Why can't I write all the data from sys.stdin to a file on Windows?

Question

I am trying to read binary data from sys.stdin using Python 2.7 on Windows XP. Binary data is a WAV file decoded by foobar2000. Typically, this data is sent to a command-line encoder, such as lame.exe, to stdin, where it is processed and written to the output file whose name is specified in the command-line arguments. I am trying to intercept the WAV data that is being output and send it to another file. However, I can only get a few kilobytes from stdin before the pipeline seems to crash, and so I only have a very short (about 75 KB) WAV file, and not the few tens of megabytes that I expect. What could be the reason for this? I tried to open both sys.stdin and the output file as binary files.

from __future__ import print_function
import os
import os.path
import sys

sys.stdin = os.fdopen(sys.stdin.fileno(), 'rb', 0) # Make sys.stdin binary

wave_fname = os.path.join(os.environ['USERPROFILE'], 'Desktop',
    'foobar_test.wav')

try:
    os.remove(wave_fname)
except Exception:
    pass

CHUNKSIZE = 8192
wave_f = open(wave_fname, 'wb')
try:
    bytes_read = sys.stdin.read(CHUNKSIZE)
    while bytes_read:
        for b in bytes_read:
            wave_f.write(b)
        bytes_read = sys.stdin.read(CHUNKSIZE)
finally:
    pass
wave_f.close()

Answer 1

: , msvcrt.setmode(fd, flags), fd sys.stdin.fileno()