Music – Instruments – Electrical musical tone generation
Reexamination Certificate
2000-07-07
2001-05-29
Witkowski, Stanley J. (Department: 2837)
Music
Instruments
Electrical musical tone generation
Reexamination Certificate
active
06239346
ABSTRACT:
This application is based on Japanese Patent Application HEI 11-194695, filed on Jul. 8, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a musical tone signal processing apparatus capable of generating an internal sync clock when an external sync clock becomes abnormal.
b) Description of the Related Art
Recent developments on networks allow a plurality of electronic musical instruments connected to networks to be played synchronously. As the standard specifications for communications between electronic musical instruments, Musical Instrument Digital Interface (MIDI) is known. Tempo clocks (F8) are used as timing signals for a synchronous performance between some of a plurality of electronic musical instruments or musical tone signal processing apparatuses connected to a network using MIDI. The tempo signal is converted into a MIDI signal and transmitted to other instruments or apparatuses via MIDI cables. Synchronously with this tempo clocks, the other instruments or apparatuses play a music performance.
Recent electronic musical instruments or musical tone signal processing apparatuses use high speed network connections such as USB and IEEE 1394 to realize faster synchronous performance. Synchronous performance is now possible not only at the level of simple automatic performance of MIDI signals but also at the level of reproduction timings of musical tone signal waveforms.
For synchronous performance at the level of timings of waveforms, a sync signal is generated from at least one of a plurality of electronic musical instruments or musical tone signal processing apparatuses connected to a high speed network using USB, IEEE 1394 or the like. This sync signal is very fast as compared to a MIDI signal. Therefore, this sync signal can be used not only for simple synchronous performance but also for timing clocks of a sound generator which reads waveforms.
Each of electronic musical instruments or musical tone signal processing apparatuses receives fast timing clocks from a high speed network, and performs a read operation, a reproduction operation or the like of waveform data synchronously with the received clocks.
More specifically, reproduction sampling clocks are generated in accordance with received sync data (such as a time stamp) and supplied to a sound generator (made of LSI or the like) as its clocks. In this manner, synchronous performance between instruments or apparatuses becomes possible at the level of read timings of waveform data.
Network troubles such as disconnection and transfer abnormality may occur during synchronous performance on the network interconnecting a plurality of electronic musical instruments or musical tone signal processing apparatuses. In such a case, data integrity or data transfer is not possible among some instruments or apparatuses. For example, if F8 does not reach unexpectedly during synchronous performance of MIDI data, each instrument or apparatus performs a dump process of the tone generator to effect an instant muting process.
It is therefore possible to prevent continuous reproduction of sounds or generation of abnormal noises to be caused upon occurrence of discontinuous phenomena.
In such a system in which sampling clocks are generated in accordance with sync data received from a high speed network and used as synchronizing clocks of a tone generator, however, if sampling clocks are suspended or become abnormal from some reasons, the tone generator itself cannot operate normally because of an abnormal state of its sampling clocks.
For example, even if the tone generator is instructed to execute the dump process, the muting process cannot be effected. Therefore, sounds continue to be reproduced or abnormal noises are generated.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a musical tone signal processing apparatus capable of dealing with abnormality of external sync clocks.
According to one aspect of the present invention, there is provided A musical tone signal processing apparatus which synchronizes a read timing of a reader unit for reading a musical tone signal from a memory at least temporarily storing the musical tone signal, the musical tone signal processing apparatus comprising: a master clock input unit for externally inputting a master clock information used for synchronizing the read timing of the musical tone signal; a first sync clock generator unit for generating a first sync clock used for synchronizing the read timing of the musical tone signal, in accordance with the master clock information externally input; a second sync clock generator unit for generating a second sync clock used for synchronizing the read timing of the musical tone signal, separately from the first sync clock; a detector unit for detecting an abnormality of an input state of the master clock information; and a sync clock switching unit for changing a sync clock used for reading the musical tone signal from the first sync clock to the second sync clock, when said detector unit detects the abnormality of the input state of the master clock information.
A circuit for generating a sampling sync signal from a network sync signal is provided with a signal generating circuit of an autonomous type for generating a signal corresponding to the sampling sync signal. Immediately after the external network signal becomes abnormal, the circuit is changed to the autonomous signal generating circuit so that reproduction sampling clocks can be supplied to a tone generator. It is therefore possible to prevent continuous reproduction of sounds or generation of abnormal noises which might be caused upon occurrence of network troubles.
A switch is provided at the front stage of a PLL circuit including a LPF. PLL can smooth an abrupt change in a clock when clocks are switched. Generation of abnormal noises or the like can therefore be prevented.
REFERENCES:
patent: 2000-78170A (2000-03-01), None
Goto Kazuhiro
Inagaki Yoshihiro
Morrison & Foerster
Witkowski Stanley J.
Yamaha Corporation
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