sndhdr.what() does not recognize wav file

[klankschap]

BPO	1611944
Files	Audio01.rar: wav in rar archive sndhdr.diff: Patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2006-12-09.02:37:48.000>
labels = ['type-bug', 'library']
title = 'sndhdr.what() does not recognize wav file'
updated_at = <Date 2020-09-19.19:04:33.906>
user = 'https://bugs.python.org/klankschap'

bugs.python.org fields:

activity = <Date 2020-09-19.19:04:33.906>
actor = 'georg.brandl'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2006-12-09.02:37:48.000>
creator = 'klankschap'
dependencies = []
files = ['2251', '11501']
hgrepos = []
issue_num = 1611944
keywords = ['patch']
message_count = 7.0
messages = ['30765', '30766', '30767', '30768', '30769', '30770', '73294']
nosy_count = 2.0
nosy_names = ['klankschap', 'matthijs']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue1611944'
versions = ['Python 3.1', 'Python 2.7', 'Python 3.2']

[klankschap]

using 2.5 on osx 10.4
the sndhdr.what() function fails to recognize some wav headers.
however these wav files are recognized correctly by other 'standard' applications like quicktime and itunes.

[birkenfeld]

We'd need some more information about these specific wave files in order to improve sndhdr.what().

Can you try to find out why they aren't recognized correctly, or what their header (sndhdr reads the first 512 bytes) looks like?

[klankschap]

Attached you find (in a rar file) a 260kb wav file, 2 tracks, 24 bit, 44.1kHz
You can play it, ask either OSX or XP to show the properties.
Yet sndhdr.what() returns None

File Added: Audio01.rar

[klankschap]

Apparently the sndhdr.what() function does not skip the embedded comment chunk at the start.

[birkenfeld]

I see. The problem is, as the "bext" chunk can be arbitrarily long, the test function would need more than 512 bytes to read the "fmt " chunk, or it could return that it cannot read the format details.

Would you like to work on a patch?

[klankschap]

this could be a start.
however the initial 512 bytes might be too short.
i don't see (yet) how to increase that in a snazzy way.
i just changed it into a read(1024)

def test_wav_test( h ):
    if h[:4] != 'RIFF' or h[8:12] != 'WAVE':
        return None
    if h[12:16] == 'fmt ':
        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
    elif h[12:16] == 'bext':
        offset = 12
        while True:
            try:
                if h[offset:offset+4] == 'fmt ':
                    nchannels =  get_short_le( h[offset+10:offset+12] )
                    rate = get_long_le( h[offset+12:offset+16] )
                    sample_bits =  get_short_le( h[offset+22:offset+24] )
                    return 'wav', rate, nchannels, -1, sample_bits
                offset += ( get_long_le( h[offset+4:offset+8] ) + 8 )
            except IndexError:
                print 'header buffer too short'
                return None

[matthijs]

I've written a new patch, which works a bit better. You can find the new
patch attached.

I've restructed the patch to prevent code duplication. Also, it now
works with other chunks than bext (I had a file with a list chunk which
triggered my interest in this bug). This is done with a hardcoded list
of valid chunks. However, it seems that there is no complete list of
valid chunk types, so it might be better to remove the chunk type check
alltogether.

Also, this patch explicitly checks for overflow, since taking a slice of
a sequence does not seem to trigger an IndexError, but just return an
empty sequence.

[hugovk]

Note the sndhdr module is deprecated in 3.11 and set for removal in 3.13.

See PEP 594 – Removing dead batteries from the standard library and #91217.

[AlexWaygood]

Note the sndhdr module is deprecated in 3.11 and set for removal in 3.13.

See PEP 594 – Removing dead batteries from the standard library and #91217.

snhdr has been deprecated in part because it has no active maintainer in the core dev team. Now that the module is deprecated, bugfixes and improvements to the module will be low priority; moreover, the fact that this issue has not seen any activity since 2008 indicates that this problem probably does not affect a large number of users. I am therefore closing this issue.

Cc. @klankschap, @matthijs