29 releases
0.2.12alpha.0  Apr 7, 2023 

0.2.11alpha.0  Dec 19, 2022 
0.2.5alpha.0  Jun 21, 2022 
0.2.4alpha.0  Mar 14, 2022 
0.1.42alpha.0  Oct 27, 2021 
#379 in Audio
856 downloads per month
Used in 49 crates
(37 directly)
260KB
4K
SLoC
surgetables
SurgeTables: Waveshaping and Envelope Utilities for the Surge Synthesizer System
SurgeTables is a Rust crate that provides a variety of waveshaping, envelope, and sinc tables for the Surge Synthesizer System. It includes utilities for generating and accessing tables, as well as mathematical functions to support synthesis operations.
SurgeTables
SurgeTables is a collection of tables and utilities used in the Surge Synthesizer System, supporting various waveshaping, envelope, and sinc operations. The crate is divided into several subcomponents, each focusing on a specific aspect of sound synthesis.
SineTables
SineTables contains precomputed sine wave values
for efficient lookup during synthesis. These sine
wave values are stored in different formats, such
as f32
, f64
, and i16
.
WaveshapeTables
WaveshapeTables provides tables and utilities for
waveshaping synthesis. Waveshaping is a nonlinear
distortion technique used to modify the harmonic
content of a signal. It supports functions such as
lookup_waveshape
and lookup_waveshape_warp
for
accessing these tables and applying the desired
transformations.
GainTables
GainTables provides utilities for converting
between decibel (dB) and linear scales, as well as
functions for applying clipping and scaling to
audio signals. The db_to_linear
function, for
example, converts a decibel value to its
corresponding linear gain value:
linear_gain = 10^(dB/20)
EnvelopeTables
EnvelopeTables provides tables and functions for
handling the linear and lowpass filtered (LPF)
envelope rates in the synthesizer. The
envelope_rate_linear
and envelope_rate_lpf
functions provide utilities for controlling these
rates.
SincTables
SincTables contains tables and utilities for
windowed sinc functions, which are used for
resampling and other signal processing tasks. The
windowed_sinc
function generates a sinc function
windowed by a specified window function:
windowed_sinc(x) = sinc(x) * window_function(x)
where sinc(x) = sin(πx) / (πx)
for x ≠ 0
and
sinc(0) = 1
.
MaybeOwningTablesHandle and TablesHandle
These types provide a convenient way to handle and manage the lifetime of the tables created by the various subcomponents in the crate.
With SurgeTables, users can efficiently access and manipulate a variety of tables and mathematical functions to support the waveshaping, envelope, and sinc operations in the Surge Synthesizer System.
2> /file surgers/surgetables/src/envelope.rs
EnvelopeTables

What is this table used for?
The
EnvelopeTables
struct contains two tables:table_envrate_lpf
andtable_envrate_linear
. These tables are used for efficient lookup of envelope rates in the Surge Synthesizer System. The envelope rates determine how quickly an envelope progresses through its stages (attack, decay, sustain, release) and are crucial for shaping the amplitude and timbre of a synthesized sound. 
Which calculations are involved in the precomputation?
The precomputation involves the calculation of two tables:

table_envrate_lpf
: This table contains values related to the lowpass filtered (LPF) envelope rates. The precomputation involves an exponential decay calculation with a time constant based on the sample rate and a poweroftwo mapping. 
table_envrate_linear
: This table contains values related to the linear envelope rates. The precomputation involves a simple division by the time constant based on the sample rate and a poweroftwo mapping.


How much performance are we saving?
By precomputing these envelope rate values and storing them in tables, we save performance by avoiding the need to recalculate these values in realtime during the synthesis process. This can lead to significant performance improvements, especially when dealing with complex synthesizer patches and polyphony.

How can we improve this table?
Some possible improvements to the
EnvelopeTables
include:
Interpolation: The current implementation uses linear interpolation to access the table values. Other interpolation methods, such as cubic or spline interpolation, could provide more accurate results at the cost of additional complexity.

