Scale_npp sample ffmpeg code

I am encoding and decoding the h264 file with nvenc encoders.

When I transcode the file, I also want to resize the the decoded frame with code. I already made ffmpeg build with enable libnpp and with command line i can scale file with scale_npp.

I am Using filtering_video.c ffmpeg sample file.
And instead write

const char *filter_descr = “scale=78:24,transpose=cclock”;

I write const char *filter_descr = “scale_npp=78:24” and run same code but it gives me error–

impossible to convert between the formats supported by the filter scale_npp and the filter

Please help.

I’ve got the same question.Maybe there’s something we are lack of like hardware acceleration.I google it and it’s all about command line,not the code.