The MDCT buffers in the decoder are only sized for up to 11 bits. The
reverse engineered documentation for WMA1/2 headers say that that for
all samplerates above 32kHz 11 bits are used. 12 and 13 bit support
were added for WMAPro. I was unable to make any Microsoft tools generate
a test file at a samplerate above 48kHz.

Discovered by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind

CC: libav-stable@libav.org