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bumble_mirror/bumble/decoder.py

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# Copyright 2023 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# -----------------------------------------------------------------------------
# Constants
# -----------------------------------------------------------------------------
# fmt: off
WL = [-60, -30, 58, 172, 334, 538, 1198, 3042]
RL42 = [0, 7, 6, 5, 4, 3, 2, 1, 7, 6, 5, 4, 3, 2, 1, 0]
ILB = [
2048,
2093,
2139,
2186,
2233,
2282,
2332,
2383,
2435,
2489,
2543,
2599,
2656,
2714,
2774,
2834,
2896,
2960,
3025,
3091,
3158,
3228,
3298,
3371,
3444,
3520,
3597,
3676,
3756,
3838,
3922,
4008,
]
WH = [0, -214, 798]
RH2 = [2, 1, 2, 1]
# Values in QM2/QM4/QM6 left shift three bits than original g722 specification.
QM2 = [-7408, -1616, 7408, 1616]
QM4 = [
0,
-20456,
-12896,
-8968,
-6288,
-4240,
-2584,
-1200,
20456,
12896,
8968,
6288,
4240,
2584,
1200,
0,
]
QM6 = [
-136,
-136,
-136,
-136,
-24808,
-21904,
-19008,
-16704,
-14984,
-13512,
-12280,
-11192,
-10232,
-9360,
-8576,
-7856,
-7192,
-6576,
-6000,
-5456,
-4944,
-4464,
-4008,
-3576,
-3168,
-2776,
-2400,
-2032,
-1688,
-1360,
-1040,
-728,
24808,
21904,
19008,
16704,
14984,
13512,
12280,
11192,
10232,
9360,
8576,
7856,
7192,
6576,
6000,
5456,
4944,
4464,
4008,
3576,
3168,
2776,
2400,
2032,
1688,
1360,
1040,
728,
432,
136,
-432,
-136,
]
QMF_COEFFS = [3, -11, 12, 32, -210, 951, 3876, -805, 362, -156, 53, -11]
# fmt: on
# -----------------------------------------------------------------------------
# Classes
# -----------------------------------------------------------------------------
class G722Decoder(object):
"""G.722 decoder with bitrate 64kbit/s.
For the Blocks in the sub-band decoders, please refer to the G.722
specification for the required information. G722 specification:
https://www.itu.int/rec/T-REC-G.722-201209-I
"""
def __init__(self):
self._x = [0] * 24
self._band = [Band(), Band()]
# The initial value in BLOCK 3L
self._band[0].det = 32
# The initial value in BLOCK 3H
self._band[1].det = 8
def decode_frame(self, encoded_data) -> bytearray:
result_array = bytearray(len(encoded_data) * 4)
self.g722_decode(result_array, encoded_data)
return result_array
def g722_decode(self, result_array, encoded_data) -> int:
"""Decode the data frame using g722 decoder."""
rlow = 0
rhigh = 0
xout1 = 0
xout2 = 0
code = 0
result_length = 0
j = 0
for j in range(0, len(encoded_data)):
code = encoded_data[j]
higher_bits = (code >> 6) & 0x03
lower_bits = code & 0x3F
rlow = self.lower_sub_band_decoder(lower_bits)
rhigh = self.higher_sub_band_decoder(higher_bits)
# Apply the receive QMF
for i in range(22):
self._x[i] = self._x[i + 2]
self._x[22] = rlow + rhigh
self._x[23] = rlow - rhigh
xout1 = 0
xout2 = 0
for i in range(12):
xout2 += self._x[2 * i] * QMF_COEFFS[i]
xout1 += self._x[2 * i + 1] * QMF_COEFFS[11 - i]
result_length = self.update_decoded_result(
xout1, result_length, result_array
)
result_length = self.update_decoded_result(
xout2, result_length, result_array
)
return result_length
def update_decoded_result(self, xout, byte_length, byte_array) -> int:
result = (int)(xout >> 11)
bytes_result = result.to_bytes(2, 'little', signed=True)
byte_array[byte_length] = bytes_result[0]
byte_array[byte_length + 1] = bytes_result[1]
return byte_length + 2
def lower_sub_band_decoder(self, lower_bits) -> int:
"""Lower sub-band decoder for last six bits."""
