Audio Decoder Recovery After Packet Loss in Sub-Band ADPCM
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Solution Overview
Problem
Existing packet loss concealment methods are inadequate for sub-band predictive coders like the ITU-T G.722 wideband speech coder, as they fail to address sub-band-specific architectural issues and the challenges posed by backward-adaptive ADPCM coders.
Innovation Solution
A method and system that alter decoding parameters in response to packet loss, using waveform extrapolation and time-warping to generate a decoded audio signal, specifically designed for sub-band predictive coders, which updates the states of ADPCM decoders and reduces audible artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior-art packet loss concealment methods are applied to sub-band predictive coders, then packet loss can be concealed to some extent, but sub-band-specific architectural issues and backward-adaptive ADPCM challenges are not addressed, resulting in inadequate concealment quality
Solution Approach 1:
The patent applies local quality by implementing packet loss concealment specifically tailored for sub-band predictive coders. The method handles each sub-band independently with specific processing for backward-adaptive ADPCM coders, ensuring the concealment technique is locally optimized for the particular architecture rather than applying a generic solution.
Solution Approach 2:
The patent employs parameter changes by modifying decoding parameters in response to detected packet loss. The system alters at least one parameter associated with decoding when packet loss is detected, adapting the decoding process to compensate for the lost data and maintain audio quality.
2Productivity
If normal decoding is performed after packet loss, then decoding speed is maintained, but audible artifacts are generated due to abrupt transitions and parameter mismatches
Solution Approach 1:
The patent applies preliminary action by detecting packet loss and altering decoding parameters before the actual decoding of the received frame occurs. This preparatory step ensures that the decoding process is pre-configured to handle the post packet-loss conditions, preventing audible artifacts rather than correcting them afterward.
Solution Approach 2:
The patent implements dynamics by making the decoding process adaptive rather than static. The system dynamically adjusts decoding parameters based on the detection of packet loss, allowing the decoding behavior to change in response to network conditions. This dynamic adaptation prevents the abrupt transitions that cause audible artifacts while maintaining efficient decoding.
Data Source
AI summary
A technique is described herein for reducing audible artifacts in an audio output signal generated by decoding a received frame in a series of frames representing an encoded audio signal in a predictive coding system. In accordance with the technique, it is determined if the received frame is one of a predefined number of received frames that follow a lost frame in the series of the frames. Responsive to determining that the received frame is one of the predefined number of received frames, at least one parameter or signal associated with the decoding of the received frame is altered from a state associated with normal decoding. The received frame is then decoded in accordance with the at least one parameter or signal to generate a decoded audio signal. The audio output signal is then generated based on the decoded audio signal.