/usr/include/x86_64-linux-gnu/libavcodec/ is in libavcodec-dev 7:2.8.6-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/x86_64-linux-gnu/libavcodec/avcodec.h
/usr/include/x86_64-linux-gnu/libavcodec/avfft.h
/usr/include/x86_64-linux-gnu/libavcodec/d3d11va.h
/usr/include/x86_64-linux-gnu/libavcodec/dv_profile.h
/usr/include/x86_64-linux-gnu/libavcodec/dxva2.h
/usr/include/x86_64-linux-gnu/libavcodec/old_codec_ids.h
/usr/include/x86_64-linux-gnu/libavcodec/qsv.h
/usr/include/x86_64-linux-gnu/libavcodec/vaapi.h
/usr/include/x86_64-linux-gnu/libavcodec/vda.h
/usr/include/x86_64-linux-gnu/libavcodec/vdpau.h
/usr/include/x86_64-linux-gnu/libavcodec/version.h
/usr/include/x86_64-linux-gnu/libavcodec/videotoolbox.h
/usr/include/x86_64-linux-gnu/libavcodec/vorbis_parser.h
/usr/include/x86_64-linux-gnu/libavcodec/xvmc.h