CELP Speech Coding Dynamic Codebook Search Switching
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Solution Overview
Problem
Existing CELP-type speech coding apparatuses face inefficiencies in fixed codebook search due to suboptimal selection of adaptive and fixed codebook vectors, with orthogonal and non-orthogonal search methods not always yielding the best results, and the choice between them is often based on heuristic thresholds rather than precise evaluation of their effectiveness.
Innovation Solution
A speech coding apparatus that dynamically switches between orthogonal and non-orthogonal fixed codebook searches based on the correlation value or distance between the target vector and the adaptive codebook vector, ensuring a more precise selection of codebook vectors to minimize error and improve coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If orthogonal fixed codebook search is performed, then coding performance is improved, but calculation amount increases
Solution Approach 1:
The patent dynamically switches between orthogonal and non-orthogonal search methods based on the correlation value between the target vector and adaptive codebook vector. When correlation exceeds a threshold, non-orthogonal search is used to reduce calculation; otherwise orthogonal search is used to maintain coding performance. This dynamic adaptation resolves the contradiction by adjusting the search method according to real-time signal characteristics.
Solution Approach 2:
The patent changes the search method parameter (orthogonal vs. non-orthogonal) based on the correlation value parameter. By monitoring the correlation between target vector and adaptive codebook vector, the system selects the appropriate search method, thereby optimizing the balance between coding performance and calculation amount through parameter-based decision making.
2Device complexity
If non-orthogonal fixed codebook search is performed, then calculation amount is reduced, but coding performance deteriorates
Solution Approach 1:
The system dynamically selects between non-orthogonal and orthogonal search methods based on correlation value thresholds. Non-orthogonal search is used when correlation is high (reducing calculation), while orthogonal search is activated when correlation is low (maintaining performance). This dynamic switching resolves the contradiction by adapting the search method to signal conditions.
Solution Approach 2:
The patent uses the correlation value as a decision parameter to switch between search methods. When the correlation parameter exceeds a threshold, non-orthogonal search is selected for efficiency; otherwise orthogonal search is used for performance, thereby optimizing the trade-off through parameter-based control.
3Ease of operation
If adaptive codebook vector is determined first without considering fixed codebook vector combination, then search process is simplified, but the combination is not necessarily optimum
Solution Approach 1:
The patent introduces feedback by calculating the correlation value between the target vector and the determined adaptive codebook vector. This correlation metric provides feedback information that guides the selection of the fixed codebook search method, enabling the system to optimize the codebook vector combination while maintaining a simplified search process through threshold-based decision making.
Solution Approach 2:
The correlation value acts as an intermediary parameter that bridges the adaptive codebook determination and fixed codebook search processes. By using this intermediate metric to guide search method selection, the system achieves near-optimum codebook combinations without the complexity of joint optimization, effectively mediating between the two search stages.
Data Source
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AI summary
In a CELP-type speech coding apparatus, switching between an orthogonal search of a fixed codebook and a non-orthogonal search is performed in a practical and effective manner. The CELP-type speech coding apparatus (100) includes a parameter quantization unit (108) that selects an adaptive codebook vector and a fixed codebook vector so as to minimize an error between a synthesized speech signal and an input speech signal. The parameter quantization unit (108) includes a fixed codebook search unit (300) that switches between the orthogonal fixed codebook search and the non-orthogonal fixed codebook search based on a correlation value between a target vector for the fixed codebook search and the adaptive codebook vector obtained as a result of a synthesis filtering process.