On a whim today, I suddenly want to start studying the source code of ffmpeg. After downloading all the dependent libraries, I use the command configure

sh configure --prefix=/usr/local/ffmpeg \
--enable-gpl \
--enable-version3 \
--enable-nonfree \
--enable-postproc \
--enable-libass \
--disable-libcelt \
--enable-libfdk-aac \
--enable-libfreetype \
--enable-libmp3lame \
--enable-libopencore-amrnb \
--enable-libopencore-amrwb \
--enable-libopenjpeg \
--enable-openssl \
--enable-libopus \
--enable-libspeex \
--enable-libtheora \
--enable-libvorbis \
--enable-libvpx \
--enable-libx264 \
--enable-libxvid \
--disable-static \
--disable-x86asm \
--enable-shared

appear. Error: an error is reported when OpenSSL is not found. The version of OpenSSL I use is

Then the solution is seen from here

export LDFLAGS="-L/usr/local/opt/openssl/lib"
export CPPFLAGS="-I/usr/local/opt/openssl/include"

After writing, configure succeeded!

If you encounter some other problems, such as the following, you only need to delete the corresponding file and reconfigure it

config.h is unchanged
libavutil/avconfig.h is unchanged
libavfilter/filter_list.c is unchanged
libavcodec/codec_list.c is unchanged
libavcodec/parser_list.c is unchanged
libavcodec/bsf_list.c is unchanged
libavformat/demuxer_list.c is unchanged
libavformat/muxer_list.c is unchanged
libavdevice/indev_list.c is unchanged
libavdevice/outdev_list.c is unchanged
libavformat/protocol_list.c is unchanged
ffbuild/config.sh is unchanged