QMF Domain SPAR Filter Bank Emulation via Time-Domain Conversion
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Solution Overview
Problem
There is a need for techniques to enable efficient use of decoder filter banks in the QMF domain for SPAR decoded content, allowing for the emulation of filters from a first filter bank in the domain of a second filter bank without additional conversion steps.
Innovation Solution
The method involves applying a second filter bank to the first channel of a multichannel audio signal to obtain banded versions, generating time-domain filters based on prediction parameters and first filters of the first filter bank, and using these filters to generate predictions for the second channel without transforming the signal into the domain of the first filter bank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SPAR filter bank runs in the MDFT domain for faithful signal reconstruction, then the encoder and decoder filter banks can match exactly, but the decoder is less suitable for signal manipulation operations
Solution Approach 1:
The patent introduces time-domain filters as an intermediary mechanism that bridges the MDFT domain encoding and QMF domain decoding. These filters enable the decoder to operate in the QMF domain (providing signal manipulation capability) while still faithfully reconstructing signals by emulating the MDFT domain filter bank behavior through the time-domain filter responses.
Solution Approach 2:
The patent changes the domain of operation from MDFT to QMF by transforming the filter bank parameters. Specifically, it converts the frequency-domain filters of the first filter bank into time-domain filters that can be applied in the QMF domain, allowing the same filtering functionality to be achieved in a different domain with different computational characteristics.
2Adaptability or versatility
If the decoder uses a different filter bank (QMF) than the encoder (SPAR MDFT), then signal manipulation capability improves, but additional conversion steps are required
Solution Approach 1:
The patent replaces the mechanical approach of converting signals between domains with a mathematical approach of converting filter parameters. Instead of transforming the signal from MDFT to QMF domain (which would require additional conversion steps), it transforms the filter bank parameters into time-domain filters that can be directly applied in the QMF domain, eliminating the need for domain conversion of the signal itself.
3Adaptability or versatility
If the decoder uses a different filter bank (QMF) than the encoder (SPAR MDFT), then signal manipulation capability improves, but computational complexity increases
Solution Approach 1:
The patent creates a copy of the filter bank functionality in the QMF domain by generating time-domain filters that emulate the behavior of the original MDFT domain filters. This copying approach allows the decoder to use QMF filters for signal manipulation while maintaining compatibility with the encoder's filtering characteristics, avoiding the need for expensive real-time domain conversions.
Data Source
AI summary
A method of processing a representation of a multichannel audio signal is provided. The representation includes a first channel and metadata relating to a second channel. The metadata includes, for each of a plurality of first bands of a first filter bank, a respective prediction parameter. The method includes: applying a second filterbank with a plurality of second bands to the first channel to obtain, for each second band, a banded version of the first channel; for each second band, generating a respective time-domain filter based on the prediction parameters and first filters corresponding to the first bands; and for each second band, generating a prediction for the second channel based on a filtered version of the first channel, the filtered version being obtained by applying the respective time-domain filter in that second band to the banded version of the first channel. Also provided are corresponding apparatus, programs, and computer-readable storage media.