[FFmpeg-user] Best way to scale interlaced video

[Andy Furniss]

Massimo Battistel wrote:
> I've removed padding filter and audio track. The issue is still
> reproducible.
>
> You can download HD reference sample from here:
> http://www.datafilehost.com/d/f8185302

A better test would also have some solid colour as one of the pitfalls
of working with interlaced is that it's possible to subtly mess up the
chroma.

>
> This is the command line for solution #1: ffmpeg -i sample1080i.mp4
> -vcodec rawvideo -vf scale=w=720:h=432:interl=1 -an out_interl.avi

Why 432 PAL is 576, I see in this case the 16/9 ratio gets filled in the
avi by ffmpeg. I also notice that the interlaced flag/field order  do not.

> This is the command line for solution #2: ffmpeg -i sample1080i.mp4
> -vcodec rawvideo -vf
> yadif=1:0,scale=w=720:h=432:interl=0,tinterlace=4 -an out_yadif.avi
>
> To summarize: Solution #1 should be the proper choice, but you'll
> notice horizontal lines low definition compared to vertical ones.

Well 432 is too low - 576 may look better, but as the source is
interlaced it may be softer vertically to start with. It should also be
de-interlaced for display on a progressive screen or you will see the
weave artifacts. It doesn't actually look that bad to me @720x576
(scaled by player to 1024x576).

> Solution #2 gives better result for still video, but can produce
> artifacts/moiré issues. Plus it takes more cpu (about 3 times).
>
> Effect is more noticeable on an interlaced scan monitor, but you can
> see it even on the progressive scan pc monitor.

Doesn't really seem the best source for seeing moire.

I don't know your test setup for the interlaced, but I would be tempted
to dismiss anything I saw with PC -> interlaced monitor because the
fields won't be synced properly.