What IPP version are you using? There are some ways to using more threads
1) you can create your own external threading on the function. The external threading is recommended, which is more effective than the internal threading.
2) using IPP internal threading,
Please see more in the article.
Threading in Intel IPP 8.1 and earlier versions
Threading within the deprecated multi-threaded add-on packages of the Intel IPP library is accomplished by use of the OpenMP* library. Intel IPP 8.0 continues the process of deprecating threading inside Intel IPP functions that was started in version 7.1. Though not installed by default, the threaded libraries can be installed so code written with these libraries will still work as before. However, moving to external threading is recommended.
The functions ippiWarpAffineLinear_8u_C3R and ippiResizeNearest_8u_C3R do not support internal threading.
However these functions can be used for image processing by tiles with external threading.
Resizing a Tiled Image with One Prior Initialization: https://software.intel.com/en-us/node/504353#TILING_IMAGE_WITH_ONE_INIT
Warping a Tiled Image with One Prior Initialization: https://software.intel.com/en-us/node/529049#TILED_IMAGE_WITH_ONE_INIT