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WO1992015087A1 - Techniques de stockage de donnees musicales - Google Patents

Techniques de stockage de donnees musicales Download PDF

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Publication number
WO1992015087A1
WO1992015087A1 PCT/GB1992/000269 GB9200269W WO9215087A1 WO 1992015087 A1 WO1992015087 A1 WO 1992015087A1 GB 9200269 W GB9200269 W GB 9200269W WO 9215087 A1 WO9215087 A1 WO 9215087A1
Authority
WO
WIPO (PCT)
Prior art keywords
data
mass storage
fast
blocks
block
Prior art date
Application number
PCT/GB1992/000269
Other languages
English (en)
Inventor
Michael Joseph Kemp
Andrew Jeremy Bull
Original Assignee
Studio Audio & Video Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Studio Audio & Video Limited filed Critical Studio Audio & Video Limited
Publication of WO1992015087A1 publication Critical patent/WO1992015087A1/fr

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H7/00—Instruments in which the tones are synthesised from a data store, e.g. computer organs
    • G10H7/02—Instruments in which the tones are synthesised from a data store, e.g. computer organs in which amplitudes at successive sample points of a tone waveform are stored in one or more memories
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H2250/00—Aspects of algorithms or signal processing methods without intrinsic musical character, yet specifically adapted for or used in electrophonic musical processing
    • G10H2250/541—Details of musical waveform synthesis, i.e. audio waveshape processing from individual wavetable samples, independently of their origin or of the sound they represent
    • G10H2250/611—Waveform decimation, i.e. integer division of the sampling rate for reducing the number of samples in a discrete-time signal, e.g. by low-pass anti-alias filtering followed by the actual downsampling
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H2250/00—Aspects of algorithms or signal processing methods without intrinsic musical character, yet specifically adapted for or used in electrophonic musical processing
    • G10H2250/541—Details of musical waveform synthesis, i.e. audio waveshape processing from individual wavetable samples, independently of their origin or of the sound they represent
    • G10H2250/635—Waveform resolution or sound quality selection, e.g. selection of high or low sampling rates, lossless, lossy or lossier compression algorithms

