Scalable LSP Encoding via Autocorrelation Conversion
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Solution Overview
Problem
The existing methods for converting narrowband LSP parameters to wideband LSP parameters suffer from inappropriate correlation between the two, leading to suboptimal encoding performance due to the position of LSP parameters on the low-order side of the wideband signal not corresponding accurately to those of the narrowband signal, especially when the analysis orders differ significantly.
Innovation Solution
A scalable encoding apparatus that includes a first conversion section to convert narrowband LSP parameters into autocorrelation coefficients, an up-sampling section to up-sample these coefficients, and a second conversion section to convert them into wideband LSP parameters, thereby improving the predictive accuracy and scalability of the encoding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a simple conversion equation (fw(i)=0.5×fn(i)) is used to convert narrowband LSP to wideband LSP, then the conversion process is simple and fast, but the conversion efficiency and predictive accuracy deteriorate because the position of LSP parameters does not correspond accurately
Solution Approach 1:
The patent introduces autocorrelation coefficients as an intermediary parameter to bridge narrowband LSP and wideband LSP conversion. Instead of directly converting LSP parameters with a simple equation, the system converts narrowband LSP to autocorrelation coefficients, then converts these coefficients to wideband LSP. This intermediary approach maintains accurate correlation relationships while achieving both simplicity and high predictive accuracy.
Solution Approach 2:
The patent changes the parameter representation from direct LSP parameters to autocorrelation coefficients during the conversion process. By transforming the parameter domain through autocorrelation coefficients, the system achieves accurate mapping between narrowband and wideband LSP while maintaining computational efficiency. This parameter transformation resolves the contradiction between simplicity and accuracy.
2Measurement precision
If the analysis order of LSP parameter is increased to improve encoding performance, then encoding accuracy improves, but the complexity of the encoding apparatus and processing requirements increase
Solution Approach 1:
The patent makes the autocorrelation coefficient conversion process universal by using the same conversion mechanism for both narrowband to wideband LSP conversion and for handling different analysis orders. The autocorrelation coefficient representation can accommodate various analysis orders (e.g., 8th order to 16th order) using the same structural approach, avoiding the need for separate complex processing for each order.
Solution Approach 2:
The patent transitions from direct LSP parameter conversion to a higher-dimensional representation using autocorrelation coefficients. This dimensional change allows the system to handle different analysis orders uniformly and achieves better encoding performance without proportionally increasing apparatus complexity, as the autocorrelation coefficient framework provides a natural extension for higher orders.
Data Source
AI summary
There is provided a scalable encoding device capable of realizing a bandwidth scalable LSP encoding with high performance by improving the conversion performance from narrow band LSPs to wide band LSPs. The device includes: an autocorrelation coefficient conversion unit (301) for converting the narrow band LSPs of Mn order to an autocorrelation coefficients of Mn order; an inverse lag window unit (302) for applying a window which has an inverse characteristic of a lag window supposed to be applied to the autocorrelation coefficients; an extrapolation unit (303) for extending the order of the autocorrelation coefficients to (Mn+Mi) order by extrapolating the inverse lag windowed autocorrelation coefficients; an up-sample unit (304) for performing an up-sample process in the autocorrelation domain which is equivalent to an up-sample process in a time domain for the autocorrelation coefficients of the (Mn+Mi) order so as to obtain autocorrelation coefficients of Mw order; a lag window unit (305) for applying a lag window to the autocorrelation coefficients of Mw order; and an LSP conversion unit (306) for converting the lag windowed autocorrelation coefficients into LSPs.