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lmadf.jl
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lmadf.jl
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# Log Magnitude Approximation (LMA) digital filter
type LMABaseFilter <: Filter
order::Int
delay::Vector{Float64}
function LMABaseFilter(order::Int)
new(order, zeros(order+1))
end
end
function filt!(f::LMABaseFilter, x::Float64, coef::Vector{Float64},
m1::Int, m2::Int)
@assert length(coef) == f.order+1
@assert m1 >= 1
@assert m2 < length(coef)
d = delay(f)
for i=length(coef)-1:-1:2
@inbounds d[i] = d[i-1]
end
d[1] = x
result = 0.0
for i=m1+1:m2+1
@inbounds result += coef[i] * d[i-1]
end
result
end
# LMACascadeFilter represents a cascade filter which contains LMA base
# filters.
type LMACascadeFilter <: Filter
filters::Vector{LMABaseFilter}
padecoef::Vector{Float64}
delay::Vector{Float64}
function LMACascadeFilter(order::Int, pade::Int)
padecoef = Array(Float64, pade+1)
if pade == 4
padecoef = padecoef4th
elseif pade == 5
padecoef = padecoef5th
else
error("LMADF: Order of pade approximation 4 or 5 is only supported.")
end
filters = Array(LMABaseFilter, pade+1)
for i=1:length(filters)
filters[i] = LMABaseFilter(order)
end
new(filters, padecoef, zeros(pade+1))
end
end
padecoef(f::LMACascadeFilter) = f.padecoef
function filt!(f::LMACascadeFilter, x::Float64, coef::Vector{Float64},
m1::Int, m2::Int)
d = delay(f)
pade = padecoef(f)
result, feedback = 0.0, 0.0
for i=length(pade):-1:2
@inbounds d[i] = filt!(f.filters[i], d[i-1], coef, m1, m2)
@inbounds val = d[i] * pade[i]
if iseven(i)
feedback += val
else
feedback -= val
end
result += val
end
d[1] = feedback + x
result += d[1]
result
end
type LMADF <: MelGeneralizedCepstrumSynthesisFilter
filters::Vector{LMACascadeFilter}
function LMADF(order::Int; pade::Int=5)
filters = Array(LMACascadeFilter, 2)
filters[1] = LMACascadeFilter(order, pade)
filters[2] = LMACascadeFilter(order, pade)
new(filters)
end
end
first(f::LMADF) = f.filters[1]
last(f::LMADF) = f.filters[2]
allpass_alpha(f::LMADF) = 0.0
glog_gamma(f::LMADF) = 0.0
function filt!(f::LMADF, x::Float64, coef::Vector{Float64})
m = length(coef)-1
y = filt!(first(f), x, coef, 1, 1)
filt!(last(f), y, coef, 2, m)
end
function to_filtcoef(f::LMADF, c::SpectralParamState{LinearCepstrum})
copy(rawdata(c))
end