Definitions

  • This invention relates to data storage techniques and in particular to a method and apparatus for substantially instantaneously reading at least- one of a plurality of data segments and to a method and apparatus for the simulation of fast playback of data.
  • Fig. 1 illustrates an example of this prior art in which a musical keyboard 1 is connected physically to a number of electrical contacts 2, 3, 4 one set of contacts per key. These contacts are arranged to select the appropriate addresses in addressing unit 5 to address the appropriate area of computer memory 12 in which different sound segments are stored, e.g. at location 6, 7, 8.
  • the addressing circuit once triggered, addresses sequential memory locations in order until the entire musical sound is read out of memory. These areas are indicated by areas 9, 10, 11 in the figure.
  • the data read out is fed to a digital to analogue converter 13 where it is converted to analogue form. This is amplified at 14 and heard via loudspeaker 15.
  • a digital to analogue converter 13 where it is converted to analogue form. This is amplified at 14 and heard via loudspeaker 15.
  • In practice is is arranged that several notes can be played simultaneously, or overlapping, by multiplexing data as it is read out of memory and forming the sum of samples of data from several musical segments before feeding them to the Digital to Analogue
  • a major limitation of existing devices is in the amount of random access memory required for complex effects. It is not unknown to require say 10 segments each of 20 seconds, or as many as 88 segments of 3 seconds each. Thus 200 seconds of digital storage is commonly required. This is doubled if all sounds are stored as stereo segments.
  • a 300M byte disc can store around one hour of audio and it is possible to play any section of this sound with only the delay in the disc locating to the right section, usually up to half a second.
  • Fig. 3 shows a typical prior art hard disc recording system.
  • the disc is full of blocks of data numbered for convenience which contain the sequential data representing an audio recording.
  • Blocks 51, 52, 53 are shown as a representation of these blocks on disc 120. (Note that these blocks can be distributed randomly over physical locations as long as there is a list retained, e.g. in control unit 102, and/or on disc, of where they all are in order to recreate the original order).
  • Sufficient RAM is provided to allow three blocks to be loaded from disc at any one time, shown at 109, 110, 111.
  • disc block 52 is currently being played from disc transfer area 110. While this is happening the control unit 102 requests that disc block 53 be transferred to area 111. This is complete by the time block 52 is finished and so playing can continue seamlessly into block 53. Control unit 102 then proceeds to load one of the now unused buffer areas 109 or 110 with disc block 54. For this sort of playing only two such buffers are needed, but three are often used for reasons outlined below.
  • control unit 102 When it is desired to slow down the playing speed like an analogue tape recorder being slowed down. (This might be desirable to locate an edit point for example) It is clearly only necessary to slow down the rate at which data is transferred out of the RAM, in other respects the operation performs exactly as before. If the system is then used to simulate tape running backwards it is necessary for control unit 102 to load the block of a lower number from disc so that when the recording reaches (running backwards) the start of a block, e.g. block 53 stored in disc transfer area 111, block 52 must be loaded into area 110 ready for a seamless transition in the backward direction. This process is eased by the use of three disc transfer areas as it cannot be known if the user will suddenly want to change direction. Therefore control unit 102 usually arranges for the next and the previous block to be ready on either side of the block being played so as to accommodate either possibility.
  • One preferred embodiment of the invention provides a method and apparatus for substantially instantaneously reading data segments stored at least partially on a mass storage device such as a hard disc.
  • a data segment to be read is selected and a first portion is located in RAM and read therefrom. Whilst this first portion is being read a second portion is located on the hard disc and subsequently read therefrom.
  • Another preferred embodiment of the present invention provides a method and apparatus for simulating the fast playback of recorded data and appropriate recording apparatus.
  • a mass storage device for the data is addressable in blocks and the data stream is recorded sequentially in these blocks.
  • Fig. 1 shows prior art relating to musical sampling
  • Fig. 2 shows one embodiment of the invention in which audio data is replayed partially from disc and partially from RAM;
  • Fig. 3 shows prior art relating to hard disc recording
  • Fig. 4 shows one embodiment of the recording process, according to the invention, in which data is stored on the disc, is schematically illustrated;
  • Fig. 5 shows the replay process appropriate to the embodiment of fig. 4
  • Fig. 6 shows a preferred embodiment of the invention in which appropriate low pass filtering and decimation are employed in the recording process to allow simulated fast wind replay;
  • Fig. 7 shows the replay process appropriate to the embodiment of fig.6
  • Fig. 8 shows the storage method according to the second method of fast replay simulation
  • Figure 9 shows a block diagram of a multi-track system embodying the invention.
  • this invention provides a new method by which these large amounts of RAM can be avoided, and in which an indefinite length of audio segment can be stored partially on disc and partially on a much more limited amoung of RAM required per individual sample.
  • Fig. 2 illustrates this first embodiment of the invention.
  • each desired sound segment is split into two sections.
  • the first section is stored in i.e. memory 12 so as to be instantly available, and the rest of the sound is stored on disc 21. This is true of all sounds which it is desired to have available instantly, thus the RAM 12 contains the first section of all desired sounds, rather than the entire segments as in the prior art.
  • the addressing is split into two sections, the RAM addressing 5 for controlling the i.e. RAM 12, and the disc addressing circuitry 20 which locates blocks of data stored in disc 21.
  • the play requests from the keyboard 1 are now fed to control circuitry 10 which for a given sound first selects the location of the start of the selected sound segment stored in RAM e.g. at 22. This is then read steadily out to a Digital to Analogue converter 13 so that the sound is instantly heard.
  • the control circuit 10 instructs disc addressing 20 to find the next section of the sound segment stored on disc 21, and instructs DMA (Direct Memory Access) controller 24 to transer data as it becomes available from disc 21 to a disc transfer area of the disc at 23.
