Stereo Sound Decoding with Shared LP Filters at Low Bit-Rates
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Solution Overview
Problem
Existing stereo sound encoding technologies struggle to maintain good quality at low bit-rates and low delays, especially in complex audio scenes with fluctuating background noise and interfering talkers, leading to inefficient bit-rate usage and reduced sound quality.
Innovation Solution
A method and system for decoding left and right channels of a stereo sound signal using encoding parameters, including LP filter coefficients, multiple coding models, and a factor β to determine channel contributions, allowing for efficient bit allocation and time domain up-mixing to produce high-quality stereo sound at reduced bit-rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual monophonic coding is used for stereo transmission, then stereo information can be transmitted, but the bit-rate needs to be doubled and sound quality suffers at low bit-rates
Solution Approach 1:
The patent merges the encoding of left and right channels into a unified stereo encoding framework. Instead of independently encoding L and R channels with separate monophonic codecs, the system encodes them jointly using shared parameters (LP filter coefficients, gain parameters, codebook indices) to exploit inter-channel redundancy and correlation, achieving stereo transmission at lower total bit-rates
Solution Approach 2:
The patent creates a universal encoding framework that can handle both monophonic and stereophonic signals. The same encoding structure serves dual purposes: it can encode single-channel signals and stereo signals, with the ability to adapt between modes. The encoded parameters serve multiple functions in reconstructing both channels from a shared parameter set
2Quantity of substance
If parametric stereo with ITD and IID parameters is used, then stereo transmission is achieved at low bit-rate, but the bit budget is insufficient for efficient parameter transmission and sound quality suffers
Solution Approach 1:
The patent changes the parameter representation from traditional parametric stereo (ITD, IID per frequency band) to a different parameterization based on LP filter coefficients and gain parameters. This parameter transformation allows for more efficient bit allocation and exploitation of signal correlations, achieving better sound quality at the same bit-rate or lower
3Quantity of substance
If panning factor encoding is used for basic stereo effect, then bit-rate is reduced, but ambiance preservation fails and speech quality suffers in complex audio scenes
Solution Approach 1:
The patent introduces dynamic adaptation of encoding parameters based on the audio scene characteristics. The system dynamically adjusts the encoding strategy by analyzing inter-channel correlations and adapting the parameter quantization and bit allocation in real-time, allowing it to handle complex scenarios with interfering talkers and background noise while maintaining speech quality
Solution Approach 2:
The patent implements feedback mechanisms where the encoder analyzes the stereo signal characteristics (correlations, energy distribution) and uses this information to adapt the encoding parameters. The decoded signal quality is optimized through iterative refinement of parameter selection based on the actual audio content being encoded
Data Source
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AI summary
A stereo sound decoding method and system decode left and right channels of a stereo sound signal, using received encoding parameters comprising encoding parameters of a primary channel, encoding parameters of a secondary channel, and a factor β. The primary channel encoding parameters comprise LP filter coefficients of the primary channel. The primary channel is decoded in response to the primary channel encoding parameters. The secondary channel is decoded using one of a plurality of coding models, wherein at least one of the coding models uses the primary channel LP filter coefficients to decode the secondary channel. The decoded primary and secondary channels are time domain up-mixed using the factor β to produce the decoded left and right channels of the stereo sound signal, wherein the factor β determines respective contributions of the primary and secondary channels upon production of the left and right channels.