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laser2wav.py
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laser2wav.py
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#! /usr/bin/env python3
# laser2wav.py
#
# Copyright (c) 2005--2015 by Sidney Cadot <sidney@jigsaw.nl>
# This software is licensed under the GNU General Public License (GPL).
#
# This file is part of Laser2Wav, a software-only implementation of
# an audio CD decoder.
import sys, wave
import galois_field as gf
from efm import EFM
goodsym = 0
def analyze_frame(frame):
assert len(frame) == 588 # verify that each frame is 588 bits long
sync24 = frame[0:24]
merge3 = frame[24:27] # ignore
assert sync24 == "100000000001000000000010"
global goodsym
framedata = []
for i in range(33):
channel14 = frame[27+17*i:41+17*i]
merge3 = frame[41+17*i:44+17*i] # ignore
data8 = 0
try:
data8 = EFM[channel14]
goodsym = goodsym + 1
except KeyError:
print("argh-data")
data8 = 0
framedata.append(data8)
return (framedata[0], framedata[1:])
def invert_last_16(Q):
return Q[:-16] + str.join("", [str(1 - int(x)) for x in Q[-16:]])
def valid_crc(Q):
# this is a simple way to check the CRC
if len(Q) == 0:
return True
if Q[0] == '0':
return valid_crc(Q[1:])
if len(Q)<17:
return False
# subtract multiple of the CRC generator polynomial
Q = [int(x) for x in Q]
Q[ 0] = 1 - Q[ 0]
Q[ 4] = 1 - Q[ 4]
Q[11] = 1 - Q[11]
Q[16] = 1 - Q[16]
Q = str.join("", [str(x) for x in Q])
return valid_crc(Q)
def to_signed(n):
if n >= 32768:
n -= 65536
return n
def to_unsigned(n):
if n < 0:
n += 65536
return n
def bcd2int(S):
assert len(S)==8
hi = int(S[0:4], 2)
#assert (hi>=0) and (hi<=9)
lo = int(S[4:8], 2)
#assert (lo>=0) and (lo<=9)
return hi*10+lo
def analyze_control_stream(control_stream):
print("Analyzing control stream ...")
all_zeros = 96 * "0"
all_ones = 96 * "1"
ok_map = {False: "ERROR", True: "ok"}
while len(control_stream) >= 98:
if control_stream[0] != 'SYNC0':
# discard a control byte - not part of a sector
control_stream = control_stream[1:]
else:
if control_stream[0] != 'SYNC0':
print("BAD SYNC0")
if control_stream[1] != 'SYNC1':
print("BAD SYNC1")
for i in range(2, len(control_stream)):
if (control_stream[i] == 'SYNC0') or (control_stream[i] == 'SYNC1'):
control_stream[i] = 0
control_sector = control_stream[2:98]
control_stream = control_stream[98:]
P = str.join("", [str(int((x & 0x80) != 0)) for x in control_sector])
Q = str.join("", [str(int((x & 0x40) != 0)) for x in control_sector])
R = str.join("", [str(int((x & 0x20) != 0)) for x in control_sector])
S = str.join("", [str(int((x & 0x10) != 0)) for x in control_sector])
T = str.join("", [str(int((x & 0x08) != 0)) for x in control_sector])
U = str.join("", [str(int((x & 0x04) != 0)) for x in control_sector])
V = str.join("", [str(int((x & 0x02) != 0)) for x in control_sector])
W = str.join("", [str(int((x & 0x01) != 0)) for x in control_sector])
p_ok = (P in [all_zeros, all_ones])
q_ok = valid_crc(invert_last_16(Q))
r_ok = (R == all_zeros) # for most CDs
s_ok = (S == all_zeros) # for most CDs
t_ok = (T == all_zeros) # for most CDs
u_ok = (U == all_zeros) # for most CDs
v_ok = (V == all_zeros) # for most CDs
w_ok = (W == all_zeros) # for most CDs
print(" Sector sub-channels:")
print(" P: <{}> {}".format(P, ok_map[p_ok]))
print(" Q: <{}> {}".format(Q, ok_map[q_ok]))
if q_ok:
q_control = Q[0:4]
q_mode = int(Q[4:8], 2)
q_data = Q[8:80]
if q_mode == 1:
(tno,index,min,sec,frac,zero,amin,asec,afrac) = [bcd2int(q_data[8*i:8*i+8]) for i in range(9)]
assert zero == 0
print(" CONTROL .......... : <{}> [#channels / reserved / copy-protect / pre-emphasis]".format(q_control))
print(" MODE ............. : {}".format(q_mode))
print(" DATA ............. : trackno. {:02d} indexno. {:02d} track-time {:02d}:{:02d}.{:02d} [mm:ss.ff] disc-time {:02d}:{:02d}.{:02d} [mm:ss.ff]".format(tno, index, min, sec, frac, amin, asec, afrac))
else:
print(" CONTROL .......... : <{}>".format(q_control))
print(" MODE ............. : {}".format(q_mode))
print(" DATA ............. : <{}>".format(q_data))
print(" R: <{}> {}".format(R, ok_map[r_ok]))
print(" S: <{}> {}".format(S, ok_map[s_ok]))
print(" T: <{}> {}".format(T, ok_map[t_ok]))
print(" U: <{}> {}".format(U, ok_map[u_ok]))
print(" V: <{}> {}".format(V, ok_map[v_ok]))
print(" W: <{}> {}".format(W, ok_map[w_ok]))
def verify_data_stream(data):
errorsP = 0
errorsQ = 0
# make the Reed-Solomon check calculations
invert = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 255, 255]
# check C1 a.k.a. P-parity
print("Checking C1 / P parity ...")