  • DMA Direct Memory Access
  • the RAM addressing switches to the disc transfer area 23 to continue playing the sound, which continues without audio interruption. If the desired sound segment is longer than the amount transferred, the disc is instructed to load another block of data into RAM into a second disc transfer area (not shown) which is played out in turn. If yet more blocks of data are required, the first disc transfer area 23 can be used again. In this way sound segments up to the limit of the size of disc 21 can be played out with the instant start provided by having the first section in RAM.
  • control circuit 10 keep track of a number of sections of sound on the disc, and to load these in the above way into a number of disc transfer areas.
  • a typical Winchester disc can easily play four sound segments simultaneously, and can be prepared to have its data loaded within half a second from request. The first half second of each sound which might be required must therefore be stored in RAM.
  • this invention removes the limitations on sound segment duration, as in the case above each sound could be 30 seconds long with no increase in RAM storage and reduction in number of simulataneous channels possible.
  • Data compression techniques may also be employed to reduce total storage required, with data decompression occuring prior to the digital to analogue converter, or on transfer of data from disc to RAM.
  • This technique would also be applicable to e.g. CD players where it is unknown which track the listener wishes to play, but it is desired to play a track instantly on selection.
  • a short section of each track is loaded into RAM immediiately following insertion of the disc.
  • the operator selects a track it is played instantly from RAM and the rest of the track is located on disc before that initial section is exhausted. This would be useful in radio stations where the half second typical delay of selecting a track would be avoided.
  • Fig. 4 shows an embodiment of the first method showing the recording process to be employed to achieve the desired arrangement of data on disc.
  • the organisation of blocks on disc is shown at 202.
  • Sound is recorded, e.g. from microphone 204 and is digitised in converter 203 and the resulting samples are fed to RAM 105.
  • it is stored first in area 109 under control of RAM addressing 103.
  • every 4th sample is also stored in the new disc transfer area 4, 112.
  • area 109 is full the area is transferred to disc (assume this is block 51).
  • data continues to be read into RAM 105 in area 110, and the process of storing every fourth sample in area 112 continues.
  • area 110 is full it is transferred to disc as block 52.
  • Incoming audio data is now stored in area 109.
  • area 112 is now also full. This is stored in an additional transfer to disc as 'fast block' 51 (it is convenient to use the numbers of the first of the four blokes which were used in compiling the fast block to provide a number for the fast block).
  • Fig. 5 shows the appropriate replay process applicable to this method.
  • the normal speed blocks are loaded in the normal way into the triple buffered area of RAM at 109, 110, 111.
  • Fast blocks are similarly loaded at 1/4 of this rate into triple buffered areas 112, 113, 114, once again so that samples representing the time instant currently being replayued are held in RAM together with the blocks containing data on either side of this point.
  • the data in areas 112, 113 and 114 is ignored, and switch 145 is selected to the normal speed blocks in 109, 110,11.
  • the whole system speeds up again until when running at 16 times the speed the disc is again running at maximum data transfer speed.
  • the loading of normal speed data from the disc is stopped at the disc cannot transfer data at this speed.
  • the user slows down below 4 times speed these may be loaded again.
  • the user may be fed with silence, or preferably the user is fed with interpolated data from the fast blocks slowed down to the desired speed until the exact data from the normal blocks is again available.
  • the process may be arbitrarily continued. If just up to 16-times replay speed is desired it can beseen that 25% more disc storage is required than if this technique is not employed. If 64-times replay speed is require an additional 6% disc space is consumed, and in fact the process can be continued indefinitely as the sum of this series would require less than a further 6% disc space to be used to store an indefinite number of such fast blocks at 1/4, 1/16, 1/64 etc divisions of the original sampling rate.
  • Switch 145 is usually implemented in the addressing mechanism by selecting the different appropriate addresses to access the data from the common block of RAM 105 during read out of audio data.
  • decimation In practice the operation of using every fourth sample (known as decimation) is modified by known sample rate conversion techniques to avoid aliasing components being generated. See for example "The Art of Digital Audio” (John Watkinson, Focal Press, revised reprint 1989).
  • the operation is also usually modified slightly from that described in that during fast replay, although all the data from the disc is used, it is not clocked out to the digital to analogue converter at a faster rate.
  • Sample rate conversion techniques are used to reduce the sample rate to a fixed output rate.
  • additional samples are interpolated to allow for a fixed output rate. The above reference describes appropriate techniques.
  • a further improvement to this technique may be effected by realising that during fast replay it is no longer necessary to preserve the full audio bandwidth. If the bandwidth (of, for example, up to 20kHz) is preserved, as the sound is progressively sped up, the movement of sound up to the higher frequencies creates an unacceptable volume of higher frequency noise. This is improved while maintaining the desired audio cues to the user if an upper filter of 5kHz is employed. This means the the 'fast block' can have its sampling rate reduced by a further factor.
  • Fig 6 shows the recording process.
  • the audio data is built up in the 4th disc transfer area 112 by first filtering the data to l/16th of its original frequency range, e.g. by 1.25kHz low pass filter 140 (in systems where the full bandwidth is 20kHz, otherwise the appropriate low pass filter is used), then every sixteenth sample is taken in decimator 141, and transferred to disc for every 16 blocks of ordinary data.
  • Buffer 112 may be duplicated (113) for double buffering or following its being written to disc it may be refilled by initially using data stored at the normal rate in buffers 1 - 3 via filter and decimator until it has caught up with incoming data missed during the disc transfer.
  • Fig 7 shows the method for replaying data.
  • the normal replay data is loaded from disc into the triple buffered memory 109, 110, 111 so that one block is in memory on either side of the block currently being replayed.
