Audio Decoder Reducing Arithmetic Operations via Selective Real Number Processing
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Solution Overview
Problem
Conventional audio decoders have large circuit sizes due to high arithmetic operations and often result in aliasing noise when processing complex numbers as real numbers, which increases circuit size without effectively suppressing noise.
Innovation Solution
An audio decoder that decodes bitstreams to generate N-channel audio signals by using a frequency band signal generation unit to convert coded data into real number representations, with an aliasing noise detection unit to suppress noise, reducing arithmetic operations and circuit size while maintaining sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex number processing is used in the analysis filter bank, then sound quality is maintained, but arithmetic operations increase and circuit size increases
Solution Approach 1:
The patent applies different processing methods to different frequency bands. Specifically, real number processing is applied to low-frequency bands where aliasing noise is less problematic, while complex number processing is applied to high-frequency bands where sound quality is more critical. This localized approach maintains sound quality where needed while reducing overall arithmetic operations and circuit size.
Solution Approach 2:
The patent changes the numerical representation parameter from complex numbers to real numbers in specific frequency bands. By switching between real and complex number processing based on frequency band characteristics, the system reduces computational complexity and circuit size while maintaining acceptable sound quality through selective application of processing methods.
2Device complexity
If complex number processing is converted to real number processing, then arithmetic operations are reduced and circuit size is reduced, but aliasing noise occurs
Solution Approach 1:
The patent applies real number processing selectively to frequency bands where aliasing noise is less perceptible or less problematic. By making the processing method quality-dependent on the local frequency characteristics, the system reduces overall aliasing noise impact while maintaining circuit size reduction benefits.
Solution Approach 2:
The patent converts the potential harm of aliasing noise into a benefit by strategically applying real number processing only where aliasing is less problematic. This transforms what would be a uniform harmful effect into a selective, manageable characteristic that actually helps reduce overall system complexity while maintaining acceptable quality.
3Object-generated harmful factors
If aliasing noise cancellation processing is added, then aliasing noise is suppressed, but arithmetic operations increase and circuit size increases
Solution Approach 1:
The patent performs preliminary action by selectively applying real number processing to specific frequency bands before the aliasing noise becomes a problematic issue. This preventive approach avoids the need for complex post-processing noise cancellation circuits, as the aliasing noise is prevented from occurring in the first place in those frequency bands.
Solution Approach 2:
The patent applies noise suppression through selective real number processing only in frequency bands where it is most effective, rather than applying uniform noise cancellation across all bands. This localized approach suppresses aliasing noise where critical while avoiding unnecessary arithmetic operations and circuit complexity in bands where it is less important.
Data Source
AI summary
Provided is an audio decoder which can reduce an amount of arithmetic operations while suppressing occurrence of aliasing noise. The audio decoder includes: a decoder (102) and an analysis filter bank (110) which generate, from a coded down-mixed signal, the first frequency band signal (x) corresponding to a down-mixed signal (M); a channel expansion unit (130) which converts the first frequency band signal (x) generated by the analysis filter bank (110) into output signals (y) corresponding to respective audio signals of N channels, using BC information; an synthesis filter bank (140) which performs band synthesis for the output signals (y) generate by the channel expansion unit (130) and thereby converts the output signals (y) into the respective audio signals of the N channels on a time axis; and an aliasing noise detection unit (120) which detects occurrence of aliasing noise in the first frequency band signal (x). The channel expansion unit (130) further prevents the aliasing noise from being included in the output signals (y), based on information detected by the aliasing noise detection unit (120).