Abstract: A method and apparatus for improving the performance of coding systems in the presence of frame erasures or lost packets. The encoded signal is modified after transmission but prior to decoding by a decoder preprocessor. The preprocessor recognizes that a given frame has been corrupted and modifies the encoded signal so that the decoding thereof will result in improved coding system performance. Specifically, based on the decoding process and on a predetermined target signal, the encoded signal is modified so that the decoding thereof will generate an approximation to the target signal. In a first illustrative embodiment, a CELP speech coder is used and the target signal is an excitation signal comprised of all-zero excitation vectors. In this case, the portion of the corrupted excitation signal indices which identify the corresponding gain factors are set to values which represent a low gain factor.

Abstract: A technique is provided for the association of constraints with data object classes in an object-oriented database. Given a constraint comprising zero or more quantifiers followed by a quantifier-free boolean expression, a non-primitive reference expression is identified in the boolean expression. The constraint is then modified as follows. First, the primitive reference expression at the head of the identified non-primitive reference expression is replaced with a variable. Then a universal quantifier which quantifies the added variable over all data objects in the class comprising that primitive reference expression is added to the constraint. Finally, a disjunctive condition specifying that the added variable is not equal to the primitive reference expression is added to the boolean expression. The modified constraint may then be associated with the class comprising the aforesaid primitive reference expression.

Abstract: A technique for the masking of quantizing noise in the coding of audio signals is usable with the types of channel coding known as "noiseless" or Huffman coding and with variable radix packing. In a multichannel environment, noise masking thresholds may be determined by combining sets of power spectra for each of the channels. The stereophonic embodiment eliminates redundancies in the sum and difference signals, so that the stereo coding uses significantly less than twice the bit rate of the comparable monaural signal. The technique can be used both in transmission of signals and in recording for reproduction, particularly recording and reproduction of music. Compatibility with the ISDN transmission rates known as 1B, 2B and 3B rates has been achieved.

Abstract: An automated method for modifying a speech signal communicated over a telephone network by applying a gain factor in a telephone set before any side tone is added thereto. The gain factor is a function of a received signal indicative of the background noise at the location of the telephone set. The gain applied may be a function of both the background noise level and the original speech signal. Either a linear or a non-linear (e.g., compressed) amplification of the original speech signal may be performed, where a compressed amplification results in the higher level portions of the speech signal being amplified by a smaller gain factor than lower level portions. The speech signal may be separated into a plurality of subbands, each resultant subband signal being individually modified in accordance with the present invention.

Abstract: An automated method for modifying a speech signal in a telephone network by applying a gain factor which is a function of the level of background noise at a given destination, and transmitting the modified speech signal to the destination. The gain applied may be a function of both the background noise level and the original speech signal. Either a linear or a non-linear (e.g., compressed) amplification of the original speech signal may be performed, where a compressed amplification results in the higher level portions of the speech signal being amplified by a smaller gain factor than lower level portions. The speech signal may be separated into a plurality of subbands, each resultant subband signal being individually modified in accordance with the present invention. In this case, each subband speech signal is amplified by a gain factor based on a corresponding subband noise signal, generated by separating the background noise signal into a corresponding plurality of subbands.

Abstract: The invention is a method for testing an electronic device (10) of the type having on one side thereof an array of conductive projections, such as solder balls (15), arranged in a first configuration. An array of spring-loaded probes (25) is arranged in the first configuration. An insulative template (18) is formed comprising an array of apertures (19) arranged in the first configuration which is aligned with the spring-loaded conductive probes. The electronic device (10) is then forced against the template (18) such that each solder ball (15) projects into the aperture to contact a spring-loaded conductive probe (25). Electrical current is passed through at least part of the electronic device, at least some of the solder balls, and at least some of the conductive probes as is required for electrical testing of the electronic device.

Abstract: A method and apparatus for reducing correlated errors in subband coding systems with quantizers is disclosed. A subband coding system comprises a plurality of subband analysis filters to divide the frequency spectrum of the input signal into subbands, individual subband quantizers for coding each subband by a preselected number of quantization levels, corresponding subband decoders and subband synthesis filters. The transfer function of each of the subband synthesis filters is advantageously determined based on the transfer functions of the subband analysis filters as well as on the characteristics of the quantizer used to code the corresponding subband. Specifically, the synthesis filter transfer functions may be based on a perfect reconstruction filter bank or a quadrature mirror filter bank, as well as on the gain factors of a gain plus additive noise linear model for the Lloyd-Max quantizers used to code the corresponding subbands.