  • the triple buffers 112, 113, 114 are loaded from the fast blocks once again so that one block on either side of the block containing data for the time currently being replayed is always available.
  • This loading requires 1/16 of the disc bandwidth so it is necessary to use a disc with a bandwidth capable of running at 4.25 times the audio bandwidth. This is normally still within normal disc technology. If not, it is possible to disallow this parallel loading of normal and fast blocks, instead switching from one to the other on demand. This leads to a pause as the user moves across the 4-times replay speed boundary, as it is necessary to wait for the 'fast data to be loaded from the disc).
  • the data from buffers 109, 110, 111 are selected via switch 145 to the variable filter and sample rate converter 146 (which at normal speed is set to pass the data unchanged to its output). Data is fed at a fixed sampling rate to digital to analogue converter 106 and/or an appropriate digital interface 143 to provide an industry standard data stream output.
  • the filter/sample rate converter 146 is adapted to discard excess samples according to known techniques and still provides a fixed data stream to the output. It is also preferably arranged to progressively filter the audio to a lower and lower cut off frequency as the speed increased, decreasing to a filter of 5kHz at 4 times speed. It is convenient to make this user selectable in case the user has an application, e.g. musical sampling, where he does not wish to limit the frequency range. As an additional preferred refinement some attenuation of the audio is performed progressively as the speed increases to further reduce unpleasant sound levels to the user.
  • switch 145 When the user-selected speed reaches 4 times faster than normal, switch 145 changes to select data coming from the fast blocks. Since this contains data at l/16th of the original sampling rate, and we desire to replay at 4 times the original sampling rate, it is necessary for filter/sample rate converter 146 to generate additional samples. This is done according to known techniques. Note that at four times speed the original frequency limitation to 1.25kHz means that audio will be heard up to 5kHz, which is acceptable. At this speed blocks are only required from disc at 1/4 the normal play rate. As in the previous embodiment loading of normal speed blocks is suspended while running at these speeds.
  • filter/sample rate converter 146 progressively adapting to produce a fixed output rate, and continuing to limit the actual replayed frequencies to 5kHz maximum. Finally at 64 times normal speed it is not possible to play the audio faster. This is normally an acceptable limit in audio applications as it represents an audio shift of 6 octaves and is is not usually necessary to provide audible cue replay at higher speeds.
  • a typical user interface would provide visual indication of position beyond this speed and the transition can be made inaudible by continuing the attenuation process described above to fade the audio to silence as 64 times speed is reached.
  • this method has an additional benefit (which still survives even if discs fast enough to provide 64 times play speed become commonly available) in that the filtering process on replay is relieved of the necessity of processing all the normal speed data in order to provide properly anti-aliased replay.
  • Such processing is a heavy load on the filter when data is arriving significantly faster than normal. Because the high speed data is pre-filtered during the recording process to l/16th the sampling rate (running at normal input speed), the maximum input data rate on replay is limited to four times normal speed even at extreme replay rates. This puts the necessary processing to implement the low pass filter into the range of moderate cost digital signal processing devices over the entire speed range.
  • Fig. 8 shows an embodiment of the invention relating to the recording process in which each disc transfer area 161, 162, 163 is increased to four times the size of a disc block.
  • Each of these areas is divided into the four constituent disc blocks, e.g. 161 is composed of blocks 170, 171, 172, 173.
  • the first sample of input audio data is to be stored in area 170.
  • a switch 180 is interposed in the audio data path and sends successive samples of data to successive block areas 170, 171, 172, 173 then again into area 170 and so on. In this way the first, fifth, ninth etc samples are stored in area 170.
  • each block 170, 171, 172, 173 are transferred to disc. This is shown schematically at the bottom of fig. 8 where these are shown as block 1, 2, 3, and 4, each of 16 samples. (In practice however blocks are usually several thousand samples in length). The samples are also numbered 1 to 64. It can be seen that block 1 contains samples 1, 5, 9, etc.
  • interleaving it is possible to use interleaving over eight blocks instead of four blocks as described above to achieve replay speeds up 32 times, or indeed interleaving over even more blocks.
  • more interleaving used more RAM is required for the additional buffers and more blocks are required to be loaded before normal speed replay can commence.
  • the interleaving described is easy to implement and effective.
  • One method is to interleave the normal speed blocks to allow the high speed blocks to be less frequent. For example if the basic embodiment of fig 4 as applied to the four way interleaving described above, since 16 times speed may be easily achieved, it is only necessary to store fast blocks containing every sixteenth sample, allowing replay speeds up to 64 times. The fast blocks may be further interleaved amongst themselves to allow replay speeds up to 256 times.
  • RAM and discs are described, these methods are applicable to any situation in which it is desired to use slower mass storage to reduce the need for fast instant access storage.
  • the method of using fast blocks of data to simulate fast playback can be combined with the instant access of the first embodiment described. This would enable a keyboard to be controlled to play different notes by selecting different playback speeds from a mass storage device.
  • a multitrack recording and playback system can be produced which incorporates the features of instant access and fast simulation of playback described above.
  • Such a system is illustrated in figure 9.
  • access to a plurality of discs 300 is controlled by a CPU 302 via a bus 304 and an audio processor 306.
  • Each audio processor in response to signals from the CPU can record and playback data in fast blocks on the associated disc 300.
  • each audio processor contains a RAM in which is stored a first portion of each data segment stored on the disc 300.
  • Each audio processor will typically be able to provide four inputs and outputs to a disc and thus if a total of eight discs and audio processors are provided a 32 track recording and playback system can be made. Other combinations are possible thus giving any desired number of tracks.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)

