[FFmpeg-user] Concatenate multiple (<10) movies with xfade filter

[Kentaro Fukuchi]

Hi,

Here I have more than 10 movies and want to concatenate into a single movie
with cross-fade effect. I tried to use 'xfade' filter with many thanks to
the authors of it, but I had no luck.

What I did:
ffmpeg -f concat -i movies.txt -filter_complex "xfade=transition=fade:duration=1" output.mp4

What I received:
ffmpeg version N-98092-g7ab375f574 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
  configuration: 
  libavutil      56. 52.100 / 56. 52.100
  libavcodec     58. 92.100 / 58. 92.100
  libavformat    58. 46.101 / 58. 46.101
  libavdevice    58. 11.100 / 58. 11.100
  libavfilter     7. 86.100 /  7. 86.100
  libswscale      5.  8.100 /  5.  8.100
  libswresample   3.  8.100 /  3.  8.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55aa7f382000] Auto-inserting h264_mp4toannexb bitstream filter
Input #0, concat, from 'movies.txt':
  Duration: N/A, start: 0.000000, bitrate: 5521 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 5521 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc
    Metadata:
      handler_name    : VideoHandler
Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_xfade_0

Additional note:
The following worked as expected:
ffmpeg -i movie1.mp4 -i movie2.mp4 -filter_complex xfade=transition=fade:duration=1 output.mp4

Seems that the combination of filter_complex and concat format does not work as expected.
How can I use filter_complex and xfade filter with concat format? Any suggestions are welcome.

Kentaro