def get_metadata(self): """returns a MetaData object, or None raises IOError if unable to read the file""" from io import BytesIO from audiotools.bitstream import BitstreamReader from audiotools.ogg import PacketReader, PageReader reader = PacketReader(PageReader(open(self.filename, "rb"))) identification = reader.read_packet() comment = BitstreamReader(BytesIO(reader.read_packet()), True) if (comment.read_bytes(8) == "OpusTags"): vendor_string = \ comment.read_bytes(comment.read(32)).decode('utf-8') comment_strings = [ comment.read_bytes(comment.read(32)).decode('utf-8') for i in range(comment.read(32)) ] return VorbisComment(comment_strings, vendor_string) else: return None
def get_metadata(self): """returns a MetaData object, or None raises IOError if unable to read the file""" from cStringIO import StringIO from audiotools.bitstream import BitstreamReader from audiotools.ogg import PacketReader, PageReader from audiotools.vorbiscomment import VorbisComment reader = PacketReader(PageReader(open(self.filename, "rb"))) identification = reader.read_packet() comment = BitstreamReader(StringIO(reader.read_packet()), True) (packet_type, packet_header) = comment.parse("8u 6b") if ((packet_type == 3) and (packet_header == 'vorbis')): vendor_string = \ comment.read_bytes(comment.read(32)).decode('utf-8') comment_strings = [ comment.read_bytes(comment.read(32)).decode('utf-8') for i in xrange(comment.read(32))] if (comment.read(1) == 1): # framing bit return VorbisComment(comment_strings, vendor_string) else: return None else: return None
def get_metadata(self): """returns a MetaData object, or None raises IOError if unable to read the file""" from audiotools.ogg import PacketReader,PageReader from cStringIO import StringIO from audiotools.bitstream import BitstreamReader packets = PacketReader(PageReader(open(self.filename, "rb"))) identification = packets.read_packet() comment = BitstreamReader(StringIO(packets.read_packet()), True) if (comment.read_bytes(8) == "OpusTags"): vendor_string = \ comment.read_bytes(comment.read(32)).decode('utf-8') comment_strings = [ comment.read_bytes(comment.read(32)).decode('utf-8') for i in xrange(comment.read(32))] return VorbisComment(comment_strings, vendor_string) else: return None
def get_metadata(self): """returns a MetaData object, or None raises IOError if unable to read the file""" from io import BytesIO from audiotools.bitstream import BitstreamReader from audiotools.ogg import PacketReader, PageReader from audiotools.vorbiscomment import VorbisComment with PacketReader(PageReader(open(self.filename, "rb"))) as reader: identification = reader.read_packet() comment = BitstreamReader(BytesIO(reader.read_packet()), True) vendor_string = \ comment.read_bytes(comment.read(32)).decode('utf-8') comment_strings = [ comment.read_bytes(comment.read(32)).decode('utf-8') for i in range(comment.read(32))] return VorbisComment(comment_strings, vendor_string)
def __init__(self, filename): """filename is a plain string""" from audiotools.bitstream import BitstreamReader from audiotools import ChannelMask from io import BytesIO WaveContainer.__init__(self, filename) try: f = open(filename, 'rb') except IOError as msg: raise InvalidShorten(str(msg)) reader = BitstreamReader(f, 0) try: if (reader.parse("4b 8u") != ["ajkg", 2]): raise InvalidShorten("invalid Shorten header") except IOError: raise InvalidShorten("invalid Shorten header") def read_unsigned(r, c): MSB = r.unary(1) LSB = r.read(c) return MSB * 2 ** c + LSB def read_long(r): return read_unsigned(r, read_unsigned(r, 2)) # populate channels and bits_per_sample from Shorten header (file_type, self.__channels__, block_length, max_LPC, number_of_means, bytes_to_skip) = [read_long(reader) for i in range(6)] if ((1 <= file_type) and (file_type <= 2)): self.__bits_per_sample__ = 8 elif ((3 <= file_type) and (file_type <= 6)): self.__bits_per_sample__ = 16 else: # FIXME raise InvalidShorten("unsupported Shorten file type") # setup some default dummy metadata self.__sample_rate__ = 44100 if (self.__channels__ == 1): self.__channel_mask__ = ChannelMask(0x4) elif (self.__channels__ == 2): self.__channel_mask__ = ChannelMask(0x3) else: self.__channel_mask__ = ChannelMask(0) self.__total_frames__ = 0 # populate sample_rate and total_frames from first VERBATIM command command = read_unsigned(reader, 2) if (command == 9): verbatim_bytes = "".join([chr(read_unsigned(reader, 8) & 0xFF) for i in range(read_unsigned(reader, 5))]) try: wave = BitstreamReader(BytesIO(verbatim_bytes), 1) header = wave.read_bytes(12) if (header.startswith("RIFF") and header.endswith("WAVE")): # got RIFF/WAVE header, so parse wave blocks as needed total_size = len(verbatim_bytes) - 12 while (total_size >= 8): (chunk_id, chunk_size) = wave.parse("4b 32u") total_size -= 8 if (chunk_id == 'fmt '): from audiotools.wav import parse_fmt (channels, self.__sample_rate__, bits_per_sample, self.__channel_mask__) = parse_fmt( wave.substream(chunk_size)) elif (chunk_id == 'data'): self.__total_frames__ = \ (chunk_size // (self.__channels__ * (self.__bits_per_sample__ // 8))) 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 except (IOError, ValueError): pass try: aiff = BitstreamReader(BytesIO(verbatim_bytes), 0) header = aiff.read_bytes(12) if (header.startswith("FORM") and header.endswith("AIFF")): # got FORM/AIFF header, so parse aiff blocks as needed total_size = len(verbatim_bytes) - 12 while (total_size >= 8): (chunk_id, chunk_size) = aiff.parse("4b 32u") total_size -= 8 if (chunk_id == 'COMM'): from audiotools.aiff import parse_comm (channels, total_sample_frames, bits_per_sample, self.__sample_rate__, self.__channel_mask__) = parse_comm( aiff.substream(chunk_size)) elif (chunk_id == 'SSND'): # subtract 8 bytes for "offset" and "block size" self.__total_frames__ = \ ((chunk_size - 8) // (self.__channels__ * (self.__bits_per_sample__ // 8))) 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 except IOError: pass
