Audio Decoder Transition Without Adaptive Dictionary Updates
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Solution Overview
Problem
Existing audio coding techniques face complexity spikes during transitions between transform coding and predictive coding, particularly in conversational applications, due to the need for updating adaptive dictionaries and resampling, which increases processing delay and complexity.
Innovation Solution
A method for transition predictive decoding that reinitializes predictive decoding states to default values and uses overlap-add to combine signal segments from inverse transform decoding, eliminating the need for adaptive dictionary updates and simplifying the transition process, thereby reducing complexity and avoiding artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive dictionary updates are performed during transition between transform coding and predictive coding, then coding continuity is improved, but processing complexity and algorithmic delay increase
Solution Approach 1:
The patent extracts and eliminates the adaptive dictionary update mechanism during mode transitions. Instead of maintaining and updating the adaptive dictionary across transform and predictive coding modes, the invention resets the adaptive dictionary to default values during transitions, thereby removing the complexity of dictionary management while maintaining coding effectiveness through the overlap-add technique.
Solution Approach 2:
The patent changes the state parameters of the adaptive dictionary during mode transitions by resetting them to default values rather than maintaining continuity. This parameter change simplifies the transition process and reduces computational complexity while the overlap-add technique ensures smooth signal reconstruction without artifacts.
2Reliability
If adaptive dictionary updates are performed during transition between transform coding and predictive coding, then coding continuity is improved, but processing delay increases
Solution Approach 1:
The patent removes the time-consuming adaptive dictionary update operations during mode transitions. By eliminating these updates and resetting to default values, the invention significantly reduces the algorithmic delay associated with transitions, making the coding system more suitable for real-time conversational applications.
3Reliability
If overlap-add is used to combine signal segments during transition, then transition smoothness is improved, but processing complexity increases
Solution Approach 1:
The patent applies preliminary windowing functions to signal segments before the overlap-add operation. By pre-processing the segments with appropriate window functions, the invention ensures smooth transitions and eliminates artifacts while keeping the actual overlap-add operation simple and efficient, thereby minimizing the increase in processing complexity.
4Device complexity
If predictive decoding states are reinitialized to default values, then transition complexity is reduced, but coding continuity may be affected
Solution Approach 1:
The patent introduces the overlap-add technique as an intermediary mechanism that bridges the gap caused by reinitializing predictive decoding states. This intermediary approach ensures that even though states are reset to default values (simplifying transitions), the coding continuity and signal smoothness are maintained through the careful combination of signal segments from both transform and predictive coding modes.
Data Source
AI summary
Methods and apparatus are provided for coding and decoding a digital audio signal. Decoding includes: decoding according to an inverse transform decoding of a previous frame of samples of the digital signal, which is received and coded according to a transform coding; and decoding according to a predictive decoding of a current frame of samples of the digital signal, which is received and coded according to a predictive coding. The predictive decoding of the current frame is a transition predictive decoding which does not use any adaptive dictionary arising from the previous frame. At least one state of the predictive decoding is reinitialized to a predetermined default value, and an add-overlap step combines a signal segment synthesized by predictive decoding of the current frame and a signal segment synthesized by inverse transform decoding, corresponding to a stored segment of the decoding of the previous frame.