Audio Encoder Feedback Loop for Clipping-Free Compression
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Solution Overview
Problem
Current audio content production and delivery chains experience clipping issues due to quantization errors and parametric coding, leading to audible artifacts, which cannot be resolved after delivery and require decoder-side modifications, necessitating the prevention of clipping at the encoder level to avoid decoder upgrades and information loss.
Innovation Solution
An integrated codec system that decodes audio segments in parallel with encoding, using a clipping detector to adjust encoding parameters, such as reducing quantization thresholds or modifying frequency coefficients, to prevent clipping, allowing for re-encoding with modified parameters to reduce clipping probability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If quantization is applied to reduce transmission data rate, then data rate is reduced, but clipping probability increases due to quantization errors
Solution Approach 1:
The patent applies preliminary clipping detection and prevention measures during the encoding process. The encoder detects potential clipping conditions before transmission and adjusts encoding parameters proactively, preventing clipping from occurring at the decoder side rather than reacting to it after the fact.
Solution Approach 2:
The patent implements a feedback mechanism where the encoder monitors the encoded signal for potential clipping conditions and adjusts quantization parameters based on this feedback. When clipping is detected or predicted, the encoder modifies subsequent quantization decisions to prevent clipping, creating a closed-loop control system.
2Productivity
If parametric coding methods are used to compress audio, then compression efficiency is improved, but waveform preservation deteriorates leading to clipping
Solution Approach 1:
The patent dynamically changes encoding parameters based on signal conditions. When clipping risk is detected, the encoder adjusts quantization thresholds, bit allocation, or other encoding parameters to improve waveform accuracy in critical regions while maintaining compression efficiency in less critical regions.
Solution Approach 2:
The patent applies different encoding precision to different parts of the audio signal. Instead of uniformly reducing precision across all frequency bands and time segments, the encoder identifies regions prone to clipping and applies higher precision quantization locally to those regions while maintaining lower precision elsewhere, thus preventing clipping without sacrificing overall compression efficiency.
3Object-affected harmful factors
If decoder-side clipping prevention is implemented, then clipping artifacts are reduced, but device complexity and upgrade requirements increase
Solution Approach 1:
The patent moves the clipping prevention action from the decoder side to the encoder side. By detecting and preventing clipping during encoding, the harmful clipping artifacts are eliminated before transmission, so the decoder does not need complex clipping prevention mechanisms, thus reducing decoder complexity and avoiding upgrade requirements.
Solution Approach 2:
The patent introduces an intermediary clipping detection and prevention mechanism at the encoder side that acts as a mediator between the source audio and the transmission channel. This intermediary process ensures the encoded signal is clipping-free before transmission, eliminating the need for complex intermediary clipping prevention measures at the decoder side.
Data Source
AI summary
An audio encoding apparatus includes an encoder for encoding a time segment of an input audio signal to be encoded to obtain a corresponding encoded signal segment. The audio encoding apparatus further includes a decoder for decoding the encoded signal segment to obtain a re-decoded signal segment. A clipping detector is provided for analyzing the re-decoded signal segment with respect to at least one of an actual signal clipping or an perceptible signal clipping and for generating a corresponding clipping alert. The encoder is further configured to again encode the time segment of the audio signal with at least one modified encoding parameter resulting in a reduced clipping probability in response to the clipping alert.