second frame.