class AiffReader(object): """a PCMReader object for reading AIFF file contents""" def __init__(self, aiff_filename): """aiff_filename is a string""" from audiotools.bitstream import BitstreamReader self.stream = BitstreamReader(open(aiff_filename, "rb"), False) # ensure FORM<size>AIFF header is ok try: (form, total_size, aiff) = self.stream.parse("4b 32u 4b") except struct.error: from audiotools.text import ERR_AIFF_INVALID_AIFF raise InvalidAIFF(ERR_AIFF_INVALID_AIFF) if form != b'FORM': from audiotools.text import ERR_AIFF_NOT_AIFF raise ValueError(ERR_AIFF_NOT_AIFF) elif aiff != b'AIFF': from audiotools.text import ERR_AIFF_INVALID_AIFF raise ValueError(ERR_AIFF_INVALID_AIFF) else: total_size -= 4 comm_chunk_read = False # walk through chunks until "SSND" chunk encountered while total_size > 0: try: (chunk_id, chunk_size) = self.stream.parse("4b 32u") except struct.error: from audiotools.text import ERR_AIFF_INVALID_AIFF raise ValueError(ERR_AIFF_INVALID_AIFF) if not frozenset(chunk_id).issubset(AiffAudio.PRINTABLE_ASCII): from audiotools.text import ERR_AIFF_INVALID_CHUNK_ID raise ValueError(ERR_AIFF_INVALID_CHUNK_ID) else: total_size -= 8 if chunk_id == b"COMM": # when "COMM" chunk encountered, # use it to populate PCMReader attributes (self.channels, self.total_pcm_frames, self.bits_per_sample, self.sample_rate, channel_mask) = parse_comm(self.stream) self.channel_mask = int(channel_mask) self.bytes_per_pcm_frame = ((self.bits_per_sample // 8) * self.channels) self.remaining_pcm_frames = self.total_pcm_frames comm_chunk_read = True elif chunk_id == b"SSND": # when "SSND" chunk encountered, # strip off the "offset" and "block_size" attributes # and ready PCMReader for reading if not comm_chunk_read: from audiotools.text import ERR_AIFF_PREMATURE_SSND_CHUNK raise ValueError(ERR_AIFF_PREMATURE_SSND_CHUNK) else: self.stream.skip_bytes(8) self.ssnd_start = self.stream.getpos() return else: # all other chunks are ignored self.stream.skip_bytes(chunk_size) if chunk_size % 2: if len(self.stream.read_bytes(1)) < 1: from audiotools.text import ERR_AIFF_INVALID_CHUNK raise ValueError(ERR_AIFF_INVALID_CHUNK) total_size -= (chunk_size + 1) else: total_size -= chunk_size else: # raise an error if no "SSND" chunk is encountered from audiotools.text import ERR_AIFF_NO_SSND_CHUNK raise ValueError(ERR_AIFF_NO_SSND_CHUNK) def __enter__(self): return self def __exit__(self, exc_type, exc_value, traceback): self.close() def read(self, pcm_frames): """try to read a pcm.FrameList with the given number of PCM frames""" # try to read requested PCM frames or remaining frames requested_pcm_frames = min(max(pcm_frames, 1), self.remaining_pcm_frames) requested_bytes = (self.bytes_per_pcm_frame * requested_pcm_frames) pcm_data = self.stream.read_bytes(requested_bytes) # raise exception if "SSND" chunk exhausted early if len(pcm_data) < requested_bytes: from audiotools.text import ERR_AIFF_TRUNCATED_SSND_CHUNK raise IOError(ERR_AIFF_TRUNCATED_SSND_CHUNK) else: self.remaining_pcm_frames -= requested_pcm_frames # return parsed chunk return FrameList(pcm_data, self.channels, self.bits_per_sample, True, True) def read_closed(self, pcm_frames): raise ValueError("cannot read closed stream") def seek(self, pcm_frame_offset): """tries to seek to the given PCM frame offset returns the total amount of frames actually seeked over""" if pcm_frame_offset < 0: from audiotools.text import ERR_NEGATIVE_SEEK raise ValueError(ERR_NEGATIVE_SEEK) # ensure one doesn't walk off the end of the file pcm_frame_offset = min(pcm_frame_offset, self.total_pcm_frames) # position file in "SSND" chunk self.stream.setpos(self.ssnd_start) self.stream.seek((pcm_frame_offset * self.bytes_per_pcm_frame), 1) self.remaining_pcm_frames = (self.total_pcm_frames - pcm_frame_offset) return pcm_frame_offset def seek_closed(self, pcm_frame_offset): raise ValueError("cannot seek closed stream") def close(self): """closes the stream for reading""" self.stream.close() self.read = self.read_closed self.seek = self.seek_closed
def wave_header_footer(self): """returns a pair of data strings before and after PCM data the first contains all data before the PCM content of the data chunk the second containing all data after the data chunk for example: >>> w = audiotools.open("input.wav") >>> (head, tail) = w.wave_header_footer() >>> f = open("output.wav", "wb") >>> f.write(head) >>> audiotools.transfer_framelist_data(w.to_pcm(), f.write) >>> f.write(tail) >>> f.close() should result in "output.wav" being identical to "input.wav" """ from audiotools.bitstream import BitstreamReader from audiotools.bitstream import BitstreamRecorder head = BitstreamRecorder(1) tail = BitstreamRecorder(1) current_block = head fmt_found = False wave_file = BitstreamReader(open(self.filename, 'rb'), 1) try: # transfer the 12-byte "RIFFsizeWAVE" header to head (riff, size, wave) = wave_file.parse("4b 32u 4b") if (riff != 'RIFF'): from audiotools.text import ERR_WAV_NOT_WAVE raise ValueError(ERR_WAV_NOT_WAVE) elif (wave != 'WAVE'): from audiotools.text import ERR_WAV_INVALID_WAVE raise ValueError(ERR_WAV_INVALID_WAVE) else: current_block.build("4b 32u 4b", (riff, size, wave)) total_size = size - 4 while (total_size > 0): # transfer each chunk header (chunk_id, chunk_size) = wave_file.parse("4b 32u") if (not frozenset(chunk_id).issubset(self.PRINTABLE_ASCII)): from audiotools.text import ERR_WAV_INVALID_CHUNK raise ValueError(ERR_WAV_INVALID_CHUNK) else: current_block.build("4b 32u", (chunk_id, chunk_size)) total_size -= 8 # and transfer the full content of non-audio chunks if (chunk_id != "data"): if (chunk_id == "fmt "): if (not fmt_found): fmt_found = True else: from audiotools.text import ERR_WAV_MULTIPLE_FMT raise ValueError(ERR_WAV_MULTIPLE_FMT) if (chunk_size % 2): current_block.write_bytes( wave_file.read_bytes(chunk_size + 1)) total_size -= (chunk_size + 1) else: current_block.write_bytes( wave_file.read_bytes(chunk_size)) total_size -= chunk_size else: wave_file.skip_bytes(chunk_size) current_block = tail if (chunk_size % 2): current_block.write_bytes(wave_file.read_bytes(1)) total_size -= (chunk_size + 1) else: total_size -= chunk_size if (fmt_found): return (head.data(), tail.data()) else: from audiotools.text import ERR_WAV_NO_FMT_CHUNK return ValueError(ERR_WAV_NO_FMT_CHUNK) finally: wave_file.close()
def read_metadata(self): command = self.unsigned(2) if (command == 9): # got verbatim, so read data verbatim_bytes = "".join([chr(self.unsigned(8) & 0xFF) for i in range(self.unsigned(5))]) try: wave = BitstreamReader(cStringIO.StringIO(verbatim_bytes), 1) header = wave.read_bytes(12) if (header.startswith("RIFF") and header.endswith("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 == '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(cStringIO.StringIO(verbatim_bytes), 0) header = aiff.read_bytes(12) if (header.startswith("FORM") and header.endswith("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 == '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
