Trouble When Combining two video fields into one (to create an interlaced video) I'm having trouble with the command found here: Combining two video fields into one (to create an interlaced video)
ffmpeg -i tf.avi -i bf.avi -filter_complex vstack,il=l=i:c=i -c:v ffv1 out_i.avi
It seems to combine the fields correctly, the output, however, appears to be progressive. To test, I used
the video 'in_i.mxf' (XCDCAM HD 422, 1080i25) and separated the fields in tf.avi and bf.avi, using this:
ffmpeg -i in_i.mxf -vf field=top -c:v ffv1 -an tf.avi -vf field=bottom -c:v ffv1 -an bf.avi
That's the result of 'ffmpeg -i in_i.mxf -i tf.avi -i bf.avi -i out_i.avi':
Input #0, mxf, from 'in_i.mxf':
  Metadata:
    operational_pattern_ul: 060e2b34.04010101.0d010201.01010900
    uid             : 25e9aa02-7405-4800-809e-0700022483ea
    generation_uid  : 25e9aa02-7405-4800-811e-0700022483ea
    company_name    : CANON
    product_name    : XF105
    product_version : 1.00
    product_uid     : 060e2b34-0401-010d-0e15-005658460100
    modification_date: 2016-01-15T14:48:13.000000Z
    material_package_umid: 0x060A2B340101010501010D43130000000A25E9AB0274058000008500022483EA
    timecode        : 13:13:46:14
  Duration: 00:00:10.08, start: 0.000000, bitrate: 51874 kb/s  
  Stream #0:0: Video: mpeg2video (4:2:2), yuv422p(tv, bt709, top first), 1920x1080 [SAR 1:1 DAR 16:9], 50000 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
  Metadata:
  file_package_umid: 0x060A2B340101010501010D43130000000A25E9AA0274058000008500022483EA
    Side data:          cpb: bitrate max/min/avg: 50000000/0/0 buffer size: 17825792 vbv_delay: N/A
Stream #0:1: Audio: pcm_s16le, 48000 Hz, mono, s16, 768 kb/s
Metadata:
  file_package_umid: 0x060A2B340101010501010D43130000000A25E9AA0274058000008500022483EA
Stream #0:2: Audio: pcm_s16le, 48000 Hz, mono, s16, 768 kb/s
Metadata:
  file_package_umid: 0x060A2B340101010501010D43130000000A25E9AA0274058000008500022483EA

Input #1, avi, from 'tf.avi':
  Metadata:
    software        : Lavf58.67.100
    timecode        : 13:13:46:14
  Duration: 00:00:10.08, start: 0.000000, bitrate: 98506 kb/s
  Stream #1:0: Video: ffv1 (FFV1 / 0x31564646), yuv422p, 1920x540, 98889 kb/s, SAR 1:1 DAR 32:9, 25 fps, 25 tbr, 25 tbn, 25 tbc

Input #2, avi, from 'bf.avi':
  Metadata:
    software        : Lavf58.67.100
    timecode        : 13:13:46:14
  Duration: 00:00:10.08, start: 0.000000, bitrate: 98381 kb/s
  Stream #2:0: Video: ffv1 (FFV1 / 0x31564646), yuv422p, 1920x540, 98763 kb/s, SAR 1:1 DAR 32:9, 25 fps, 25 tbr, 25 tbn, 25 tbc

Input #3, avi, from 'out_i.avi':
  Metadata:
    software        : Lavf58.67.100
    timecode        : 13:13:46:14
  Duration: 00:00:10.08, start: 0.000000, bitrate: 201187 kb/s
  Stream #3:0: Video: ffv1 (FFV1 / 0x31564646), yuv422p, 1920x1080, 201979 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 25 tbn, 25 tbc          

It might be just a metadata problem? Any ideas how to optimize?
Use the setparams filter to mark the frames as interlaced.
ffmpeg -i tf.avi -i bf.avi -filter_complex vstack,il=l=i:c=i,setparams=field_mode=tff -c:v ffv1 out_i.avi