class SHNDecoder(object):
def __init__(self, filename):
self.reader = BitstreamReader(open(filename, "rb"), False)
(self.file_type,
self.channels,
self.block_length,
self.max_LPC,
self.number_of_means) = self.read_header()
if (1 <= self.file_type) and (self.file_type <= 2):
self.bits_per_sample = 8
self.signed_samples = (self.file_type == 1)
elif (3 <= self.file_type) and (self.file_type <= 6):
self.bits_per_sample = 16
self.signed_samples = (self.file_type in (3, 5))
else:
raise ValueError("unsupported Shorten file type")
self.wrapped_samples = [[0] * 3 for c in range(self.channels)]
self.means = [[0] * self.number_of_means
for c in range(self.channels)]
self.left_shift = 0
self.stream_finished = False
# try to read the first command for a wave/aiff header
data_start = self.reader.getpos()
self.read_metadata()
self.reader.setpos(data_start)
def read_metadata(self):
from io import BytesIO
command = self.unsigned(2)
if command == 9:
# got verbatim, so read data
verbatim_bytes = ints_to_bytes([self.unsigned(8) & 0xFF
for i in range(self.unsigned(5))])
try:
wave = BitstreamReader(BytesIO(verbatim_bytes), True)
header = wave.read_bytes(12)
if header.startswith(b"RIFF") and header.endswith(b"WAVE"):
# got RIFF/WAVE header, so parse wave blocks as needed
total_size = len(verbatim_bytes) - 12
while total_size > 0:
(chunk_id, chunk_size) = wave.parse("4b 32u")
total_size -= 8
if chunk_id == b'fmt ':
(channels,
self.sample_rate,
bits_per_sample,
channel_mask) = parse_fmt(
wave.substream(chunk_size))
self.channel_mask = int(channel_mask)
return
else:
if chunk_size % 2:
wave.read_bytes(chunk_size + 1)
total_size -= (chunk_size + 1)
else:
wave.read_bytes(chunk_size)
total_size -= chunk_size
else:
# no fmt chunk, so use default metadata
pass
except (IOError, ValueError):
pass
try:
aiff = BitstreamReader(BytesIO(verbatim_bytes), False)
header = aiff.read_bytes(12)
if header.startswith(b"FORM") and header.endswith(b"AIFF"):
# got FORM/AIFF header, so parse aiff blocks as needed
total_size = len(verbatim_bytes) - 12
while total_size > 0:
(chunk_id, chunk_size) = aiff.parse("4b 32u")
total_size -= 8
if chunk_id == b'COMM':
(channels,
total_sample_frames,
bits_per_sample,
self.sample_rate,
channel_mask) = parse_comm(
aiff.substream(chunk_size))
self.channel_mask = int(channel_mask)
return
else:
if chunk_size % 2:
aiff.read_bytes(chunk_size + 1)
total_size -= (chunk_size + 1)
else:
aiff.read_bytes(chunk_size)
total_size -= chunk_size
else:
# no COMM chunk, so use default metadata
pass
except IOError:
pass
# got something else, so invent some PCM parameters
self.sample_rate = 44100
if self.channels == 1:
self.channel_mask = 0x4
elif self.channels == 2:
self.channel_mask = 0x3
else:
self.channel_mask = 0
def unsigned(self, c):
MSB = self.reader.unary(1)
LSB = self.reader.read(c)
return MSB * 2 ** c + LSB
def signed(self, c):
u = self.unsigned(c + 1)
if (u % 2) == 0:
return u // 2
else:
return -(u // 2) - 1
def long(self):
return self.unsigned(self.unsigned(2))
def skip_unsigned(self, c):
self.reader.skip_unary(1)
self.reader.skip(c)
def read_header(self):
magic = self.reader.read_bytes(4)
if magic != b"ajkg":
raise ValueError("invalid magic number")
version = self.reader.read(8)
if version != 2:
raise ValueError("unsupported version")
file_type = self.long()
channels = self.long()
block_length = self.long()
max_LPC = self.long()
number_of_means = self.long()
bytes_to_skip = self.long()
self.reader.read_bytes(bytes_to_skip)
return (file_type, channels, block_length, max_LPC, number_of_means)
def read(self, pcm_frames):
if self.stream_finished:
