Does libav have any form of documentation particularlly for NVENC

Question

I want to use ffmpeg's libav library to encode video in an application I am developing. Unfortunately, software encoding is just too slow. So I went back the "documentation" and began to search for documentation on NVENC but I could only find VAAPI examples and documentation. All of NVIDIA's "docs" are for the ffmpeg utility not the api. Just changing the encoder from libx264 to h264_nvenc just causes a crash, adding hwaccel cuda to the dict doesn't work either