Audio Decoder Zero-Input Response for Smooth Codec Transitions
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Solution Overview
Problem
Existing switched audio codecs face challenges in achieving smooth transitions between CELP and MDCT coding schemes, leading to issues like aliasing and discontinuities due to differences in coding domains, with existing solutions often introducing delays or requiring significant additional bitrates.
Innovation Solution
An audio decoder that utilizes a transition processor to modify decoded audio information using a zero-input response of a linear predictive filter, considering both initial states of the first and second decoded audio information to achieve a smooth transition without additional delay or increased bitrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switched audio codecs switch between CELP and MDCT coding schemes, then coding quality and bitrate efficiency are improved, but discontinuities and artifacts are introduced at mode transitions
Solution Approach 1:
The patent applies preliminary action by computing the zero-input-response of the linear predictive filter in advance, based on the first decoded audio information before the actual mode transition occurs. This pre-computed response is then used to modify the second decoded audio information, ensuring a smooth transition from CELP to MDCT mode without introducing discontinuities or artifacts.
2Object-generated harmful factors
If existing solutions modify decoded audio information to achieve smooth transitions, then audio quality is improved, but additional delay is introduced
Solution Approach 1:
The zero-input-response is computed in advance based on the first decoded audio information before the mode transition. By preparing this response beforehand, the system can immediately apply it to modify the second decoded audio information without introducing additional delay, thus maintaining real-time performance while ensuring smooth transitions.
3Object-generated harmful factors
If existing solutions use overlap-and-add operations to reduce discontinuities, then audio quality is improved, but computational complexity increases
Solution Approach 1:
The patent extracts and utilizes only the essential characteristic of the linear predictive filter, which is its zero-input-response. By focusing on this specific property and using it to modify the second decoded audio information, the system achieves smooth transitions without requiring complex overlap-and-add operations, thus reducing computational complexity while maintaining audio quality.
Data Source
AI summary
An audio decoder is disclosed. In one example, the audio decoder is for providing a decoded audio information on the basis of an encoded audio information includes a linear-prediction-domain decoder configured to provide a first decoded audio information on the basis of an audio frame encoded in a linear prediction domain, a frequency domain decoder configured to provide a second decoded audio information on the basis of an audio frame encoded in a frequency domain, and a transition processor. The transition processor is configured to obtain a zero-input-response of a linear predictive filtering, wherein an initial state of the linear predictive filtering is defined depending on the first decoded audio information and the second decoded audio information, and modify the second decoded audio information depending on the zero-input-response, to obtain a smooth transition between the first and the modified second decoded audio information.