return from_channels([empty_framelist(1, self.bits_per_sample)
for channel in range(self.channels)])
c = 0
samples = []
unshifted = []
while True:
command = self.unsigned(2)
if (((0 <= command) and (command <= 3) or
(7 <= command) and (command <= 8))):
# audio data commands
if command == 0: # DIFF0
samples.append(self.read_diff0(self.block_length,
self.means[c]))
elif command == 1: # DIFF1
samples.append(self.read_diff1(self.block_length,
self.wrapped_samples[c]))
elif command == 2: # DIFF2
samples.append(self.read_diff2(self.block_length,
self.wrapped_samples[c]))
elif command == 3: # DIFF3
samples.append(self.read_diff3(self.block_length,
self.wrapped_samples[c]))
elif command == 7: # QLPC
samples.append(self.read_qlpc(self.block_length,
self.means[c],
self.wrapped_samples[c]))
elif command == 8: # ZERO
samples.append([0] * self.block_length)
# update means for channel
self.means[c].append(shnmean(samples[c]))
self.means[c] = self.means[c][1:]
# wrap samples for next command in channel
self.wrapped_samples[c] = samples[c][-(max(3, self.max_LPC)):]
# apply left shift to samples
if self.left_shift > 0:
unshifted.append([s << self.left_shift
for s in samples[c]])
else:
unshifted.append(samples[c])
c += 1
if c == self.channels:
# return a FrameList from shifted data
return from_channels([from_list(channel, 1,
self.bits_per_sample,
self.signed_samples)
for channel in unshifted])
else:
# non audio commands
if command == 4: # QUIT
self.stream_finished = True
return from_channels(
[empty_framelist(1, self.bits_per_sample)
for channel in range(self.channels)])
elif command == 5: # BLOCKSIZE
self.block_length = self.long()
elif command == 6: # BITSHIFT
self.left_shift = self.unsigned(2)
elif command == 9: # VERBATIM
# skip this command during reading
size = self.unsigned(5)
for i in range(size):
self.skip_unsigned(8)
else:
raise ValueError("unsupported Shorten command")
def read_diff0(self, block_length, means):
offset = shnmean(means)
energy = self.unsigned(3)
samples = []
for i in range(block_length):
residual = self.signed(energy)
samples.append(residual + offset)
return samples
def read_diff1(self, block_length, previous_samples):
samples = previous_samples[-1:]
energy = self.unsigned(3)
for i in range(1, block_length + 1):
residual = self.signed(energy)
samples.append(samples[i - 1] + residual)
return samples[1:]
def read_diff2(self, block_length, previous_samples):
samples = previous_samples[-2:]
energy = self.unsigned(3)
for i in range(2, block_length + 2):
residual = self.signed(energy)
samples.append((2 * samples[i - 1]) - samples[i - 2] + residual)
return samples[2:]
def read_diff3(self, block_length, previous_samples):
samples = previous_samples[-3:]
energy = self.unsigned(3)
for i in range(3, block_length + 3):
residual = self.signed(energy)
samples.append((3 * (samples[i - 1] - samples[i - 2])) +
samples[i - 3] + residual)
return samples[3:]
def read_qlpc(self, block_length, means, previous_samples):
offset = shnmean(means)
energy = self.unsigned(3)
LPC_count = self.unsigned(2)
LPC_coeff = [self.signed(5) for i in range(LPC_count)]
unoffset = []
samples = previous_samples[-LPC_count:]
for i in range(block_length):
residual = self.signed(energy)
LPC_sum = 2 ** 5
for j in range(LPC_count):
if (i - j - 1) < 0:
# apply offset to warm-up samples
LPC_sum += (LPC_coeff[j] *
(samples[LPC_count + (i - j - 1)] - offset))
else:
LPC_sum += LPC_coeff[j] * unoffset[i - j - 1]
unoffset.append(LPC_sum // 2 ** 5 + residual)
return [u + offset for u in unoffset]
def close(self):
self.reader.close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
self.close()
class SHNDecoder(object):