class WaveReader(object): """a PCMReader object for reading wave file contents""" def __init__(self, wave_filename): """wave_filename is a string""" from audiotools.bitstream import BitstreamReader self.stream = BitstreamReader(open(wave_filename, "rb"), True) # ensure RIFF<size>WAVE header is ok try: (riff, total_size, wave) = self.stream.parse("4b 32u 4b") except struct.error: from audiotools.text import ERR_WAV_INVALID_WAVE self.stream.close() raise ValueError(ERR_WAV_INVALID_WAVE) if riff != b'RIFF': from audiotools.text import ERR_WAV_NOT_WAVE self.stream.close() raise ValueError(ERR_WAV_NOT_WAVE) elif wave != b'WAVE': from audiotools.text import ERR_WAV_INVALID_WAVE self.stream.close() raise ValueError(ERR_WAV_INVALID_WAVE) else: total_size -= 4 fmt_chunk_read = False # walk through chunks until "data" chunk encountered while total_size > 0: try: (chunk_id, chunk_size) = self.stream.parse("4b 32u") except struct.error: from audiotools.text import ERR_WAV_INVALID_WAVE self.stream.close() raise ValueError(ERR_WAV_INVALID_WAVE) if not frozenset(chunk_id).issubset(WaveAudio.PRINTABLE_ASCII): from audiotools.text import ERR_WAV_INVALID_CHUNK self.stream.close() raise ValueError(ERR_WAV_INVALID_CHUNK) else: total_size -= 8 if chunk_id == b"fmt ": # when "fmt " chunk encountered, # use it to populate PCMReader attributes (self.channels, self.sample_rate, self.bits_per_sample, channel_mask) = parse_fmt(self.stream) self.channel_mask = int(channel_mask) self.bytes_per_pcm_frame = ((self.bits_per_sample // 8) * self.channels) fmt_chunk_read = True elif chunk_id == b"data": # when "data" chunk encountered, # use its size to determine total PCM frames # and ready PCMReader for reading if not fmt_chunk_read: from audiotools.text import ERR_WAV_PREMATURE_DATA self.stream.close() raise ValueError(ERR_WAV_PREMATURE_DATA) else: self.total_pcm_frames = (chunk_size // self.bytes_per_pcm_frame) self.remaining_pcm_frames = self.total_pcm_frames self.data_start = self.stream.getpos() return else: # all other chunks are ignored self.stream.skip_bytes(chunk_size) if chunk_size % 2: if len(self.stream.read_bytes(1)) < 1: from audiotools.text import ERR_WAV_INVALID_CHUNK self.stream.close() raise ValueError(ERR_WAV_INVALID_CHUNK) total_size -= (chunk_size + 1) else: total_size -= chunk_size else: # raise an error if no "data" chunk is encountered from audiotools.text import ERR_WAV_NO_DATA_CHUNK self.stream.close() raise ValueError(ERR_WAV_NO_DATA_CHUNK) def __enter__(self): return self def __exit__(self, exc_type, exc_value, traceback): self.close() def read(self, pcm_frames): """try to read a pcm.FrameList with the given number of PCM frames""" # try to read requested PCM frames or remaining frames requested_pcm_frames = min(max(pcm_frames, 1), self.remaining_pcm_frames) requested_bytes = (self.bytes_per_pcm_frame * requested_pcm_frames) pcm_data = self.stream.read_bytes(requested_bytes) # raise exception if "data" chunk exhausted early if len(pcm_data) < requested_bytes: from audiotools.text import ERR_WAV_TRUNCATED_DATA_CHUNK raise IOError(ERR_WAV_TRUNCATED_DATA_CHUNK) else: self.remaining_pcm_frames -= requested_pcm_frames # return parsed chunk return FrameList(pcm_data, self.channels, self.bits_per_sample, False, self.bits_per_sample != 8) def read_closed(self, pcm_frames): raise ValueError("cannot read closed stream") def seek(self, pcm_frame_offset): """tries to seek to the given PCM frame offset returns the total amount of frames actually seeked over""" if pcm_frame_offset < 0: from audiotools.text import ERR_NEGATIVE_SEEK raise ValueError(ERR_NEGATIVE_SEEK) # ensure one doesn't walk off the end of the file pcm_frame_offset = min(pcm_frame_offset, self.total_pcm_frames) # position file in "data" chunk self.stream.setpos(self.data_start) self.stream.seek(pcm_frame_offset * self.bytes_per_pcm_frame, 1) self.remaining_pcm_frames = (self.total_pcm_frames - pcm_frame_offset) return pcm_frame_offset def seek_closed(self, pcm_frame_offset): raise ValueError("cannot seek closed stream") def close(self): """closes the stream for reading""" self.stream.close() self.read = self.read_closed self.seek = self.seek_closed
def __init__(self, filename): """filename is a plain string""" from audiotools.bitstream import BitstreamReader from audiotools import ChannelMask from io import BytesIO WaveContainer.__init__(self, filename) try: f = open(filename, 'rb') except IOError as msg: raise InvalidShorten(str(msg)) reader = BitstreamReader(f, 0) try: if (reader.parse("4b 8u") != ["ajkg", 2]): raise InvalidShorten("invalid Shorten header") except IOError: raise InvalidShorten("invalid Shorten header") def read_unsigned(r, c): MSB = r.unary(1) LSB = r.read(c) return MSB * 2**c + LSB def read_long(r): return read_unsigned(r, read_unsigned(r, 2)) # populate channels and bits_per_sample from Shorten header (file_type, self.__channels__, block_length, max_LPC, number_of_means, bytes_to_skip) = [read_long(reader) for i in range(6)] if ((1 <= file_type) and (file_type <= 2)): self.__bits_per_sample__ = 8 elif ((3 <= file_type) and (file_type <= 6)): self.__bits_per_sample__ = 16 else: # FIXME raise InvalidShorten("unsupported Shorten file type") # setup some default dummy metadata self.__sample_rate__ = 44100 if (self.__channels__ == 1): self.__channel_mask__ = ChannelMask(0x4) elif (self.__channels__ == 2): self.__channel_mask__ = ChannelMask(0x3) else: self.__channel_mask__ = ChannelMask(0) self.__total_frames__ = 0 # populate sample_rate and total_frames from first VERBATIM command command = read_unsigned(reader, 2) if (command == 9): verbatim_bytes = "".join([ chr(read_unsigned(reader, 8) & 0xFF) for i in range(read_unsigned(reader, 5)) ]) try: wave = BitstreamReader(BytesIO(verbatim_bytes), 1) header = wave.read_bytes(12) if (header.startswith("RIFF") and header.endswith("WAVE")): # got RIFF/WAVE header, so parse wave blocks as needed total_size = len(verbatim_bytes) - 12 while (total_size >= 8): (chunk_id, chunk_size) = wave.parse("4b 32u") total_size -= 8 if (chunk_id == 'fmt '): from audiotools.wav import parse_fmt (channels, self.__sample_rate__, bits_per_sample, self.__channel_mask__) = parse_fmt( wave.substream(chunk_size)) elif (chunk_id == 'data'): self.__total_frames__ = \ (chunk_size // (self.__channels__ * (self.__bits_per_sample__ // 8))) 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 except (IOError, ValueError): pass try: aiff = BitstreamReader(BytesIO(verbatim_bytes), 0) header = aiff.read_bytes(12) if (header.startswith("FORM") and header.endswith("AIFF")): # got FORM/AIFF header, so parse aiff blocks as needed total_size = len(verbatim_bytes) - 12 while (total_size >= 8): (chunk_id, chunk_size) = aiff.parse("4b 32u") total_size -= 8 if (chunk_id == 'COMM'): from audiotools.aiff import parse_comm (channels, total_sample_frames, bits_per_sample, self.__sample_rate__, self.__channel_mask__) = parse_comm( aiff.substream(chunk_size)) elif (chunk_id == 'SSND'): # subtract 8 bytes for "offset" and "block size" self.__total_frames__ = \ ((chunk_size - 8) // (self.__channels__ * (self.__bits_per_sample__ // 8))) 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 except IOError: pass
