Audio Decoder Concealment Using Embedded Recovery Parameters
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Solution Overview
Problem
Existing error concealment mechanisms in audio codecs, particularly in VoIP systems, face challenges in reconstructing defective audio frames due to packet loss, corruption, or delay, often resulting in reduced audio quality and perceptible gaps in speech or music.
Innovation Solution
The proposed solution involves embedding error concealment helper parameters within the bitstream to enhance decoder-sided concealment, allowing for guided concealment of lost, corrupted, or delayed frames by transmitting partial copies that contain specific parameters, rather than low-bitrate redundant copies, and enabling selection between different concealment modes based on signal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant copies of audio frames are transmitted to handle packet loss, then error concealment capability is improved, but bitrate consumption increases
Solution Approach 1:
The patent extracts only the essential parameters needed for error concealment (such as spectral envelope parameters, pitch information, and signal classification) from the full audio frame and transmits them as separate redundant data. This allows the decoder to reconstruct lost frames without transmitting complete redundant frame copies, thereby reducing bitrate while maintaining error concealment capability.
Solution Approach 2:
The patent segments the audio encoding into core parameters and error concealment parameters. The error concealment parameters are transmitted in a separate data structure within the bitstream, allowing independent transmission and reception. This segmentation enables selective transmission of concealment data without increasing the core audio bitrate.
2Reliability
If complete redundant frames are transmitted for error correction, then packet loss recovery is improved, but data transmission volume increases
Solution Approach 1:
Instead of transmitting complete redundant frames, the patent extracts only the critical parameters needed for frame reconstruction (spectral envelope parameters, excitation parameters, timing information) and transmits these extracted elements as compact redundant data structures, significantly reducing transmission volume while maintaining recovery capability.
Solution Approach 2:
The patent changes the representation from complete frame data to parameter-only data. By transmitting parameter sets (such as LSF parameters, gain values, and pitch lag) rather than full spectral data, the transmission volume is reduced while the decoder can regenerate the complete frame parameters for lossless reconstruction of lost packets.
3Reliability
If error concealment parameters are embedded in every frame, then concealment quality is improved, but processing complexity increases
Solution Approach 1:
The patent implements dynamic selection of error concealment parameter transmission based on channel conditions and signal characteristics. The encoder determines whether to include redundant concealment parameters in each frame based on packet loss statistics and signal type (voiced/unvoiced), allowing adaptive adjustment of processing complexity while maintaining high concealment quality when needed.
Solution Approach 2:
The patent applies different error concealment strategies to different parts of the audio signal based on local characteristics. For example, voiced segments receive different parameter sets than unvoiced segments, and the density of redundant parameter transmission varies by signal region, optimizing quality without uniform complexity increase across all frames.
Data Source
AI summary
Described are an encoder for coding speech-like content and/or general audio content, wherein the encoder is configured to embed, at least in some frames, parameters in a bitstream, which parameters enhance a concealment in case an original frame is lost, corrupted or delayed, and a decoder for decoding speech-like content and/or general audio content, wherein the decoder is configured to use parameters which are sent later in time to enhance a concealment in case an original frame is lost, corrupted or delayed, as well as a method for encoding and a method for decoding.