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July 17, 2018 08:23
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Fun things for Dabeaz's superbad superboard
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"""Fun things for Dabeaz's superbad superboard. | |
Default Audio Format: | |
Frame rate: 48kHz | |
Channels: 1 | |
Bytes per sample: 1 | |
Superboard Encoding: | |
Baud rate: 300 | |
Start bit: 0b0 | |
Stop bits: 0b11 | |
0: 4 square wave cycles at 1200 Hz | |
40 samples (1 cycle) @ 48k Hz | |
160 samples (4 cycles) @ 48 kHz (bit) | |
1760 samples (44 cycles) @ 48 kHz (byte payload) | |
1: 8 square wave cycles at 2400 Hz | |
20 samples (1 cycle) @ 48 kHz | |
160 samples (8 cycles) @ 48 kHz (bit) | |
1760 samples (88 cycles) @ 48 kHz (byte payload) | |
Thoughts: | |
* Why not use a slower sample rate (i.e. 2400 Hz)? | |
""" | |
import wave | |
def encode_bit(value, frame_rate=48000): | |
cycles, frequency = ((4, 1200), (8, 2400))[value] | |
data = bytearray() | |
n_samples = frame_rate // frequency | |
for i in range(n_samples // 2): | |
data.append(0) | |
for i in range(n_samples // 2): | |
data.append(255) | |
return cycles * data | |
def encode_byte(byte): | |
data = bytearray(encode_bit(0)) # Start bit | |
for bit in range(0, 8): | |
if byte & 0x1: | |
data.extend(encode_bit(1)) | |
else: | |
data.extend(encode_bit(0)) | |
byte = byte >> 1 | |
data.extend(encode_bit(1) * 2) # Stop bits | |
return data | |
def encode_data(in_data): | |
data = bytearray(encode_bit(1) * 1000) # Padding | |
for byte in in_data: | |
data.extend(encode_byte(byte)) | |
data.extend(encode_bit(1) * 1000) # Padding | |
return data | |
def decode_samples(samples, frame_rate=48000): | |
ref_samples = [encode_bit(n, frame_rate=frame_rate) for n in (0, 1)] | |
bit_len = len(ref_samples[0]) | |
# Convert samples into bits | |
bits = [] | |
for idx in range(0, len(samples), bit_len): | |
bit = ref_samples.index(samples[idx:idx + bit_len]) | |
bits.append(bit) | |
# Starting at first start bit, extract bytes from 11-bit chunks, skip | |
# chunks with invalid start/stop bits | |
data = bytearray() | |
for idx in range(bits.index(0), len(bits), 11): | |
bit_set = bits[idx:idx+11] | |
if bit_set[0] != 0 or bit_set[-2:] != [1, 1]: | |
continue | |
value = 0 | |
for bit in bit_set[-3:0:-1]: | |
value = (value << 1) | bit | |
data.append(value) | |
# data = data.replace(b'\n', b'\r\n') | |
return data | |
def ascii_to_wav(in_file, out_file, frame_rate=48000, sample_width=1, channels=1): | |
with open(in_file, "rb") as fh: | |
in_data = fh.read() | |
in_data = in_data.replace(b'\n', b'\r\n') | |
data = encode_data(in_data) | |
with wave.open(out_file, "wb") as w: | |
w.setnchannels(channels) | |
w.setsampwidth(sample_width) | |
w.setframerate(frame_rate) | |
w.writeframes(data) | |
return data | |
def wav_to_ascii(in_file, out_file): | |
with wave.open(in_file, "rb") as w: | |
samples = w.readframes(w.getnframes()) | |
data = decode_samples(samples, w.getframerate()) | |
with open(out_file, "wb") as fh: | |
fh.write(data) | |
return data | |
assert decode_samples(encode_data(b'A')) == b'A' | |
assert decode_samples(encode_data(b'A')) == b'A' | |
ascii_to_wav("haiku_1_in.bas", "haiku_1_out.wav") | |
wav_to_ascii("haiku_1_out.wav", "haiku_1_out.bas") |
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