class FlacDecoder(object): CHANNEL_COUNT = [ 1, 2, 3, 4, 5, 6, 7, 8, 2, 2, 2, None, None, None, None, None ] (SUBFRAME_CONSTANT, SUBFRAME_VERBATIM, SUBFRAME_FIXED, SUBFRAME_LPC) = range(4) def __init__(self, filename, channel_mask): self.reader = BitstreamReader(open(filename, "rb"), False) if (self.reader.read_bytes(4) != b'fLaC'): raise ValueError("invalid FLAC file") self.current_md5sum = md5() # locate the STREAMINFO, # which is sometimes needed to handle non-subset streams for (block_id, block_size, block_reader) in self.metadata_blocks(self.reader): if (block_id == 0): # read STREAMINFO self.minimum_block_size = block_reader.read(16) self.maximum_block_size = block_reader.read(16) self.minimum_frame_size = block_reader.read(24) self.maximum_frame_size = block_reader.read(24) self.sample_rate = block_reader.read(20) self.channels = block_reader.read(3) + 1 self.channel_mask = channel_mask self.bits_per_sample = block_reader.read(5) + 1 self.total_frames = block_reader.read(36) self.md5sum = block_reader.read_bytes(16) # these are frame header lookup tables # which vary slightly depending on STREAMINFO's values self.BLOCK_SIZE = [ self.maximum_block_size, 192, 576, 1152, 2304, 4608, None, None, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768 ] self.SAMPLE_RATE = [ self.sample_rate, 88200, 176400, 192000, 8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000, None, None, None, None ] self.BITS_PER_SAMPLE = [ self.bits_per_sample, 8, 12, None, 16, 20, 24, None ] def metadata_blocks(self, reader): """yields a (block_id, block_size, block_reader) tuple per metadata block where block_reader is a BitstreamReader substream""" (last_block, block_id, block_size) = self.reader.parse("1u 7u 24u") while (last_block == 0): yield (block_id, block_size, self.reader.substream(block_size)) (last_block, block_id, block_size) = self.reader.parse("1u 7u 24u") else: yield (block_id, block_size, self.reader.substream(block_size)) def read(self, pcm_frames): # if the stream is exhausted, # verify its MD5 sum and return an empty pcm.FrameList object if (self.total_frames < 1): if (self.md5sum == self.current_md5sum.digest()): return empty_framelist(self.channels, self.bits_per_sample) else: raise ValueError("MD5 checksum mismatch") crc16 = CRC16() self.reader.add_callback(crc16.update) # fetch the decoding parameters from the frame header (block_size, channel_assignment, bits_per_sample) = self.read_frame_header() channel_count = self.CHANNEL_COUNT[channel_assignment] if (channel_count is None): raise ValueError("invalid channel assignment") # channel data will be a list of signed sample lists, one per channel # such as [[1, 2, 3, ...], [4, 5, 6, ...]] for a 2 channel stream channel_data = [] for channel_number in range(channel_count): if ((channel_assignment == 0x8) and (channel_number == 1)): # for left-difference assignment # the difference channel has 1 additional bit channel_data.append( self.read_subframe(block_size, bits_per_sample + 1)) elif ((channel_assignment == 0x9) and (channel_number == 0)): # for difference-right assignment # the difference channel has 1 additional bit channel_data.append( self.read_subframe(block_size, bits_per_sample + 1)) elif ((channel_assignment == 0xA) and (channel_number == 1)): # for average-difference assignment # the difference channel has 1 additional bit channel_data.append( self.read_subframe(block_size, bits_per_sample + 1)) else: # otherwise, use the frame's bits-per-sample value channel_data.append( self.read_subframe(block_size, bits_per_sample)) # one all the subframes have been decoded, # reconstruct them depending on the channel assignment if (channel_assignment == 0x8): # left-difference samples = [] for (left, difference) in zip(*channel_data): samples.append(left) samples.append(left - difference) elif (channel_assignment == 0x9): # difference-right samples = [] for (difference, right) in zip(*channel_data): samples.append(difference + right) samples.append(right) elif (channel_assignment == 0xA): # mid-side samples = [] for (mid, side) in zip(*channel_data): samples.append((((mid * 2) + (side % 2)) + side) // 2) samples.append((((mid * 2) + (side % 2)) - side) // 2) else: # independent samples = [0] * block_size * channel_count for (i, channel) in enumerate(channel_data): samples[i::channel_count] = channel self.reader.byte_align() # read and verify the frame's trailing CRC-16 footer self.reader.read(16) self.reader.pop_callback() if (int(crc16) != 0): raise ValueError("CRC16 mismatch in frame footer") # deduct the amount of PCM frames from the remaining amount self.total_frames -= block_size # build a pcm.FrameList object from the combined samples framelist = from_list(samples, channel_count, bits_per_sample, True) # update the running MD5 sum calculation with the frame's data self.current_md5sum.update(framelist.to_bytes(0, 1)) # and finally return the frame data return framelist def read_frame_header(self): crc8 = CRC8() self.reader.add_callback(crc8.update) # read the 32-bit FLAC frame header sync_code = self.reader.read(14) if (sync_code != 0x3FFE): raise ValueError("invalid sync code") self.reader.skip(1) blocking_strategy = self.reader.read(1) block_size_bits = self.reader.read(4) sample_rate_bits = self.reader.read(4) channel_assignment = self.reader.read(4) bits_per_sample_bits = self.reader.read(3) self.reader.skip(1) # the frame number is a UTF-8 encoded value # which takes a variable number of whole bytes frame_number = self.read_utf8() # unpack the 4 bit block size field # which is the total PCM frames in the FLAC frame # and may require up to 16 more bits if the frame is usually-sized # (which typically happens at the end of the stream) if (block_size_bits == 0x6): block_size = self.reader.read(8) + 1 elif (block_size_bits == 0x7): block_size = self.reader.read(16) + 1 else: block_size = self.BLOCK_SIZE[block_size_bits] # unpack the 4 bit sample rate field # which is used for playback, but not needed for decoding # and may require up to 16 more bits # if the stream has a particularly unusual sample rate if (sample_rate_bits == 