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dsp.jl
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dsp.jl
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# This file is a part of Julia. License is MIT: https://julialang.org/license
module DSP
import Base.trailingsize
export filt, filt!, deconv, conv, conv2, xcorr
_zerosi(b,a,T) = zeros(promote_type(eltype(b), eltype(a), T), max(length(a), length(b))-1)
"""
filt(b, a, x, [si])
Apply filter described by vectors `a` and `b` to vector `x`, with an optional initial filter
state vector `si` (defaults to zeros).
"""
function filt(b::Union{AbstractVector, Number}, a::Union{AbstractVector, Number},
x::AbstractArray{T}, si::AbstractArray{S} = _zerosi(b,a,T)) where {T,S}
filt!(Array{promote_type(eltype(b), eltype(a), T, S)}(size(x)), b, a, x, si)
end
# in-place filtering: returns results in the out argument, which may shadow x
# (and does so by default)
"""
filt!(out, b, a, x, [si])
Same as [`filt`](@ref) but writes the result into the `out` argument, which may
alias the input `x` to modify it in-place.
"""
function filt!(out::AbstractArray, b::Union{AbstractVector, Number}, a::Union{AbstractVector, Number},
x::AbstractArray{T}, si::AbstractArray{S,N} = _zerosi(b,a,T)) where {T,S,N}
isempty(b) && throw(ArgumentError("filter vector b must be non-empty"))
isempty(a) && throw(ArgumentError("filter vector a must be non-empty"))
a[1] == 0 && throw(ArgumentError("filter vector a[1] must be nonzero"))
if size(x) != size(out)
throw(ArgumentError("output size $(size(out)) must match input size $(size(x))"))
end
as = length(a)
bs = length(b)
sz = max(as, bs)
silen = sz - 1
ncols = trailingsize(x,2)
if size(si, 1) != silen
throw(ArgumentError("initial state vector si must have max(length(a),length(b))-1 rows"))
end
if N > 1 && trailingsize(si,2) != ncols
throw(ArgumentError("initial state vector si must be a vector or have the same number of columns as x"))
end
size(x,1) == 0 && return out
sz == 1 && return scale!(out, x, b[1]/a[1]) # Simple scaling without memory
# Filter coefficient normalization
if a[1] != 1
norml = a[1]
a ./= norml
b ./= norml
end
# Pad the coefficients with zeros if needed
bs<sz && (b = copy!(zeros(eltype(b), sz), b))
1<as<sz && (a = copy!(zeros(eltype(a), sz), a))
initial_si = si
for col = 1:ncols
# Reset the filter state
si = initial_si[:, N > 1 ? col : 1]
if as > 1
_filt_iir!(out, b, a, x, si, col)
else
_filt_fir!(out, b, x, si, col)
end
end
return out
end
function _filt_iir!(out, b, a, x, si, col)
silen = length(si)
@inbounds for i=1:size(x, 1)
xi = x[i,col]
val = si[1] + b[1]*xi
for j=1:(silen-1)
si[j] = si[j+1] + b[j+1]*xi - a[j+1]*val
end
si[silen] = b[silen+1]*xi - a[silen+1]*val
out[i,col] = val
end
end
function _filt_fir!(out, b, x, si, col)
silen = length(si)
@inbounds for i=1:size(x, 1)
xi = x[i,col]
val = si[1] + b[1]*xi
for j=1:(silen-1)
si[j] = si[j+1] + b[j+1]*xi
end
si[silen] = b[silen+1]*xi
out[i,col] = val
end
end
"""
deconv(b,a) -> c
Construct vector `c` such that `b = conv(a,c) + r`.
Equivalent to polynomial division.
"""
function deconv(b::StridedVector{T}, a::StridedVector{T}) where T
lb = size(b,1)
la = size(a,1)
if lb < la
return [zero(T)]
end
lx = lb-la+1
x = zeros(T, lx)
x[1] = 1
filt(b, a, x)
end
"""
conv(u,v)
Convolution of two vectors. Uses FFT algorithm.
"""
function conv(u::StridedVector{T}, v::StridedVector{T}) where T<:Base.LinAlg.BlasFloat
nu = length(u)
nv = length(v)
n = nu + nv - 1
np2 = n > 1024 ? nextprod([2,3,5], n) : nextpow2(n)
upad = [u; zeros(T, np2 - nu)]
vpad = [v; zeros(T, np2 - nv)]
if T <: Real
p = plan_rfft(upad)
y = irfft((p*upad).*(p*vpad), np2)
else
p = plan_fft!(upad)
y = ifft!((p*upad).*(p*vpad))
end
return y[1:n]
end
conv(u::StridedVector{T}, v::StridedVector{T}) where {T<:Integer} = round.(Int, conv(float(u), float(v)))
conv(u::StridedVector{<:Integer}, v::StridedVector{<:Base.LinAlg.BlasFloat}) = conv(float(u), v)
conv(u::StridedVector{<:Base.LinAlg.BlasFloat}, v::StridedVector{<:Integer}) = conv(u, float(v))
"""
conv2(u,v,A)
2-D convolution of the matrix `A` with the 2-D separable kernel generated by
the vectors `u` and `v`.
Uses 2-D FFT algorithm.
"""
function conv2(u::StridedVector{T}, v::StridedVector{T}, A::StridedMatrix{T}) where T
m = length(u)+size(A,1)-1
n = length(v)+size(A,2)-1
B = zeros(T, m, n)
B[1:size(A,1),1:size(A,2)] = A
u = fft([u;zeros(T,m-length(u))])
v = fft([v;zeros(T,n-length(v))])
C = ifft(fft(B) .* (u * v.'))
if T <: Real
return real(C)
end
return C
end
"""
conv2(B,A)
2-D convolution of the matrix `B` with the matrix `A`. Uses 2-D FFT algorithm.
"""
function conv2(A::StridedMatrix{T}, B::StridedMatrix{T}) where T
sa, sb = size(A), size(B)
At = zeros(T, sa[1]+sb[1]-1, sa[2]+sb[2]-1)
Bt = zeros(T, sa[1]+sb[1]-1, sa[2]+sb[2]-1)
At[1:sa[1], 1:sa[2]] = A
Bt[1:sb[1], 1:sb[2]] = B
p = plan_fft(At)
C = ifft((p*At).*(p*Bt))
if T <: Real
return real(C)
end
return C
end
conv2(A::StridedMatrix{T}, B::StridedMatrix{T}) where {T<:Integer} =
round.(Int, conv2(float(A), float(B)))
conv2(u::StridedVector{T}, v::StridedVector{T}, A::StridedMatrix{T}) where {T<:Integer} =
round.(Int, conv2(float(u), float(v), float(A)))
"""
xcorr(u,v)
Compute the cross-correlation of two vectors.
"""
function xcorr(u, v)
su = size(u,1); sv = size(v,1)
if su < sv
u = [u;zeros(eltype(u),sv-su)]
elseif sv < su
v = [v;zeros(eltype(v),su-sv)]
end
flipdim(conv(flipdim(u, 1), v), 1)
end
end # module