Audio renderer is leaking memory when AC3 encoding is enabled.

h4. Steps to Reproduce
1) Select MP Audio Renderer to be used
2) Enable AC3 encoding (set forced to be able to reproduce without any specific content
3) Start video

As a result memory usage climbs constatly up until MP crashes.

h4. Additional Information
d:\mediaportal-1\directshowfilters\mpaudiorenderer\source\ac3encoderfilter.cpp(291) : {8510} normal block at 0x0E1BE128, 40 bytes long.

d:\mediaportal-1\directshowfilters\mpaudiorenderer\source\ac3encoderfilter.cpp(515) : {24585} normal block at 0x130F6F80, 1792 bytes long.