ffmpeg -i rec.avi -i audio_edited.wav -filter_complex \
"[0:v]trim=start=1805:end=6176,setpts=PTS-STARTPTS[bv];\
 [1:a]atrim=start=1805:end=6176,asetpts=PTS-STARTPTS[ba];\
 [0:v]trim=start=8215:end=14590,setpts=PTS-STARTPTS[dv];\
 [1:a]atrim=start=8215:end=14590,asetpts=PTS-STARTPTS[da];\
 [bv][ba][dv][da]concat=n=2:v=1:a=1[outv][outa]" \
 -map [outv] -map [outa] -c:v libvpx -crf 10 -b:v 5M -c:a libvorbis out.webm