Audio Coding with Look-Ahead Side Information for Packet Loss
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Solution Overview
Problem
Existing audio encoding technologies face challenges in maintaining audio quality during packet loss in communication networks, particularly in CELP encoding, due to inconsistencies in adaptive codebooks and increased algorithmic delay, which degrades voice communication quality.
Innovation Solution
An audio coding system that includes an audio encoding device and method for encoding audio signals using side information calculated from a look-ahead signal, which encodes and transmits parameters like pitch lag and gain, and an audio decoding device that decodes and synthesizes audio signals using accumulated side information to recover from packet loss without increasing algorithmic delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If packet loss concealment is performed by copying decoded audio signal without using side information, then the implementation is simple, but the concealment effect is unsatisfactory when audio properties change suddenly
Solution Approach 1:
The encoder performs preliminary analysis of the audio signal to detect sudden changes in audio properties (such as pitch, energy, or spectral characteristics) before packet loss occurs. When such changes are detected, the encoder prepares and transmits side information indicating the change to the decoder, enabling the decoder to switch from simple copying to more appropriate concealment methods that account for the changed audio properties.
2Reliability
If side information is transmitted to improve packet loss concealment accuracy, then concealment quality improves, but transmission bandwidth increases
Solution Approach 1:
Instead of transmitting side information for all audio frames, the system applies local quality by transmitting side information only for specific frames where sudden audio property changes are detected. This selective transmission approach maintains high concealment quality when needed while minimizing the increase in transmission bandwidth by limiting side information to only those frames where it provides benefit.
3Loss of time
If traditional packet loss concealment methods are used, then algorithmic delay is reduced, but audio quality degrades due to adaptive codebook inconsistencies
Solution Approach 1:
The system employs feedback mechanisms where the encoder monitors the consistency of adaptive codebooks and detects when inconsistencies occur that would degrade audio quality. When inconsistencies are detected, the encoder transmits side information to the decoder, which uses this feedback to correct or compensate for the inconsistencies, thereby maintaining audio quality without introducing significant algorithmic delay.
Data Source
AI summary
An audio signal transmission device for encoding an audio signal includes an audio encoding unit that encodes an audio signal and a side information encoding unit that calculates and encodes side information from a look-ahead signal. An audio signal receiving device for decoding an audio code and outputting an audio signal includes: an audio code buffer that detects packet loss based on a received state of an audio packet, an audio parameter decoding unit that decodes an audio code when an audio packet is correctly received, a side information decoding unit that decodes a side information code when an audio packet is correctly received, a side information accumulation unit that accumulates side information obtained by decoding a side information code, an audio parameter missing processing unit that outputs an audio parameter upon detection of audio packet loss, and an audio synthesis unit that synthesizes decoded audio from the audio parameter.