42 results about "Spectral flatness" patented technology

In accordance with an embodiment, a method of decoding an encoded audio bitstream at a decoder includes receiving the audio bitstream, decoding a low band bitstream of the audio bitstream to get low band coefficients in a frequency domain, and copying a plurality of the low band coefficients to a high frequency band location to generate high band coefficients. The method further includes processing the high band coefficients to form processed high band coefficients. Processing includes modifying an energy envelope of the high band coefficients by multiplying modification gains to flatten or smooth the high band coefficients, and applying a received spectral envelope decoded from the received audio bitstream to the high band coefficients. The low band coefficients and the processed high band coefficients are then inverse-transformed to the time domain to obtain a time domain output signal.

The invention discloses a method for classifying digital audio automatically. The method particularly comprises the following steps: pretreating an audio signal: pre-emphasis treatment, framing treatment and windowing treatment; extracting an audio characteristics comprising frequency spectrum mass center, spectrum spreading, frequency spectrum flatness, frequency spectrum transition parameters, short time energy, fundamental frequency and Mel frequency cepstrum coefficient (MFCC) and MFCC first order difference; indexing and classifying according to the audio characteristic, and finding out the similar audio. According to the invention, the problem of error caused by indexing audio by adopting a single audio characteristic in the prior art is solved; moreover, the method is simple in computation process, is easy to apply practically, and is high in indexing efficiency.

An audio signal is divided among exponentially related subband filters. The spectral flatness measure in each subband signal is determined and the measures are weighted and combined. The sum is compared with a threshold to determine the presence of music or noise. If music is detected, the noise estimation process in the noise reduction circuitry is turned off to avoid distorting the signal. If music is detected, residual echo suppression circuitry is also turned off to avoid inserting comfort noise.

A method is disclosed of compensating the output of an ADC for non-linearity in the response of the ADC. The method comprises converting an analog input signal to uncorrected digital ADC output samples, applying a vector of correction variables to each of a block of uncorrected ADC output samples to provide a block of corrected ADC samples, and iteratively minimizing a measure of the spectral flatness of the block of corrected ADC samples with response to the vector of correction variables.

The embodiment of the invention discloses a band spreading method and device, electronic equipment and a computer readable storage medium. The method comprises the steps of performing time-frequency transformation on a narrow-band signal to be processed to acquire a corresponding initial low frequency spectrum; based on the initial low frequency spectrum, acquiring correlation parameters of a highfrequency part and a low frequency part of a target wideband spectrum via a neural network model, wherein the correlation parameters comprise at least one of a high frequency spectrum envelop and relative flatness information, and the relative flatness information represents correlation between the spectrum flatness of the high frequency part and the spectrum flatness of the low frequency part ofthe target wideband spectrum; based on the correlation parameters and the initial low frequency spectrum, acquiring an initial high frequency spectrum; and acquiring a broadband signal after band spreading according to a target low frequency spectrum and a target high frequency spectrum, wherein the target low frequency spectrum is the initial low frequency spectrum or the spectrum acquired afterfiltering treatment is performed on the initial low frequency spectrum, and the target high frequency spectrum is the initial high frequency spectrum or the spectrum acquired after filtering treatment is performed on the initial high frequency spectrum.

A method for simplifying acoustic model analysis through applying audio frame frequency spectrum flatness and a device thereof, which applies the audio frame frequency spectrum flatness to simplify the acoustic model analysis of a voice signal, if the voice signal contains a plurality of frames, firstly the energy of the voice signal in frequency domain is computed, computing a plurality of frequency spectrum flatness according to the computed energy, and then transforming each audio frame through evolutional discrete cosine transform of short block or long block. If the voice signal contains left and right channel signal, the invention firstly performs the acoustic model analysis of the voice signal, computes the energy of the left and right channel signal in frequency domain, computes the frequency spectrum flatness of the left and right channel signal, and then uses signal or left and right channel coding to transform the left and right channel signal.

