modified from https://gist.github.com/Brainiarc7/3f7695ac2a0905b05c5b

gistfile1.txt

#!/bin/bash

#This script will compile and install a static ffmpeg build with support for nvenc un ubuntu.
#See the prefix path and compile options if edits are needed to suit your needs.

echo "you must manually install your nvidia drivers first"
read -p "Press any key if you have done that..."
echo "and you must install cuda manually (if you already installed drivers, deselect 'install drivers' from cuda install):"
echo "wget http://developer.download.nvidia.com/compute/cuda/10.1/Prod/local_installers/cuda_10.1.243_418.87.00_linux.run"
echo "sudo sh cuda_10.1.243_418.87.00_linux.run"
read -p "Press any key if you have done that..."
echo "add /usr/local/cuda-10.1/lib64 to /etc/ld.so.conf and run ldconfig as root"


#install required things from apt
installLibs(){
echo "Installing prerequisites"
sudo apt-get update
sudo apt-get -y --force-yes install autoconf automake build-essential libass-dev libfreetype6-dev libgpac-dev \
  libsdl1.2-dev libtheora-dev libtool libva-dev libvdpau-dev libvorbis-dev libxcb1-dev libxcb-shm0-dev \
  libxcb-xfixes0-dev pkg-config texi2html zlib1g-dev
}

#Install nvidia SDK
installSDK(){
echo "Installing the nVidia NVENC SDK."
cd ~/ffmpeg_sources
cd ~/ffmpeg_sources
git clone https://git.videolan.org/git/ffmpeg/nv-codec-headers.git
cd nv-codec-headers
make
sudo make install
}

#Compile nasm
compileNasm(){
echo "Compiling nasm"
cd ~/ffmpeg_sources
wget http://www.nasm.us/pub/nasm/releasebuilds/2.14rc0/nasm-2.14rc0.tar.gz
tar xzvf nasm-2.14rc0.tar.gz
cd nasm-2.14rc0
./configure --prefix="$HOME/ffmpeg_build" --bindir="$HOME/bin"
make -j$(nproc)
make -j$(nproc) install
make -j$(nproc) distclean
}

#Compile libx264
compileLibX264(){
echo "Compiling libx264"
cd ~/ffmpeg_sources
wget http://download.videolan.org/pub/x264/snapshots/last_x264.tar.bz2
tar xjvf last_x264.tar.bz2
cd x264-snapshot*
PATH="$HOME/bin:$PATH" ./configure --prefix="$HOME/ffmpeg_build" --bindir="$HOME/bin" --enable-static
PATH="$HOME/bin:$PATH" make -j$(nproc)
make -j$(nproc) install
make -j$(nproc) distclean
}


#Compile libvpx
compileLibPvx(){
echo "Compiling libvpx"
cd ~/ffmpeg_sources
git clone https://chromium.googlesource.com/webm/libvpx
cd libvpx
PATH="$HOME/bin:$PATH" ./configure --prefix="$HOME/ffmpeg_build" --disable-examples --enable-runtime-cpu-detect --enable-vp9 --enable-vp8 \
--enable-postproc --enable-vp9-postproc --enable-multi-res-encoding --enable-webm-io --enable-better-hw-compatibility --enable-vp9-highbitdepth --enable-onthefly-bitpacking --enable-realtime-only \
--cpu=native --as=nasm
PATH="$HOME/bin:$PATH" make -j$(nproc)
make -j$(nproc) install
make -j$(nproc) clean
}

#Compile ffmpeg
compileFfmpeg(){
echo "Compiling ffmpeg"
cd ~/ffmpeg_sources
git clone https://github.com/FFmpeg/FFmpeg -b master
cd FFmpeg
PATH="$HOME/bin:$PATH" PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" ./configure \
  --prefix="$HOME/ffmpeg_build" \
  --extra-cflags="-I$HOME/ffmpeg_build/include" \
  --extra-ldflags="-L$HOME/ffmpeg_build/lib" \
  --bindir="$HOME/bin" \
  --enable-cuvid \
  --enable-libnpp \
  --extra-cflags="-I/usr/local/cuda/include/" \
  --extra-ldflags=-L/usr/local/cuda/lib64/ \
  --enable-gpl \
  --enable-libass \
  --enable-vaapi \
  --enable-libfreetype \
  --enable-libvpx \
  --enable-libx264 \
  --enable-nonfree \
  --enable-nvenc
PATH="$HOME/bin:$PATH" make -j$(nproc)
make -j$(nproc) install
make -j$(nproc) distclean
hash -r
}

#The process
cd ~
mkdir ffmpeg_sources
installLibs
installSDK
compileNasm
compileLibX264
compileLibfdkcc
compileLibPvx
compileFfmpeg
echo "Complete!"