[FFmpeg-user] "interlace"

Mark Filipak markfilipak.windows+ffmpeg at gmail.com
Mon Sep 7 00:56:49 EEST 2020

On 09/06/2020 05:24 PM, Edward Park wrote:
>> I have great respect for you, Ted. Tell me: What is interlaced video?
> Well that is unwarranted, possibly spiteful, even, to someone as insecure as me ;)

Hahahaha... Ted I want you to do something for me. Take your right hand, put it over your left 
shoulder, extend it down your back, and, with an open palm, slap it against your back two or three 
times. This list is a better place with you in it.

> That is the real question isn't it. Probably won't be very satisfying but I'll try to describe it. Probably not useful to say it's video that is interlaced (or to be interlaced) lines.

Well, that's interesting. Is interlaced *lines* a requirement for interlaced video? I would say so, 
but tell me: How does what is called interlaced video related to interlaced *lines*?

> Video as in not film? When individual frames don't correspond to a single moment in time.

Well, there you go. That's what everyone says. But a video that is field-based (aka "interlaced", 
yuck!) can also portray a single moment in time. In fact, the vast majority of so-called 
"interlaced" video is actually concurrent. I'm sure you agree with that, eh? So, if "interlaced" is 
not really a good word for "in fields" or "composed of fields", then what is a good term?

Frame-based v. field-based
Concurrent v. successive (or, if you prefer, pictures v. scans)

There are 4 combinations:
1, Frame-based pictures
2, Field-based pictures
3, Frame-based scans
4, Field-based scans

Number 1 seems reasonable. Agreed?
If a picture is an image that completely fills the frame, then number 2 is a contradiction in terms. 
Agreed? I use the term "half-picture" for the fields extracted from a frame. What do you think of that?
Number 3 is possible, but not desirable due to excessive combing. Agreed?
Number 4 applies to streams that were generated by scanning cameras (TV studios) to be viewed on 
scanning TVs (CRTs), so is not really applicable for new video, today. Nonetheless, they do exist, 
if only as legacy video. Agreed?

1, Frame-based pictures
2, Field-based half-pictures
3, Frame-based scans -- beware!
4, Field-based scans -- legacy

What do you think?

> Regards,
> Ted Park

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