Abstract

Une multiplicité de segments de données, tels que des enregistrements sonores, sont stockés sur un dispositif de stockage (21) de grande capacité. Une première partie de chaque segment sonore est stockée dans une mémoire (12) à circuits intégrés de manière à être immédiatement disponible. Des circuits d'adressage (20, 5) sont prévus et peuvent être activés en réponse à des signaux provenant d'un dispositif de commande (10) afin de lire tout d'abord la partie d'un segment de données stockées dans la mémoire (12) à circuits intégrés, puis la partie se trouvant dans le dispositif de stockage (21) de grande capacité afin de permettre la lecture pratiquement simultanée de données. Il est souhaitable de simuler une lecture rapide de données, et, afin d'y parvenir, ces données sont enregistrées dans un dispositif de stockage (120) de grande capacité avec chaque nième échantillon du flux de données qui est aussi en train d'être enregistré dans un bloc rapide (51). Alors que la vitesse de lecture désirée est augmentée, seules les données provenant du bloc rapide (51) sont relues.
PCT/GB1992/000269 1991-02-15 1992-02-14 Techniques de stockage de donnees musicales WO1992015087A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB919103239A GB9103239D0 (en) 1991-02-15 1991-02-15 Improvements relating to data storage techniques
GB9103239.1 1991-02-15

Publications (1)

Publication Number Publication Date
WO1992015087A1 true WO1992015087A1 (fr) 1992-09-03