# Block 5L
# INVQBL
wd1 = lower_bits
wd2 = QM6[wd1]
wd1 >>= 2
wd2 = (self._band[0].det * wd2) >> 15
# RECONS
rlow = self._band[0].s + wd2
# Block 6L
# LIMIT
if rlow > 16383:
rlow = 16383
elif rlow < -16384:
rlow = -16384
# Block 2L
# INVQAL
wd2 = QM4[wd1]
dlowt = (self._band[0].det * wd2) >> 15
# Block 3L
# LOGSCL
wd2 = RL42[wd1]
wd1 = (self._band[0].nb * 127) >> 7
wd1 += WL[wd2]
if wd1 < 0:
wd1 = 0
elif wd1 > 18432:
wd1 = 18432
self._band[0].nb = wd1
# SCALEL
wd1 = (self._band[0].nb >> 6) & 31
wd2 = 8 - (self._band[0].nb >> 11)
if wd2 < 0:
wd3 = ILB[wd1] << -wd2
else:
wd3 = ILB[wd1] >> wd2
self._band[0].det = wd3 << 2
# Block 4L
self._band[0].block4(dlowt)
return rlow
def higher_sub_band_decoder(self, higher_bits) -> int:
"""Higher sub-band decoder for first two bits."""
# Block 2H
# INVQAH
wd2 = QM2[higher_bits]
dhigh = (self._band[1].det * wd2) >> 15
# Block 5H
# RECONS
rhigh = dhigh + self._band[1].s
# Block 6H
# LIMIT
if rhigh > 16383:
rhigh = 16383
elif rhigh < -16384:
rhigh = -16384
# Block 3H
# LOGSCH
wd2 = RH2[higher_bits]
wd1 = (self._band[1].nb * 127) >> 7
wd1 += WH[wd2]
if wd1 < 0:
wd1 = 0
elif wd1 > 22528:
wd1 = 22528
self._band[1].nb = wd1
# SCALEH
wd1 = (self._band[1].nb >> 6) & 31
wd2 = 10 - (self._band[1].nb >> 11)
if wd2 < 0:
wd3 = ILB[wd1] << -wd2
else:
wd3 = ILB[wd1] >> wd2
self._band[1].det = wd3 << 2
# Block 4H
self._band[1].block4(dhigh)
return rhigh
# -----------------------------------------------------------------------------
class Band(object):
"""Structure for G722 decode proccessing."""
s: int = 0
nb: int = 0
det: int = 0
def __init__(self):
self._sp = 0
self._sz = 0
self._r = [0] * 3
self._a = [0] * 3
self._ap = [0] * 3
self._p = [0] * 3
self._d = [0] * 7
self._b = [0] * 7
self._bp = [0] * 7
self._sg = [0] * 7
def saturate(self, amp: int) -> int:
if amp > 32767:
return 32767
elif amp < -32768:
return -32768
else:
return amp
def block4(self, d: int) -> None:
"""Block4 for both lower and higher sub-band decoder."""
wd1 = 0
wd2 = 0
wd3 = 0
# RECONS
self._d[0] = d
self._r[0] = self.saturate(self.s + d)
# PARREC
self._p[0] = self.saturate(self._sz + d)
# UPPOL2
for i in range(3):
self._sg[i] = (self._p[i]) >> 15
wd1 = self.saturate((self._a[1]) << 2)
wd2 = -wd1 if self._sg[0] == self._sg[1] else wd1
if wd2 > 32767:
wd2 = 32767
wd3 = 128 if self._sg[0] == self._sg[2] else -128
wd3 += wd2 >> 7
wd3 += (self._a[2] * 32512) >> 15
if wd3 > 12288:
wd3 = 12288
elif wd3 < -12288:
wd3 = -12288
self._ap[2] = wd3
# UPPOL1
self._sg[0] = (self._p[0]) >> 15
self._sg[1] = (self._p[1]) >> 15
wd1 = 192 if self._sg[0] == self._sg[1] else -192
wd2 = (self._a[1] * 32640) >> 15
self._ap[1] = self.saturate(wd1 + wd2)
wd3 = self.saturate(15360 - self._ap[2])
if self._ap[1] > wd3:
self._ap[1] = wd3
elif self._ap[1] < -wd3:
self._ap[1] = -wd3
# UPZERO
wd1 = 0 if d == 0 else 128
self._sg[0] = d >> 15
for i in range(1, 7):
self._sg[i] = (self._d[i]) >> 15
wd2 = wd1 if self._sg[i] == self._sg[0] else -wd1
wd3 = (self._b[i] * 32640) >> 15
self._bp[i] = self.saturate(wd2 + wd3)
# DELAYA
for i in range(6, 0, -1):
self._d[i] = self._d[i - 1]
self._b[i] = self._bp[i]
for i in range(2, 0, -1):
self._r[i] = self._r[i - 1]
self._p[i] = self._p[i - 1]
self._a[i] = self._ap[i]
# FILTEP
self._sp = 0
for i in range(1, 3):
wd1 = self.saturate(self._r[i] + self._r[i])
self._sp += (self._a[i] * wd1) >> 15
self._sp = self.saturate(self._sp)
# FILTEZ
self._sz = 0
for i in range(6, 0, -1):
wd1 = self.saturate(self._d[i] + self._d[i])
self._sz += (self._b[i] * wd1) >> 15
self._sz = self.saturate(self._sz)
# PREDIC
self.s = self.saturate(self._sp + self._sz)
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