公开(公告)号：DE69126655D1

公开(公告)日：1997-07-31

申请号：DE69126655

申请日：1991-10-23

Applicant: IBM

Inventor： LISLE RONALD J ,  MCDONALD B SCOTT ,  WILKES MICHAEL D

IPC: G10H1/00 ,  G10H7/00 ,  G10H1/26

Abstract: A method and apparatus are disclosed for simultaneously outputting digital audio and MIDI synthesised music utilising a single digital signal processor. The Musical Instrumert Digital Interface (MIDI) permits music to be recorded and/or synthesised utilising 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, utilising 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 utilising 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 synthesiser. Decompressed audio and MIDI synthesised music are then alternately coupled to two separate buffers. The contents of these buffers are then additively mixed and coupled through a digital-to-analog convertor to an audio output device to create an output having concurrent digital audio and MIDI synthesised music.

公开(公告)号：SK41393A3

公开(公告)日：1993-07-07

申请号：SK41393

申请日：1991-10-29

Applicant: IBM

Inventor： LISLE RONALD J

IPC: G06F3/05 ,  G06F5/16 ,  G06F9/38 ,  G06F9/445 ,  G06F15/16 ,  G06F15/177 ,  G10H7/00 ,  H03M11/00

Abstract: A system is provided including a host processor 22 and an audio capture and playback adapter 24 having a DSP co-processor 26. The adapter includes shared memory 28 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 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. When the host begins to relink to a buffer, it first sets pointer B equal to pointer A, relinks into the opposite buffer as pointer A, and then sets pointer B to this opposite buffer. The host is thereby prevented from updating a buffer currently being executed by the DSP. Real time dynamic linking of code segments in a tightly coupled co-processing system is thereby provided.

公开(公告)号：DE69127048T2

公开(公告)日：1998-02-12

申请号：DE69127048

申请日：1991-10-23

Applicant: IBM

Inventor： LISLE RONALD J ,  MOORE DANIEL J ,  PENN STEVEN C ,  WILKES MICHAEL D

IPC: G10H1/00 ,  G10H1/18

公开(公告)号：DE69127048D1

公开(公告)日：1997-09-04

申请号：DE69127048

申请日：1991-10-23

Applicant: IBM

Inventor： LISLE RONALD J ,  MOORE DANIEL J ,  PENN STEVEN C ,  WILKES MICHAEL D

IPC: G10H1/00 ,  G10H1/18

公开(公告)号：DE69126187D1

公开(公告)日：1997-06-26

申请号：DE69126187

申请日：1991-10-30

Applicant: IBM

Inventor： LISLE RONALD J ,  MCDONALD BRADLEY SCOTT

IPC: G10H1/00 ,  G10H1/053 ,  G10H1/12

Abstract: 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 utilised to calculate appropriate filter coefficients so that the centre frequency and filter Q of the digital filter may be dynamically and optimally controlled. In a preferred embodiment of the present invention a filter control circuit is also utilised to limit the output of the filter to a maximum level so that output stability is always maintained, independent of the initial conditions and filter coefficients of the filter.

公开(公告)号：GB2296123A

公开(公告)日：1996-06-19

申请号：GB9425091

申请日：1994-12-13

Applicant: IBM

Inventor： ASHOUR GAL ,  LISLE RONALD J ,  SHARIR NAFTALY

IPC: G10H1/00

Abstract: A MIDI playback system is described in which a sequencer is characterised by: logic for generating a sequence of events, the sequence comprising groups of events, each group comprising events to be executed within a first time interval, the groups being separated in the sequence by marker events for indicating the time intervals, the sequencer being arranged to send the sequence of events together to a synthesizer. A synthesizer is described comprising storage means to receive and store the sequences of events; logic for reading an event from the storage; and logic for determining if the event is a marker event, the synthesizer being arranged to wait, if the event is a marker event, a time equal to the first time interval before reading another event from storage. Using this arrangement, the sequencer is no longer required to schedule the MIDI commands precisely on time and therefore the timing services that a software implementation of such a sequencer might ask from a computer system are reduced.

公开(公告)号：CA2052770A1

公开(公告)日：1992-05-02

申请号：CA2052770

申请日：1991-10-04

Applicant: IBM

Inventor： LISLE RONALD J ,  MCDONALD B SCOTT

IPC: G10H1/043 ,  G10H1/057 ,  G10H1/06 ,  G10H1/14 ,  G10H5/10 ,  G10H5/12

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 digital 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. By varying the selectable offset in response to variations in the frequency of the sawtooth waveform, it is possible to efficiently vary the amount of conversion which occurs.

公开(公告)号：CA1290061C

公开(公告)日：1991-10-01

申请号：CA552058

申请日：1987-11-17

Applicant: IBM

Inventor： LISLE RONALD J ,  MOSS EUAL A ,  RYDER JOHN H

IPC: G06F5/00 ,  G06F17/22 ,  H03M7/30 ,  H03M7/42

Abstract: RA986014 TEXT COMPRESSION AND EXPANSION METHOD AND APPARATUS A text compression method and apparatus are disclosed that enable overall compression ratios of more than six or eight to one for normal language test. 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.