QMF Harmonic Transposer Pre-computed Coefficients for USAC Decoding
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Solution Overview
Problem
Unified Audio and Speech (USAC) encoders and decoders require significant computational resources due to complex computation steps, leading to a high computational load during runtime.
Innovation Solution
The implementation of a core decoder for USAC streams that includes an upmixing unit with a decorrelator unit using pre-computed filter coefficients, a QMF based harmonic transposer, and a fast Fourier transform module based on the Cooley-Tuckey algorithm, reducing computational load by referencing pre-computed values for filter coefficients and twiddle factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex computation steps are used in USAC encoders and decoders, then audio quality is improved, but computational load increases
Solution Approach 1:
The patent pre-computes filter coefficients for the decorrelation filter and stores them in a lookup table before runtime. During decoding, the core decoder references these pre-computed values instead of calculating them in real-time, significantly reducing computational load while maintaining audio quality
Solution Approach 2:
The patent creates a copy of the computationally intensive filter coefficient data and stores it in a lookup table. The core decoder uses this copied data structure to avoid repeated complex calculations, thereby reducing runtime computational requirements while preserving the exact same audio processing quality
2Device complexity
If pre-computed values are used for filter coefficients, then computational load is reduced, but memory requirements increase
Solution Approach 1:
The patent changes the state of filter coefficients from dynamic computed values to static pre-computed values stored in a lookup table. This parameter change allows the system to trade computational operations for memory storage, reducing runtime processing requirements while accepting increased memory usage for storing the coefficient data
Data Source
AI summary
The present disclosure relates to an apparatus for decoding an encoded Unified Audio and Speech stream. The apparatus comprises a core decoder for decoding the encoded Unified Audio and Speech stream. The core decoder includes an eSBR unit for extending a bandwidth of an input signal, the eSBR unit including a QMF based harmonic transposer. The QMF based harmonic transposer is configured to process the input signal in the QMF domain, in each of a plurality of synthesis subbands, to extend the bandwidth of the input signal. The QMF based harmonic transposer is configured to operate at least in part based on pre-computed information. The present disclosure further relates to corresponding methods and storage media.