Terry J. Reedy added the comment:
The Wikipedia sentence "The WAV format is limited to files that are less than 4
GB, because of its use of a 32-bit unsigned integer to record the file size
header" is unambiguous and appears correct (see below). The rest of the
Wikipedia sentence "(some programs limit the file size to 2 GB)" must be
because some programs mistakenly read into signed instead of unsigned ints and
fail to later adjust (by, for instance, later casting to unsigned).
The statement reflects the original specification given in reference 3, a .pdf.
On page 11, it has
'''
The basic building block of a RIFF file is called a chunk. Using C syntax, a
chunk can be defined
as follows:
typedef unsigned long DWORD;
typedef DWORD CKSIZE; // 32-bit unsigned size value
typedef struct { // Chunk structure
CKID ckID; // Chunk type identifier
CKSIZE ckSize; // Chunk size field (size of ckData)
'''
and on page 19
"<WORD> 16-bit unsigned quantity in Intel format unsigned int"
INT and LONG are defined as 16 and 32 bit signed versions.
The WAVE specification, start on p. 56, uses WORD and DWORD, not INT and LONG
for chunk header fields. Certainly, the 2 bytes for samples/sec should be
unsigned to allow the standard 44100 CD rate.
http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html
(reference 4) summarized the .wav chunk formats. I think it just takes it for
granted that sizes and counts are unsigned.
The patch given did not touch the write format in line 469(3.3.0):
self._file.write(struct.pack('<l4s4slhhllhh4s',
The first 'l' is filled with 36 + self._datalength and I believe the whole
thing should be '<L4s4sLHHLLHH4s'. The two struct.unpack formats on lines 264
and 266 should also be changed.
A workaround is to write large numbers as signed negatives.
>>> struct.unpack('L', struct.pack('l', 3000000000 -2**32))
(3000000000,)
>>> struct.unpack('H', struct.pack('h', 44100 - 2**16))[0]
44100
It is possible that someone is using this to write CD-quality files. It is also
possible that anyone who has tried just gave up.
----------
nosy: +terry.reedy
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<http://bugs.python.org/issue16461>
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