Abstract: An automated method for modifying a speech signal in a telephone network by applying a gain factor which is a function of the level of background noise at a given destination, and transmitting the modified speech signal to the destination. The gain applied may be a function of both the background noise level and the original speech signal. Either a linear or a non-linear (e.g., compressed) amplification of the original speech signal may be performed, where a compressed amplification results in the higher level portions of the speech signal being amplified by a smaller gain factor than lower level portions. The speech signal may be separated into a plurality of subbands, each resultant subband signal being individually modified in accordance with the present invention. In this case, each subband speech signal is amplified by a gain factor based on a corresponding subband noise signal, generated by separating the background noise signal into a corresponding plurality of subbands.

Abstract: A small, stylus-based keyboard in which the arrangement of the keys is a function of predetermined estimated probabilities of the occurrence of various possible sequences of keystrokes. Sequences of keystrokes which are estimated to have a high likelihood of occurrence result in the associated keys being placed adjacent to one another. In this manner, the ease, speed and accuracy of use of small, stylus-based keyboards may be improved. Multiple keys representing the same character may be provided to increase the likelihood that keys included in high probability sequences will be adjacent. The probability estimates may be determined based on a statistical analysis of a preselected sample of text. In addition, keys may be color-coded for ease of identification and grooves may be cut into the housing between adjacent keys for ease of stylus operation. Lights (e.g., light-emitting-diodes) may also be inserted between adjacent keys or beneath the keys for purposes of word identification or next letter prediction.

Abstract: A method of coding a set of multi- level signals, such as video signals comprises filtering the set of multi-level signals into one or more sets of multi-level sub-band signals; allocating a first quantity of bits for use in coding a first set of sub-band signals; coding the first set of multi-level sub-band signals using zero or more of the first quantity of allocated bits; allocating a second quantity of bits for use in coding a second set of sub-band signals, the second quantity of bits comprising zero or more of the first quantity of bits not used in coding the first set of multi-level sub-band signals; and coding the second set of multi-level sub-band signals using zero or more of the second quantity of allocated bits. Three examples of the method am provided. A hardware implementation involving the use of digital signal processors operating in parallel is also provided.

Abstract: A method of regulating backpressure traffic in a packet switched network made up of a plurality of switching elements each having a local buffer memory identifies at least one switching element which succeeds at least one other switching element in a transmission path. The at least one succeeding switching element has a congested local buffer memory. A backpressure signal is transmitted to the at least one other switching element. Packets destined for the succeeding switching element are queued in the local buffer memory of the at least one other switching element. Next, it is determined when the occupancy of the local buffer memory for the other switching element has exceeded a predetermined threshold. In response to the exceeded predetermined threshold, the other switching element ignores the backpressure signal transmitted from the succeeding switching element and transmits the queued packets to the succeeding switching element.

Abstract: A method and apparatus for generating a voice message based on a text message from a text messaging system is disclosed. The voice message stored in a voice messaging system or may be directly transmitted to a recipient telephone number. The text messaging system comprises one or more addressable nodes including a messaging system interface node, which receives the text message from the text messaging system based on its node address and generates a voice message responsive to the text message. Signals may be generated to access the voice messaging system, and the voice message may be communicated to the voice messaging system for storage. The voice message may comprise speech corresponding to the text of the text message, created, for example, by conventional text-to-speech synthesis techniques. The text message may also be communicated to a text message addressee with use of the text messaging system, and the voice message may comprise speech reflecting that a text message has been so communicated.

Abstract: In a modulation scheme involving differential encoding and Reed-Solomon encoding, the differential encoding is performed before the Reed-Solomon encoding in the transmitter. In the receiver, a differential decoding operation is performed after an RS decoding operation. The overall coding scheme and the RS decoding are so arranged as to ensure that the RS decoding will be proper in the presence of phase rotations, notwithstanding the fact that the differential encoding is performed before the RS encoding in the transmitter and the fact that the RS decoding is performed before the differential decoding in the receiver.

