ffmpeg \
-loop 1 -i bg.png \
-i audio.flac \
-loop 1 -i 'img1.png' \
-loop 1 -i 'img2.png' \
-loop 1 -i 'img3.png' \
-loop 1 -i 'img4.png' \
-loop 1 -i 'img5.png' \
-loop 1 -i 'img6.png' \
-filter_complex "\
 [2:v]trim=duration=5,setpts=PTS-STARTPTS,split[v1a][v1b]; \
 [3:v]trim=duration=5,setpts=PTS-STARTPTS,split[v2a][v2b]; \
 [4:v]trim=duration=5,setpts=PTS-STARTPTS,split[v3a][v3b]; \
 [5:v]trim=duration=5,setpts=PTS-STARTPTS,split[v4a][v4b]; \
 [6:v]trim=duration=5,setpts=PTS-STARTPTS,split[v5a][v5b]; \
 [7:v]trim=duration=5,setpts=PTS-STARTPTS[v6]; \
 [v2a][v1a]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v0]; \
 [v3a][v2b]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v1]; \
 [v4a][v3b]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v2]; \
 [v5a][v4b]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v3]; \
 [v6][v5b]blend=all_expr='A*(if(gte(T,3),1,T/3))+B*(1-(if(gte(T,3),1,T/3)))'[v4]; \
 [v1b][v0][v1][v2][v3][v4]concat=n=6:v=1:a=0[ss];
 [0:v][ss]overlay=(W-w)/2:(H-h)/2:shortest=1,format=yuv420p[v]" \
-map "[v]" \
-map 1:a  \
-shortest \
-r 60 \