System and methods for memory-constrained sound synthesis using harmonic coding

• US 7,211,721 B2
• Filed: 10/13/2004
• Issued: 05/01/2007
• Est. Priority Date: 10/13/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Khawand, Jean, Boillot, Marc A., Frangopol, Radu C.
• Primary Examiner(s): FLETCHER, MARLON T
• Application Number:
  US10/964,385
• Publication Number:
  US 20060075880A1
• Time in Patent Office: 930 Days
• Field of Search: None
• US Class Current: 84/622
• CPC Class Codes: G10H 2250/031 Spectrum envelope processing
• CPC Class Codes: G10H 2250/485 Formant correction therefor
• CPC Class Codes: G10H 2250/571 Waveform compression, adapted for music synthesisers, sound banks or wavetables audio compression G10L19/00
• CPC Class Codes: G10H 7/105 using Fourier coefficients
• CPC Class Codes: G10L 19/093 using sinusoidal excitation models

Abstract

Systems (100 or 300) and methods (400 or 500) are provided for selecting a post-compression waveform from a post-compression waveform table (106) and supplying it to a synthesis engine (108). The post-compression waveform is based upon a set of post-compression coefficients determined by generating a frequency-domain representation of a periodic signal, the representation including at least one pre-compression frequency-domain sample (204), and performing a threshold-based compression of the pre-compression frequency-domain samples. Systems and methods also include indexing and storing (502) post-compression coefficients in a post-compression coefficient table (102), generating (506) a post-compression waveform based upon the set of post-compression coefficients, and placing (508) the post-compression waveform in the table prior to the selecting (510). The system and method also include performing (504) a read-ahead operation on a sound file before selecting the post-compression waveform, the read-ahead operation indicating the post-compression waveform to be selected and supplied to the synthesis engine.

Claims

1. A processor-based method of providing waveforms for use in synthesizing a sound signal with a sound synthesis engine based upon processing of a sound file, the method comprising:

performing a read-ahead operation on the sound file during the synthesizing of the sound signal;

identifying an instruction in the sound file for synthesizing a waveform of a musical instrument;

finding an index of the waveform in a waveform table used by the sound synthesis engine;

selecting a set of post-compression coefficients in a post-compression coefficient table corresponding to the index;

generating at least one post-compression waveform from the set of post-compression coefficients;

placing the at least one post-compression waveform at the index in the waveform table; and

supplying the at least one post-compression waveform to the sound synthesis engine in advance of the sound synthesis engine requesting the waveform;

wherein the at least one post-compression waveform is based upon the set of post-compression coefficients, the set of post-compression coefficients having been determined by

generating a frequency-domain representation of a periodic signal, the frequency-domain representation comprising at least one pre-compression frequency-domain sample, and

performing a threshold-based compression of pre-compression frequency-domain samples if the at least one pre-compression frequency-domain sample comprises a plurality of pre-compression frequency-domain samples.

2. The method of claim 1, further comprising:

indexing and storing each post-compression coefficient belonging to the set of post-compression coefficients in the post-compression coefficient table prior to synthesizing the sound signal; and

replacing the waveform table with the post-compression coefficient table prior to synthesizing the sound signal, wherein the sound synthesis engine indexes the at least one post-compression waveform in the post-compression coefficient table at a location corresponding to the index of the waveform in the waveform table.

3. The method of claim 1, wherein the frequency-domain representation is based upon a fast Fourier transform (FFT) of the periodic signal.

4. The method of claim 3, wherein the at least one waveform is based upon an inverse FFT using the set of post-compression coefficients.

5. The method of claim 1, wherein the sound file and the compression waveform table each conform to a Musical Instrument Digital Interface (MIDI) protocol.

6. The method of claim 1, wherein the frequency-domain representation of a periodic signal is based upon a waveform stored in a pre-compression waveform table.

7. The method of claim 1, wherein the frequency-domain representation of a periodic signal is based upon a waveform corresponding to an actual rendering of a pre-selected musical note by a pre-selected musical instrument.

8. A system for use in synthesizing a sound signal with a sound synthesis engine based upon processing of a sound file, the system comprising:

a post-compression coefficient table containing at least one set of post-compression coefficients representing a waveform in a waveform table, wherein an index of the waveform in the waveform table corresponds to the set of post-compression coefficients in the post-compression coefficient table; and

a waveform module for generating at least one post-compression waveform based upon the set of post-compression coefficients at the index in the post-compression coefficient table;

wherein each post-compression coefficient belonging to the set of post-compression coefficients has been determined by

generating a frequency-domain representation of a periodic signal, the frequency-domain representation comprising at least one frequency-domain sample, and

performing a threshold-based compression of frequency-domain samples if the at least one frequency-domain sample comprises a plurality of frequency-domain samples.

9. The system of claim 8, further comprising:

a sampling module for generating a set of pre-compression samples based upon the periodic signal; and

a compression module for generating the set of post-compression coefficients based upon the set of pre-compression samples.

10. The system of claim 8, further comprising a read-ahead module for performing a read-ahead operation on the sound file before selecting the at least one post-compression waveform, the read-ahead operation indicating the at least one post-compression waveform to be selected and supplied to the sound synthesis engine.

11. The system of claim 8, wherein the frequency-domain representation is based upon a fast Fourier transform (FFT) of the periodic signal.

12. The system of claim 11, wherein the at least one waveform is based upon an inverse FFT performed using the set of post-compression coefficients.

13. The system of claim 8, wherein the sound file and the compression waveform table each conform to a Musical Instrument Digital Interface (MIDI) protocol.

14. The system of claim 8, wherein the periodic signal is a replicate of a waveform stored in a pre-compression waveform table.

15. The system of claim 8, wherein the periodic signal is a replicate of a waveform based upon an actual rendering of a pre-selected musical note by a pre-selected musical instrument.

16. A computer-readable storage medium for use in synthesizing a sound signal with a sound synthesis engine in response to a processor processing a sound file, the storage medium comprising computer instructions for:

performing a read-ahead operation on the sound file during the synthesizing of the sound signal;

identifying an instruction in the sound file for synthesizing a waveform of a musical instrument;

finding an index of the waveform in a waveform table used by the sound synthesis engine;

selecting a set of post-compression coefficients in a post-compression coefficient table corresponding to the index;

generating at least one post-compression waveform from the set of post-compression coefficients;

placing the at least one post-compression waveform at the index in the waveform table; and

supplying the at least one post-compression waveform to the sound synthesis engine in advance of the sound synthesis engine requesting the waveform;

wherein the at least one post-compression waveform is based upon a set of post-compression coefficients, the set of post-compression coefficients having been determined by

generating a frequency-domain representation of a periodic signal, the frequency-domain representation based upon a fast Fourier transform (FFT) of the periodic signal and comprising at least one pre-compression frequency-domain sample, and

performing a threshold-based compression of pre-compression frequency-domain samples if the at least one pre-compression frequency-domain sample comprises a plurality of pre-compression frequency-domain samples.

17. The computer-readable storage medium of claim 16, further comprising computer instructions for:

indexing and storing each post-compression coefficient belonging to the set of post-compression coefficients in the post-compression coefficient table prior to synthesizing the sound signal; and

replacing the waveform table with the post-compression coefficient table prior to synthesizing the sound signal, wherein the sound synthesis engine indexes the at least one post-compression waveform in the post-compression coefficient table at a location corresponding to the index of the waveform in the waveform table.