Audio Transform Coding With Pitch-Adaptive Sampling
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Solution Overview
Problem
Existing audio processing methods face challenges in maintaining coding efficiency for signals with varying pitch, as they often result in reduced coding efficiency due to spread energy across multiple transform coefficients, and previous approaches like warping introduce undesirable constraints or difficulties in synchronization.
Innovation Solution
An audio processor that samples audio signals based on pitch contours, using adaptive sampling rates to create a constant pitch within each frame, allowing for efficient transform coding while maintaining high-quality encoding and decoding, by employing a sampler, transform window calculator, and windower to derive and apply scaling windows for re-sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the sampling rate is varied proportionally to the pitch to create a constant pitch representation, then coding efficiency is improved, but the signal bandwidth varies strongly and synchronization becomes difficult
Solution Approach 1:
The audio signal is divided into multiple frames, and the sampling rate is varied independently for each frame based on its local pitch characteristics. This segmentation allows coding efficiency to be improved locally without causing strong variations in the overall signal bandwidth, as each frame is processed independently with its own pitch-adaptive sampling rate.
Solution Approach 2:
The sampling rate is adapted locally to the pitch characteristics of each individual frame rather than applying a global sampling rate variation. This local adaptation allows the system to improve coding efficiency for each frame based on its specific pitch contour while maintaining more stable overall signal properties and avoiding strong bandwidth variations.
2Productivity
If the sampling rate is varied to adapt to pitch changes, then energy compaction is improved, but time segments of fixed sample blocks represent varying durations leading to synchronization difficulties
Solution Approach 1:
The audio signal is processed in discrete frames with independent pitch-adaptive sampling. Each frame represents a fixed time segment in the original signal, but is sampled at a rate adapted to its local pitch. This segmentation allows energy compaction to be improved within each frame while maintaining clear temporal boundaries that facilitate synchronization.
Solution Approach 2:
The sampling rate is dynamically adapted to the pitch characteristics of each frame, allowing the system to optimize energy compaction for varying pitch conditions. However, the dynamic adaptation is applied independently to each frame, maintaining fixed temporal boundaries that prevent time segment duration variation issues and enable proper synchronization.
3Productivity
If pitch-dependent re-sampling is applied to the entire signal, then coding efficiency increases, but applications with limited coding delay become nearly impossible
Solution Approach 1:
Pitch-dependent re-sampling is applied independently to each frame rather than to the entire signal. This segmentation allows coding efficiency to be improved in each frame with minimal delay, as each frame can be processed and encoded independently without waiting for the entire signal to be analyzed.
Solution Approach 2:
The pitch characteristics of each frame are analyzed and the sampling rate is adapted before encoding that frame. This preliminary pitch analysis and adaptive sampling for each frame enables efficient coding with limited delay, as each frame is prepared independently rather than requiring global signal analysis.
Data Source
AI summary
A processed representation of an audio signal having a sequence of frames is generated by sampling the audio signal within first and second frames of the sequence of frames, the second frame following the first frame, the sampling using information on a pitch contour of the first and second frames to derive a first sampled representation. The audio signal is sampled within the second and third frames, the third frame following the second frame in the sequence of frames. The sampling uses the information on the pitch contour of the second frame and information on a pitch contour of the third frame to derive a second sampled representation. A first scaling window is derived for the first sampled representation, and a second scaling window is derived for the second sampled representation, the scaling windows depending on the samplings applied to derive the first sampled representations or the second sampled representation.