def __init__(self, filename):
self.reader = BitstreamReader(open(filename, "rb"), False)
(self.file_type, self.channels, self.block_length, self.max_LPC,
self.number_of_means) = self.read_header()
if ((1 <= self.file_type) and (self.file_type <= 2)):
self.bits_per_sample = 8
self.signed_samples = (self.file_type == 1)
elif ((3 <= self.file_type) and (self.file_type <= 6)):
self.bits_per_sample = 16
self.signed_samples = (self.file_type in (3, 5))
else:
raise ValueError("unsupported Shorten file type")
self.wrapped_samples = [[0] * 3 for c in range(self.channels)]
self.means = [[0] * self.number_of_means for c in range(self.channels)]
self.left_shift = 0
self.stream_finished = False
# try to read the first command for a wave/aiff header
self.reader.mark()
self.read_metadata()
self.reader.rewind()
self.reader.unmark()
def read_metadata(self):
from io import BytesIO
command = self.unsigned(2)
if (command == 9):
# got verbatim, so read data
verbatim_bytes = ints_to_bytes(
[self.unsigned(8) & 0xFF for i in range(self.unsigned(5))])
try:
wave = BitstreamReader(BytesIO(verbatim_bytes), True)
header = wave.read_bytes(12)
if (header.startswith(b"RIFF") and header.endswith(b"WAVE")):
# got RIFF/WAVE header, so parse wave blocks as needed
total_size = len(verbatim_bytes) - 12
while (total_size > 0):
(chunk_id, chunk_size) = wave.parse("4b 32u")
total_size -= 8
if (chunk_id == b'fmt '):
(channels, self.sample_rate, bits_per_sample,
channel_mask) = parse_fmt(
wave.substream(chunk_size))
self.channel_mask = int(channel_mask)
return
else:
if (chunk_size % 2):
wave.read_bytes(chunk_size + 1)
total_size -= (chunk_size + 1)
else:
wave.read_bytes(chunk_size)
total_size -= chunk_size
else:
# no fmt chunk, so use default metadata
pass
except (IOError, ValueError):
pass
try:
aiff = BitstreamReader(BytesIO(verbatim_bytes), False)
header = aiff.read_bytes(12)
if (header.startswith(b"FORM") and header.endswith(b"AIFF")):
# got FORM/AIFF header, so parse aiff blocks as needed
total_size = len(verbatim_bytes) - 12
while (total_size > 0):
(chunk_id, chunk_size) = aiff.parse("4b 32u")
total_size -= 8
if (chunk_id == b'COMM'):
(channels, total_sample_frames, bits_per_sample,
self.sample_rate, channel_mask) = parse_comm(
aiff.substream(chunk_size))
self.channel_mask = int(channel_mask)
return
else:
if (chunk_size % 2):
aiff.read_bytes(chunk_size + 1)
total_size -= (chunk_size + 1)
else:
aiff.read_bytes(chunk_size)
total_size -= chunk_size
else:
# no COMM chunk, so use default metadata
pass
except IOError:
pass
# got something else, so invent some PCM parameters
self.sample_rate = 44100
if (self.channels == 1):
self.channel_mask = 0x4
elif (self.channels == 2):
self.channel_mask = 0x3
else:
self.channel_mask = 0
def unsigned(self, c):
MSB = self.reader.unary(1)
LSB = self.reader.read(c)
return MSB * 2**c + LSB
def signed(self, c):
u = self.unsigned(c + 1)
if ((u % 2) == 0):
return u // 2
else:
return -(u // 2) - 1
def long(self):
return self.unsigned(self.unsigned(2))
def skip_unsigned(self, c):
self.reader.skip_unary(1)
self.reader.skip(c)
def read_header(self):
magic = self.reader.read_bytes(4)
if (magic != b"ajkg"):
raise ValueError("invalid magic number")
version = self.reader.read(8)
if (version != 2):
raise ValueError("unsupported version")
file_type = self.long()
channels = self.long()
block_length = self.long()
max_LPC = self.long()
number_of_means = self.long()
bytes_to_skip = self.long()
self.reader.read_bytes(bytes_to_skip)
return (file_type, channels, block_length, max_LPC, number_of_means)
def read(self, pcm_frames):
if (self.stream_finished):
return from_channels([
