I’m new to ffmpeg and trying to wrap my head around the filtergraph. I have a number of clips, and for each one I want to:

• trim the start and end
• fade it to the next one
• don’t re-encode anything except the fade

My best attempt at this (trying to use 1 second long clips for testing):

ffmpeg -i part-1.mp4 -i part-2.mp4 
-filter_complex "[0:v]trim=start=227:duration=1[0_middle];
[0:v]trim=start=228:duration=1[0_end];
[1:v]trim=start=30:duration=1[1_start];
[1:v]trim=start=31:duration=1[1_middle];
[0_end][1_start]xfade=transition=fade:duration=1[fade_0_1];
[0_middle][fade_0_1][1_middle]concat=n=3[output]" 
-map "[output]" 
output.mp4

However this just hangs and eventually says:

More than 1000 frames duplicated

So I have 2 questions — what am I doing wrong? And how do I copy, instead of re-encode, 0_middle and 1_middle? If I add -vcodec copy it tells me filtering and a streamcopy can’t be used together, but I can’t find another way of specifying this.