# Copyright 2022 CR-Suite Development Team
#
# 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.
import cr.wavelets as crwt
from .blocks import *
[docs]def build_codec(wavelet_name, level,
block_length, max_prd, thresholds):
"""Builds an encoder and decoder function for a given choice
of wavelet, decomposition level, signal block length, target
percentage root mean square difference and coefficient energy thresholding
targets
"""
wavelet = crwt.to_wavelet(wavelet_name)
def encode(block):
coeffs = crwt.wavedec(block, wavelet, level=level)
th_coeffs, binmaps = threshold(coeffs, thresholds)
nz_th_coeffs = remove_zeros(th_coeffs, binmaps)
scaled_coeffs, shifts, scales = scale_to_0_1(nz_th_coeffs)
# quantize_to_prd_target
num_bits = 9
cur_prd = 0
prd_vals = np.empty(num_bits)
while num_bits >= 5 and cur_prd <= max_prd:
num_bits -= 1
quantized_coeffs = quantize_1(scaled_coeffs, num_bits)
inv_quant_coeffs = inv_quantize_1(quantized_coeffs, num_bits)
unscaled_coeffs = descale_from_0_1(inv_quant_coeffs, shifts, scales)
unscaled_coeffs = add_zeros(unscaled_coeffs, binmaps)
reconstructed = crwt.waverec(unscaled_coeffs, wavelet)
cur_prd = crn.prd(block, reconstructed)
prd_vals[num_bits] = cur_prd
if cur_prd > max_prd:
num_bits += 1
cur_prd = prd_vals[num_bits]
quantized_coeffs = quantize_1(scaled_coeffs, num_bits)
combined_coeffs = combine_arrays(quantized_coeffs)
combined_binmaps = combine_arrays(binmaps)
result = encode_cbss_to_bits(
combined_coeffs, combined_binmaps,
shifts, scales, num_bits)
return result
def decode(bits):
(c_coeffs, c_binmaps,
shifts, scales, num_bits) = decode_cbss_from_bits(
wavelet_name, level, block_length, bits)
coeffs, binmaps = split_coefs_binmaps(
wavelet_name, level, block_length, c_coeffs, c_binmaps)
inv_quant_coeffs = inv_quantize_1(coeffs, num_bits)
unscaled_coeffs = descale_from_0_1(inv_quant_coeffs, shifts, scales)
unscaled_coeffs = add_zeros(unscaled_coeffs, binmaps)
reconstructed = crwt.waverec(unscaled_coeffs, wavelet)
return reconstructed
return encode, decode
