Abstract: A system is provided including a host processor and an audio capture and playback adapter having a DSP co-processor. The adapter includes shared memory accessible from both the DSP and the host. A DSP program is periodically written to the shared memory by the host and executed by the DSP. A non ping-pong dual buffer technique is disclosed wherein alternately one buffer is executed by the DSP while the remaining buffer is updated or linked by the host. In one embodiment, two pointer variables are used, each indicating respectively which buffer is currently being executed by the DSP and which has been updated by the host. Initially both pointer A and pointer B point to buffer A containing the initial DSP code. Each time the DSP requires execution of the configurable program, it reads pointer B, copies it to pointer A, and then branches to the buffer pointer A points to.

Abstract: A system and method are provided for improving quality of sound generated by computerized systems having limited memory. A wavetable synthesizer is implemented wherein data utilized to synthetically generate acoustic waveforms is stored. A plurality of datasets is also generated and stored, each comprised of a digitized acoustic waveform. In response to a MIDI datastream, the system determines if an appropriate stored acoustic sample corresponding thereto resides in the system's memory. If so, the system will generate the desired sound utilizing the stored acoustic sample data. If not, the system automatically determines in real time the appropriate wavetable dataset which will generate a sound most closely approximating the acoustic sound. The system thus dynamically reconfigures in real time between wavetable and acoustic sample synthesis, being configured for the former when appropriate acoustic samples are not present.

Abstract: A centralized digital signal processor resource manager acquires through software techniques, configuration and related data for multimedia hardware devices from BIOS device drivers interposed to functionally insulate the resource manager from hardware device specific information. The resource manager manages hardware devices in a multiple DSP environment using a unique software based hardware device identification scheme to identify and manage the location and availability of each hardware device.

Abstract: An extended selection field for use in selecting one or more choices from a list on an information system display. The extended selection field exhibits the behavior and appearance of a standard single choice field, with the additional capability to switch into a multiple choice mode to override the single choice restriction. A single choice is selected using the standard technique of moving the selection bar to the desired choice and pressing the Enter key. However, the single choice restriction may be overridden by using the standard multiple choice selection technique of moving the selection bar to a first desired choice and pressing (instead of the Enter key) a choice selection key such as the space bar. The field then exhibits the behavior and appearance of a standard multiple choice field. The single choice selection bar immediately changes to a multiple choice indicator and the operator receives immediate visual feedback that the system is enabled to accept multiple choices.

Abstract: A method and apparatus are disclosed for the audio editing of MIDI (Musical Instrument Digital Interface) files. MIDI files make it possible to exchange information such as: musical notes, program changes, expression control and channel information between musical instruments, sequencers, computers, lighting controllers and mixers. MIDI files generally consist of serially listed channel and system messages which include at least program status messages and matching note on and note off messages. The method and apparatus of the present invention may be utilized to ensure the integrity of a source file, a copied or lifted section or a target file by automatically inserting matching note on or note off messages into a file or file section to correct inconsistencies created by such editing.

Abstract: Variable frequency sawtooth waveforms are often utilized as an excitation signal in a digital musical synthesizer. A problem exists at lower sampling rates in such systems due to an aliasing problem which occurs at frequencies near the Nyquist rate. Low pass filtering may be utilized to mask this problem; however, low pass filtering is very time consuming to implement in a ditigal signal processor. The method and apparatus of the present invention reduces the upper harmonic content of a sawtooth waveform by proportionally converting the sawtooth waveform to a triangle waveform in response to variations in the frequency of the sawtooth waveform. This is accomplished by adding a selectable offset to the sawtooth waveform and then taking the absolute value of the resultant waveform. By restoring this waveform to a zero offset, the sawtooth waveform excitation signal will be converted to a triangle waveform having a substantially reduced upper harmonic content.

Abstract: A perspective view of a pointer icon is displayed such that toward the middle of the display frame the icon appears to point toward the display surface, rather than toward an edge of the display frame. This creates an illusion that the icon, such as an arrowhead, is reversing its direction smoothly in three dimensional space. Although the display screen is only a two dimensional surface, the multiple icons can readily be configured to be shown in perspective and, therefore, appear to be three dimensional, without the requirement for gray scale or half tone display technology. The invention is readily implemented with conventional monochromatic or color graphics hardware commonly available for personal computers.

Abstract: A system and method for translating MIDI files is used with a sequencer and synthesizer. When a MIDI file is imported into a system, the file is scanned and voice assignment information extracted. This information is stored in a converted file. If desired, the extracted information can be stored using MIDI system exclusives. This allows either any original program change information, or the extracted information, to be used during a performance of the converted MIDI file.

Abstract: A method and apparatus are disclosed for the dynamic control of a MIDI synthesizer filter. A digital filter controlled by a plurality of filter coefficients is preferably coupled to the output of an excitation signal source within a MIDI synthesizer. The excitation signal source is typically controlled by a MIDI data file comprising a sequential series of program control commands and matching note on and note off commands. A plurality of filter coefficient factors are stored in memory and periodically accessed in response to variations in the program control commands and matching note on and note off commands. The selected filter coefficient factors are then utilized to calculate appropriate filter coefficients so that the center frequency and filter Q of the digital filter may be dynamically and optimally controlled.

Abstract: A method and apparatus are disclosed for simultaneously outputting digital audio and MIDI synthesized music utilizing a single digital signal processor. The Musical Instrument Digital Interface (MIDI) permits music to be recorded and/or synthesized utilizing a data file containing multiple serially listed program status messages and matching note on and note off messages. In contrast, digital audio is generally merely compressed, utilizing a suitable data compression technique, and recorded. The audio content of such a digital recording may then be restored by decompressing the recorded data and converting that data utilizing a digital-to-analog convertor. The method and apparatus of the present invention selectively and alternatively couples portions of a compressed digital audio file and a MIDI file to a single digital signal processor which alternately decompresses the digital audio file and implements a MIDI synthesizer.

Abstract: A text compression method and apparatus are disclosed that enable overall compression ratios of more than six or eight to one for normal language text. Plural multiple-word dictionaries that are specialized for the particular field of use are employed together with a header transmission format that identifies which dictionaries are to be used. In addition, entries in these dictionaries are categorized by a weighted frequency of use ranking in which the product of the word length in characters and the frequency of occurrence of that word in the text is taken as the weighted figure of merit for ranking words to be placed in the individual dictionaries.