0xC): sample_rate = self.reader.read(8) * 1000 elif (sample_rate_bits == 0xD): sample_rate = self.reader.read(16) elif (sample_rate_bits == 0xE): sample_rate = self.reader.read(16) * 10 elif (sample_rate_bits == 0xF): raise ValueError("invalid sample rate") else: sample_rate = self.SAMPLE_RATE[sample_rate_bits] # unpack the 3 bit bits-per-sample field # this never requires additional bits if ((bits_per_sample_bits == 0x3) or (bits_per_sample_bits == 0x7)): raise ValueError("invalid bits per sample") else: bits_per_sample = self.BITS_PER_SAMPLE[bits_per_sample_bits] # read and verify frame's CRC-8 value self.reader.read(8) self.reader.pop_callback() if (int(crc8) != 0): raise ValueError("CRC8 mismatch in frame header") return (block_size, channel_assignment, bits_per_sample) def read_subframe_header(self): """returns a tuple of (subframe_type, subframe_order, wasted_bps)""" self.reader.skip(1) subframe_type = self.reader.read(6) if (self.reader.read(1) == 1): wasted_bps = self.reader.unary(1) + 1 else: wasted_bps = 0 # extract "order" value from 6 bit subframe type, if necessary if (subframe_type == 0): return (self.SUBFRAME_CONSTANT, None, wasted_bps) elif (subframe_type == 1): return (self.SUBFRAME_VERBATIM, None, wasted_bps) elif ((subframe_type & 0x38) == 0x08): return (self.SUBFRAME_FIXED, subframe_type & 0x07, wasted_bps) elif ((subframe_type & 0x20) == 0x20): return (self.SUBFRAME_LPC, (subframe_type & 0x1F) + 1, wasted_bps) else: raise ValueError("invalid subframe type") def read_subframe(self, block_size, bits_per_sample): (subframe_type, subframe_order, wasted_bps) = self.read_subframe_header() # read a list of signed sample values # depending on the subframe type, block size, # adjusted bits per sample and optional subframe order if (subframe_type == self.SUBFRAME_CONSTANT): subframe_samples = self.read_constant_subframe( block_size, bits_per_sample - wasted_bps) elif (subframe_type == self.SUBFRAME_VERBATIM): subframe_samples = self.read_verbatim_subframe( block_size, bits_per_sample - wasted_bps) elif (subframe_type == self.SUBFRAME_FIXED): subframe_samples = self.read_fixed_subframe( block_size, bits_per_sample - wasted_bps, subframe_order) else: subframe_samples = self.read_lpc_subframe( block_size, bits_per_sample - wasted_bps, subframe_order) # account for wasted bits-per-sample, if necessary if (wasted_bps): return [sample << wasted_bps for sample in subframe_samples] else: return subframe_samples def read_constant_subframe(self, block_size, bits_per_sample): sample = self.reader.read_signed(bits_per_sample) return [sample] * block_size def read_verbatim_subframe(self, block_size, bits_per_sample): return [ self.reader.read_signed(bits_per_sample) for x in range(block_size) ] def read_fixed_subframe(self, block_size, bits_per_sample, order): # "order" number of warm-up samples samples = [ self.reader.read_signed(bits_per_sample) for i in range(order) ] # "block_size" - "order" number of residual values residuals = self.read_residual(block_size, order) # which are applied to the warm-up samples # depending on the FIXED subframe order # and results in "block_size" number of total samples if (order == 0): return residuals elif (order == 1): for residual in residuals: samples.append(samples[-1] + residual) return samples elif (order == 2): for residual in residuals: samples.append((2 * samples[-1]) - samples[-2] + residual) return samples elif (order == 3): for residual in residuals: samples.append((3 * samples[-1]) - (3 * samples[-2]) + samples[-3] + residual) return samples elif (order == 4): for residual in residuals: samples.append((4 * samples[-1]) - (6 * samples[-2]) + (4 * samples[-3]) - samples[-4] + residual) return samples else: raise ValueError("unsupported FIXED subframe order") def read_lpc_subframe(self, block_size, bits_per_sample, order): # "order" number of warm-up samples samples = [ self.reader.read_signed(bits_per_sample) for i in range(order) ] # the size of each QLP coefficient, in bits qlp_precision = self.reader.read(4) # the amount of right shift to apply # during LPC calculation # (though this is a signed value, negative shifts are noops # in the reference FLAC decoder) qlp_shift_needed = max(self.reader.read_signed(5), 0) # "order" number of signed QLP coefficients qlp_coeffs = [ self.reader.read_signed(qlp_precision + 1) for i in range(order) ] # QLP coefficients are applied in reverse order qlp_coeffs.reverse() # "block_size" - "order" number of residual values residuals = self.read_residual(block_size, order) # which are applied to the running LPC calculation for residual in residuals: samples.append((sum([ coeff * sample for (coeff, sample) in zip(qlp_coeffs, samples[-order:]) ]) >> qlp_shift_needed) + residual) return samples def read_residual(self, block_size, order): residuals = [] coding_method = self.reader.read(2) partition_order = self.reader.read(4) # each parititon contains block_size / 2 ** partition_order # number of residuals for partition_number in range(2**partition_order): if (partition_number == 0): # except for the first partition # which contains "order" less than the rest residuals.extend( self.read_residual_partition( coding_method, (block_size // 2**partition_order) - order)) else: residuals.extend( self.read_residual_partition( coding_method, block_size // 2**partition_order)) return residuals def read_residual_partition(self, coding_method, residual_count): if (coding_method == 0): # the Rice parameters determines the number of # least-significant bits to read for each residual rice_parameter = self.reader.read(4) if (rice_parameter == 0xF): escape_code = self.reader.read(5) return [ self.reader.read_signed(escape_code) for i in range(residual_count) ] elif (coding_method == 1): # 24 bps streams may use a 5-bit Rice parameter # for better compression rice_parameter = self.reader.read(5) if (rice_parameter == 0x1F): escape_code = self.reader.read(5) return [ self.reader.read_signed(escape_code) for i in range(residual_count) ] else: raise ValueError("invalid Rice coding parameter") # a list of signed residual values partition_residuals = [] for i in range(residual_count): msb = self.reader.unary(1) # most-significant bits lsb = self.reader.read(rice_parameter) # least-significant bits value = (msb << rice_parameter) | lsb # combined into a value if (value & 1): # whose least-significant bit is the sign value partition_residuals.append(-(value >> 1) - 1) else: partition_residuals.append(value >> 1) return partition_residuals def read_utf8(self): total_bytes = self.reader.unary(0) value = self.reader.read(7 - total_bytes) while (total_bytes > 1): value = ((value << 6) | self.reader.parse("2p 6u")[0]) total_bytes -= 1 return value def close(self): self.reader.close() def __enter__(self): return self def __exit__(self, exc_type, exc_value, traceback): self.close()
