下载并安装x264

git clone https://code.videolan.org/videolan/x264.git
cd x264
./configure --help
# 报缺少asm 时 可加入--disable-asm
./configure --enable-shared --enable-static --disable-asm
make
# x264将会安装到 ：/usr/local/ 目录下
sudo make install

重新编译 ffmpeg

# 下载ffmpeg
wget https://ffmpeg.org/releases/ffmpeg-snapshot.tar.bz2 --no-check-certificate
tar xjf ffmpeg-snapshot.tar.bz2
cd ffmpeg/

./configure --prefix=/usr/local/ffmpeg --enable-shared --enable-yasm --enable-libx264 --enable-gpl --enable-pthreads --extra-cflags=-I/usr/local/x264/include --extra-ldflags=-L/usr/local/x264/lib
make
sudo make install
sudo vim /etc/ld.so.conf  
# 将下面两行添加到 /etc/ld.so.conf  的最后
/usr/local/ffmpeg/lib/
/usr/local/lib/

sudo ldconfig 
# 如果出现 ffmpeg commend not found 可以通过下面加入环境变量
# 将ffmpeg 加入PATH
vim ~/.bashrc
# 最后增加一行:
export PATH=$PATH:/usr/local/ffmpeg/bin
source ~/.bashrc

ffmpeg -formats | grep h26

参考链接

linux ffmpeg Unknown encoder h264
Linux下安装 ffmpeg，并加入H264编码支持