In u-law and A-law compressed AIFC files the sampleSize field is equal to 8 (bits). The aifc module transparently compress/uncompress audio data to 16-bit, but doesn't support the samplewidth parameter in consistency. This causes two bugs:

1. On read getsampwidth() returns 1, but should return 2 (bytes per sample in uncompressed audio data). readframes() returns twice less data than expected.

>>> import aifc
>>> f = aifc.open('pluck-ulaw.aifc', 'r')
>>> f.getparams()
_aifc_params(nchannels=2, sampwidth=1, framerate=11025, nframes=3307, comptype=b'ulaw', compname=b'')
>>> f.readframes(1)
b',\x02'

f.readframes(1) should return 4 bytes (2 channels, 16-bit uncompressed data).

2. On write wrong value 2 is saved in the sampleSize field. Resulting file is invalid and can't be read in other programs.

Here is a patch and sample file. For tests see issue18919.

I'm sure G722 support is broken too, but I have no any testing files.

New changeset 567241d794bd by Serhiy Storchaka in branch '2.7':
Issue #19131: The aifc module now correctly reads and writes sampwidth of
http://hg.python.org/cpython/rev/567241d794bd

New changeset 863a92cc9e03 by Serhiy Storchaka in branch '3.3':
Issue #19131: The aifc module now correctly reads and writes sampwidth of
http://hg.python.org/cpython/rev/863a92cc9e03

New changeset cff4dd674efe by Serhiy Storchaka in branch 'default':
Issue #19131: The aifc module now correctly reads and writes sampwidth of
http://hg.python.org/cpython/rev/cff4dd674efe