"""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, 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 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"]

def what(filename):

    """Guess the type of a sound file"""

    res = whathdr(filename)

    return res

def whathdr(filename):

    """Recognize sound headers"""

    f = open(filename, 'rb')

    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 ***'

if __name__ == '__main__':

    test()