Abstract: A decompression method uses four coefficient inverse perfect reconstruction digital filters. The coefficients of these inverse perfect reconstruction digital filters require a small number of additions to implement thereby enabling rapid decompression in software. The method partially inverse transforms a sub-band decomposition to generate a small low pass component image. This small image is expanded in one dimension by performing interpolation on the rows of the small image and is expanded in a second dimension by replicating rows of the interpolated small image. Transformed chrominance data values may be inverse transformed using inverse perfect reconstruction digital filters having a fewer number of coefficients than the inverse perfect reconstruction digital filters used to inverse transform the corresponding transformed luminance data values.

Abstract: An expansion card for a personal computer digitizes, optionally processes and/or compresses, stores, and then relays to the personal computer video information without the use of a frame store memory. An analog-to-digital converter on the expansion card digitizes at least part of a frame of an analog video signal received on a video connector of the expansion card. After optional processing and/or compressing of the digitized video information of the frame, part of the digitized video information is stored into a relatively small memory on the expansion card. Once stored, the digitized video information is transferred from the memory and to the personal computer over a parallel bus of the personal computer. Another part of the digitized video information of the frame is then stored into the same memory on the expansion card for subsequent transfer to the personal computer over the parallel bus.

Abstract: A compression and decompression method using a wavelet decomposition, frequency based tree encoding, tree based motion encoding, frequency weighted quantization, Huffman encoding, and tree based activity estimation for bit rate control. Forward and inverse quasi-perfect reconstruction transforms are used to generate the wavelet decomposition and to reconstruct data values close to the original data values. The forward and inverse quasi-perfect reconstruction transforms utilize special filters at the boundaries of the data being transformed and/or inverse transformed.

Abstract: A circuit is provided for filtering asynchronous metastability. The circuit includes two or more output lines that provide signals indicative of the assertion of control or data input signals at a plurality of input lines. Despite the simultaneous assertion of two or more input signals, the circuit prevents the simultaneous assertion of more than one output signal, thereby preventing adverse effects within a digital system connected to the circuit.

Abstract: The present invention provides a display subsystem which includes a frame buffer, a Digital to Analog Converter (DAC), a first color look up table and a second color look up table. The first color look up table is located in front of the frame buffer. The second color look up table is located between the frame buffer and the DAC. When the display subsystem receives a command that involves pixels from a Device Independent Bit Map (DIB) file, the translation table provided with the DIB is stored in the first color look up table. This translation table has a number of entries equal to the number of combinations available with the particular DIB format. For example, if the DIB has a one bit color format the first translation table has two entries one for each possible state of the color bits in the DIB. If the DIB uses a four bit color format the first table has sixteen entries, if the DIB uses an eight bit color format the table would have two hundred and fifty six entries, etc.

Abstract: Synthesizer models for emulating musical instruments are improved to take into account sympathetic string vibrations. One embodiment of the present invention scales an output signal from a sound synthesis model and uses the scaled signal as an input signal for a number of single-string emulations causing the single-string emulations to produce sound signals corresponding to sympathetic string vibrations. The output signals from the synthesis model and from all of the single-string emulations are added together. Another embodiment employs an octave's worth of single-string emulations to emulate the lower strings of an emulated instrument. Still another embodiment is a synthesizer which includes an input bus for accepting a sound signal, scaling means, a plurality of single-string emulations, and means for summing output signals from the string emulations. Embodiments preferably employ waveguide synthesis or the plucked string model to emulate single-strings.

Abstract: A timing generator contains an oscillator section (10) formed with a plural number of stages (S.sub.1 -S.sub.N) for respectively producing a like number of stage signals (V.sub.S1 -V.sub.SN) that sequentially change signal values at a basic oscillator frequency (f.sub.O). The oscillator section is typically implemented as a ring oscillator. In response to the stage signals, a timing-signal generating section (14) generates one or more timing signals (V.sub.T1 -V.sub.TM), each having at least two transitions corresponding to transitions of two or more of the stage signals. A control section (12), preferably arranged in a phase-locked loop, causes the oscillator frequency and a reference frequency (f.sub.R) to have a substantially fixed relationship.

Abstract: An audio power amplifier is provided that includes circuitry to prevent popping noises when the amplifier is turned on and turned off. The amplifier can be powered with a single-ended voltage power supply, and thus may be used within systems such as personal computer. The amplifier includes a control circuit that prevents the fast charging of the output AC coupling capacitor when the amplifier is turned on and turned off. The control circuit controls a driver stage such that the output transistors turn on slowly when power is first applied, and such that the output transistors turn off quickly when the supply voltage is removed.