Scalable CELP Encoding with Extended Adaptive Codebook Updates
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Solution Overview
Problem
Conventional CELP encoding schemes struggle to maintain sound quality when encoding speech signals with temporal changes, such as transient voiced signals or speech onset segments, due to the adaptive codebook's inability to handle these changes effectively.
Innovation Solution
The proposed speech encoding apparatus incorporates an extended adaptive codebook that includes both past enhancement layer excitation signals and core layer excitation signals succeeding in time, allowing for improved estimation of sub-frame excitations during scalable CELP encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the adaptive codebook is generated using only past enhancement layer excitation signals, then the encoding complexity is reduced, but the sound quality deteriorates when encoding speech signals with temporal changes
Solution Approach 1:
The patent merges the enhancement layer excitation signals with core layer excitation signals to create an extended adaptive codebook. This combination allows the system to utilize both past enhancement layer information and future core layer information, thereby improving sound quality for transient signals while maintaining manageable encoding complexity through the structured merging approach.
Solution Approach 2:
The patent performs preliminary action by incorporating core layer excitation signals that succeed in time into the extended adaptive codebook before the actual encoding of transient speech segments. This preliminary inclusion of future core layer information enables the system to anticipate and handle temporal changes more effectively, improving sound quality without significantly increasing complexity.
2Loss of time
If the adaptive codebook search is performed using only past excitation signals, then the processing time is reduced, but the ability to handle temporal changes in speech signals deteriorates
Solution Approach 1:
The patent extends the adaptive codebook into the time dimension by incorporating core layer excitation signals that succeed in time. This dimensional extension allows the system to search not only in the past but also to utilize future information, thereby improving adaptability to temporal changes while maintaining efficient processing through the structured search approach.
Solution Approach 2:
By preliminarily incorporating core layer excitation signals into the extended adaptive codebook, the system prepares in advance for temporal changes in speech signals. This preliminary action enables faster adaptation during encoding without requiring complex real-time adjustments, thus reducing processing time while improving handling of temporal variations.
3Manufacturing precision
If the extended adaptive codebook includes core layer excitation signals succeeding in time, then the sound quality of encoded speech signals improves, but the device complexity increases
Solution Approach 1:
The patent employs merging by combining enhancement layer and core layer excitation signals into a unified extended adaptive codebook structure. This merging approach improves sound quality by utilizing complementary information from both layers while managing device complexity through the systematic integration methodology that leverages existing codebook structures.
Solution Approach 2:
The extended adaptive codebook serves multiple functions: it maintains backward compatibility with existing enhancement layer encoding while simultaneously incorporating core layer information to improve transient signal handling. This multi-functionality improves sound quality across different signal types without proportionally increasing device complexity, as the same structure serves multiple encoding needs.
Data Source
AI summary
An audio encoding apparatus and the like are disclosed which can improve the sound quality of encoded audio signals even in a case of scalable CELP encoding the audio signals in sections that vary with time. In this apparatus, an enhancement layer extended adaptive codebook generating part (102) generates an extended adaptive codebook (d_enh_ext[i]) from both one frame of core layer drive sound source signals (exc_core[n]) received from a core layer CELP encoding part (101) and past enhancement layer drive sound source signals (exc_enh[n]) received from an adder (106), and further inputs the generated extended adaptive codebook (d_enh_ext[i]) to an enhancement layer extended adaptive codebook (103) for each of sub-frames. That is, the enhancement layer extended adaptive codebook generating part (102) updates the extended adaptive codebook (d_enh_ext[i]) for each of the sub-frames.