Stereo Coding Method Using Group Delay and Phase Estimation
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Solution Overview
Problem
Existing stereo coding methods face challenges in restoring an accurate stereo signal at low bit rates due to the high bit requirements for transmitting interchannel phase difference (IPD), interchannel cross correlation (ICC), and overall phase difference (OPD) parameters, leading to an uncomfortable listening experience.
Innovation Solution
A method that transforms stereo signals into the frequency domain, down-mixes them to generate a monophonic signal, extracts spatial parameters, estimates group delay and group phase, and performs quantization coding on these parameters to efficiently transmit sound field information at a low bit rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IPD, ICC and OPD parameters are transmitted for each sub-band to enhance sound field information, then the sound field restoration quality is improved, but the coding bit rate increases significantly
Solution Approach 1:
The patent segments the stereo signal into multiple sub-bands using filter banks, and processes each sub-band separately. This allows selective enhancement of sound field information in different frequency regions, reducing the overall bit rate requirement compared to processing the entire frequency spectrum uniformly.
Solution Approach 2:
The patent applies different coding strategies to different sub-bands based on their characteristics. In sub-bands where sound field information is critical, IPD, ICC and OPD parameters are transmitted, while in other sub-bands, fewer parameters or simplified models are used, optimizing the trade-off between quality and bit rate.
2Loss of information
If multiple stereo parameters (ILD, IPD, ICC, OPD) are transmitted to restore original stereo signal, then the sound field information is enhanced, but the number of bits required increases
Solution Approach 1:
The patent extracts only the essential sound field parameters needed for reconstruction. Instead of transmitting all possible parameters, it selectively extracts and transmits ILD, IPD, ICC and OPD parameters that provide the most significant contribution to sound field restoration, reducing the bit rate while maintaining quality.
Solution Approach 2:
The patent transmits a partial set of parameters for each sub-band rather than all parameters. By carefully selecting which parameters to transmit based on sub-band characteristics and importance, it achieves adequate sound field restoration with fewer bits than transmitting complete parameter sets for all sub-bands.
3Quantity of substance
If ILD parameter is transmitted as side information to restore stereo signal, then the basic stereo effect is achieved, but the background space and directional information are insufficient
Solution Approach 1:
The patent merges multiple parameters (ILD, IPD, ICC, OPD) into a unified coding framework. By combining these parameters and processing them together across multiple sub-bands, it achieves complete sound field information representation while optimizing the total bit rate through joint coding strategies.
Data Source
AI summary
A stereo coding method includes transforming a stereo left channel signal and a stereo right channel signal in a time domain to a frequency domain to form a left channel signal and a right channel signal in the frequency domain; down-mixing the left channel signal and the right channel signal in the frequency domain to generate a monophonic down-mix signal, and transmitting bits obtained after quantization coding is performed on the down-mix signal; extracting spatial parameters of the left channel signal and the right channel signal in the frequency domain; estimating a group delay and a group phase between stereo left and right channels by using the left channel signal and the right channel signal in the frequency domain; and performing quantization coding on the group delay, the group phase and the spatial parameters, so as to obtain a high-quality stereo coding performance at a low bit rate.