Combining two video fields into one (to create an interlaced video)

Question

I have two separate video fields (top.avi and bottom.avi) and I would like to merge them to create an interlaced video.

Is it possible to do this with ffmpeg? (or any other tool for Windows or Linux)

ffmpeg log:

Input #0, avi, from 'top.avi':
  Metadata:
    encoder         : Lavf58.20.100
  Duration: 00:03:16.03, start: 0.000000, bitrate: 13509 kb/s
    Stream #0:0: Video: ffv1 (FFV1 / 0x31564646), yuv420p, 640x224, 13506 kb/s, SAR 1:1 DAR 20:7, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc

Input #1, avi, from 'bottom.avi':
  Metadata:
    encoder         : Lavf58.20.100
  Duration: 00:03:16.03, start: 0.000000, bitrate: 13507 kb/s
    Stream #0:0: Video: ffv1 (FFV1 / 0x31564646), yuv420p, 640x224, 13503 kb/s, SAR 1:1 DAR 20:7, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc

Answer 1

Use

ffmpeg -i top.avi -i bottom.avi -filter_complex vstack,il=l=i:c=i -c:v ffv1 il.avi

See docs for http://www.ffmpeg.org/ffmpeg-filters.html#vstack and http://www.ffmpeg.org/ffmpeg-filters.html#il