Abstract: A database server contains pointers to useful information, such as on the World Wide Web. Users of the server may have hypertext links added automatically into documents they submit. Users may additionally contribute to the link database, thereby extending it, and may add additional qualifying information pertaining to the links.

Abstract: A database server contains pointers to useful information, such as on the World Wide Web. Users of the server may have hypertext links added automatically into documents they submit. Users may additionally contribute to the link database, thereby extending it, and may add additional qualifying information pertaining to the links.

Abstract: A method for recognizing an audio sample locates an audio file that most closely matches the audio sample from a database indexing a large set of original recordings. Each indexed audio file is represented in the database index by a set of landmark timepoints and associated fingerprints. Landmarks occur at reproducible locations within the file, while fingerprints represent features of the signal at or near the landmark timepoints. To perform recognition, landmarks and fingerprints are computed for the unknown sample and used to retrieve matching fingerprints from the database. For each file containing matching fingerprints, the landmarks are compared with landmarks of the sample at which the same fingerprints were computed. If a large number of corresponding landmarks are linearly related, i.e., if equivalent fingerprints of the sample and retrieved file have the same time evolution, then the file is identified with the sample.

Abstract: A tone synthesis system employs digital filtering methods to enable the practical usage of unstable filter elements in a real-time synthesis model. Truncated infinite impulse response (TIIR) filters are used to approximate portions of the reflection impulse response of an acoustic horn such as a trumpet bell. Methods for resetting filter state enable the use of internal unstable filter poles. Similar state resetting methods enable the use of unstable one-pole filters in the scattering junction formed between two conical acoustic bores. High quality tone synthesis can be achieved without the necessity of a complicated filter representing large sections of the bore of a woodwind instrument.

Abstract: A sampled data, delay line structure that includes a sampled data delay line, two readers for reading data at corresponding positions of the delay line, controller that controls when the read position of each reader is updated for a new note of a different pitch, and a crossfader that crossfades between the outputs of the two readers to produce a legato transition between the two discrete notes associated with the two readers. The controller receives a control signal indicating a sequence of note events to be implemented by the delay line structure. When a new note on event occurs while a previous note is still playing, a legato crossfade sequence is performed. In particular, the delay line reader not used by the previous note is set to a delay position associated with the new note, and the crossfader is enabled. The crossfader gradually transitions its output from that of the reader used for the previous note to the output of the reader used from the new note.

Abstract: An efficient digital waveguide synthesizer is disclosed for simulating the tones produced by a non-linearly excited vibrational element coupled to a resonator, such as in a piano. In a preferred embodiment, the synthesizer creates an excitation pulse from a table containing the impulse response of a piano soundboard and enclosure. Alternatively, this excitation pulse can be synthesized by filtering white noise. The excitation pulse is fed into a filter that simulates the collision of the piano hammer and string. Because the hammer-string interaction is nonlinear, the characteristics of this filter vary with the amplitude of the tone produced. The filtered excitation pulse is then fed into a filtered delay line loop which models the vibration of a piano string. Because the excitation pulse already contains the effects of the resonator, the tone produced by the delay line loop does not require additional filtering in order to model the resonator.

Abstract: Sinusoidal waveforms are synthesized using one or more waveguide resonance oscillators. The waveguide resonance oscillator has two digital delay elements coupled to a digital waveguide junction. Each digital delay element receives a signal on its respective input node and outputs the received signal on its respective output node after a delay of one sample period. In the preferred embodiment, the waveguide junction has three digital signal adders and one signal multiplier interconnected so as to compute, once each sample period, a new input value for each digital delay element as a function of the two signals output by the digital delay elements. The multiplier coefficient used by the waveguide junction's multiplier determines the generated waveform's frequency of oscillation. The two output signals from the waveguide junction are sinusoidal waveforms that are 90 degrees out of phase with each other.

Abstract: A signal synthesizer uses a digital waveguide network having at least a three dimensional matrix of waveguide sections interconnected by junctions to filter one or more excitation signals so as to generate an array of synthesized output signals. The digital waveguide network has sets of waveguide sections interconnected by junctions. Each waveguide section includes two digital delay lines running parallel to each other for propagating signals in opposite directions and each junction has reflection and propagation coefficients assigned to it for controlling reflection and propagation of signals in the waveguide sections connected to that junction. Except for junctions along boundaries of the digital waveguide matrix, a majority of the junctions are 2.sup.w -way junctions, where W is an integer greater than 1.