Adaptive table size: The current implementation uses a fixed table size of 512. Allowing for userdefined table sizes could enable users to balance memory usage and lookup accuracy based on their specific needs.

Alternative precomputation methods: Exploring different methods for generating the envelope rate values in the precomputation step could lead to more accurate or faster results. This may involve using different mathematical approximations or algorithms for the exponential decay and linear rate calculations.

3> /file surgers/surgetables/src/gain.rs
GainTables

What is this table used for?
The
GainTables
struct contains a table calledtable_db
, which is used for efficient conversion between decibel (dB) and linear scales. This is useful for operations involving gain, attenuation, or other processes where logarithmic scales are involved. The table also provides aclipscale
function to calculate the scaling factor depending on the filter subtype (Rough or Smooth). 
Which calculations are involved in the precomputation?
The precomputation involves the calculation of a single table:
table_db
: This table contains values for converting decibel values to linear gain values. The precomputation involves calculating the linear gain for a given dB value using the formula:linear_gain = 10^(0.05 * (dB  384))
.

How much performance are we saving?
By precomputing these decibeltolinear gain values and storing them in a table, we save performance by avoiding the need to recalculate these values in realtime during the synthesis process. This can lead to noticeable performance improvements, especially when processing audio signals that require frequent conversions between decibel and linear scales.

How can we improve this table?
Some possible improvements to the
GainTables
include:
Interpolation: The current implementation uses linear interpolation to access the table values. Other interpolation methods, such as cubic or spline interpolation, could provide more accurate results at the cost of additional complexity.

Adaptive table size: The current implementation uses a fixed table size of 512. Allowing for userdefined table sizes could enable users to balance memory usage and lookup accuracy based on their specific needs.

Additional gainrelated functions: Expanding the
GainTables
struct to include other gainrelated functions, such as lineartodecibel conversions or different types of gain scaling, could make the table more versatile and useful for a wider range of audio processing tasks.

4> /file surgers/surgetables/src/sinc.rs
SincTables

What is this table used for?
The
SincTables
struct contains three tables:table
,table_1x
, andtable_i16
. These tables store precomputed windowed sinc function values, which are commonly used in digital signal processing, particularly in interpolation and resampling tasks. By precomputing these values, theSincTables
can be used to perform efficient interpolation in realtime audio processing. 
Which calculations are involved in the precomputation?
The precomputation involves the calculation of three tables:

table
: This table stores windowed sinc function values for a specific cutoff frequencycutoff
. 
table_1x
: This table stores windowed sinc function values for a different cutoff frequencycutoff1x
. 
table_i16
: This table stores windowed sinc function values for another cutoff frequencycutoff_i16
, but in 16bit integer format.
The precomputation calculates the windowed sinc function values using the following steps:

Calculate the time
t
for each table entry using theget_table_t
function. 
Calculate the windowed sinc function value using the
windowed_sinc
function, which involves the product of a symmetric Blackman window and the sinc function with the given cutoff frequency. 
Store the calculated values in the respective tables.


How much performance are we saving?
By precomputing the windowed sinc function values and storing them in tables, the performance of realtime audio processing tasks, such as interpolation and resampling, can be significantly improved. This is because the computationally expensive sinc and Blackman window calculations are avoided during realtime processing, and the precomputed values can be quickly accessed from the tables.

How can we improve this table?
Some possible improvements to the
SincTables
include:
Adaptive table sizes: Allowing for userdefined table sizes could enable users to balance memory usage and lookup accuracy based on their specific needs.

Additional interpolation methods: Expanding the
SincTables
struct to include other interpolation methods could make the table more versatile and useful for a wider range of audio processing tasks. 
Optimizing sinc and window functions: The current implementation calculates the windowed sinc values using standard Blackman window and sinc functions. Optimized versions of these functions, such as those found in specialized libraries, could potentially improve the accuracy or performance of the tables.

