Temporal Envelope Coding for Energy Attack Signals
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Solution Overview
Problem
Low bit rate audio/speech coding algorithms face challenges in efficiently encoding fast-changing signals like energy attack signals, leading to unstable decoded signals and audible echoes due to errors in fine spectrum generation, particularly at very low bit rates.
Innovation Solution
The method involves detecting the energy attack signal and quantizing its peak area energy, average energies before and after the attack point, and energy variations to improve temporal envelope shaping, which are then sent to the decoder to rebuild the signal shape efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional temporal envelope quantization is used for energy attack signal, then decoding stability is improved, but bit rate consumption increases significantly
Solution Approach 1:
The temporal envelope is segmented into peak area and non-peak areas. Only the peak area parameters are quantized and transmitted, while non-peak areas use default or coarsely quantized values. This segmentation allows precise representation of critical attack regions without uniformly quantizing the entire envelope, thus reducing overall bit rate while maintaining decoding stability for energy attack signals.
Solution Approach 2:
Different quantization precision is applied to different regions of the temporal envelope. High precision quantization is applied specifically to the peak area where energy attack occurs, while lower precision or default values are used for non-peak areas. This local quality approach ensures that critical regions are accurately represented without wasting bits on less important regions, resolving the contradiction between stability and bit rate consumption.
2Productivity
If fine spectrum generation is used at very low bit rate, then coding efficiency is improved, but signal stability deteriorates leading to audible echoes
Solution Approach 1:
The energy attack point is detected and marked in advance during encoding. The location and parameters of the attack point are identified before quantization and transmission. This preliminary action allows the decoder to know in advance where critical energy changes occur, enabling it to allocate resources appropriately and maintain signal stability at those critical points even under low bit rate conditions.
Solution Approach 2:
The temporal envelope parameters, particularly the peak area parameters, serve as an intermediary between the original signal and the reconstructed signal. By accurately representing the temporal envelope through selective quantization of peak areas, the intermediary preserves the essential characteristics of energy attack signals, thereby maintaining signal stability and preventing audible echoes while still achieving low bit rate coding.
Data Source
AI summary
A method of transceiving an audio signal is disclosed. An input audio signal is provided. It is determined whether an energy attack signal exists within the input audio signal and a decision flag is set if the energy attack signal exists. A temporal location of the energy attack point in the input audio signal is detected. Energy variations before and after the temporal location of an energy attack point are determined. The energy variations to produce quantized energy variations and a peak area energy of the input audio signal to produce a quantized peak area energy are quantized. The decision flag, the temporal location of the energy attack point, the quantized energy variations, and the quantized peak energy are transmitted.