Abstract: A tone synthesis system employs a filtered delay loop which is excited by an excitation signal. The excitation signal corresponds to a partial impulse response of a body filter to the system which is to be simulated. Additional components of the impulse response of the body filter are imparted to an output from the filtered delay loop. High quality tone synthesis can be achieved without the necessity of providing a complicated body filter.

Abstract: A tone synthesis system employs a filtered delay loop which is excited by an excitation signal. The excitation signal corresponds to the impulse response of a body filter to the system which is to be simulated. High quality tone synthesis can be achieved without the necessity of providing a complicated body filter.

Abstract: A signal synthesizer uses a digital waveguide network having at least a two dimensional matrix of waveguide sections interconnected by junctions to filter one or more excitation signals so as to generate an array of synthesized output signals. The digital waveguide network has sets of waveguide sections interconnected by junctions. Each waveguide section includes two digital delay lines running parallel to each other for propagating signals in opposite directions and each junction has reflection and propagation coefficients assigned to it for controlling reflection and propagation of signals in the waveguide sections connected to that junction. Except for junctions along boundaries of the digital waveguide matrix, each junction is at least a four-way junction that interconnect at least four waveguide sections so as to scatter and intermix signals in flowing through those waveguide sections.

Abstract: A musical sound synthesizer simulates interaction of a hammer having a compressible striking surface with a resonating medium. A digital waveguide resonator that simulates operation of a resonating medium and generates digital resonator waveforms representing signals propagating in said digital waveguide resonator. A hammer filter simulates the hammer striking the resonating medium and generates first and second hammer waveforms. The hammer filter includes a scattering junction that couples the hammer filter to the digital waveguide resonator.

Abstract: A tone generation system includes one or more digital waveguide networks coupled to one or more junctions, one of which receives a control signal for controlling tone generation. The control signal initiates and interacts with a wave signal propagating through the waveguide networks to form a tone signal. A non-linear junction may be employed which receives a signal from a waveguide, converts it in accordance with a non-linear function based upon the value of the control signal and provides it back to the waveguide. A tone signal whose pitch is determined by the wave transmission characteristics of the waveguide network is thereby produced.

Abstract: A quasi-periodic signal is sampled at a specified rate, and then a predicted value of the signal is computed from a set of 2M+1 time lagged signal samples. The time lagged samples are centered in time at an integer multiple P of the signal's sampling period T.sub.s, where P.multidot.T.sub.s is approximately one period of the input signal. The predicted signal value is computed by multiplying each of the 2M+1 time lagged samples by a corresponding predictor coefficient c(i) and then summing the resulting products. The predicted signal value is subtracted from the actual signal value to obtain an error signal .epsilon.. During each successive sampling period, the predictor coefficients are updated by adjusting the previously computed predictor coefficients by an amount proportional to the error .epsilon. multiplied by each of the 2M+1 time lagged signal values. Using the updated coefficient values, a phase delay is computed, and then the signal's period is computed as the sum of phase delay and P.multidot.T.

Abstract: The restoration of a band-limited signal which has undergone amplitude clipping is viewed as recovery from signal drop-outs (missing samples over an interval of time), with the extrapolated signal constrained to lie outside the clipping interval during the drop out. If the signal is oversampled, and the clipping threshold moderate, a unique reconstruction may result from application of signal matching and bandwidth constraints. More generally, however, candidate reconstructions are seen to lie on or inside a polyhedron in the space of sampled signals. In contrast to the case of extrapolation through missing samples, upper and lower limits typically can be placed on the reconstructed signal at every sample point. In light of this finding, methods for choosing a unique reconstruction are achieved. The use of inequality constraints allows practical restoration of clipped signals.

Abstract: A tone generation system includes one or more digital waveguide networks coupled to one or more junctions, one of which receives a control signal for controlling tone generation. The control signal initiates and interacts with a wave signal propagating through the waveguide networks to form a tone signal. A non-linear junction may be employed which receives a signal from a waveguide, converts it in accordance with a non-linear function based upon the value of the control signal and provides it back to the waveguide. A tone signal whose pitch is determined by the wave transmission characteristics of the waveguide network is thereby produced.

Abstract: Disclosed is a signal processor formed using digital waveguide networks. The digital waveguide networks have signal scattering junctions. A junction connects two waveguide sections together or terminates a waveguide. The junctions are constructed from conventional digital components such as multipliers, adders, and delay elements. The signal processor of the present invention is typically used for digital reverberation and for synthesis of reed, string or other instruments.