(largest size according to spec: 64k). Fixes playback of
mmsh://a1635.v24937.c2493.g.vm.akamaistream.net/7/1635/2493/v0001/premrad.download.akamai.com/2493/premiere_rock_report/Country_Report.wma

Patch by Zhentan Feng <spyfeng gmail com>.

Originally committed as revision 26047 to svn://svn.ffmpeg.org/ffmpeg/trunk