SBR Frame Class Reduces Decoding Delay and Bit Rate
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Solution Overview
Problem
Existing audio encoding techniques using SBR (Spectral Band Replication) face challenges in minimizing bit rate while avoiding audible artefacts like pre-echo, particularly at transients, due to the need for a fine temporal grid that increases bit consumption.
Innovation Solution
Introducing a new SBR frame class, LD_TRAN, where frame boundaries are synchronized with the encoder and decoder, and a transient position indication is used to determine grid boundaries, allowing for a short transient envelope and reduced bit transmission, eliminating the need for variable SBR frames and minimizing delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fine temporal grid is used for spectral envelope encoding, then audible artefacts like pre-echo are reduced, but bit rate consumption increases
Solution Approach 1:
The patent applies local quality by using a fine temporal grid only in specific regions where transients are detected, while using a coarse temporal grid in stationary regions. The encoder identifies transient locations and adjusts the grid resolution locally to those areas, thereby reducing overall bit rate consumption while maintaining artefact-free reconstruction at critical moments.
Solution Approach 2:
The patent implements dynamics by making the temporal grid configuration adaptive and variable rather than fixed. The grid resolution changes dynamically based on the presence and position of transients in the audio signal, allowing the system to optimize between bit rate efficiency and reconstruction quality in real-time according to signal characteristics.
2Quantity of substance
If a coarse temporal grid is used for spectral envelope encoding, then bit rate consumption is reduced, but audible artefacts appear at transients
Solution Approach 1:
The patent applies preliminary action by detecting transients in advance and preparing a fine temporal grid configuration before the transient occurs. The encoder identifies transient positions and pre-configures the appropriate grid resolution for the upcoming transient region, ensuring high-quality reconstruction is ready when needed without requiring continuous high bit rate consumption.
3Manufacturing precision
If variable SBR frames are used to handle transients, then transient reconstruction quality improves, but decoding delay increases
Solution Approach 1:
The patent applies segmentation by dividing the audio signal into distinct regions based on transient detection, and further segmenting the temporal grid into fine and coarse regions. This segmentation allows the system to process different parts of the signal with appropriate resolution independently, reducing the need for extensive variable frame processing and thereby minimizing decoding delay while maintaining transient quality.
Data Source
AI summary
The transient problem may be sufficiently addressed, and for this purpose, a further delay on the side of the decoding may be reduced if a new SBR frame class is used wherein the frame boundaries are not shifted, i.e. the grid boundaries are still synchronized with the frame boundaries, but wherein a transient position indication is additionally used as a syntax element so as to be used, on the encoder and/or decoder sides, within the frames of these new frame class for determining the grid boundaries within these frames.