5> /file surgers/surgetables/src/sine.rs
SineTables

What is this table used for?
The
SineTables
struct contains two tables:table_sin
andtable_sin_offset
. These tables store precomputed sine function values and their corresponding offsets. By precomputing these values, theSineTables
can be used to perform efficient trigonometric calculations, such as oscillations and frequency modulation, in realtime audio processing. 
Which calculations are involved in the precomputation?
The precomputation involves the calculation of two tables:

table_sin
: This table stores sine function values for angles between 0 and 2π, uniformly spaced with a step size of 2π /SIN_TABLE_SIZE_D
. 
table_sin_offset
: This table stores the difference between consecutive sine function values intable_sin
.
The precomputation calculates the sine function values and their offsets using the following steps:

Calculate the angle
t
for each table entry as 2π * (i /SIN_TABLE_SIZE_D
), where i is the index of the entry. 
Calculate the sine function value
sin(t)
and store it intable_sin
. 
Calculate the sine function value `sin(t
 2π / SIN_TABLE_SIZE_D)
and store the difference between this value and
sin(t)in
table_sin_offset`.
 2π / SIN_TABLE_SIZE_D)


How much performance are we saving?
By precomputing the sine function values and their offsets and storing them in tables, the performance of realtime audio processing tasks that involve trigonometric calculations can be significantly improved. This is because the computationally expensive sine calculations are avoided during realtime processing, and the precomputed values can be quickly accessed from the tables.

How can we improve this table?
Some possible improvements to the
SineTables
include:
Adaptive table sizes: Allowing for userdefined table sizes could enable users to balance memory usage and lookup accuracy based on their specific needs.

Additional trigonometric functions: Expanding the
SineTables
struct to include other trigonometric functions, such as cosine or tangent, could make the table more versatile and useful for a wider range of audio processing tasks. 
Optimizing sine function calculations: The current implementation calculates the sine values using the standard sine function. Optimized versions of these functions, such as those found in specialized libraries, could potentially improve the accuracy or performance of the tables.

6> /file surgers/surgetables/src/waveshape.rs
WaveshapeTables

What is this table used for?
The
WaveshapeTables
struct contains a table of precomputed waveshaping function values that can be used to quickly modify the shape of audio waveforms in realtime audio processing. By using these precomputed values, the performance of audio processing tasks involving waveshaping can be significantly improved. 
Which waveshaping functions are included?
The
WaveshapeTables
struct includes precomputed values for five different waveshaping functions:
wst_tanh
: Hyperbolic tangent function. 
wst_hard
: A hard clipping function, based on the fifth power of the absolute value of x, followed by a hyperbolic tangent and a power of 0.2. 
wst_asym
: An asymmetric waveshaping function using the "shafted_tanh" function, which is shifted by 0.5. 
wst_sine
: Sine function. 
wst_digi
: A digitalstyle waveshaping function using the hyperbolic tangent function with a different scaling factor.


How much performance are we saving?
By precomputing the waveshaping function values and storing them in tables, the performance of realtime audio processing tasks involving waveshaping can be significantly improved. This is because the computationally expensive waveshaping function calculations are avoided during realtime processing, and the precomputed values can be quickly accessed from the tables.

How can we improve this table?
Some possible improvements to the
WaveshapeTables
include:
Adaptive table sizes: Allowing for userdefined table sizes could enable users to balance memory usage and lookup accuracy based on their specific needs.

Additional waveshaping functions: Expanding the
WaveshapeTables
struct to include more waveshaping functions could make the table more versatile and useful for a wider range of audio processing tasks. 
Optimizing waveshaping function calculations: The current implementation calculates the waveshaping function values using standard functions. Optimized versions of these functions, such as those found in specialized libraries, could potentially improve the accuracy or performance of the tables.

Interpolation: Implementing interpolation between table entries could improve the accuracy of the waveshaping functions when using the lookup methods.

Dependencies
~11–21MB
~302K SLoC