Audio Encoding Gain Correction via Differential Prediction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional audio encoding techniques are insufficient in reducing the code rate of gain information and fail to provide fine control over each frequency band, resulting in unsatisfactory sound quality.
Innovation Solution
The method corrects gain information from past and initial gains to suppress the gain code rate, allowing for control of gain per band as a minimum unit, reducing the code rate of gain information, and improving sound quality with reduced calculation and bit rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the initial gain A is always encoded for each band, then the gain information can be accurately represented, but the code rate of gain information increases
Solution Approach 1:
The patent applies preliminary action by predicting the gain value for the current frame based on gain values from previous frames before actual encoding. The prediction unit calculates predicted gain information using past frame data, and this predicted value serves as a baseline that requires minimal encoding. Only the difference between actual and predicted gain needs to be encoded, significantly reducing the code rate while maintaining accuracy.
Solution Approach 2:
The patent changes the parameter representation from encoding absolute gain values to encoding differential values (d_scf). By transforming the gain parameter from its original form to a difference form relative to predicted values, the encoding efficiency improves. The differential values have smaller magnitudes and can be encoded with fewer bits, thus reducing the gain code rate while preserving the necessary information.
2Loss of information
If the same gain is applied to multiple frequency bands, then the gain code rate is reduced, but fine control over each band is lost resulting in unsatisfactory sound quality
Solution Approach 1:
The patent applies segmentation by dividing the frequency spectrum into multiple bands and applying independent gain control to each band. Instead of using a single common gain for all bands, the system calculates and encodes separate gain information for each frequency band. This segmentation enables fine-grained control over each band's amplitude characteristics, improving sound quality while the prediction mechanism keeps the overall code rate manageable.
Solution Approach 2:
The patent implements local quality by allowing different encoding precision and prediction strategies for different frequency bands. Each band can have its own predicted gain value and differential encoding parameters tailored to its specific characteristics. This localized approach optimizes the balance between code rate and sound quality for each band individually, rather than applying a uniform strategy across all frequencies.
3Measurement precision
If Huffman code length increases for large gain differences, then large gain variations are accurately encoded, but the overall code rate increases
Solution Approach 1:
The patent uses feedback by continuously using previously decoded gain information to predict current frame gain values. The prediction unit incorporates past frame gain data and uses it to generate predictions for the current frame. This feedback mechanism ensures that gain differences to be encoded are typically small, allowing the Huffman coding scheme to use shorter code lengths for the majority of cases while still accurately representing larger variations when they occur.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An audio encoding device (1A) corrects initial gain information calculated for an arbitrary frame, based on gain information of a stored past frame, thereby calculating gain information to be used in the frame. The audio encoding device (1A) encodes the calculated gain information as a difference from the gain information of the past frame. An audio decoding deice (3A) receives the differential gain, and calculates the gain of the arbitrary frame based on the gain used in the past frame, thereby generating a decoded audio signal.