Change field order while deinterlacing progressive videos with interlacing artifacts

[JonathanBeresford]

Description of problem or question:
You will sometimes find a video on YouTube which has interlacing artifacts; that is, if you view a video at 1080p, you will notice some combing. This usually happens when a 1080i50/1080i60 video isn't deinterlaced before uploading. As an experiment, I sometimes download these videos and try to deinterlace them to 50/60 fps myself; however, as these videos are progressive, HandBrake has to guess the field order, and gets it wrong. The effect is that the video goes forwards 2 frames, the goes backwards 1 frame, then goes forward 2 frames etc.

Steps to reproduce the problem (If Applicable):

1. Download any video that exhibits combing at 1080p. For this experiment, I used Lasith Malinga's four-ball 4-wicket hat-trick.
2. Import downloaded video to HandBrake.
3. Set output framerate to twice the original framerate and set deinterlace preset to Bob.
4. Start Encode.

Observe as the encoded video looks jittery instead of smooth. It may help if you play the encoded video frame by frame.

HandBrake version (e.g., 1.0.0):
1.3.1

Operating system and version (e.g., Ubuntu 16.04 LTS, macOS 10.13 High Sierra, Windows 10 Creators Update):
Windows 8.1

HandBrake Activity Log
https://pastebin.com/6DBR1vcX

[Woodstock]

The deinterlace filters assume the source is interlaced, not "previously improperly deinterlaced progressive". The information on frame order is not there to work with.

[musicvid]

Unfortunately you cannot unbake that cake.
Reason: There are no discrete fields in the progressive frames; only a mashup remains.