Ntt Docomo, Inc.

Ntt Mobile Communications Network, Inc.

Nobuhiko Naka

Kei Kikuiri

Kosuke Tsujino

Tomoyuki Ohya

Toshiro Kawahara

Vesa Ruoppila

Takashi Suzuki

Toshio Miki

Masashi Morioka

Yasuyo Yasuda

Masahito Saigusa

Toyokazu Hama

The purpose of the present invention is to estimate, with a small amount of computation, a linear prediction synthesis filter after conversion of an internal sampling frequency. A linear prediction coefficient conversion device is a device that converts first linear prediction coefficients calculated at a first sampling frequency to second linear prediction coefficients at a second sampling frequency different from the first sampling frequency, which includes a means for calculating, on the real axis of the unit circle, a power spectrum corresponding to the second linear prediction coefficients at the second sampling frequency based on the first linear prediction coefficients or an equivalent parameter, a means for calculating, on the real axis of the unit circle, autocorrelation coefficients from the power spectrum, and a means for converting the autocorrelation coefficients to the second linear prediction coefficients at the second sampling frequency.

Linear prediction coefficient conversion device and linear prediction coefficient conversion method

A linear prediction coefficient of a signal represented in a frequency domain is obtained by performing linear prediction analysis in a frequency direction by using a covariance method or an autocorrelation method. After the filter strength of the obtained linear prediction coefficient is adjusted, filtering may be performed in the frequency direction on the signal by using the adjusted coefficient, whereby the temporal envelope of the signal is shaped. This reduces the occurrence of pre-echo and post-echo and improves the subjective quality of the decoded signal, without significantly increasing the bit rate in a bandwidth extension technique in the frequency domain represented by SBR.

Speech decoder with high-band generation and temporal envelope shaping

When a frame immediately preceding an encoding target frame to be encoded by a first encoding unit operating under a linear predictive coding scheme is encoded by a second encoding unit operating under a coding scheme different from the linear predictive coding scheme, the encoding target frame can be encoded under the linear predictive coding scheme by initializing the internal state of the first encoding unit. Therefore, encoding processing performed under a plurality of coding schemes including the linear predictive coding scheme and a coding scheme different from the linear predictive coding scheme can be realized.

Audio signal encoding method, audio signal decoding method, encoding device, decoding device, audio signal processing system, audio signal encoding program, and audio signal decoding program

A linear prediction coefficient of a signal represented in a frequency domain is obtained by performing linear prediction analysis in a frequency direction by using a covariance method or an autocorrelation method. After the filter strength of the obtained linear prediction coefficient is adjusted, filtering may be performed in the frequency direction on the signal by using the adjusted coefficient, whereby the temporal envelope of the signal is transformed. This reduces the occurrence of pre-echo and post-echo and improves the subjective quality of the decoded signal, without significantly increasing the bit rate in a band extension technique in the frequency domain represented by SBR.

Speech decoding system with temporal envelop shaping and high-band generation

A linear prediction coefficient of a signal represented in a frequency domain is obtained by performing linear prediction analysis in a frequency direction by using a covariance method or an autocorrelation method. After the filter strength of the obtained linear prediction coefficient is adjusted, filtering may be performed in the frequency direction on the signal by using the adjusted coefficient, whereby the temporal envelope of the signal is shaped. This reduces the occurrence of pre-echo and post-echo and improves the subjective quality of the decoded signal, without significantly increasing the bit rate in a bandwidth extension technique in the frequency domain represented by spectral band replication.

Speech encoding/decoding device

It is provided a voice activity decision apparatus capable of accurately performing the decision on the state being associated with a sound interval or a silence interval also in terms of the input signal having many aperiodic components and/or plural mixed different periodic components. The apparatuscomprises: an autocorrelation calculating unitfor calculating autocorrelation values of an input signal; a delay calculating unitfor calculating plural delays at which autocorrelation values calculated by the autocorrelation calculating unitbecome maximums; a noise deciding unitfor deciding whether the input signal is a noise or not based on the plurality of delays calculated by the delay calculating unit; and an activity decision unitfor performing the activity decision in terms of the input signal based on results of decision by the noise deciding unitand the input signal.

Apparatus and method for voice activity detection

To provide a data transmitter-receiver bidirectional transmitting system, and data transmitting-receiving method capable of reducing influences of a transmission delay when performing bidirectional communication with an other-communication-party apparatus in an environment in which various states are dynamically changed depending on time. A data obtaining portionof a terminalobtains positional directional information D(Tn) and a time information obtaining portionobtains time information Tn. The terminalstores D(Tn) and Tn in a memory portionand a transmitting portiontransmits D(Tn) and Tn to a server. A data generating portionof the servergenerates stereophonic data S(Tn) by using D(Tn), a time information copying portioncopies Tn, a transmitting portiontransmits S(Tn) and Tn to the terminal. A data obtaining portionof the terminalobtains positional directional information D(Tm), the time information obtaining portionobtains time information Tm, and a correcting portioncorrects the difference between D(Tm) and D(Tn) to generate S'(m).

Data transmitter-receiver, bidirectional data transmitting system, and data transmitting-receiving method

The present invention intends to render quantization noise virtually imperceptible for a user and to prevent reduction in frequency resolution and reduction in encoding efficiency. A signal encoding apparatus includes: a quantization unit for quantizing an input signal based on a plurality of quantization methods; a dequantization unit for obtaining decoded signals by performing the dequantizing process; an error signal calculation unit for calculating a plurality of error signals between the decoded signals and the input signal; a weighting calculation unit for calculating, for each subblock, a weight related to degree concerning whether or not quantization noise corresponding to error signal is virtually imperceptible for a user; a quantization method selection unit for selecting a given quantization method from among the plurality of quantization methods, when a plurality of weighted error signals, obtained by assigning a weight of each subblock to an error signal of the subblock, are generated, based on the of weighted error signals; and an output unit for outputting the input signal quantized based on the given quantization method as an output signal.

Growing community of inventors

Yokohama, Japan

Nobuhiko Naka