Showing papers by "Dolby Laboratories published in 1996"

Lossless coding method for waveform data

Abstract: In a method of lossless processing of an integer value signal in a prediction filter which includes a quantiser, a numerator of the prediction filter is implemented prior to the quantiser and a denominator of the prediction filter is implemented recursively around the quantiser to reduce the peak data rate of an output signal. In the lossless processor, at each sample instant, an input to the quantiser is jointly responsive to a first sample value of a signal input to the prediction filter, a second sample value of a signal input to the prediction filter at a previous sample instant, and an output value of the quantiser at a previous sample incident. In a preferred embodiment, the prediction filter includes noise shaping for affecting the output of the quantiser.

Method and apparatus for efficient implementation of single-sideband filter banks providing accurate measures of spectral magnitude and phase

Abstract: Accurate measures of estimated spectral power and phase are derived from two spectral representations of each of one or more input signals generated by critically-sampled filter banks. The derived measures may be used in various applications including adaptive bit allocation in perceptual coding systems. An efficient implementation of one particular single-sideband critically-sampled filter bank is disclosed.

Method subband of coding and decoding audio signals using variable length windows

Abstract: A method of encoding time-discrete audio signals comprises the steps of weighting the time-discrete audio signal by means of window functions overlapping each other so as to form blocks, the window functions producing blocks of a first length for signals varying weakly with time and blocks of a second length for signals varying strongly with time. A start window sequence is selected for the transition from windowing with blocks of the first length to windowing with blocks of the second length, whereas a stop window sequence is selected for the opposite transition. The start window sequence is selected from at least two different start window sequences having different lengths, whereas the stop window sequence is selected from at least two different stop window sequences having different lengths. A method of decoding blocks of encoded audio signals selects a suitable inverse transformation as well as a suitable synthesis window as a reaction to side information associated with each block.

Method and apparatus for applying linear prediction to critical band subbands of split-band perceptual coding systems

Abstract: A split-band perceptual coding system utilizes generalized waveform predictive coding in frequency bands to further reduce coded signal information requirements. The system including frequency subband each having a bandwidth commensurate with or less than a corresponding critical band of human perception. The order of the predictors are selected to balance requirements for prediction accuracy and rapid response time. Predictive coding may be adaptively inhibited in a band during intervals in which no predictive coding gain is realized.

Decoder for compressed digital signals

Abstract: In an encoder for decoding compression data obtained by conducting a compression encoding for digital data through subband division, logarithmic compression, and variable-bit-length quantization, an exponent of an exponent operation is separated into an integer part and a fraction part to obtain an operation formula such that an operation related to the fraction part is executed through a multiplication and an operation associated with the integer part is accomplished through a shift operation. In addition, using a correlation between results of the calculations, the number of calculation steps is reduced. Moreover, one type of information data is written in an area in which another type of information data is beforehand written so as to minimize the necessary memory capacity.

Coding and decoding apparatus which transmits and receives tool information for constructing decoding scheme

Abstract: A coding and decoding apparatus is constructed so that the coding side transmits coded data together with identifying information for identifying the device of decoding the coded data, and the decoding side is capable of storing a number of decoding schemes so as to perform decoding based on one of the previously stored schemes. The apparatus further has devices for storing the received tools and tool-correspondent information which numerically represents the capacities of the tools so that it can make a comparison between the decoding capacity and the processing capacities of the tools to determine the possibility of the operations of the received tools. Further, a set of the tools are hierarchized so that the coded data produced by the n-ranked tool can be decoded by the (n+1)-ranked tool. Alternatively, the tools are defined in a hierarchical manner so that the decoding tools installed in the decoding apparatus will be able to assure the minimum quality and the requested decoding process can be performed by the received decoding tool. Further, the identification code of the decoding scheme used can be transmitted as required so that the decoding scheme can be expanded by transmitting the differential information from the basic decoding scheme.

Compatible audio system for special playback applications with surround system

Abstract: When an audio stream signal is transmitted, the bit stream information for determining the surround mode and special-use mode, including karaoke use, is sensed from the signal at a mode sensor (163). After the surround mode has been sensed, the audio data is converted by a decoder into a front left, front center, and front right main audio signals and a back left and back right surround audio signals in the surround mode, which are converted into analog signals and outputted to the corresponding speakers (8L, 8C, 8R, 8LS, 8RS). When the special-use mode has been sensed, by using the central main audio signal of the front left, front center, and front right main audio signals and back left and back right surround audio signals converted at the decoder, a normally used first-type accompanying sound selectively made unused, for example, guide melody, is generated. In addition, by using the back left and back right surround audio signals, a normally unused second-type accompanying sound selectively used, for example, vocals, is generated. The first- and second-type accompanying sounds, together with the front left and front right main audio signals, are reproduced selectively. Consequently, a system that transmits surround sound using a plurality of channels can maintain compatibility with a surround system easily, when the plurality of channels are applied to special use, such as karaoke, not being restricted to surround use.

A method of coding and decoding audio signals

Abstract: A method of encoding time-discrete audio signals comprises the steps of weighting the time-discrete audio signal by means of window functions overlapping each other so as to form blocks, the window functions producing blocks of a first length for signals varying weakly with time and blocks of a second length for signals varying strongly with time. A start window sequence is selected for the transition from windowing with blocks of the first length to windowing with blocks of the second length, whereas a stop window sequence is selected for the opposite transition. The start window sequence is selected from at least two different start window sequences having different lengths, whereas the stop window sequence is selected from at least two different stop window sequences having different lengths. A method of decoding blocks of encoded audio signals selects a suitable inverse transformation as well as a suitable synthesis window as a reaction to side information associated with each block.

Transmission system with selection of coding and decoding algorithm

Abstract: An image data coding apparatus comprising: a motion compensator comprising at least two different motion compensating tools; a transformer; a quantizer comprising at least two different quantizing tools; an inverse quantizer comprising at least two different inverse quantizing tools; and an inverse transformer; wherein said image data coding apparatus transmitting (a) information indicating a motion compensating tool for performing motion compensation and (b) information indicating an inverse quantizing tool for inverse quantizing the coded image data.

Coding and decoding apparatus

Abstract: A coding and decoding apparatus is constructed so that the coding side transmits coded data together with identifying information for identifying the device of decoding the coded data, and the decoding side is capable of storing a number of decoding schemes so as to perform decoding based on one of the previously stored schemes. The apparatus further has devices for storing the received tools and tool-correspondent information which numerically represents the capacities of the tools so that it can make a comparison between the decoding capacity and the processing capacities of the tools to determine the possibility of the operations of the received tools. Further, a set of the tools are hierarchized so that the coded data produced by the n-ranked tool can be decoded by the (n+1)-ranked tool. Alternatively, the tools are defined in a hierarchical manner so that the decoding tools installed in the decoding apparatus will be able to assure the minimum quality and the requested decoding process can be performed by the received decoding tool. Further, the identification code of the decoding scheme used can be transmitted as required so that the decoding scheme can be expanded by transmitting the differential information from the basic decoding scheme.