Switched Audio Encoding with Variable Time-Frequency Resolution
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Solution Overview
Problem
Existing audio coding technologies face challenges in maintaining quality for both speech and music signals at low bitrates, with frequency-domain encoders excelling for music but struggling with speech, and speech encoders performing well for speech but poorly for other signals.
Innovation Solution
A dual-mode switched coding/encoding scheme that combines different algorithms, such as speech and audio coding, with time/frequency converters in both branches, allowing for variable resolution and domain conversion using LPC processors, to optimize coding based on signal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency-domain encoding is used, then quality for music signals is improved, but quality for speech signals deteriorates
Solution Approach 1:
The patent implements dynamic switching between frequency-domain encoding and speech encoding algorithms based on real-time signal type detection. The encoder analyzes input signals to determine whether they are music or speech, then dynamically selects the appropriate encoding algorithm, allowing the system to adapt its behavior to different signal characteristics and achieve high quality for both music and speech signals.
Solution Approach 2:
The patent changes the encoding parameter (algorithm selection) based on the detected signal type. When music signals are detected, frequency-domain encoding parameters are applied; when speech signals are detected, speech encoding parameters are applied. This parameter adaptation resolves the contradiction by optimizing encoding quality for the specific signal type being processed.
2Measurement precision
If speech encoding is used, then quality for speech signals is improved, but quality for other signals deteriorates
Solution Approach 1:
The system dynamically adjusts the encoding algorithm based on signal type detection. Speech encoding is activated when speech signals are detected, providing high quality for speech. The system remains versatile by switching to frequency-domain encoding when non-speech signals are detected, thus maintaining high quality across different signal types.
Solution Approach 2:
The encoder changes its operating parameters (encoding algorithm selection) based on the detected signal characteristics. Speech encoding parameters are applied specifically for speech signals, while frequency-domain encoding parameters are applied for other signals, resolving the contradiction between optimizing for speech quality and maintaining versatility.
3Device complexity
If a single encoding algorithm is used, then device complexity is reduced, but coding efficiency for different signal types deteriorates
Solution Approach 1:
The patent segments the encoding process into two distinct algorithmic paths: frequency-domain encoding for music signals and speech encoding for speech signals. The signal analyzer divides the input signal processing based on detected signal type, routing to the appropriate encoding algorithm. This segmentation allows each algorithm to be optimized for its target signal type, improving overall coding efficiency while maintaining manageable complexity through modular architecture.
Solution Approach 2:
The encoder is designed with multi-functionality, incorporating both frequency-domain encoding and speech encoding capabilities within a single device. The signal analyzer and switching mechanism enable the encoder to perform multiple functions (encoding different signal types) using a unified structure, thus improving coding efficiency for diverse signals without proportionally increasing device complexity.
Data Source
AI summary
An audio encoder for encoding an audio signal has a first coding branch, the first coding branch comprising a first converter for converting a signal from a time domain into a frequency domain. Furthermore, the audio encoder has a second coding branch comprising a second time/frequency converter. Additionally, a signal analyzer for analyzing the audio signal is provided. The signal analyzer, on the hand, determines whether an audio portion is effective in the encoder output signal as a first encoded signal from the first encoding branch or as a second encoded signal from a second encoding branch. On the other hand, the signal analyzer determines a time/frequency resolution to be applied by the converters when generating the encoded signals. An output interface includes, in addition to the first encoded signal and the second encoded signal, a resolution information identifying the resolution used by the first time/frequency converter and used by the second time/frequency converter.