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
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()
class AuReader(object): def __init__(self, au_filename): from audiotools.bitstream import BitstreamReader from audiotools.text import (ERR_AU_INVALID_HEADER, ERR_AU_UNSUPPORTED_FORMAT) self.stream = BitstreamReader(open(au_filename, "rb"), False) (magic_number, self.data_offset, data_size, encoding_format, self.sample_rate, self.channels) = self.stream.parse("4b 5* 32u") if (magic_number != b'.snd'): self.stream.close() raise ValueError(ERR_AU_INVALID_HEADER) try: self.bits_per_sample = {2: 8, 3: 16, 4: 24}[encoding_format] except KeyError: self.stream.close() raise ValueError(ERR_AU_UNSUPPORTED_FORMAT) self.channel_mask = {1: 0x4, 2: 0x3}.get(self.channels, 0) self.bytes_per_pcm_frame = ((self.bits_per_sample // 8) * self.channels) self.total_pcm_frames = (data_size // self.bytes_per_pcm_frame) self.remaining_pcm_frames = self.total_pcm_frames def __enter__(self): return self def __exit__(self, exc_type, exc_value, traceback): self.close() def read(self, pcm_frames): # try to read requested PCM frames or remaining frames requested_pcm_frames = min(max(pcm_frames, 1), self.remaining_pcm_frames) requested_bytes = (self.bytes_per_pcm_frame * requested_pcm_frames) pcm_data = self.stream.read_bytes(requested_bytes) # raise exception if data block exhausted early if (len(pcm_data) < requested_bytes): from audiotools.text import ERR_AU_TRUNCATED_DATA raise IOError(ERR_AU_TRUNCATED_DATA) else: self.remaining_pcm_frames -= requested_pcm_frames # return parsed chunk return FrameList(pcm_data, self.channels, self.bits_per_sample, True, True) def read_closed(self, pcm_frames): raise ValueError("cannot read closed stream") def seek(self, pcm_frame_offset): if (pcm_frame_offset < 0): from audiotools.text import ERR_NEGATIVE_SEEK raise ValueError(ERR_NEGATIVE_SEEK) # ensure one doesn't walk off the end of the file pcm_frame_offset = min(pcm_frame_offset, self.total_pcm_frames) # position file in data block self.stream.seek( self.data_offset + (pcm_frame_offset * self.bytes_per_pcm_frame), 0) self.remaining_pcm_frames = (self.total_pcm_frames - pcm_frame_offset) return pcm_frame_offset def seek_closed(self, pcm_frame_offset): raise ValueError("cannot seek closed stream") def close(self): self.stream.close() self.read = self.read_closed self.seek = self.seek_closed
def aiff_header_footer(self): """returns (header, footer) tuple of strings containing all data before and after the PCM stream if self.has_foreign_aiff_chunks() is False, may raise ValueError if the file has no header and footer for any reason""" from audiotools.bitstream import BitstreamReader from audiotools.bitstream import BitstreamRecorder from audiotools.text import (ERR_AIFF_NOT_AIFF, ERR_AIFF_INVALID_AIFF, ERR_AIFF_INVALID_CHUNK_ID) head = BitstreamRecorder(0) tail = BitstreamRecorder(0) current_block = head aiff_file = BitstreamReader(open(self.filename, 'rb'), 0) try: # transfer the 12-byte "RIFFsizeWAVE" header to head (form, size, aiff) = aiff_file.parse("4b 32u 4b") if (form != 'FORM'): raise InvalidAIFF(ERR_AIFF_NOT_AIFF) elif (aiff != 'AIFF'): raise InvalidAIFF(ERR_AIFF_INVALID_AIFF) else: current_block.build("4b 32u 4b", (form, size, aiff)) total_size = size - 4 while (total_size > 0): # transfer each chunk header (chunk_id, chunk_size) = aiff_file.parse("4b 32u") if (not frozenset(chunk_id).issubset(self.PRINTABLE_ASCII)): raise InvalidAIFF(ERR_AIFF_INVALID_CHUNK_ID) else: current_block.build("4b 32u", (chunk_id, chunk_size)) total_size -= 8 # and transfer the full content of non-audio chunks if (chunk_id != "SSND"): if (chunk_size % 2): current_block.write_bytes( aiff_file.read_bytes(chunk_size + 1)) total_size -= (chunk_size + 1) else: current_block.write_bytes( aiff_file.read_bytes(chunk_size)) total_size -= chunk_size else: # transfer alignment as part of SSND's chunk header align = aiff_file.parse("32u 32u") current_block.build("32u 32u", align) aiff_file.skip_bytes(chunk_size - 8) current_block = tail if (chunk_size % 2): current_block.write_bytes(aiff_file.read_bytes(1)) total_size -= (chunk_size + 1) else: total_size -= chunk_size return (head.data(), tail.data()) finally: aiff_file.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 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 FlacDecoder: CHANNEL_COUNT = [1, 2, 3, 4, 5, 6, 7, 8, 2, 2, 2, None, None, None, None, None] (SUBFRAME_CONSTANT, SUBFRAME_VERBATIM, SUBFRAME_FIXED, SUBFRAME_LPC) = range(4) def __init__(self, filename, channel_mask): self.reader = BitstreamReader(open(filename, "rb"), 0) if (self.reader.read_bytes(4) != 'fLaC'): raise ValueError("invalid FLAC file") self.current_md5sum = md5() #locate the STREAMINFO, #which is sometimes needed to handle non-subset streams for (block_id, block_size, block_reader) in self.metadata_blocks(self.reader): if (block_id == 0): #read STREAMINFO self.minimum_block_size = block_reader.read(16) self.maximum_block_size = block_reader.read(16) self.minimum_frame_size = block_reader.read(24) self.maximum_frame_size = block_reader.read(24) self.sample_rate = block_reader.read(20) self.channels = block_reader.read(3) + 1 self.channel_mask = channel_mask self.bits_per_sample = block_reader.read(5) + 1 self.total_frames = block_reader.read64(36) self.md5sum = block_reader.read_bytes(16) #these are frame header lookup tables #which vary slightly depending on STREAMINFO's values self.BLOCK_SIZE = [self.maximum_block_size, 192, 576, 1152, 2304, 4608, None, None, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768] self.SAMPLE_RATE = [self.sample_rate, 88200, 176400, 192000, 8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000, None, None, None, None] self.BITS_PER_SAMPLE = [self.bits_per_sample, 8, 12, None, 16, 20, 24, None] def metadata_blocks(self, reader): """yields a (block_id, block_size, block_reader) tuple per metadata block where block_reader is a BitstreamReader substream""" (last_block, block_id, block_size) = self.reader.parse("1u 7u 24u") while (last_block == 0): yield (block_id, block_size, self.reader.substream(block_size)) (last_block, block_id, block_size) = self.reader.parse("1u 7u 24u") else: yield (block_id, block_size, self.reader.substream(block_size)) def