Audio Packet Loss Concealment Using Look-Ahead Side Information
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Solution Overview
Problem
Existing audio encoding methods in packet loss scenarios, such as CELP encoding, suffer from increased algorithmic delay and adaptive codebook inconsistency, leading to degraded audio quality due to packet loss in IP and mobile communication networks.
Innovation Solution
An audio encoding device that generates and transmits side information, including pitch lag and gain, for a look-ahead signal, allowing for immediate packet loss concealment without additional delay, thereby reducing adaptive codebook inconsistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If packet loss concealment technology without using side information is used, then the receiving end can perform concealment independently, but the concealment effect is insufficient when audio properties change suddenly
Solution Approach 1:
The encoder performs preliminary encoding of the previous frame using both main encoding (at normal bit rate) and redundant encoding (at lower bit rate) before transmission. This preliminary action ensures that when packet loss occurs, the decoder already has backup encoded data available immediately, eliminating the need for complex real-time concealment algorithms and achieving both independence and accuracy.
2Reliability
If redundant encoding at lower bit rate is performed for the previous frame, then packet loss concealment can be achieved, but the transmission bandwidth increases
Solution Approach 1:
The system changes the bit rate parameter for redundant encoding, using a lower bit rate for the previous frame's redundant encoding compared to the main encoding. This parameter change reduces the amount of backup data needed while still providing sufficient information for effective packet loss concealment, thus balancing reliability with transmission efficiency.
3Reliability
If the receiving end waits for the arrival of two or more temporally successive packets before decoding, then packet loss concealment can be performed, but the algorithmic delay increases
Solution Approach 1:
The encoder prepares redundant encoded data of the previous frame in advance and transmits it with the current frame. This preliminary preparation allows the decoder to immediately use the redundant data for concealment when packet loss is detected, without needing to wait for subsequent packets to arrive, thus reducing algorithmic delay while maintaining audio quality.
4Ease of manufacture
If packet loss concealment is performed by copying decoded audio signal on pitch-by-pitch basis with attenuation, then the process is simple, but the concealment effect cannot be obtained when audio properties differ from previous audio
Solution Approach 1:
Instead of copying the decoded audio signal, the system copies the encoded data (codebooks and parameters) of the previous frame through redundant encoding. This copying approach at the encoding level allows the decoder to regenerate the audio signal using the same synthesis process, ensuring consistency and accuracy even when audio properties change, while keeping the concealment process relatively simple.
Data Source
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Figure 2
Figure 3(a)~3(c)
AI summary
An objective of the present invention is, when packet loss occurs in audio encoding, to recover audio quality without increasing algorithmic delay. 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. On the other hand, 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 when audio packet loss is detected, and an audio synthesis unit that synthesizes a decoded audio from an audio parameter.