An apparatus, method, and medium for detecting a voiced sound and an unvoiced sound. The apparatus includes a blocking unit for dividing an input signal into block units; a parameter calculator for calculating a first parameter to determine the voiced sound and a second parameter to determine the unvoiced sound by using a slope and spectral flatness measure (SFM) of a mel-scaled filter bank spectrum of an input signal existing in a block; and a determiner for determining a voiced sound zone and an unvoiced sound zone in the block by comparing the first and second parameters to predetermined threshold values.

Methods, systems, and devices are described for wireless communications. A wireless station includes a transmitter to generate a wideband contiguous waveform in a band. The transmitter transmits the waveform that conforms to spectral masking attributes and spectral flatness attributes. The wireless station, or another device supporting spectrum analysis functions, detects a wideband contiguous waveform and performs spectrum analysis of the waveform. The wireless station includes a resolution bandwidth of 25 KHz and a video bandwidth of 7.5 KHz.

The invention relates to a semiconductor laser, in particular to a no-time-delay flat-frequency-spectrum broadband photon integrated chaos semiconductor laser which solves the problems that chaos lasers generated by an existing semiconductor laser have the time delay characteristic, the signal band width is small, and the frequency spectrum is not flat. The no-time-delay flat-frequency-spectrum broadband photon integrated chaos semiconductor laser comprises a chip substrate, an optical waveguide, an erbium-doped passive optical waveguide, a left distributed feedback semiconductor laser chip, a no-isolation two-way amplified semiconductor light amplification chip, a right distributed feedback semiconductor laser chip and a high-speed photoelectric detection chip. The no-time-delay flat-frequency-spectrum broadband photon integrated chaos semiconductor laser is suitable for the fields of synchronization of chaos, secrecy light communication, high-speed random number secret key generation, laser radar, optical fiber network fault detection, ultra broadband technology, distributed optical fiber sensing and the like.

The invention described herein provides a method and apparatus that allows direct digital to IF / RF conversion using pulse-shaping. The method facilitates obtaining a flat or near flat output spectrum after digital to analog conversion with a minimal loss in signal energy. As opposed to pulse-shortening, where the DAC output pulse and consequently the energy per sample are reduced to a fraction a<1 of the maximum, the pulse-shaping does not shorten the DAC pulse. For each sample, pulse-shaping first stores the energy delivered by DAC and then releases the stored energy to the output during a short period of time aT. This way little signal energy is lost even for very small values of a. With pulse-shaping, the duration aT of the output pulse contributes to the spectral flatness in a way similar to that pulse-shortening, but has the additional benefit that the shape of the output pulse contributes significantly to a flat spectrum. Two embodiments of the pulse-shaping method are described in the context of two types of DAC that are used: one with current output and the other with voltage output. Then, two examples of pulse-shaping implementation are given for a single-ended current-output DAC and for a differential current-output DAC.

Methods, systems, and devices for wireless communication are described. A wireless device may identify a transmission mode for transmission of an input signal to be transmitted. The input signal may thus be modulated according to the identified transmission mode, and the modulated signal may then be transmitted at some power level to produce a transmitted signal having a spectral envelope. In somecases, the spectral envelope may be defined in terms of a power spectral density (PSD) of the transmitted waveform. The PSD may generally define the power of the waveform signal distributed over frequencies of the waveform. Further, the wireless device may control the modulation of the input signal, in addition to the power level of the input signal, to maintain the spectral envelope to be withina spectral mask defined for the implemented transmission mode as well as to conform to spectral flatness parameters.

The invention relates to the technology of communication cable fault detection, specifically a chaotic laser transmitter for communication cable fault detection. The invention solves problems that the low-frequency energy of the chaotic laser generated by a conventional chaotic laser generation device is low in percentage, and the frequency spectrum flatness is poor. The transmitter comprises a semiconductor laser, a polarization controller, a 1*2 main fiber coupler, an optical attenuator, a fiber feedback mirror, an optical isolator, a light amplifier, and a low-frequency enhancement device. An output end of the semiconductor laser is connected with the input end of the polarization controller. The output end of the polarization controller is connected with the input end of the 1*2 main fiber coupler. The two output ends of the 1*2 main fiber coupler are respectively connected with the input end of the optical attenuator and the input end of the optical isolator. The output end of the optical attenuator is connected with the input end of the fiber feedback mirror. The transmitter is suitable for the detection of a communication cable fault.