步骤基本上从网上抄袭就行。主要是3安装nv-codec-headers的版本，需要跟自己的驱动一致。我由于没有一致，安装cuda,安装其他的什么都没搞定，其中安装驱动还导致重装系统了，血的教训。
(输入命令nvidia-smi查看显卡驱动版本，nv-codec-headers/readme里面查看是否匹配)
如参考：
https://blog.csdn.net/weixin_45091328/article/details/103606433
sudo apt-get -y remove ffmpeg x264 libx264-dev
sudo apt-get -y install build-essential git yasm nasm unzip wget sysstat pkg-config
1.
wget https://www.nasm.us/pub/nasm/releasebuilds/2.14.02/nasm-2.14.02.tar.bz2
然后解压在cd到目录下，再编译安装。
./configure
make
sudo make install
2.
git clone http://git.videolan.org/git/x264.git
cd x264
./configure --disable-cli --enable-static --enable-shared --enable-strip
make -j 4
sudo make install
sudo ldconfig
3.nv-codec-headers
里面有nv-codec-headers/readme，看看跟显卡驱动是否匹配，驱动418对9.0，(输入命令nvidia-smi查看显卡驱动版本)否则会提示：
[h264_nvenc @ 0x1b42940] Driver does not support the required nvenc API version. Required: 9.1 Found: 9.0
https://github.com/FFmpeg/nv-codec-headers/tree/sdk/9.0
cd nv-codec-headers
make
sudo make install
4.
https://github.com/FFmpeg/FFmpeg/tree/release/4.0
./configure --enable-shared --enable-gpl --enable-pthreads --enable-nvenc --enable-cuda --enable-cuvid --enable-libx264 --prefix=/usr/local/ffmpeg
make
sudo make install
5.
sudo gedit /etc/ld.so.conf
add: /usr/local/ffmpeg/lib
sudo ldconfig
6.
sudo gedit ~/.bashrc
FFMPEG="/usr/local/ffmpeg"
export PATH="$FFMPEG/bin:$PATH"
source ~/.bashrc
7.
ffmpeg -version
ffmpeg -codecs | grep cuvid
ffmpeg -codecs | grep nvenc
ffmpeg -encoders | grep 264