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 and decoding audio signals, utilizing side information calculated from a look-ahead signal to encode and transmit parameters like pitch lag and gain, allowing for accurate packet loss concealment without increasing algorithmic delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If packet loss concealment is performed using conventional methods (copying past audio signal), then implementation is simple, but concealment accuracy deteriorates when audio properties change suddenly
Solution Approach 1:
The patent performs preliminary analysis of the lost packet's audio signal properties (pitch, power, spectral characteristics) at the transmitter before packet loss occurs. These analyzed parameters are transmitted as side information to the receiver, enabling accurate reconstruction of the lost packet without simply copying past signals. This preliminary action resolves the contradiction by preparing accurate reconstruction data in advance while maintaining implementation feasibility through parameter-based transmission.
2Measurement precision
If side information is transmitted for accurate packet loss concealment, then concealment accuracy improves, but transmission bit rate increases
Solution Approach 1:
The patent transmits condensed audio parameters (pitch lag, power values, spectral coefficients) rather than full audio waveforms as side information. By changing the representation from time-domain signals to compressed parameter-space descriptors, the system achieves accurate packet loss concealment while minimizing the bit rate overhead. The parameters are quantized and efficiently encoded to balance accuracy and transmission cost.
3Ease of operation
If audio packets are transmitted through communication networks, then audio communication is enabled, but packet loss occurs due to network congestion
Solution Approach 1:
The patent prepares reconstruction parameters and concealment data at the transmitter before packet loss actually occurs. By analyzing and encoding the audio signal characteristics in advance (including look-ahead analysis), the system creates a cushion of prepared information that can be used to reconstruct lost packets. This beforehand cushioning enables reliable audio communication over unreliable networks by having recovery data ready before transmission failures occur.
4Ease of manufacture
If conventional packet loss concealment is used, then implementation is straightforward, but adaptive codebook inconsistencies increase in CELP encoding
Solution Approach 1:
The patent transmits side information containing pitch and power parameters from the transmitter to the receiver, creating a feedback mechanism that synchronizes the adaptive codebooks at both ends. The receiver uses these transmitted parameters to reconstruct the excitation signal and update its adaptive codebook in the same way as the transmitter, ensuring consistency. This feedback-based parameter synchronization resolves the codebook inconsistency problem while maintaining implementation feasibility through parameter transmission rather than complex synchronization protocols.
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.