Transient Compensation in Transform Audio Coding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Combining speech and audio coding techniques, particularly at low bit-rates, is challenging due to the difficulty in handling transient effects when transitioning from time-domain quantization to transform coding without introducing significant delay.
Innovation Solution
A method using a transform-based time-frequency domain codec that encodes acoustic signals by selecting between different encoding methods based on criteria, performing transform analysis, and combining coefficients from long and short windows to generate additional encoding values, which are then decoded to compensate for transient effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transform coding is used for audio coding at low bit-rates, then coding gain is achieved through transform and perceptual masking, but transient effects from time domain quantization cannot be handled without extensive delay
Solution Approach 1:
The patent segments the audio signal processing into distinct time domain and transform domain sections. It applies transform coding selectively to certain frames while maintaining time domain processing for others, allowing the system to achieve coding gain where applicable without introducing delay in time-critical sections. This segmentation enables independent optimization of each domain for its specific requirements.
Solution Approach 2:
The patent dynamically switches between time domain and transform domain processing based on signal characteristics and requirements. The system adapts its processing mode frame-by-frame or section-by-section, enabling it to achieve coding gain when transform coding is beneficial while avoiding delay issues when time domain processing is more appropriate. This dynamic adaptation resolves the contradiction by making the processing method flexible rather than fixed.
2Adaptability or versatility
If model based time domain speech codec is combined with transform based time-frequency domain codec, then speech and audio coding is achieved, but transient effects cannot be handled without extensive delay
Solution Approach 1:
The patent introduces an intermediary mechanism that bridges the time domain speech codec and transform domain audio codec. This intermediary handles the transient effects by providing a transition buffer or overlap region that allows seamless switching between domains without introducing extensive delay. The intermediary acts as a mediator that reconciles the different processing requirements of speech and audio coding.
Solution Approach 2:
The patent performs preliminary actions by pre-processing the signal to prepare for domain switching. It applies preprocessing steps such as windowing, overlap-save, or buffer management before transitioning between time and transform domains. This preliminary preparation enables smooth integration of speech and audio coding while minimizing delay by having the necessary processing ready in advance rather than reacting to transients after they occur.
3Measurement precision
If transform coding is applied to transient frames, then frequency domain coding is achieved, but the transient from time domain quantization creates artifacts without compensation
Solution Approach 1:
The patent converts the harmful transient artifacts into beneficial information by capturing the transient characteristics during the transition from time to transform domain. Instead of discarding or ignoring these artifacts, the system uses them to inform the transform coding process, allowing the frequency domain representation to account for and properly represent transient events. This transforms what was previously a harmful effect into useful data for improved coding accuracy.
Solution Approach 2:
The patent applies preliminary compensation measures before the transform coding of transient frames. It detects potential transient artifacts in advance and applies corrective preprocessing to the signal or to the transform coefficients themselves. This preliminary action prevents artifacts from manifesting as harmful effects while maintaining the benefits of frequency domain coding, by preparing the signal in advance to withstand the transform process without generating artifacts.
Data Source
AI summary
The present invention provides a method for compensating transient effects in transform coding and decoding of a combined speech and audio in electronic devices by using a transform based time-frequency domain codec. The method can combine, e.g., a CELP (code excited linear prediction) type speech codec and a transform type audio codec. The invention describes a compensation method to handle the transient (e.g., from the CELP coding to the transform coding) in transform coding when the number of quantized transform coding coefficients is lower than in the output of the transform.