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WO (1) WO1992015087A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997008693A1 (fr) * 1995-08-30 1997-03-06 Philips Electronics N.V. Systeme de recherche documentaire disposant d'un stockage de donnees a acces sequentiel et d'une recherche de donnees a acces selectif
WO1997031363A1 (fr) * 1996-02-21 1997-08-28 Advanced Micro Devices, Inc. Systeme audio de micro-ordinateur a compensation en frequence des donnees de tableaux d'ondes
US5753841A (en) * 1995-08-17 1998-05-19 Advanced Micro Devices, Inc. PC audio system with wavetable cache
US5847304A (en) * 1995-08-17 1998-12-08 Advanced Micro Devices, Inc. PC audio system with frequency compensated wavetable data
WO1999001953A1 (fr) * 1997-07-02 1999-01-14 Creative Technology, Ltd. Boite a sons a decouplage d'execution des instructions et sequencement des donnees audio
WO1999065016A1 (fr) * 1998-06-10 1999-12-16 Conexant Systems, Inc. Systeme de synthetiseur utilisant des memoires de masse et destine a l'acces en temps reel a faible latence aux echantillons numeriques d'instruments de musique
US6047073A (en) * 1994-11-02 2000-04-04 Advanced Micro Devices, Inc. Digital wavetable audio synthesizer with delay-based effects processing
US6064743A (en) * 1994-11-02 2000-05-16 Advanced Micro Devices, Inc. Wavetable audio synthesizer with waveform volume control for eliminating zipper noise
US6246774B1 (en) 1994-11-02 2001-06-12 Advanced Micro Devices, Inc. Wavetable audio synthesizer with multiple volume components and two modes of stereo positioning

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7451281B2 (en) * 2003-06-05 2008-11-11 Hewlett-Packard Development Company, L.P. System and method for using swappable storage for storing program data

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Publication number Priority date Publication date Assignee Title
US4508001A (en) * 1983-07-29 1985-04-02 Nippon Gakki Seizo Kabushiki Kaisha Electronic musical instrument using large-capacity recording medium
EP0372678A2 (fr) * 1988-12-05 1990-06-13 Tsumura Mihoji Dispositif pour la reproduction de musique et l'affichage de mots

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JPS5151248A (en) * 1974-10-31 1976-05-06 Fujitsu Ltd Shingotensohoshiki

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4508001A (en) * 1983-07-29 1985-04-02 Nippon Gakki Seizo Kabushiki Kaisha Electronic musical instrument using large-capacity recording medium
EP0372678A2 (fr) * 1988-12-05 1990-06-13 Tsumura Mihoji Dispositif pour la reproduction de musique et l'affichage de mots

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6047073A (en) * 1994-11-02 2000-04-04 Advanced Micro Devices, Inc. Digital wavetable audio synthesizer with delay-based effects processing
US6064743A (en) * 1994-11-02 2000-05-16 Advanced Micro Devices, Inc. Wavetable audio synthesizer with waveform volume control for eliminating zipper noise
US6246774B1 (en) 1994-11-02 2001-06-12 Advanced Micro Devices, Inc. Wavetable audio synthesizer with multiple volume components and two modes of stereo positioning
US7088835B1 (en) 1994-11-02 2006-08-08 Legerity, Inc. Wavetable audio synthesizer with left offset, right offset and effects volume control
US5753841A (en) * 1995-08-17 1998-05-19 Advanced Micro Devices, Inc. PC audio system with wavetable cache
US5847304A (en) * 1995-08-17 1998-12-08 Advanced Micro Devices, Inc. PC audio system with frequency compensated wavetable data
WO1997008693A1 (fr) * 1995-08-30 1997-03-06 Philips Electronics N.V. Systeme de recherche documentaire disposant d'un stockage de donnees a acces sequentiel et d'une recherche de donnees a acces selectif
US5699547A (en) * 1995-08-30 1997-12-16 Philips Electronics North America Corporation Information retrieval system with serial access data storage and random access data retrieval
WO1997031363A1 (fr) * 1996-02-21 1997-08-28 Advanced Micro Devices, Inc. Systeme audio de micro-ordinateur a compensation en frequence des donnees de tableaux d'ondes
WO1999001953A1 (fr) * 1997-07-02 1999-01-14 Creative Technology, Ltd. Boite a sons a decouplage d'execution des instructions et sequencement des donnees audio
WO1999065016A1 (fr) * 1998-06-10 1999-12-16 Conexant Systems, Inc. Systeme de synthetiseur utilisant des memoires de masse et destine a l'acces en temps reel a faible latence aux echantillons numeriques d'instruments de musique

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GB9103239D0 (en) 1991-04-03
GB2253726A (en) 1992-09-16
GB9203133D0 (en) 1992-04-01

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