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"""Identify WAV file formats.
This is used only to give better error messages in the event that a sound
file is not loadable by Pygame.
This is based on the 'magic' information for the 'file' command, at
https://github.com/file/file/blob/86e34444a26860f2ad9895a2d77cb16d1ca4c48b/magic/Magdir/riff
"""
from struct import unpack_from
class MagicReader:
"""Interface to reading the magic numbers in a file's header."""
def __init__(self, path):
with open(path, 'rb') as f:
self.bytes = f.read(64 * 1024)
def read_bytes(self, offset, length=4):
return self.bytes[offset:offset + length]
def read_leshort(self, offset):
"""Read an unsigned short at the given offset."""
return unpack_from('<H', self.bytes, offset)[0]
def read_lelong(self, offset):
"""Read an unsigned long at the given offset."""
return unpack_from('<L', self.bytes, offset)[0]
CODECS = {
1: 'Microsoft PCM',
2: 'Microsoft ADPCM',
3: 'PCM (float)',
6: 'ITU G.711 A-law',
7: 'ITU G.711 ยต-law',
8: 'Microsoft DTS',
17: 'IMA ADPCM',
20: 'ITU G.723 ADPCM (Yamaha)',
34: 'DSP Group Truespeech',
49: 'GSM 6.10',
64: 'ITU G.721 ADPCM',
80: 'MPEG',
85: 'MP3',
112: 'Lernout & Hauspie CELP',
114: 'Lernout & Hauspie SBC',
0x2001: 'DTS',
}
def riff_wave(f, offset):
"""Read the WAVE format information."""
encoding = f.read_leshort(offset)
yield CODECS.get(encoding, 'unknown encoding %d' % encoding)
if encoding in (1, 3):
bitrate = f.read_leshort(offset + 14)
if 0 < bitrate < 1024:
yield '%d bit' % bitrate
channels = f.read_leshort(offset + 2)
if channels == 1:
yield 'mono'
elif channels == 2:
yield 'stereo'
elif 2 < channels < 128:
yield '%d channels' % channels
hz = f.read_lelong(offset + 4)
if 0 < hz < 1000000:
yield '%d Hz' % hz
def riff_walk(f, offset):
"""Search chunks trying to find b'fmt '"""
chunk = f.read_bytes(offset)
if chunk == b'fmt ':
if f.read_lelong(offset + 4) < 0x80:
return list(riff_wave(f, offset + 8))
elif chunk[:3] == b'VP8':
return ['VP8 encoding']
elif chunk in (b'LIST', b'DISP', b'bext', b'Fake', b'fact'):
off = f.read_lelong(offset + 4)
return riff_walk(f, off + 4)
return ["Unknown WAVE encoding"]
def identify(path):
f = MagicReader(path)
if f.read_bytes(0) != b'RIFF':
return 'Unknown format (not RIFF WAVE)'
if f.read_bytes(8) != b'WAVE':
return 'Unknown RIFF format (not WAVE)'
return 'WAV audio encoded as ' + ', '.join(riff_walk(f, 12))
if __name__ == '__main__':
import sys
tabstop = max(len(a) for a in sys.argv[1:]) + 1
for path in sys.argv[1:]:
sndfmt = identify(path)
print(('%s:' % path).ljust(tabstop), sndfmt)
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