Audio Codec Side Information for Packet Loss Concealment
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Solution Overview
Problem
Existing audio encoding technologies, such as CELP, face challenges in packet loss concealment during audio transmission over IP or mobile communication networks, leading to algorithmic delay and degradation of audio quality due to inconsistencies in adaptive codebooks and inadequate recovery from packet loss.
Innovation Solution
An audio coding system that includes an audio encoding device and method for encoding audio signals, which calculates and transmits side information like pitch lag or gain, and uses this information for error concealment, allowing for accurate packet loss concealment without increasing algorithmic delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If packet loss concealment is performed by copying decoded audio signal from past packets, then implementation complexity is reduced, but audio quality deteriorates when audio properties change suddenly
Solution Approach 1:
The patent performs LP analysis and calculates concealment parameters in advance for look-ahead frames before packet transmission. When packet loss occurs, these pre-calculated parameters enable accurate signal reconstruction without requiring complex real-time analysis, thus resolving the contradiction between implementation complexity and concealment accuracy.
Solution Approach 2:
The patent dynamically selects between different concealment strategies based on audio signal characteristics. By analyzing properties such as pitch lag and gain variations, the system adapts its concealment approach to match the actual audio content, improving accuracy while maintaining manageable complexity through selective application of sophisticated methods.
2Measurement precision
If waiting for next packet arrival before decoding is performed, then packet loss detection accuracy is improved, but algorithmic delay increases
Solution Approach 1:
The patent performs LP analysis and prepares concealment parameters in advance for future frames (look-ahead processing). This preliminary action allows the system to detect packet loss immediately when a packet is missing, without waiting for subsequent packets, thereby maintaining both detection accuracy and minimizing delay.
Solution Approach 2:
The patent divides audio processing into separate stages: look-ahead analysis for parameter preparation, immediate decoding for current frames, and selective concealment application. This segmentation allows packet loss detection to occur without artificial delays while still enabling accurate concealment when needed.
3Reliability
If redundant encoding is performed at lower bit rate, then packet loss recovery capability is improved, but transmission bandwidth consumption increases
Solution Approach 1:
The patent extracts only the essential LP analysis parameters (such as pitch lag, gain, and spectral characteristics) from the full audio signal for transmission as side information. This extraction approach provides sufficient data for accurate packet loss concealment without transmitting redundant full-bandwidth audio data, thus improving recovery capability while controlling bandwidth consumption.
Solution Approach 2:
The patent transmits condensed parameter representations (LP coefficients, pitch parameters) rather than full audio waveforms. By changing the representation from time-domain samples to frequency-domain parameters, the system achieves efficient bandwidth utilization while maintaining the information necessary for high-quality packet loss recovery.
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.