Claims
- 1. An envelope generating apparatus for an electronic musical instrument, comprising:
- envelope extracting means for extracting an envelope waveform defined by a plurality of envelope data, including:
- dividing means for dividing sampled waveform data into a plurality of segmental waveform data, each of which has a predetermined time period, and
- extracting means for extracting a plurality of envelope data from the sampled waveform data for each of the predetermined time periods, in accordance with a characteristic of a waveform defined by the segmental waveform data obtained by said dividing means; and
- envelope approximating means for approximating the envelope waveform defined by the plurality of envelope data extracted by said extracting means, including means for generating a limited number of function waveforms having characteristics that change at determined switching points, and means for determining said switching points so as to minimize error between an approximated envelope waveform produced from the limited number of function waveforms by said generating means, and the envelope waveform defined by said plurality of envelope data.
- 2. The apparatus according to claim 1, in which said envelope extracting means includes means for using the fundamental period of the waveform expressed by said sampled waveform data, for said predetermined time period.
- 3. The apparatus according to claim 2, in which said envelope extracting means includes means for extracting the envelope data in accordance with the maximum value of the segmental waveform data contained in each of said predetermined time periods.
- 4. The apparatus according to claim 1, in which said envelope extracting means includes means for obtaining maximum and minimum values of the sampled waveform data contained in each of said predetermined time periods, and determining means for determining the envelope data inherent in each predetermined time period on the basis of the maximum and minimum data as obtained for each predetermined time period.
- 5. The apparatus according to claim 4, in which said envelope extracting means includes means for using the fundamental period of the waveform expressed by said sampled waveform data, for said predetermined time period.
- 6. The apparatus according to claim 1, in which said envelope extracting means includes means for computing the waveform area of the sampled waveform data contained in each of said predetermined time periods, and determining means for determining the envelope data inherent in each predetermined time period on the basis of the waveform area computed for each predetermined time period.
- 7. The apparatus according to claim 6, in which said envelope extracting means includes means for using the fundamental period of the waveform expressed by said sampled waveform data, for said predetermined time period.
- 8. The apparatus according to claim 1, in which said envelope extracting means includes means for computing the square sum of the sampled waveform data contained in each of said predetermined time periods, and determining means for determining the envelope data inherent in each predetermined time period on the basis of the square sum computed for each predetermined time period.
- 9. The apparatus according to claim 8, in which said envelope extracting means includes means for using the fundamental period of the waveform expressed by said sampled waveform data, for said predetermined time period.
- 10. The apparatus according to claim 1, in which said envelope approximating means includes function data generating means for generating function data, computing means for computing an evaluation value of an error between said function data and the envelope data, and switching point determining means for determining a switching point to optimize said evaluation value.
- 11. The apparatus according to claim 10, in which said function data generating means uses at least one of linear, exponential, triangle and logarithmic function
- 12. The apparatus according to claim 1, in which said envelope approximating means includes linear data generating means for generating linear data, computing means for computing the total sum of the errors between the linear data from said linear data generating means and the envelope data, and switching point determining means for determining a switching point to substantially minimize the total sum of said errors.
- 13. The apparatus according to claim 1, in which said envelope approximating means includes linear data generating means for generating linear data, computing means for computing the square sum of the errors between the linear data from said linear data generating means and the envelope data, and switching point determining means for determining a switching point to substantially minimize the square sum of said errors.
- 14. The apparatus according to claim 1, in which said envelope approximating means includes exponential curve data generating means for generating exponential curve data, computing means for computing the total sum of the errors between the exponential curve data from said exponential curve data generating means and the envelope data, and switching point determining means for determining a switching point to substantially minimize the total sum of said errors.
- 15. The apparatus according to claim 1, in which said envelope approximating means includes exponential curve data generating means for generating exponential curve data, computing means for computing the square sum of the errors between the exponential curve data from said exponential curve data generating means and the envelope data, and switching point determining means for determining as switching point to substantially minimize the square sum of said errors.
- 16. The apparatus according to claim 1, in which said envelope approximating means includes linear data generating means for generating linear data connecting two points, computing means for computing a maximum distance between said linear data and the envelope data, and switching point determining means for determining a switching point on the basis of said maximum distance.
- 17. The apparatus according to claim 1, in which said envelope approximating means includes exponential curve data generating means for generating exponential curve data connecting two points, computing means for computing a maximum distance between said exponential curve data and the envelope data, and switching point determining means for determining a switching point on the basis of said maximum distance.
- 18. An envelope approximating apparatus which approximates an envelope waveform described by envelope data, in the form of a limited number of function waveforms whose characteristic changes at switching points, said apparatus comprising:
- function data generating means for generating function data corresponding to said limited number of function waveforms;
- computing means coupled to said function data generating means for computing an evaluation value corresponding to an error between said function data and the envelope data representative of said envelope waveforms and
- switching point deciding means coupled to said computing means for deciding a switching point to be provided between successive ones of the limited number of function waveforms, for optimizing said evaluation value in accordance with the limited number of function waveforms.
- 19. The apparatus according to claim 18, in which said function data generating means includes linear data generating means for generating linear data, said computing means includes means for computing errors between said linear data and the envelope data, and said switching point determining means includes means for determining a switching point to substantially minimizing the total sum of said errors.
- 20. The apparatus according to claim 1, in which said function data generating means includes linear data generating means for generating linear data, said computing means includes means for computing the square sum of errors between said linear data and the envelope data, and said switching point determining means includes means for determining a switching point to substantially minimizing the square sum of said errors.
- 21. The apparatus according to 18, in which said function data generating means includes exponential curve data generating means for generating exponential curve data, said computing means includes means for computing the total sum of errors between said exponential curve data and the envelope data, and said switching point determining means includes means for determining a switching point to substantially minimizing the total sum of said errors.
- 22. The apparatus according to claim 18, which said function data generating means includes exponential curve data generating means for generating exponential curve data, said computing means includes means for computing the square sum of errors between said exponential curve data and the envelope data, and said switching point determining means includes means for determining a switching point to substantially minimizing the square sum of said errors.
- 23. The apparatus according to claim 18, in which said function data generating means includes linear data generating means for generating linear data connecting two points, said computing means includes means for computing a maximum distance between said linear data and the envelope data, and said switching point determining means includes means for determining a switching point on the basis of said maximum distance.
- 24. The apparatus according to claim 18, in which said function data generating means includes exponential curve data generating means for generating exponential curve data connecting two points, said computing means includes means for computing a maximum distance between said exponential curve data and the envelope data, and said switching point determining means includes means for determining a switching point on the basis of said maximum distance.
Priority Claims (4)
Number |
Date |
Country |
Kind |
61-264205 |
Nov 1986 |
JPX |
|
61-264206 |
Nov 1986 |
JPX |
|
61-264207 |
Nov 1986 |
JPX |
|
61-170531[U]JPX |
Nov 1986 |
JPX |
|
Parent Case Info
This application is a continuation of application Ser. No. 117,082, filed Nov. 3, 1987, and now abandoned.
US Referenced Citations (11)
Continuations (1)
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Number |
Date |
Country |
Parent |
117082 |
Nov 1987 |
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