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23 on the fly angle #25

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merged 2 commits into from
Oct 31, 2023
Merged

23 on the fly angle #25

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76f7c8e
Ground filter IRs now calculated on-the-fly
marc1701 Oct 31, 2023
f3b484d
Combined spatialisation and filter stages.
marc1701 Oct 31, 2023
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107 changes: 46 additions & 61 deletions uasevent/environment_model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -125,10 +125,12 @@ def __init__(

# calculate spherical co-ordinates per frame
# for filters and spatialisation
position_per_frame = np.lib.stride_tricks.sliding_window_view(
flightpath, self.frame_len, 1)[:, ::self.hop_len].mean(2)
self.theta_per_frame, self.phi_per_frame, self.r_per_frame = \
utils.cart_to_sph(position_per_frame)
self.position_per_frame = utils.cart_to_sph(
np.lib.stride_tricks.sliding_window_view(
flightpath, self.frame_len, 1)[:, ::self.hop_len].mean(2)
).T
# self.theta_per_frame, self.phi_per_frame, self.r_per_frame = \
# utils.cart_to_sph(position_per_frame)

def apply_doppler(self, x):
# init output array and initial read position
Expand All @@ -149,53 +151,35 @@ def apply_doppler(self, x):
def apply_amp_env(self, x):
return x * self.amp_env

def absorbtion_effects(self, x):
def filter(self, x):
'''Apply frequency-dependent atmospheric and ground absorption'''

# neat trick to get windowed frames
x_windowed = np.lib.stride_tricks.sliding_window_view(
x, self.frame_len)[::self.hop_len] * np.hanning(self.frame_len)

atmos_filter = AtmosphericAbsorptionFilter()
# init ground filter if surface is set (reflected path)
if self.reflection_surface is not None:
refl_filter = GroundReflectionFilter(self.reflection_surface)

x_out = np.zeros(len(x))
for i, (r, angle, frame) in enumerate(
zip(self.r_per_frame, self.phi_per_frame, x_windowed)):

# apply atmospheric absorption filter
frame = atmos_filter.filter(frame, r)
# list of filter stages
filters = []

# apply ground filter if set
if self.reflection_surface is not None:
angle = np.round(np.rad2deg(np.pi - angle)) # reflection angle
frame = refl_filter.filter(frame, angle)

frame_index = i * self.hop_len
x_out[frame_index:frame_index + self.frame_len] += frame
# add atmospheric absorption
filters.append(AtmosphericAbsorptionFilter())

return x_out
# add ground filter if surface is set (reflected path)
if self.reflection_surface is not None:
filters.append(GroundReflectionFilter(self.reflection_surface))

def spatialise(self, x):
# do not spatialise if order not set (mono output)
if self.N is None:
return x

x_windowed = np.lib.stride_tricks.sliding_window_view(
x, self.frame_len)[::self.hop_len] * np.hanning(self.frame_len)
# add spatialiser (must be last as adds channels)
filters.append(SpatialFilter(self.N))

x_out = np.zeros((len(x), (self.N+1)**2))
for i, (position, frame) in enumerate(
zip(self.position_per_frame, x_windowed)):

for i, (theta, phi, frame) \
in enumerate(zip(self.theta_per_frame,
self.phi_per_frame,
x_windowed)):
for filter in filters:
frame = filter.filter(frame, position)

frame_index = i * self.hop_len
Y_mn = utils.Y_array(self.N, np.array([theta]), np.array([phi]))
x_out[frame_index:frame_index + self.frame_len] += (frame * Y_mn).T
x_out[frame_index:frame_index + self.frame_len] += frame

return x_out

Expand All @@ -204,15 +188,23 @@ def process(self, x):
raise ValueError('Input signal shorter than path to be rendered')

return \
self.spatialise(
self.absorbtion_effects(
self.apply_amp_env(
self.apply_doppler(x)
)
self.filter(
self.apply_amp_env(
self.apply_doppler(x)
)
)


class SpatialFilter():
def __init__(self, N=2):
self.N = N

def filter(self, x, position):
theta, phi, _ = position
Y_mn = utils.Y_array(self.N, np.array([theta]), np.array([phi]))
return (x * Y_mn).T


class GroundReflectionFilter():
def __init__(
self,
Expand All @@ -230,7 +222,6 @@ def __init__(
self.material = material
self.fs = fs
self.n_taps = n_taps
self.filterbank = self._compute_filterbank()

@property
def material(self):
Expand All @@ -252,24 +243,17 @@ def _Z(self):
X = -11.9 * (self.freqs / self._sigma) ** -0.73
return (R + 1j*X) * self.Z_0

def _R(self):
def _R(self, angle):
return np.real(
np.array([
(self._Z() * np.cos(p) - self.Z_0) /
(self._Z() * np.cos(p) + self.Z_0)
for p in self.phi
])
).squeeze()

def _compute_filterbank(self):
return np.array([
signal.firls(self.n_taps, self.freqs, abs(r), fs=self.fs)
for r in self._R()
])
(self._Z() * np.cos(angle) - self.Z_0)
/ (self._Z() * np.cos(angle) + self.Z_0)
)

def filter(self, x, angle):
angle = round(angle)
h = self.filterbank[angle - 1]
def filter(self, x, position):
_, phi, _ = position
phi = np.pi - phi
h = signal.firls(self.n_taps, self.freqs,
utils.rectify(self._R(phi)), fs=self.fs)
return signal.fftconvolve(x, h, 'same')


Expand Down Expand Up @@ -324,8 +308,9 @@ def alpha(self, freqs, temp=20, humidity=80, pressure=101.325):
alpha = freqs**2 * (xc + T_rel**(-5/2) * (xo + xn))
return 1 - alpha

def filter(self, x, distance):
def filter(self, x, position):
_, _, r = position
h = signal.firls(self.n_taps, self.freqs,
self.attenuation**distance,
self.attenuation**r,
fs=self.fs)
return signal.fftconvolve(x, h, 'same')
4 changes: 4 additions & 0 deletions uasevent/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -106,3 +106,7 @@ def SN3D(m, n):
)
)
)


def rectify(x):
return (np.abs(x) + x) / 2
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