Stereo Sound Encoding Using Primary-Channel Parameter Reuse
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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 inefficiencies and increased bit-rates when encoding stereo information.
Innovation Solution
A stereo sound encoding method and system that utilizes time domain down mixing to create a primary and secondary channel, where the primary channel is encoded using a modified CELP-type encoder with flexible bit-rate allocation, and the secondary channel is encoded at a minimum bit-rate, with a multiplexing process to maintain overall bit-rate consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual mono encoding is used to transmit stereo information, then stereo quality is maintained, but bit-rate doubles
Solution Approach 1:
The patent combines left and right audio channels into a single downmixed mono channel, eliminating the need to transmit separate stereo channels. This merging reduces bit-rate requirements while preserving essential stereo information through alternative encoding schemes that exploit channel redundancy.
Solution Approach 2:
The patent extracts and transmits only the essential stereo information (such as inter-channel level differences and inter-channel time differences) separately from the downmixed channel, rather than transmitting full stereo channels. This extraction approach reduces the total bit-rate while maintaining stereo quality.
2Quantity of substance
If parametric stereo is used to reduce bit-rate, then bit-rate is reduced, but stereo quality deteriorates at low bit-rates
Solution Approach 1:
The patent applies different encoding strategies to different parts of the audio signal: the downmixed channel receives full encoding resources while the stereo difference information receives minimal encoding. This local quality approach ensures that critical listening components maintain high quality while reducing overall bit-rate.
Solution Approach 2:
The patent changes the representation parameters from full stereo channel encoding to a combination of downmixed audio and stereo difference parameters. This parameter transformation allows efficient bit-rate allocation where most bits go to the downmixed channel and few bits are needed for stereo information.
3Quantity of substance
If panning factor encoding is used for basic stereo effect, then bit-rate is reduced, but ambiance and spatial quality are lost
Solution Approach 1:
The patent performs downmixing of the stereo channels into a mono channel before encoding, creating a solid audio foundation that preserves temporal and spectral characteristics. This preliminary action ensures that the core audio quality is maintained while stereo information is efficiently encoded separately.
Data Source
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AI summary
A stereo sound encoding method and system for encoding left and right channels of a stereo sound signal, down mix the left and right channels of the stereo sound signal to produce primary and secondary channels, encode the primary channel, and encode the secondary channel. Encoding the secondary channel comprises analyzing coherence between coding parameters calculated during the secondary channel encoding and coding parameters calculated during the primary channel encoding to decide if the coding parameters calculated during the primary channel encoding are sufficiently close to the coding parameters calculated during the secondary channel encoding to be re-used during the secondary channel encoding.