p_delay = [0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1]
for i in range(1, len(data)):
z_list = []
for hp_row in range(4):
z = gf.zero
for j in range(32):
if (data[i-p_delay[j]][j] == 'SYNC1') or (data[i-p_delay[j]][j] == 'SYNC0'):
data[i-p_delay[j]][j] = 0
z = gf.add(z, gf.multiply(gf.power(gf.alpha, hp_row*(31-j)), data[i-p_delay[j]][j]^invert[j]))
z_list.append(z)
if z_list != [gf.zero, gf.zero, gf.zero, gf.zero]:
print("P PARITY: ERROR DETECTED IN FRAME # {}".format(i))
errorsP = errorsP + 1
else:
print("P PARITY: FRAME # {} GOOD".format(i))
# check C2 a.k.a. Q-parity
print("Checking C2 / Q parity ...")
q_delay = [107, 104, 99, 96, 91, 88, 83, 80, 75, 72, 67, 64, 59, 56, 51, 48, 43, 40, 35, 32, 27, 24, 19, 16, 11, 8, 3, 0]
for i in range(107, len(data)):
z_list = []
for hq_row in range(4):
z = gf.zero
for j in range(28):
if (data[i-q_delay[j]][j] == 'SYNC1') or (data[i-q_delay[j]][j] == 'SYNC0'):
data[i-q_delay[j]][j] = 0
z = gf.add(z, gf.multiply(gf.power(gf.alpha, hq_row*(27-j)), data[i-q_delay[j]][j]^invert[j]))
z_list.append(z)
if z_list!= [gf.zero, gf.zero, gf.zero, gf.zero]:
print("Q PARITY: ERROR DETECTED IN FRAME # {}".format(i))
errorsQ = errorsQ + 1
else:
print("Q PARITY: FRAME # {} GOOD".format(i))
return (errorsP, errorsQ)
def extract_audio_stream(data):
audio_data = []
for i in range(105, len(data)):
for j in range(0, 28):
if (data[i - 105][j] == 'SYNC1') or (data[i - 105][j] == 'SYNC2'):
data[i - 105][j] = 0
for i in range(105, len(data)):
L0 = to_signed(data[i-105][ 0]*256 + data[i-102][ 1])
L2 = to_signed(data[i- 97][ 2]*256 + data[i- 94][ 3])
L4 = to_signed(data[i- 89][ 4]*256 + data[i- 86][ 5])
R0 = to_signed(data[i- 81][ 6]*256 + data[i- 78][ 7])
R2 = to_signed(data[i- 73][ 8]*256 + data[i- 70][ 9])
R4 = to_signed(data[i- 65][10]*256 + data[i- 62][11])
L1 = to_signed(data[i- 43][16]*256 + data[i- 40][17])
L3 = to_signed(data[i- 35][18]*256 + data[i- 32][19])
L5 = to_signed(data[i- 27][20]*256 + data[i- 24][21])
R1 = to_signed(data[i- 19][22]*256 + data[i- 16][23])
R3 = to_signed(data[i- 11][24]*256 + data[i- 8][25])
R5 = to_signed(data[i- 3][26]*256 + data[i- 0][27])
audio_data.extend([(L0, R0), (L1, R1), (L2, R2), (L3, R3), (L4, R4), (L5, R5)])
return audio_data
def write_wav_file(filename_out, audio_data):
# Python's WAV-file writer expects raw data, encoded as a string.
wave_data = bytearray()
for (left, right) in audio_data:
left = to_unsigned(left)
right = to_unsigned(right)
wave_data.append(left % 256)
wave_data.append(left // 256)
wave_data.append(right % 256)
wave_data.append(right // 256)
# Write the WAV file.
wf = wave.open(filename_out, "w")
wf.setnchannels(2) # stereo
wf.setsampwidth(2) # 16-bit signal; 2 bytes per sample
wf.setframerate(44100)
wf.writeframes(wave_data)
wf.close()
def main():
if len(sys.argv) != 3:
print("Usage: python laser2wav.py <laser-in.dat> <waveform-out.wav>")
return
filename_in = sys.argv[1]
filename_out = sys.argv[2]
print("Reading raw signal ...")
with open(filename_in, "rb") as f:
raw_signal = f.read()
print("Converting to delta signal...")
raw_signal = [int (x) for x in raw_signal]
delta_signal = [str(raw_signal[i] ^ raw_signal[i - 1]) for i in range(1, len(raw_signal))]
delta_signal = str.join("", delta_signal)
print("Walking frames...")
control_stream = []
data_stream = []
fcount = 0
prev_z = 0
z = 0
while True:
z = delta_signal.find("100000000001000000000010", z)
if z < 0:
break
print("delta at ", z, z - prev_z)
frame = delta_signal[z:z+588]
if len(frame) == 588:
(control, data) = analyze_frame(frame)
control_stream.append(control)
data_stream.append(data)
fcount = fcount + 1
prev_z = z
z = z + 22
global goodsym
print(goodsym, " good symbols")
print(fcount, " frames found")
analyze_control_stream(control_stream)
verify_data_stream(data_stream)
print("Extracting audio data ...")
audio_data = extract_audio_stream(data_stream)
print("Writing WAV file ...")
write_wav_file(filename_out, audio_data)
if __name__ == "__main__":
main()