read(self, pcm_frames): #if the stream is exhausted, #verify its MD5 sum and return an empty pcm.FrameList object if (self.total_frames < 1): if (self.md5sum == self.current_md5sum.digest()): return from_list([], self.channels, self.bits_per_sample, True) else: raise ValueError("MD5 checksum mismatch") crc16 = CRC16() self.reader.add_callback(crc16.update) #fetch the decoding parameters from the frame header (block_size, channel_assignment, bits_per_sample) = self.read_frame_header() channel_count = self.CHANNEL_COUNT[channel_assignment] if (channel_count is None): raise ValueError("invalid channel assignment") #channel data will be a list of signed sample lists, one per channel #such as [[1, 2, 3, ...], [4, 5, 6, ...]] for a 2 channel stream channel_data = [] for channel_number in xrange(channel_count): if ((channel_assignment == 0x8) and (channel_number == 1)): #for left-difference assignment #the difference channel has 1 additional bit channel_data.append(self.read_subframe(block_size, bits_per_sample + 1)) elif ((channel_assignment == 0x9) and (channel_number == 0)): #for difference-right assignment #the difference channel has 1 additional bit channel_data.append(self.read_subframe(block_size, bits_per_sample + 1)) elif ((channel_assignment == 0xA) and (channel_number == 1)): #for mid-side assignment #the side channel has 1 additional bit channel_data.append(self.read_subframe(block_size, bits_per_sample + 1)) else: #otherwise, use the frame's bits-per-sample value channel_data.append(self.read_subframe(block_size, bits_per_sample)) #one all the subframes have been decoded, #reconstruct them depending on the channel assignment if (channel_assignment == 0x8): #left-difference samples = [] for (left, difference) in zip(*channel_data): samples.append(left) samples.append(left - difference) elif (channel_assignment == 0x9): #difference-right samples = [] for (difference, right) in zip(*channel_data): samples.append(difference + right) samples.append(right) elif (channel_assignment == 0xA): #mid-side samples = [] for (mid, side) in zip(*channel_data): samples.append((((mid * 2) + (side % 2)) + side) / 2) samples.append((((mid * 2) + (side % 2)) - side) / 2) else: #independent samples = [0] * block_size * channel_count for (i, channel) in enumerate(channel_data): samples[i::channel_count] = channel self.reader.byte_align() #read and verify the frame's trailing CRC-16 footer self.reader.read(16) self.reader.pop_callback() if (int(crc16) != 0): raise ValueError("CRC16 mismatch in frame footer") #deduct the amount of PCM frames from the remaining amount self.total_frames -= block_size #build a pcm.FrameList object from the combined samples framelist = from_list(samples, channel_count, bits_per_sample, True) #update the running MD5 sum calculation with the frame's data self.current_md5sum.update(framelist.to_bytes(0, 1)) #and finally return the frame data return framelist def read_frame_header(self): crc8 = CRC8() self.reader.add_callback(crc8.update) #read the 32-bit FLAC frame header sync_code = self.reader.read(14) if (sync_code != 0x3FFE): raise ValueError("invalid sync code") self.reader.skip(1) blocking_strategy = self.reader.read(1) block_size_bits = self.reader.read(4) sample_rate_bits = self.reader.read(4) channel_assignment = self.reader.read(4) bits_per_sample_bits = self.reader.read(3) self.reader.skip(1) #the frame number is a UTF-8 encoded value #which takes a variable number of whole bytes frame_number = self.read_utf8() #unpack the 4 bit block size field #which is the total PCM frames in the FLAC frame #and may require up to 16 more bits if the frame is usually-sized #(which typically happens at the end of the stream) if (block_size_bits == 0x6): block_size = self.reader.read(8) + 1 elif (block_size_bits == 0x7): block_size = self.reader.read(16) + 1 else: block_size = self.BLOCK_SIZE[block_size_bits] #unpack the 4 bit sample rate field #which is used for playback, but not needed for decoding #and may require up to 16 more bits #if the stream has a particularly unusual sample rate if (sample_rate_bits == 0xC): sample_rate = self.reader.read(8) * 1000 elif (sample_rate_bits == 0xD): sample_rate = self.reader.read(16) elif (sample_rate_bits == 0xE): sample_rate = self.reader.read(16) * 10 elif (sample_rate_bits == 0xF): raise ValueError("invalid sample rate") else: sample_rate = self.SAMPLE_RATE[sample_rate_bits] #unpack the 3 bit bits-per-sample field #this never requires additional bits if ((bits_per_sample_bits == 0x3) or (bits_per_sample_bits == 0x7)): raise ValueError("invalid bits per sample") else: bits_per_sample = self.BITS_PER_SAMPLE[bits_per_sample_bits] #read and verify frame's CRC-8 value self.reader.read(8) self.reader.pop_callback() if (int(crc8) != 0): raise ValueError("CRC8 mismatch in frame header") return (block_size, channel_assignment, bits_per_sample) def read_subframe_header(self): """returns a tuple of (subframe_type, subframe_order, wasted_bps)""" self.reader.skip(1) subframe_type = self.reader.read(6) if (self.reader.read(1) == 1): wasted_bps = self.reader.unary(1) + 1 else: wasted_bps = 0 #extract "order" value from 6 bit subframe type, if necessary if (subframe_type == 0): return (self.SUBFRAME_CONSTANT, None, wasted_bps) elif (subframe_type == 1): return (self.SUBFRAME_VERBATIM, None, wasted_bps) elif ((subframe_type & 0x38) == 0x08): return (self.SUBFRAME_FIXED, subframe_type & 0x07, wasted_bps) elif ((subframe_type & 0x20) == 0x20): return (self.SUBFRAME_LPC, (subframe_type & 0x1F) + 1, wasted_bps) else: raise ValueError("invalid subframe type") def read_subframe(self, block_size, bits_per_sample): (subframe_type, subframe_order, wasted_bps) = self.read_subframe_header() #read a list of signed sample values #depending on the subframe type, block size, #adjusted bits per sample and optional subframe order if (subframe_type == self.SUBFRAME_CONSTANT): subframe_samples = self.read_constant_subframe( block_size, bits_per_sample - wasted_bps) elif (subframe_type == self.SUBFRAME_VERBATIM): subframe_samples = self.read_verbatim_subframe( block_size, bits_per_sample - wasted_bps) elif (subframe_type == self.SUBFRAME_FIXED): subframe_samples = self.read_fixed_subframe( block_size, bits_per_sample - wasted_bps, subframe_order) else: subframe_samples = self.read_lpc_subframe( block_size, bits_per_sample - wasted_bps, subframe_order) #account for wasted bits-per-sample, if necessary if (wasted_bps): return [sample << wasted_bps for sample in subframe_samples] else: return subframe_samples def read_constant_subframe(self, block_size, bits_per_sample): sample = self.reader.read_signed(bits_per_sample) return [sample] * block_size def read_verbatim_subframe(self, block_size, bits_per_sample): return [self.reader.read_signed(bits_per_sample) for x in xrange(block_size)] def read_fixed_subframe(self, block_size, bits_per_sample, order): #"order" number of warm-up samples samples = [self.reader.read_signed(bits_per_sample) for i in xrange(order)] #"block_size" - "order" number of residual values residuals = self.read_residual(block_size, order) #which are applied to the warm-up samples #depending on the FIXED subframe order #and results in "block_size" number of total samples if (order == 0): return residuals elif (order == 1): for residual in residuals: samples.append( samples[-1] + residual) return samples elif (order == 2): for residual in residuals: samples.append( (2 * samples[-1]) - samples[-2] + residual) return samples elif (order == 3): for residual in residuals: samples.append( (3 * samples[-1]) - (3 * samples[-2]) + samples[-3] + residual) return samples elif (order == 4): for residual in residuals: samples.append( (4 * samples[-1]) - (6 * samples[-2]) + (4 * samples[-3]) - samples[-4] + residual) return samples else: raise ValueError("unsupported FIXED subframe order") def read_lpc_subframe(self, block_size, bits_per_sample, order): #"order" number of warm-up samples samples = [self.reader.read_signed(bits_per_sample) for i in xrange(order)] #the size of each QLP coefficient, in bits qlp_precision = self.reader.read(4) #the amount of right shift to apply #during LPC calculation #(though this is a signed value, negative shifts are noops # in the reference FLAC decoder) qlp_shift_needed = max(self.reader.read_signed(5), 0) #"order" number of signed QLP coefficients qlp_coeffs = [self.reader.read_signed(qlp_precision + 1) for i in xrange(order)] #QLP coefficients are applied in reverse order qlp_coeffs.reverse() #"block_size" - "order" number of residual values residuals = self.read_residual(block_size, order) #which are applied to the running LPC calculation for residual in residuals: samples.append((sum([coeff * sample for (coeff, sample) in zip(qlp_coeffs, samples[-order:])]) >> qlp_shift_needed) + residual) return samples def read_residual(self, block_size, order): residuals = [] coding_method = self.reader.read(2) partition_order = self.reader.read(4) #each parititon contains block_size / 2 ** partition_order #number of residuals for partition_number in xrange(2 ** partition_order): if (partition_number == 0): #except for the first partition #which contains "order" less than the rest residuals.extend( self.read_residual_partition( coding_method, (block_size / 2 ** partition_order) - order)) else: residuals.extend( self.read_residual_partition( coding_method, block_size / 2 ** partition_order)) return residuals def read_residual_partition(self, coding_method, residual_count): if (coding_method == 0): #the Rice parameters determines the number of #least-significant bits to read for each residual rice_parameter = self.reader.read(4) if (rice_parameter == 0xF): escape_code = self.reader.read(5) return [self.reader.read_signed(escape_code) for i in xrange(residual_count)] elif (coding_method == 1): #24 bps streams may use a 5-bit Rice parameter #for better compression rice_parameter = self.reader.read(5) if (rice_parameter == 0x1F): escape_code = self.reader.read(5) return [self.reader.read_signed(escape_code) for i in xrange(residual_count)] else: raise ValueError("invalid Rice coding parameter") #a list of signed residual values partition_residuals = [] for i in xrange(residual_count): msb = self.reader.unary(1) # most-significant bits lsb = self.reader.read(rice_parameter) # least-significant bits value = (msb << rice_parameter) | lsb # combined into a value if (value & 1): # whose least-significant bit is the sign value partition_residuals.append(-(value >> 1) - 1) else: partition_residuals.append(value >> 1) return partition_residuals def read_utf8(self): total_bytes = self.reader.unary(0) value = self.reader.read(7 - total_bytes) while (total_bytes > 1): value = ((value << 6) | self.reader.parse("2p 6u")[0]) total_bytes -= 1 return value def close(self): self.reader.close()
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
class AuReader(object): def __init__(self, au_filename): from audiotools.bitstream import BitstreamReader from audiotools.text import (ERR_AU_INVALID_HEADER, ERR_AU_UNSUPPORTED_FORMAT) self.stream = BitstreamReader(open(au_filename, "rb"), False) (magic_number, self.data_offset, data_size, encoding_format, self.sample_rate, self.channels) = self.stream.parse("4b 5* 32u") if magic_number != b'.snd': self.stream.close() raise ValueError(ERR_AU_INVALID_HEADER) try: self.bits_per_sample = {2: 8, 3: 16, 4: 24}[encoding_format] except KeyError: self.stream.close() raise ValueError(ERR_AU_UNSUPPORTED_FORMAT) self.channel_mask = {1: 0x4, 2: 0x3}.get(self.channels, 0) self.bytes_per_pcm_frame = ((self.bits_per_sample // 8) * self.channels) self.total_pcm_frames = (data_size // self.bytes_per_pcm_frame) self.remaining_pcm_frames = self.total_pcm_frames def __enter__(self): return self def __exit__(self, exc_type, exc_value, traceback): self.close() def read(self, pcm_frames): # try to read requested PCM frames or remaining frames requested_pcm_frames = min(max(pcm_frames, 1), self.remaining_pcm_frames) requested_bytes = (self.bytes_per_pcm_frame * requested_pcm_frames) pcm_data = self.stream.read_bytes(requested_bytes) # raise exception if data block exhausted early if len(pcm_data) < requested_bytes: from audiotools.text import ERR_AU_TRUNCATED_DATA raise IOError(ERR_AU_TRUNCATED_DATA) else: self.remaining_pcm_frames -= requested_pcm_frames # return parsed chunk return FrameList(pcm_data, self.channels, self.bits_per_sample, True, True) def read_closed(self, pcm_frames): raise ValueError("cannot read closed stream") def seek(self, pcm_frame_offset): if pcm_frame_offset < 0: from audiotools.text import ERR_NEGATIVE_SEEK raise ValueError(ERR_NEGATIVE_SEEK) # ensure one doesn't walk off the end of the file pcm_frame_offset = min(pcm_frame_offset, self.total_pcm_frames) # position file in data block self.stream.seek(self.data_offset + (pcm_frame_offset * self.bytes_per_pcm_frame), 0) self.remaining_pcm_frames = (self.total_pcm_frames - pcm_frame_offset) return pcm_frame_offset def seek_closed(self, pcm_frame_offset): raise ValueError("cannot seek closed stream") def close(self): self.stream.close() self.read = self.read_closed self.seek = self.seek_closed