Audio Sampling Rate Detection via Line Spectral Frequency Coefficients
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Solution Overview
Problem
Variable bit rate speech and audio codecs incur additional coding overhead by signaling the LP coding order and sampling rate, which increases the bit stream size.
Innovation Solution
The method involves determining and quantizing linear prediction coefficients to Line Spectral Frequency (LSF) coefficients, with the highest order LSF coefficient used to distinguish between different sampling frequencies, eliminating the need to signal the LP coding order and sampling rate explicitly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LP coding order and sampling rate are explicitly signaled in the encoded bit stream, then the decoder can accurately determine the coding parameters, but the coding overhead increases and the bit stream size increases
Solution Approach 1:
The patent extracts the sampling rate information from the explicit signaling mechanism and embeds it implicitly within the LSF coefficient range. By removing the redundant explicit signaling and utilizing the inherent properties of the LSF coefficients to carry sampling rate information, the solution reduces bit stream size while maintaining decoding accuracy.
Solution Approach 2:
The LSF coefficients are made to serve multiple functions: they not only represent the spectral information but also encode the sampling rate information through their frequency ranges. This multi-functionality eliminates the need for separate signaling bits, thereby reducing coding overhead.
2Device complexity
If the LP coding order and sampling rate are signaled using index flags, then the coding overhead is minimized, but additional bits are still required in the encoded bit stream
Solution Approach 1:
The patent removes the separate index flag signaling mechanism entirely and extracts the sampling rate information from the LSF coefficient frequency ranges. This elimination of redundant signaling reduces the coding overhead while maintaining the ability to distinguish between different sampling rates.
3Adaptability or versatility
If variable order linear predictive coding is used with varying sampling rates, then the codec adapts to different audio qualities, but the coding scheme becomes more complex requiring additional signaling
Solution Approach 1:
The patent makes the LSF coefficient representation universal by having it simultaneously encode both the spectral characteristics and the sampling rate information. This multi-functional approach allows the same coding structure to handle variable sampling rates without introducing additional complexity or signaling requirements.
Data Source
AI summary
It is inter alia disclosed to receive a set of encoded audio parameters for an audio frame, wherein the set comprises indices representing at least two quantized line spectral frequency coefficients, wherein the audio frame when decoded comprises audio samples digitally sampled at a sampling frequency, wherein the sampling frequency is one of a plurality of sampling frequencies for an audio decoder; to convert the indices to the at least two quantized line spectral frequency coefficients; and to determine the sampling frequency for the audio frame by checking the value of a highest order quantized line spectral frequency coefficient of the at least two quantized line spectral frequency coefficients.