empty_framelist(1, self.bits_per_sample)
for channel in range(self.channels)
])
c = 0
samples = []
unshifted = []
while (True):
command = self.unsigned(2)
if (((0 <= command) and (command <= 3)
or (7 <= command) and (command <= 8))):
# audio data commands
if (command == 0): # DIFF0
samples.append(
self.read_diff0(self.block_length, self.means[c]))
elif (command == 1): # DIFF1
samples.append(
self.read_diff1(self.block_length,
self.wrapped_samples[c]))
elif (command == 2): # DIFF2
samples.append(
self.read_diff2(self.block_length,
self.wrapped_samples[c]))
elif (command == 3): # DIFF3
samples.append(
self.read_diff3(self.block_length,
self.wrapped_samples[c]))
elif (command == 7): # QLPC
samples.append(
self.read_qlpc(self.block_length, self.means[c],
self.wrapped_samples[c]))
elif (command == 8): # ZERO
samples.append([0] * self.block_length)
# update means for channel
self.means[c].append(shnmean(samples[c]))
self.means[c] = self.means[c][1:]
# wrap samples for next command in channel
self.wrapped_samples[c] = samples[c][-(max(3, self.max_LPC)):]
# apply left shift to samples
if (self.left_shift > 0):
unshifted.append(
[s << self.left_shift for s in samples[c]])
else:
unshifted.append(samples[c])
c += 1
if (c == self.channels):
# return a FrameList from shifted data
return from_channels([
from_list(channel, 1, self.bits_per_sample,
self.signed_samples) for channel in unshifted
])
else:
# non audio commands
if (command == 4): # QUIT
self.stream_finished = True
return from_channels([
empty_framelist(1, self.bits_per_sample)
for channel in range(self.channels)
])
elif (command == 5): # BLOCKSIZE
self.block_length = self.long()
elif (command == 6): # BITSHIFT
self.left_shift = self.unsigned(2)
elif (command == 9): # VERBATIM
# skip this command during reading
size = self.unsigned(5)
for i in range(size):
self.skip_unsigned(8)
else:
raise ValueError("unsupported Shorten command")
def read_diff0(self, block_length, means):
offset = shnmean(means)
energy = self.unsigned(3)
samples = []
for i in range(block_length):
residual = self.signed(energy)
samples.append(residual + offset)
return samples
def read_diff1(self, block_length, previous_samples):
samples = previous_samples[-1:]
energy = self.unsigned(3)
for i in range(1, block_length + 1):
residual = self.signed(energy)
samples.append(samples[i - 1] + residual)
return samples[1:]
def read_diff2(self, block_length, previous_samples):
samples = previous_samples[-2:]
energy = self.unsigned(3)
for i in range(2, block_length + 2):
residual = self.signed(energy)
samples.append((2 * samples[i - 1]) - samples[i - 2] + residual)
return samples[2:]
def read_diff3(self, block_length, previous_samples):
samples = previous_samples[-3:]
energy = self.unsigned(3)
for i in range(3, block_length + 3):
residual = self.signed(energy)
samples.append((3 * (samples[i - 1] - samples[i - 2])) +
samples[i - 3] + residual)
return samples[3:]
def read_qlpc(self, block_length, means, previous_samples):
offset = shnmean(means)
energy = self.unsigned(3)
LPC_count = self.unsigned(2)
LPC_coeff = [self.signed(5) for i in range(LPC_count)]
unoffset = []
samples = previous_samples[-LPC_count:]
for i in range(block_length):
residual = self.signed(energy)
LPC_sum = 2**5
for j in range(LPC_count):
if ((i - j - 1) < 0):
# apply offset to warm-up samples
LPC_sum += (LPC_coeff[j] * (samples[LPC_count +
(i - j - 1)] - offset))
else:
LPC_sum += LPC_coeff[j] * unoffset[i - j - 1]
unoffset.append(LPC_sum // 2**5 + residual)
return [u + offset for u in unoffset]
def close(self):
self.reader.close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
self.close()
