ffmpeg complex filter pip loop not working

Question

I am using an ffmpeg complex filter to:

1. turn a number of images into a slideshow
2. scale the slideshow to 1/6th of its original size
3. loop the slideshow infinitely
4. set the looping slideshow as a picture-in-picture over another looping video

then add audio from another file which determines the maximum length of the final video.

Everything is working except step 3.

Here is my code (broken down into individual lines):

ffmpeg -y 
-loop 1 -t 5.5 -i /uploads/2021/07/slide04-scaled.jpg 
-loop 1 -t 5.5 -i /uploads/2021/07/Slide05-scaled.jpg 
-loop 1 -t 5.5 -i /uploads/2021/07/Slide06-scaled.jpg 
-i /slowwmo-videos/intro.mp4 
-i /uploads/2021/07/busy_bees_01.mp3 
-filter_complex 
"
[1]fade=d=0.5:t=in:alpha=1,setpts=PTS-STARTPTS+5/TB[a1];
[2]fade=d=0.5:t=in:alpha=1,setpts=PTS-STARTPTS+10/TB[a2];
[0][a1]overlay[b2];
[b2][a2]overlay[slides];
[slides]loop=loop=-1,scale=iw/6:ih/6,format=yuv420p,fps=fps=25[pip];
[3][pip]overlay=W-w-100:200[v]
" 
-map [v]:v:0 -map 4:a:0 -vcodec libx264 -profile:v main -video_track_timescale 25000 -pix_fmt yuv420p -s 1280x720 -acodec aac -af aresample=44100 -shortest /slowwmo-videos/busy_bees/7494.ts

Answer 1

ffmpeg -y
-framerate 25 -loop 1 -t 5.5 -i /uploads/2021/07/slide04-scaled.jpg
-framerate 25 -loop 1 -t 5.5 -i /uploads/2021/07/Slide05-scaled.jpg
-framerate 25 -loop 1 -t 5.5 -i /uploads/2021/07/Slide06-scaled.jpg 
-stream_loop -1 -i /slowwmo-videos/intro.mp4 
-i /uploads/2021/07/busy_bees_01.mp3
-filter_complex
"[0][1]xfade=transition=fade:duration=0.5:offset=5[fade];
 [fade][2]xfade=transition=fade:duration=0.5:offset=9.5,scale=iw/6:-1,loop=loop=-1:size=375[pip];
 [3:v]scale=1280:720[bg];[bg][pip]overlay=W-w-100:200,format=yuv420p[v]"
-map "[v]" -map 4:a -c:v libx264 -c:a aac -shortest output.ts

• Use -stream_loop to loop intro.mp4
• The loop filter needs you to tell it how many frames to loop.
• xfade offers more transition effects and eliminates the need for additional setpts and overlay. To figure out offset timing see Merging multiple video files with ffmpeg and xfade filter.