WaveTableOscillator

Overview

Wave table based oscillator

Discussion

Wave table function generator with input pins to control frequency and phase of the generated wave form. The module can generate sine, square, triangle, sawtooth and custom definable waves via table readout.

The output is, e.g. for a sine: $y[n] = \sin (omega_o nT + \sum_{k=0}^n x[k] + \phi)$ where $\omega_o$ is the nominal frequency in radians/s, T is the sample period and $\phi$ is phase in radians (default is 0).

Type Definition

CODE

typedef struct _ModuleWaveTableOscillator
{
    ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
    INT32 smoothingTime;                          // Time constant of the pitch smoothing process
    INT32 smoothingFactor;                        // Update rate for smoothing coeffs (per block)
    INT32 numOutPin;                              // Mono/Stereo
    INT32 tableSize;                              // Table size in samples
    INT32 fIndex;                                 // Current sample index in the wave table
    FLOAT32 currentFStep;                         // Current (smoothed) rate at which audio is read from the input buffer
    FLOAT32 phiIndex;                             // Current phi index in the wave table
    FLOAT32 currentPhiStep;                       // Current (smoothed) phi at which audio is read from the input buffer
    INT32 tableSize2;                             // Table size in samples
    INT32 NCOFracBits;                            // Number of least-significant bits for the *fractional* part of the NCO word (word size: 32)
    FLOAT32 smoothingCoeff;                       // Smoothing (pitch) coefficient
    FLOAT32 scaleFactorFRatio;                    // Scale factor for playback rate
    FLOAT32 scaleFactorPhi;                       // Scale factor for target phi
    INT32 NCOIntBits;                             // Number of most-significant bits for the *integer* part of the NCO word (word size: 32). By default: 20 bits
    FLOAT32 formatF;                              // Integer value of left-shift by NCOFracBits. Determines the precision of the linear interpolation.
    FLOAT32 formatI;                              // Integer value of left-shift by NCOIntBits. Determines the maximum playback rate and the maximum size of a wave file in samples.
    FLOAT32* table_coeffs;                        // Table coefficients
    INT32* table;                                 // Data transferred from PC to target DSP via this buffer.
    FLOAT32* table2_coeffs;                       // Table coefficients
    INT32* table2;                                // Data transferred from PC to target DSP via this buffer.
} ModuleWaveTableOscillatorClass;

Variables

Properties

Name	Type	Usage	isHidden	Default value	Range	Units
smoothingTime	int	parameter	0	10	1:1000	msec
smoothingFactor	int	parameter	0	4	1:512
numOutPin	int	const	0	2	Unrestricted
tableSize	int	const	0	1024	Unrestricted
fIndex	int	state	0	0	Unrestricted
currentFStep	float	state	0	1	Unrestricted
phiIndex	float	state	0	0	Unrestricted
currentPhiStep	float	state	0	0	Unrestricted
tableSize2	int	const	1	1024	Unrestricted
NCOFracBits	int	const	1	12	Unrestricted
smoothingCoeff	float	derived	1	0.1248	Unrestricted
scaleFactorFRatio	float	derived	1	0.02133	Unrestricted
scaleFactorPhi	float	derived	1	2.844	Unrestricted
NCOIntBits	int	derived	1	20	Unrestricted
formatF	float	derived	1	4096	Unrestricted
formatI	float	derived	1	524300	Unrestricted
table_coeffs	float*	parameter	0	[1024 x 1]	Unrestricted
table	int*	parameter	1	[514 x 1]	Unrestricted
table2_coeffs	float*	parameter	0	[1024 x 1]	Unrestricted
table2	int*	parameter	1	[514 x 1]	Unrestricted

Pins

Input Pins

Name: freq

Description: Control Input Frequency (Hz)

Data type: float

Channel range: 1

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Name: phase

Description: Control Input Phase (0..360°)

Data type: float

Channel range: 1

Block size range: Unrestricted

Sample rate range: Unrestricted

Complex support: Real

Output Pins

Name: out1

Description: Output audio data

Data type: float

Name: out2

Description: Output audio data

Data type: float

MATLAB Usage

File Name: wave_table_oscillator_module.m

CODE

 M=wave_table_oscillator_module(NAME, MODE, BLOCKSIZE, SAMPLERATE, WAVEFORM, WAVEFORM2, TABLESIZE)
 Creates a source module that reads wave samples from a wave file and outputs blocks of data.
 Arguments:
    NAME           - name of the module.
    MODE           - Mono or Stereo (two oscillators) output
                     By default, MODE = 1 (mono).
    BLOCKSIZE      - number of samples per output channel.  
                     By default, BLOCKSIZE = 256.
    SAMPLERATE     - sample rate of the output signal, in Hz.  
                     By default, SAMPLERATE = 48000.
    WAVEFORM       - Oscillator type
                     By default, WAVEFORM = 0 (sine).
    WAVEFORM2      - Oscillator type
                     By default, WAVEFORM = 0 (sine).
    TABLESIZE      - Number of samples in wave table
                     By default, TABLESIZE = 1024.
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 AudioWeaverModule [This tag makes it appear under awe_help]