Two-Stage Audio Quantization for Low-Bitrate Stereo Coding
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Solution Overview
Problem
Existing audio codecs face challenges in efficiently encoding and decoding spectral noise shaping parameters for stereo signals, leading to high bitrate requirements and potential loss of perceptual quality, especially at low bitrates and low delays.
Innovation Solution
A two-stage vector quantization process is applied to scale parameters, where the first stage quantizes audio information items and calculates residuals, followed by a second stage quantization of these residuals, allowing for joint encoding of correlated channels to reduce bitrate and improve perceptual quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral noise shaping parameters are encoded with high precision using multiple scale factors, then perceptual quality is improved, but bitrate increases significantly
Solution Approach 1:
The patent divides the scale parameters into two distinct groups: a first group of scale parameters and a second group of scale parameters. This segmentation allows differential encoding strategies to be applied to each group, optimizing the balance between perceptual quality and bitrate. The first group can be encoded with higher precision while the second group uses lower precision, reducing overall bitrate while maintaining essential perceptual quality.
Solution Approach 2:
The patent applies different encoding precisions to different groups of scale parameters based on their perceptual importance. The first group of scale parameters is encoded with higher precision to preserve critical perceptual information, while the second group is encoded with lower precision where perceptual sensitivity is reduced. This local quality approach optimizes the trade-off between overall perceptual quality and bitrate efficiency.
2Quantity of substance
If joint encoding of correlated channels is implemented, then bitrate is reduced, but encoding complexity increases
Solution Approach 1:
The patent segments the stereo encoding process into independent first and second groups of scale parameters, where the first group can be jointly encoded across channels while the second group is encoded separately. This segmentation reduces encoding complexity by limiting the scope of joint processing while still achieving bitrate reduction through selective joint encoding of the first group where correlation exists.
Solution Approach 2:
The patent applies joint encoding only partially - specifically to the first group of scale parameters where channel correlation provides bitrate benefits - rather than applying it excessively to all parameters. This partial action approach achieves bitrate reduction without the full complexity burden of complete joint encoding, optimizing the trade-off between bitrate and encoding complexity.
Data Source
AI summary
An audio quantizer for quantizing a plurality of audio information items has: a first stage vector quantizer for quantizing the plurality of audio information items to determine a first stage vector quantization result and a plurality of intermediate quantized items corresponding to the first stage vector quantization result; a residual item determiner for calculating a plurality of residual items from the plurality of intermediate quantized items and the plurality of audio information items; and a second stage vector quantizer for quantizing the plurality of residual items to obtain a second stage vector quantization result, wherein the first stage vector quantization result and the second stage vector quantization result are a quantized representation of the plurality of audio information items.