Browse Prior Art Database

Frequency Modulation Technique that Supports 12 Operators

IP.com Disclosure Number: IPCOM000115968D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Farrett, PW: AUTHOR

Abstract

Disclosed is a software approach for a Frequency Modulation (FM) technique for 12 operators (ops). At times, this is both robust as well as practical with respect to implementation concerning timbre (tone color of instrument). This technique is also scalable regarding CPU resources: 2 - 4 ops that consume low CPU bandwidth, but with lower timbre quality; 6 - 8 ops that consume medium CPU bandwidth, but with very rich timbre quality; 10 - 12 ops that consume large CPU bandwidth, but with still a richer timbre quality. This results in the following: Game OEM backward compatibility regarding OPL2*, OPL3*, and OPL4* music synthesizer chip-sets while a very large harmonic palette that would support OEM MIDI/Electronic music markets.

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Frequency Modulation Technique that Supports 12 Operators

      Disclosed is a software approach for a Frequency Modulation
(FM) technique for 12 operators (ops).  At times, this is both robust
as well as practical with respect to implementation concerning timbre
(tone color of instrument).  This technique is also scalable
regarding CPU resources: 2 - 4 ops that consume low CPU bandwidth,
but with lower timbre quality; 6 - 8 ops that consume medium CPU
bandwidth, but with very rich timbre quality; 10 - 12 ops that
consume large CPU bandwidth, but with still a richer timbre quality.
This results in the following: Game OEM backward compatibility
regarding OPL2*, OPL3*, and OPL4* music synthesizer chip-sets while a
very large harmonic palette that would support OEM MIDI/Electronic
music markets.

      General Description: Current FM synthesis techniques are,
today, applied to 2 main areas: Game OEM manufactures and MIDI
(music) electronic synthesizers.  The former generally use 2 FM
operators while the latter is reserved for music synthesizers, and
use 4 - 6 operators (e.g., Yamaha's DX7 line).  This technology
(patents) was the vanguard of many Yamaha products and, in fact, is
still being implemented today.  However, this technique is not based
on the FM synthesis theory in total, but rather a hybrid synthesis
that also includes other techniques integrated with FM synthesis.  In
addition, this FM-hybrid synthesis embodiment is hardware based and
not software based.  This disclosure addresses several problems to be
solved: 1) A much more robust system concerning timbre, which is
(partially) implemented via a 12-operator approach; 2) A system which
is predicated on FM synthesis theory directly (i.e., no hybrid
techniques are integrated); 3) A software-only approach not found in
the consumer market or literature.

      Description of Process: The algorithm, below, is an example of
the layering I used for a 12 operator design.  It consists of 2 by 2
operator design in that, at each layer, 2 more operators are added.
(Note that the meaning of a layer indicates the timbre that would be
generated; the more layers the richer the instrument's timbre.)  As
part of the technique (although not implemented here) operators would
be switched on and off depending on the amount of available CPU
overhead
as well as the timbre (generated from the operators) that is
required.

      Description of Algorithm:  An illustration of the above
mentioned technique is listed.  The pseudo-code is based on some of
the above concepts:
  /* 12 operators set to gener...