Stereo Codec Mode Selection for Uncorrelated Audio and Cross-Talk
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Solution Overview
Problem
Existing audio codecs struggle with efficiently encoding stereo signals, particularly in scenarios with weakly correlated or uncorrelated channels, leading to increased bitrates and compromised sound quality, especially in complex audio scenes with multiple speakers or immersive experiences.
Innovation Solution
A method and device for classifying uncorrelated stereo content and detecting cross-talk in stereo sound signals, using features extracted from the left and right channels, to dynamically switch between LRTD and DFT stereo modes based on correlation and cross-talk detection, optimizing encoding efficiency and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both left and right channels are coded using a mono codec, then stereo information is transmitted, but the bitrate is doubled and redundancy between channels is not exploited
Solution Approach 1:
The patent combines the left and right channels into a single stereo codec that exploits inter-channel redundancy. By analyzing the correlation between channels and applying joint coding techniques, the system transmits stereo information at a lower bitrate than independent mono coding while maintaining audio quality.
Solution Approach 2:
The stereo codec is designed to handle multiple coding modes (joint stereo, dual channel, mid-side) within a single unified framework. This multi-functional approach allows the system to adapt to different audio scenarios and efficiently exploit redundancy across various stereo configurations.
2Quantity of substance
If a very low bitrate is used for each channel to keep overall bitrate reasonable, then bitrate is reduced, but sound quality is affected
Solution Approach 1:
By merging the coding of left and right channels into a unified stereo codec, the system exploits inter-channel redundancy to achieve better sound quality at lower bitrates. The joint analysis and coding of both channels allow for more efficient bit allocation compared to independent mono coding.
Solution Approach 2:
The stereo codec dynamically adjusts coding parameters such as bit allocation, window size, and transform type based on the audio content characteristics. This adaptive parameter adjustment optimizes sound quality for different types of stereo material while maintaining efficient bitrate utilization.
3Productivity
If parametric stereo encoding is used to reduce bitrate, then encoding efficiency is improved, but complexity of calculating and transmitting stereo parameters increases
Solution Approach 1:
The patent employs parametric stereo encoding that represents the stereo image using a compact set of parameters (inter-channel level difference, inter-channel time difference, inter-channel correlation) rather than full stereo signals. This parameter-based approach significantly reduces bitrate while maintaining stereo quality, and the parameters are efficiently calculated using standardized algorithms.
Solution Approach 2:
The stereo information is extracted from the full stereo signal in the form of compact parametric representations. By separating the essential stereo characteristics (ILD, ITD, IC) from the full audio data, the system achieves efficient compression while preserving the stereo image with minimal parameter transmission.
4Productivity
If time-domain mixing is used for stereo coding, then coding efficiency is improved, but adaptability to different stereo scene configurations is reduced
Solution Approach 1:
The stereo codec implements dynamic mode selection that adapts the coding strategy based on the stereo scene configuration. The system analyzes inter-channel correlation and other metrics to dynamically switch between joint stereo, dual channel, and mid-side coding modes, optimizing performance for different audio scenarios including uncorrelated content and cross-talk situations.
Solution Approach 2:
The codec dynamically adjusts coding parameters including transform type (MDCT vs. no transform), bit allocation between mid and side channels, and window overlap settings based on the detected stereo scene characteristics. This adaptive parameter control enables efficient coding across diverse stereo configurations while maintaining high audio quality.
Data Source
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AI summary
The present disclosure describes the classification of uncorrelated stereo content (hereinafter "UNCLR classification") and the cross-talk detection (hereinafter "XT ALK detection") in an input stereo sound signal. The present disclosure also describes the stereo mode selection, for example an automatic LRTD/DFT stereo mode selection. Additionally, the disclosure uses said classification so as to select one of a first stereo mode and a second stereo mode for coding a stereo sound signal including a left channel and a right channel; detect cross-talk in a stereo sound signal including a left channel and a right channel in response to features extracted from the stereo sound signal including the left and right channels; or classify of uncorrelated stereo content in a stereo sound signal including a left channel and a right channel in response to features extracted from the stereo sound signal including the left and right channels.