>>I'm not using OPENMP and I set H264EncoderParams.numThreads to 1. Also number of slices in par file is set to 1.
Could you have a check on the following post? This post discussed OpenMP threading performance and the steps to disable the OpenMP threading:
To disable the OMP threaded in the Codec, you can check at the \audio-video-codecs\Makefile file, and remove the following:
CFLAGS += -openmp
CFLAGS += -fopenmp
No additional threadings are expected to be created if OpenMP runtime library is not linked with your application.
The OpenMP compiling flag I suggested came from the old version of makefile. In the new version of IPP sample code, it is to remove the code you suggest.