Lib/sndhdr.py

# This module contains several routines that 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, IOError 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 whatraw() calls the "whatsound" program and interprets its
# output.  You'll have to guess the sampling rate by listening though!
#
# Function what() calls whathdr() and if it doesn't recognize the file
# then calls whatraw().
#
# 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.


#------------------------------------------------------#
# Guess the type of any sound file, raw or with header #
#------------------------------------------------------#

def what(filename):
	res = whathdr(filename)
	if not res:
		res = whatraw(filename)
	return res


#-----------------------------#
# Guess the type of raw sound #
#-----------------------------#

def whatraw(filename):
	# Assume it's always 1 channel, byte-sized samples
	# Don't assume anything about the rate
	import os
	from stat import ST_SIZE
	# XXX "whatsound" should be part of the distribution somehow...
	cmd = 'whatsound ' + filename + ' 2>/dev/null'
	cmd = 'PATH=$PATH:/ufs/guido/bin/sgi\n' + cmd
	pipe = os.popen(cmd, 'r')
	data = pipe.read()
	sts = pipe.close()
	if sts:
		return None
	if data[:13] == '-t raw -b -s ':
		type = 'sb'
		sample_size = 8
	elif data[:13] == '-t raw -b -u ':
		type = 'ub'
		sample_size = 8
	elif data[:13] == '-t raw -b -U ':
		type = 'ul'
		sample_size = 'U'
	else:
		return None
	try:
		frame_count = os.stat(filename)[ST_SIZE]
	except IOError:
		frame_count = -1
	return type, 0, 1, frame_count, sample_size


#-------------------------#
# Recognize sound headers #
#-------------------------#

def whathdr(filename):
	f = open(filename, 'r')
	h = f.read(512)
	for tf in tests:
		res = tf(h, f)
		if res:
			return res
	return None


#-----------------------------------#
# Subroutines per sound header type #
#-----------------------------------#

tests = []

def test_aifc(h, f):
	import aifc
	if h[:4] <> 'FORM':
		return None
	if h[8:12] == 'AIFC':
		fmt = 'aifc'
	elif h[8:12] == 'AIFF':
		fmt = 'aiff'
	else:
		return None
	f.seek(0)
	try:
		a = aifc.openfp(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[:4] == '.snd':
		f = get_long_be
	elif h[:4] in ('\0ds.', 'dns.'):
		f = get_long_le
	else:
		return None
	type = 'au'
	hdr_size = f(h[4:8])
	data_size = f(h[8:12])
	encoding = f(h[12:16])
	rate = f(h[16:20])
	nchannels = f(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
	return type, rate, nchannels, data_size/frame_size, sample_bits

tests.append(test_au)


def test_hcom(h, f):
	if h[65:69] <> 'FSSD' or h[128:132] <> 'HCOM':
		return None
	divisor = get_long_be(h[128+16:128+20])
	return 'hcom', 22050/divisor, 1, -1, 8

tests.append(test_hcom)


def test_voc(h, f):
	if h[:20] <> 'Creative Voice File\032':
		return None
	sbseek = get_short_le(h[20:22])
	rate = 0
	if 0 <= sbseek < 500 and h[sbseek] == '\1':
		ratecode = ord(h[sbseek+4])
		rate = int(1000000.0 / (256 - ratecode))
	return 'voc', rate, 1, -1, 8

tests.append(test_voc)


def test_wav(h, f):
	# 'RIFF' <len> 'WAVE' 'fmt ' <len>
	if h[:4] <> 'RIFF' or h[8:12] <> 'WAVE' or h[12:16] <> 'fmt ':
		return None
	style = get_short_le(h[20:22])
	nchannels = get_short_le(h[22:24])
	rate = get_long_le(h[24:28])
	sample_bits = get_short_le(h[34:36])
	return 'wav', rate, nchannels, -1, sample_bits

tests.append(test_wav)


def test_8svx(h, f):
	if h[:4] <> 'FORM' or h[8:12] <> '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[:5] == '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[:2] == '\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 strings #
#---------------------------------------------#

def get_long_be(s):
	return (ord(s[0])<<24) | (ord(s[1])<<16) | (ord(s[2])<<8) | ord(s[3])

def get_long_le(s):
	return (ord(s[3])<<24) | (ord(s[2])<<16) | (ord(s[1])<<8) | ord(s[0])

def get_short_be(s):
	return (ord(s[0])<<8) | ord(s[1])

def get_short_le(s):
	return (ord(s[1])<<8) | ord(s[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 + '/:',
			if recursive or toplevel:
				print 'recursing down:'
				import glob
				names = glob.glob(os.path.join(filename, '*'))
				testall(names, recursive, 0)
			else:
				print '*** directory (use -r) ***'
		else:
			print filename + ':',
			sys.stdout.flush()
			try:
				print what(filename)
			except IOError:
				print '*** not found ***'