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#!/usr/bin/env python3
#
# Copyright 2024 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
#
# http://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 argparse
import lc3
import struct
import sys
import wave
parser = argparse.ArgumentParser(description='LC3 Encoder')
parser.add_argument(
'wav_file', nargs='?',
help='Input wave file, default is stdin',
type=argparse.FileType('rb'), default=sys.stdin.buffer)
parser.add_argument(
'lc3_file', nargs='?',
help='Output bitstream file, default is stdout',
type=argparse.FileType('wb'), default=sys.stdout.buffer)
parser.add_argument(
'--bitrate', help='Bitrate in bps', type=int, required=True)
parser.add_argument(
'--frame_duration', help='Frame duration in ms', type=float, default=10)
parser.add_argument(
'--libpath', help='LC3 Library path')
args = parser.parse_args()
# --- WAV File input ---
f_wav = args.wav_file
wavfile = wave.open(f_wav, 'rb')
samplerate = wavfile.getframerate()
nchannels = wavfile.getnchannels()
bitdepth = wavfile.getsampwidth() * 8
stream_length = wavfile.getnframes()
# --- Setup encoder ---
enc = lc3.Encoder(
args.frame_duration, samplerate, nchannels, libpath=args.libpath)
frame_size = enc.get_frame_bytes(args.bitrate)
frame_length = enc.get_frame_samples()
bitrate = enc.resolve_bitrate(frame_size)
# --- Setup output ---
f_lc3 = args.lc3_file
f_lc3.write(struct.pack(
'=HHHHHHHI', 0xcc1c, 18,
samplerate // 100, bitrate // 100, nchannels,
int(args.frame_duration * 100), 0, stream_length))
# --- Encoding loop ---
for i in range(0, stream_length, frame_length):
f_lc3.write(struct.pack('=H', frame_size))
pcm = wavfile.readframes(frame_length)
f_lc3.write(enc.encode(pcm, frame_size, bitdepth=bitdepth))
# --- Cleanup ---
wavfile.close()
for f in (f_wav, f_lc3):
if f is not sys.stdout.buffer:
f.close()
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