Transform-Domain Transient Coding With Window Alignment
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Solution Overview
Problem
Digital audio encoding techniques struggle with transients, leading to perceptible quantization noise and pre-echo artifacts, especially in bandwidth-constrained applications, due to inefficient frequency modeling and increased bit usage.
Innovation Solution
Improved audio transient coding through parsing audio frames into smaller windows, organizing frequency-domain samples according to alignment patterns, and using vector quantization with conjugate vector codebooks to minimize distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If frequency domain coding is used to code audio content, then bandwidth efficiency is improved, but transient coding quality deteriorates due to perceptible quantization noise and pre-echo artifacts
Solution Approach 1:
The audio frame is divided into multiple sub-frames, and each sub-frame is further divided into smaller analysis windows. This segmentation allows the coding system to handle transient signals more effectively by applying different window sizes and handling strategies to different portions of the signal, thereby reducing quantization noise and pre-echo artifacts while maintaining bandwidth efficiency.
Solution Approach 2:
The patent employs dynamic windowing where the analysis window size is adapted based on the detected transient condition. During transient periods, shorter windows are used to capture the rapid changes, while longer windows are used during steady-state portions. This dynamic adaptation optimizes the balance between bandwidth efficiency and transient coding quality.
2Object-affected harmful factors
If shorter transform windows are used during transients, then transient coding quality is improved, but bit rate increases
Solution Approach 1:
By segmenting the frame into sub-frames and further into analysis windows, the system can apply shorter transforms only to the specific windows containing transients rather than the entire frame. This selective application maintains transient coding quality while limiting the increase in bit rate to only the necessary portions.
Solution Approach 2:
Different window sizes and coding parameters are applied locally to different portions of the audio signal based on transient detection. Shorter windows and more aggressive noise shaping are applied only where transients occur, while the rest of the signal uses standard parameters, thereby optimizing transient quality without unnecessarily increasing overall bit rate.
3Object-affected harmful factors
If temporal noise shaping is applied to mitigate pre-echo artifacts, then transient perception is improved, but bit usage increases
Solution Approach 1:
Temporal noise shaping is applied selectively to specific sub-frames and windows where transients are detected, rather than to the entire audio frame. This segmentation allows the system to mitigate pre-echo artifacts in problematic regions while avoiding unnecessary bit consumption in regions where transient issues do not occur.
Solution Approach 2:
The system applies temporal noise shaping with appropriate strength based on the detected transient characteristics. Rather than applying maximum noise shaping always, the system uses partial action by adapting the noise shaping strength to match the actual transient requirements, thereby reducing bit usage while still effectively mitigating pre-echo artifacts where needed.
Data Source
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AI summary
Aspects of the present disclosure provide improved techniques for coding audio signal with a transient audio sound. Improved techniques include parsing a frame of predetermined length of audio samples into a series of windows of a smaller size, and transforming the windows of time-domain samples into a series of windows of frequency-domain samples. The frequency-domain samples may be organized according to an alignment pattern and may be coded with respect to an envelope of the organized frequency-domain samples.