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# -*- coding: utf-8 -*-
# ######### COPYRIGHT #########
# Credits
# #######
#
# Copyright(c) 2015-2025
# ----------------------
#
# * `LabEx Archimède <http://labex-archimede.univ-amu.fr/>`_
# * `Laboratoire d'Informatique Fondamentale <http://www.lif.univ-mrs.fr/>`_
# (now `Laboratoire d'Informatique et Systèmes <http://www.lis-lab.fr/>`_)
# * `Institut de Mathématiques de Marseille <http://www.i2m.univ-amu.fr/>`_
# * `Université d'Aix-Marseille <http://www.univ-amu.fr/>`_
#
# This software is a port from LTFAT 2.1.0 :
# Copyright (C) 2005-2025 Peter L. Soendergaard <peter@sonderport.dk>.
#
# Contributors
# ------------
#
# * Denis Arrivault <contact.dev_AT_lis-lab.fr>
# * Florent Jaillet <contact.dev_AT_lis-lab.fr>
#
# Description
# -----------
#
# ltfatpy is a partial Python port of the
# `Large Time/Frequency Analysis Toolbox <http://ltfat.sourceforge.net/>`_,
# a MATLAB®/Octave toolbox for working with time-frequency analysis and
# synthesis.
#
# Version
# -------
#
# * ltfatpy version = 1.1.2
# * LTFAT version = 2.1.0
#
# Licence
# -------
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# ######### COPYRIGHT #########
"""Module of idgt calculation
Ported from ltfat_2.1.0/gabor/idgt.m
.. moduleauthor:: Denis Arrivault
"""
import numpy as np
from ltfatpy.gabor.dgtlength import dgtlength
from ltfatpy.gabor.gabwin import gabwin
from ltfatpy.comp.comp_isepdgt import comp_isepdgt
from ltfatpy.tools.postpad import postpad
from ltfatpy.comp.comp_sigreshape_post import comp_sigreshape_post
def idgt(coef, g, a, Ls=None, pt='freqinv'):
r"""Inverse discrete Gabor transform
- Usage:
| ``(f, g) = idgt(c, g, a)``
| ``(f, g) = idgt(c, g, a, Ls)``
| ``(f, g) = idgt(c, g, a, Ls, pt)``
- Input parameters:
:param numpy.ndarray c: Array of coefficients
:param g: Window function
:param int a: Length of time shift
:param int Ls: Length of signal
:param str pt: 'freqinv' or 'timeinv'. Default is 'freqinv'.
:type g: str, dict or numpy.ndarray
- Output parameters:
:return: Signal (dtype = complex128)
:rtype: numpy.ndarray
``idgt(c, g, a)`` computes the Gabor expansion of the input coefficients
**c** with respect to the window **g** and time shift **a**. The number of
channels is deduced from the size of the coefficients **c**.
``idgt(c, g, a, Ls)`` does as above but cuts or extends **f** to length
**Ls**.
``(f, g)=idgt(...)`` additionally outputs the window used in the
transform. This is useful if the window was generated from a description
in a string or cell array.
For perfect reconstruction, the window used must be a dual window of the
one used to generate the coefficients.
The window **g** may be a vector of numerical values, a text string or a
cell array. See the help of :func:`~ltfatpy.gabor.gabwin` for more details.
If **g** is a row vector, then the output will also be a row vector. If
**c** is 3-dimensional, then ``idgt`` will return a matrix consisting of
one column vector for each of the TF-planes in **c**.
Assume that ``f=idgt(c, g, a, L)`` for an array **c** of size
:math:`M \\times N`. Then the following holds for :math:`k=0,\\ldots,L-1`:
.. math::
f(l+1) = \\sum_{n=0}^{N-1}\\sum_{m=0}^{M-1}c(m+1,n+1)e^{2\\pi iml/M}
g(l-an+1)
- Additional parameters:
``idgt`` takes the following keyword at the end of the line of input
arguments:
pt='freqinv'
Compute a DGT using a frequency-invariant phase. This
is the default convention described above.
pt='timeinv'
Compute a DGT using a time-invariant phase. This
convention is typically used in FIR-filter algorithms.
- Examples:
The following example demonstrates the basic principles for getting
perfect reconstruction (short version)::
>>> from ltfatpy import greasy
>>> from ltfatpy import dgt
>>> f = greasy()[0] # Input test signal
>>> a = 32 # time shift
>>> M = 64 # frequency shift
>>> gs = {'name': 'blackman', 'M': 128} # synthesis window
>>> # analysis window
>>> ga = {'name' : ('dual', gs['name']), 'M' : 128}
>>> (c, Ls) = dgt(f, ga, a, M)[0:2] # analysis
>>> # ... do interesting stuff to c at this point ...
>>> r = idgt(c, gs, a, Ls)[0] # synthesis
>>> np.linalg.norm(f-r) < 1e-10 # test
True
.. seealso:: :func:`~ltfatpy.gabor.dgt.dgt`,
:func:`~ltfatpy.gabor.gabwin.gabwin`, :func:`dwilt`,
:func:`~ltfatpy.gabor.gabtight.gabtight`
"""
if (not isinstance(g, np.ndarray) and not isinstance(g, str) and
not isinstance(g, dict)):
raise TypeError('g must be a numpy.array or str or dict.')
if (isinstance(g, np.ndarray) and g.size < 2):
raise ValueError('g must be a vector (you probably forgot to supply' +
' the window function as input parameter.)')
# Define initial value for flags and key/value pairs.
if coef.ndim < 2:
raise ValueError('coef must have at least 2 dimensions')
M = coef.shape[0]
N = coef.shape[1]
if coef.ndim > 2:
W = coef.shape[2]
else:
W = 1
if not isinstance(a, int):
raise TypeError('a must be an integer')
L = N * a
Ltest = dgtlength(L, a, M)
if Ltest != L:
ValueError('Incorrect size of coefficient array or "a" parameter. ' +
' See the help of DGTLENGTH for the requirements.')
# verify pt
if pt == 'timeinv':
pt = 1
elif pt == 'freqinv':
pt = 0
else:
mes = "pt (" + str(pt) + ") argument should be 'timeinv' or 'freqinv'."
raise ValueError(mes)
# Determine the window
gnum = gabwin(g, a, M, L)[0]
f = comp_isepdgt(coef, gnum, a, pt)
# Cut or extend f to the correct length, if desired.
if Ls is not None:
f = postpad(f, Ls)
else:
Ls = L
f = comp_sigreshape_post(f, Ls, 0, (0, W))
return (f, gnum)
if __name__ == '__main__': # pragma: no cover
import doctest
doctest.testmod()
|
