Memory Leak in MFXVideoENCODE_EncodeFrameAsync

I'm seeing a slow memory leak when using mediaSDK to perform MPEG2 encoding.  I see this for both hardware/software with the attached code. In this code the main loops continually processes the same frames and contains no memory allocation.  Yet the memory used by the process continually creeps up.  The examples below show only 60 seconds of history, but the trend continues in the same manner until memory is exhausted.  This can take many hours, but eventually the process will consume all free memory in the machine.

For hardware, the example app generates a sequence like this on my system:

./msdkTest.exe
Using HW version 1.7
6 buffers suggested
Starting frame encode
Elapsed (s) DeltaMemory
          0      737280
         10     1368064
         20     2138112
         30     2625536
         40     3149824
         50     3710976
         60     4644864
 

Likewise for software, I see something like this:

./msdkTest.exe -s
Using SW version 1.8
3 buffers suggested
Starting frame encode
Elapsed (s) DeltaMemory
          0       24576
         10       36864
         20       49152
         30      118784
         40      184320
         50      253952
         60      286720

Am I doing something wrong in this simple loop?  I've run this same code on a difference machine with HW version 1.4 and SW version 1.7 and there was no leak so I believe my loop is OK.