Abstract: A method of prioritizing handoff requests in a cellular system is disclosed in which at least one handoff request for assignment of a communication channel is received from at least one mobile unit. A cutoff time for the handoff request is determined. The handoff requests are arranged in a priority queue based on the cutoff time associated with each handoff request. Available communication channels are assigned to the mobile units requesting handoff in the order of the queue.

Abstract: A method and apparatus for the coding and efficient display of overlapping windows with transparency. Each pixel within a window which is not to be displayed may be coded as a "transparent" pixel. The method identifies those pixels which have been coded as transparent and displays non-transparent pixels contained in windows of lower display priority in place of the transparent pixels contained in windows of higher display priority. A pixel coded as transparent may have associated with it an integer representative of the number of successive pixels in the window which are also transparent. A pixel may be coded as transparent by assigning to it a preselected data value which is distinct from values otherwise used to indicate, e.g., the color and/or intensity for each displayed pixel. The method and apparatus may include one or more windows which contain full motion video (i.e., television) images, each of which may also contain transparent pixels.

Abstract: A method of coding a video signal at a fixed bit rate with use of a vector quantization codebook, wherein advantageous codebook updates are determined by comparing a coding error associated with a first provisional coding of a frame with a coding error associated with a second provisional coding of the frame. The first provisional coding uses a fixed available number of bits to code a frame with use of the unmodified codebook, whereas the second provisional coding uses a modified codebook to code the same frame. However, the second provisional coding codes both the frame and the codebook updates with the fixed available number of bits. The provisional coding having the smaller coding error is selected as the coding of the frame which will be adopted. In addition, the codebook may be replaced with the modified codebook when the second provisional coding is selected. In this manner, the coder will adapt the codebook to the characteristics of the scene.

Abstract: A method and apparatus for tracking participation in a conference call is disclosed. A conference tracker at a first location transmits a status signal to another conference tracker at a second location. The conference tracker at the second location receives the status signal and recognizes it as representative of an attribute of one or more of the parties at the first location. The attribute represented may be the identity of the first location, thereby informing the conference tracker at the second location that the first location remains connected to the conference call. In this manner, the conference tracker may inform a party of the number of connected locations or that a particular location has disconnected. The attribute represented may be the identity of the first location when a party at that location is speaking. In this manner, the conference tracker at the second location may thereby inform a listening party of the location of the speaking party.

Abstract: The present invention provides a method and apparatus for detecting control signal information for an element of a communication system. The control signal information is included in one or more segments of a signal communicated over a communication system channel. The invention provides for the application of a plurality of tapers to a segment of a communicated signal; the transformation of a tapered segment; the determination of a similarity score based on a transform of a tapered segment and a model of a control signal; the identification of control signal information based on a similarity score; and the creation of an indicator signal representative of the identified control signal information to the communication system element. The control signal information may comprise a dual-tone multi-frequency signal. The tapers may comprise a discrete prolate spheroidal sequence. A similarity score may be determined based on a ratio of energy distributions.

Abstract: A technique for coding color components of video signals wherein a color component of an image signal sequence is filtered into a plurality of subband image signals. One or more pixels of a first subband image signal are coded using one or more bits of a first quantity of bits. The first subband image signal reflects an image structure of a color component of the image signal sequence. The first subband includes low spatial and temporal frequencies of the color component. A second quantity of bits is used for coding one or more pixels of a second subband image signal. This second quantity of bits comprises one or more bits of the first quantity of bits not used in coding pixels of the first subband image signal. One or more pixels of the second subband image signal are coded using one or more of the second quantity of bits. The second subband image signal reflects image object motion information of the color component of the image signal sequence.

Abstract: An electret transducer array and fabrication technique are disclosed. The array comprises a foil having a layer of insulating material and a layer of metal in contact therewith. The layer of metal comprises one or more discrete areas of metal which define the active areas of one or more transducers in the array. Electrical leads are coupled to the discrete areas of metal. By means of these leads, electrical signals produced by each transducer in response to incident acoustic signals may be accessed. The areas of metal may be formed by selectively removing metal from the foil, or by selective metal deposition. The layer of insulating material is electrostatically charged. The electret transducer array further comprises a porous backplate of sintered metal. The backplate further comprises a rough surface in contact with the layer of insulating material. The backplate serves as a common electrode for transducers of the array.