CELP Codec Gain Quantization for Frame Erasure Robustness
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Solution Overview
Problem
Existing codec technologies face challenges in robustness against frame erasures or packet losses during the transmission of encoding parameters, particularly in the quantization of adaptive and fixed excitation contributions in CELP codec structures.
Innovation Solution
The proposed solution involves quantizing the gains of adaptive and fixed excitation contributions without inter-frame prediction, using an estimator to calculate the gain of the fixed contribution based on parameters available at both the coder and decoder, and employing a predictive quantizer to improve robustness against frame erasures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inter-frame prediction is used for quantizing excitation gains, then quantization precision is improved, but robustness against frame erasures deteriorates
Solution Approach 1:
The patent segments the gain quantization process into two independent parts: adaptive codebook gain quantization and fixed codebook gain quantization. This segmentation allows the fixed codebook gain to be quantized independently without relying on previous frame information, thereby resolving the contradiction between precision and robustness.
Solution Approach 2:
The patent extracts the fixed codebook contribution from the overall excitation structure and quantizes its gain separately. By taking out the fixed codebook gain quantization from the inter-frame prediction chain, the system achieves robustness against frame erasures while maintaining acceptable quantization precision through dedicated fixed codebook gain codebooks.
2Measurement precision
If previous frame information is used for gain quantization, then quantization accuracy is improved, but transmission reliability deteriorates
Solution Approach 1:
The patent performs preliminary quantization of the fixed codebook gain using dedicated gain codebooks before transmission. This preliminary action ensures that the fixed codebook gain can be accurately reconstructed at the decoder without requiring previous frame information, thus maintaining transmission reliability while achieving good quantization accuracy.
Solution Approach 2:
The patent creates separate gain codebooks specifically for the fixed codebook contribution, copying the essential gain information into these dedicated structures. This copying mechanism allows the decoder to retrieve accurate gain values without relying on potentially lost inter-frame prediction data from previous frames.
3Reliability
If separate quantization of adaptive and fixed contributions is performed, then robustness is improved, but device complexity increases
Solution Approach 1:
The patent merges the quantization of adaptive and fixed codebook gains into a unified CELP coding framework while maintaining their independence. By combining the two quantization processes within the same coding structure and using shared codebook search mechanisms, the patent reduces the overall complexity compared to completely separate processing systems.
Solution Approach 2:
The patent designs the gain codebooks to serve multiple functions: they provide quantization for the fixed codebook gain while also enabling efficient codebook search and excitation generation. This multi-functionality reduces the need for separate dedicated structures, thereby limiting the increase in device complexity while maintaining robustness.
Data Source
AI summary
A device and method for quantizing a gain of a fixed contribution of an excitation in a frame, including sub-frames, of a coded sound signal, wherein the gain of the fixed excitation contribution is estimated in a sub-frame using a parameter representative of a classification of the frame. The gain of the fixed excitation contribution is then quantized in the sub-frame using the estimated gain. The device and method is used in jointly quantizing gains of adaptive and fixed contributions of an excitation in a frame of a coded sound signal. For retrieving a quantized gain of a fixed contribution of an excitation in a sub-frame of a frame, the gain of the fixed excitation contribution is estimated using a parameter representative of a classification of the frame, a gain codebook supplies a correction factor in response to a received, gain codebook index, and a multiplier multiplies the estimated gain by the correction factor to provide a quantized gain of the fixed excitation contribution.