Audio Device High Frequency Band Estimation via Harmonic Generation
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Solution Overview
Problem
Existing audio devices face challenges in performing high-quality high frequency band interpolation with a simple configuration, especially when compressed audio data is downloaded from a network to a compact portable terminal device and needs to be transmitted to another device for output, requiring additional functionality.
Innovation Solution
An audio device comprising a harmonic generation unit, variable high pass filter units with different cutoff frequencies, and a control unit that estimates missing high frequency bands by comparing output signals from first and second high pass filters, allowing for high frequency interpolation without needing separate transmission of bit rate information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the prior art technique is applied to perform high frequency band interpolation, then high quality audio output is achieved, but additional functionality is required in portable terminal devices to transmit bit rate information separately
Solution Approach 1:
The system uses the audio signal itself to carry the information needed for high frequency band interpolation. The bit rate information is embedded within the audio data stream, allowing the receiving device to extract and use this information without requiring separate transmission channels or additional functionality in portable terminal devices.
Solution Approach 2:
The invention combines the audio signal transmission and bit rate information transmission into a single data stream. By embedding the bit rate information within the audio data structure, the system merges two separate information channels into one, eliminating the need for separate transmission paths and reducing device complexity.
2Measurement precision
If bit rate information is transmitted via a separate path from the compressed audio signal, then accurate high frequency interpolation is enabled, but the configuration becomes more complex and additional functionality is required
Solution Approach 1:
The invention merges the transmission of audio data and bit rate information into a single integrated data stream. The bit rate information is embedded within the audio data structure, allowing both the audio signal and the information needed for accurate frequency band estimation to be transmitted together through the same channel, simplifying the transmission process.
Solution Approach 2:
The audio data structure serves as an intermediary that carries both the compressed audio signal and the bit rate information. By using the existing audio data structure as a container for additional information, the system avoids the need for separate transmission paths while maintaining accurate frequency band estimation.
Data Source
AI summary
During high-frequency interpolation, a harmonic generation unit first generates a harmonic signal for an input compressed audio signal. An HPF unit, having a cutoff frequency, extracts a high frequency component from the compressed audio signal in parallel with the generation of the harmonic signal. An HPF unit, having a cutoff frequency, extracts a high frequency component from the compressed audio signal. An estimation unit estimates a missing band in the compressed audio signal on the basis of a ratio of the signal level of a difference signal to the signal level of an output signal, the difference signal being obtained by subtracting the output signal of the HPF unit from the output signal of the HPF unit. The estimation unit controls the cutoff frequency of a variable HPF unit that extracts a signal component for high-frequency interpolation from the harmonic signal on the basis of the estimated missing band.