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File name : sndhdr.py

Content :"""Routines to help recognizing sound files. Function whathdr() recognizes various types of sound file headers. It understands almost all headers that SOX can decode. The return tuple contains the following items, in this order: - file type (as SOX understands it) - sampling rate (0 if unknown or hard to decode) - number of channels (0 if unknown or hard to decode) - number of frames in the file (-1 if unknown or hard to decode) - number of bits/sample, or 'U' for U-LAW, or 'A' for A-LAW If the file doesn't have a recognizable type, it returns None. If the file can't be opened, OSError is raised. To compute the total time, divide the number of frames by the sampling rate (a frame contains a sample for each channel). Function what() calls whathdr(). (It used to also use some heuristics for raw data, but this doesn't work very well.) Finally, the function test() is a simple main program that calls what() for all files mentioned on the argument list. For directory arguments it calls what() for all files in that directory. Default argument is "." (testing all files in the current directory). The option -r tells it to recurse down directories found inside explicitly given directories. """ # The file structure is top-down except that the test program and its # subroutine come last. __all__ = ['what', 'whathdr'] from collections import namedtuple SndHeaders = namedtuple('SndHeaders', 'filetype framerate nchannels nframes sampwidth') SndHeaders.filetype.__doc__ = ("""The value for type indicates the data type and will be one of the strings 'aifc', 'aiff', 'au','hcom', 'sndr', 'sndt', 'voc', 'wav', '8svx', 'sb', 'ub', or 'ul'.""") SndHeaders.framerate.__doc__ = ("""The sampling_rate will be either the actual value or 0 if unknown or difficult to decode.""") SndHeaders.nchannels.__doc__ = ("""The number of channels or 0 if it cannot be determined or if the value is difficult to decode.""") SndHeaders.nframes.__doc__ = ("""The value for frames will be either the number of frames or -1.""") SndHeaders.sampwidth.__doc__ = ("""Either the sample size in bits or 'A' for A-LAW or 'U' for u-LAW.""") def what(filename): """Guess the type of a sound file.""" res = whathdr(filename) return res def whathdr(filename): """Recognize sound headers.""" with open(filename, 'rb') as f: h = f.read(512) for tf in tests: res = tf(h, f) if res: return SndHeaders(*res) return None #-----------------------------------# # Subroutines per sound header type # #-----------------------------------# tests = [] def test_aifc(h, f): import aifc if not h.startswith(b'FORM'): return None if h[8:12] == b'AIFC': fmt = 'aifc' elif h[8:12] == b'AIFF': fmt = 'aiff' else: return None f.seek(0) try: a = aifc.open(f, 'r') except (EOFError, aifc.Error): return None return (fmt, a.getframerate(), a.getnchannels(), a.getnframes(), 8 * a.getsampwidth()) tests.append(test_aifc) def test_au(h, f): if h.startswith(b'.snd'): func = get_long_be elif h[:4] in (b'\0ds.', b'dns.'): func = get_long_le else: return None filetype = 'au' hdr_size = func(h[4:8]) data_size = func(h[8:12]) encoding = func(h[12:16]) rate = func(h[16:20]) nchannels = func(h[20:24]) sample_size = 1 # default if encoding == 1: sample_bits = 'U' elif encoding == 2: sample_bits = 8 elif encoding == 3: sample_bits = 16 sample_size = 2 else: sample_bits = '?' frame_size = sample_size * nchannels if frame_size: nframe = data_size / frame_size else: nframe = -1 return filetype, rate, nchannels, nframe, sample_bits tests.append(test_au) def test_hcom(h, f): if h[65:69] != b'FSSD' or h[128:132] != b'HCOM': return None divisor = get_long_be(h[144:148]) if divisor: rate = 22050 / divisor else: rate = 0 return 'hcom', rate, 1, -1, 8 tests.append(test_hcom) def test_voc(h, f): if not h.startswith(b'Creative Voice File\032'): return None sbseek = get_short_le(h[20:22]) rate = 0 if 0 <= sbseek < 500 and h[sbseek] == 1: ratecode = 256 - h[sbseek+4] if ratecode: rate = int(1000000.0 / ratecode) return 'voc', rate, 1, -1, 8 tests.append(test_voc) def test_wav(h, f): import wave # 'RIFF' <len> 'WAVE' 'fmt ' <len> if not h.startswith(b'RIFF') or h[8:12] != b'WAVE' or h[12:16] != b'fmt ': return None f.seek(0) try: w = wave.open(f, 'r') except (EOFError, wave.Error): return None return ('wav', w.getframerate(), w.getnchannels(), w.getnframes(), 8*w.getsampwidth()) tests.append(test_wav) def test_8svx(h, f): if not h.startswith(b'FORM') or h[8:12] != b'8SVX': return None # Should decode it to get #channels -- assume always 1 return '8svx', 0, 1, 0, 8 tests.append(test_8svx) def test_sndt(h, f): if h.startswith(b'SOUND'): nsamples = get_long_le(h[8:12]) rate = get_short_le(h[20:22]) return 'sndt', rate, 1, nsamples, 8 tests.append(test_sndt) def test_sndr(h, f): if h.startswith(b'\0\0'): rate = get_short_le(h[2:4]) if 4000 <= rate <= 25000: return 'sndr', rate, 1, -1, 8 tests.append(test_sndr) #-------------------------------------------# # Subroutines to extract numbers from bytes # #-------------------------------------------# def get_long_be(b): return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3] def get_long_le(b): return (b[3] << 24) | (b[2] << 16) | (b[1] << 8) | b[0] def get_short_be(b): return (b[0] << 8) | b[1] def get_short_le(b): return (b[1] << 8) | b[0] #--------------------# # Small test program # #--------------------# def test(): import sys recursive = 0 if sys.argv[1:] and sys.argv[1] == '-r': del sys.argv[1:2] recursive = 1 try: if sys.argv[1:]: testall(sys.argv[1:], recursive, 1) else: testall(['.'], recursive, 1) except KeyboardInterrupt: sys.stderr.write('\n[Interrupted]\n') sys.exit(1) def testall(list, recursive, toplevel): import sys import os for filename in list: if os.path.isdir(filename): print(filename + '/:', end=' ') if recursive or toplevel: print('recursing down:') import glob names = glob.glob(os.path.join(glob.escape(filename), '*')) testall(names, recursive, 0) else: print('*** directory (use -r) ***') else: print(filename + ':', end=' ') sys.stdout.flush() try: print(what(filename)) except OSError: print('*** not found ***') if __name__ == '__main__': test()

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