# pkg-config --cflags libavcodec
ah, ffmpeg includes not found ...
does "pkg-config --cflags libavcodec" print anything?
-I/usr/include/ffmpeg
alternatively you can look with "ls" into /usr/include, may be current ffmpeg includes live there under ffmpeg7 directory?
# ls /usr/include/ffmpeg
libavcodec libavdevice libavfilter libavformat libavutil libpostproc libswresample libswscale
of course you need ffmpeg(7?)-devel package installed
# zypper se -i ffmpeg-7
Loading repository data...
Reading installed packages...
S | Name | Summary | Type
---+------------------------------+---------------------------------------------------------------------+--------
i | ffmpeg-7 | Set of libraries for working with various multimedia formats | package
i | ffmpeg-7-libavcodec-devel | Development files for FFmpeg's codec library | package
i+ | ffmpeg-7-libavdevice-devel | Development files for FFmpeg's device library | package
i | ffmpeg-7-libavfilter-devel | Development files for FFmpeg's audio/video filter library | package
i | ffmpeg-7-libavformat-devel | Development files for FFmpeg's stream format library | package
i | ffmpeg-7-libavutil-devel | Development files for FFmpeg's utility library | package
i | ffmpeg-7-libpostproc-devel | Development files for the FFmpeg post-processing library | package
i | ffmpeg-7-libswresample-devel | Development files for the FFmpeg software resampling library | package
i | ffmpeg-7-libswscale-devel | Development files for FFmpeg's image scaling and colorspace library | package
This way?
After you located includes try to re-run ./configure but set CFLAGS variable before it with -I/path_to_ffmpeg_includes directive, like
CFLAGS=-I/usr/include/ffmpeg7 ./configure <..>
# CFLAGS=-I/usr/include/ffmpeg ./configure --with-single-user --disable-static-build --without-thirdparty --without-libdpx