encode 264 on AM5x

hi experts,

According to https://e2e.ti.com/support/arm/sitara_arm/f/791/p/480819/1732168 , I try to generate videnctest from GLSDK and put it on AM5x.  

By my testing, the performance is 50fps around, which does not match the spec as below in AM5728 TRM 1.1

6.1 IVA Overview
The IVA supports resolutions up to 1080 p/i with full performance of 30 fps (or 60 fields) for encode only,
and 60 fps (or 120 fields) for decode only 60 fps (or 120 fields), achievable for encode or decode only (not
for simultaneous encode and decode).

Is there anything I misunderstand ?? version or ??

Thanks.