Audio Decoder Aliasing Cancellation for Cross-Domain Frame Transitions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing audio coders face difficulties in transitioning between frames encoded in different domains without significant bitrate sacrifice, particularly when combining speech and audio coding.
Innovation Solution
An audio signal decoder that performs spectral shaping of spectral coefficients in the frequency-domain and time-domain filtering of an aliasing-cancellation stimulus signal, using linear-prediction-domain parameters for efficient transitions between frames encoded in different modes, including transform-coded-excitation-linear-prediction-domain, frequency-domain, and algebraic-code-excited-linear-prediction modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transitions between frames encoded in different domains are implemented, then adaptability of the audio coder is improved, but bitrate efficiency deteriorates due to significant bitrate sacrifice
Solution Approach 1:
An aliasing-cancellation stimulus filter is introduced as an intermediary component that processes the aliasing-cancellation stimulus signal to generate the aliasing-cancellation synthesis signal. This mediator enables smooth transitions between transform domain mode and linear-prediction-domain mode by canceling aliasing artifacts that would otherwise require significant bitrate overhead, thus resolving the contradiction between adaptability and bitrate efficiency.
Solution Approach 2:
The aliasing-cancellation stimulus signal is generated in advance based on linear-prediction-domain parameters before the actual frame transition occurs. By preparing the cancellation signal preliminarily using already-available parameters, the system enables efficient mode transitions without requiring additional bitrate expenditure during the transition itself, thereby maintaining bitrate efficiency while improving adaptability.
2Quantity of substance
If spectral shaping and aliasing-cancellation are performed using linear-prediction-domain parameters, then bitrate efficiency is improved, but device complexity increases
Solution Approach 1:
Linear-prediction-domain parameters are designed to serve multiple functions simultaneously: they are used for both spectral shaping of the audio signal and for generating the aliasing-cancellation stimulus signal. This multi-functionality reduces the need for separate parameter sets, thereby improving bitrate efficiency without proportionally increasing device complexity, as the same parameters are reused across different processing stages.
Solution Approach 2:
The system uses its own existing linear-prediction-domain parameters to generate the aliasing-cancellation stimulus signal, rather than requiring external or additional parameters. This self-service approach allows the decoder to perform aliasing cancellation using resources already allocated for normal audio decoding, thereby reducing bitrate overhead without significantly increasing device complexity.
3Reliability
If aliasing-cancellation synthesis signal is generated by filtering the stimulus signal, then auditory quality is improved, but device complexity increases
Solution Approach 1:
The aliasing-cancellation stimulus filter acts as a dedicated intermediary component that specializes in generating the cancellation signal. By isolating this function in a separate filter module, the system improves auditory quality through effective aliasing cancellation while managing device complexity through functional separation, allowing each component to be optimized independently.
Solution Approach 2:
The system replaces complex time-domain aliasing cancellation mechanisms with a frequency-domain filtering approach using the aliasing-cancellation stimulus filter. This substitution simplifies the overall device architecture by using straightforward filtering operations rather than complex time-domain processing, thereby improving auditory quality while keeping device complexity manageable.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An audio signal decoder (200) for providing a decoded representation (212) of an audio content on the basis of an encoded representation (310) of the audio content comprises a transform domain path (230, 240, 242, 250, 260) configured to obtain a time-domain representation (212) of a portion of the audio content encoded in a transform-domain mode on the basis of a first set (220) of spectral coefficients, a representation (224) of an aliasing-cancellation stimulus signal and a plurality of linear-prediction-domain parameters (222). The transform domain path comprises a spectrum processor (230) configured to apply a spectrum shaping to the first set of spectral coefficients in dependence on at least a subset of the linear-prediction-domain parameters, to obtain a spectrally-shaped version (232) of the first set of spectral coefficients. The transform domain path comprises a first frequency-domain-to-time-domain converter (240) configured to obtain a time-domain representation of the audio content on the basis of the spectrally-shaped version of the first set of spectral coefficients. The transform domain path comprises an aliasing-cancellation stimulus filter configured to filter (250) the aliasing-cancellation stimulus signal (324) in dependence on at least a subset of the linear-prediction-domain parameters (222), to derive an aliasing-cancellation synthesis signal (252) from the aliasing-cancellation stimulus signal. The transform domain path also comprises a combiner (260) configured to combine the time-domain representation (242) of the audio content with the aliasing-cancellation synthesis signal (252), or a post-processed version thereof, to obtain an aliasing reduced time-domain signal.