[FFmpeg-user] decomb versus deinterlace

[Mark Filipak]

Forgive me if this subject seems pedantic to you. I think it's important and the source of a lot of 
misunderstanding.

As always, correct me if I'm wrong.

According to the MPEG spec, interlace relates to fields that are temporally offset by 1/60th second 
(NTSC) or 1/50th second (PAL) that typically originate as telecast streams.

Deinterlacing is conversion of the i30-telecast (or i25-telecast) to p30 (or p25) and, optionally, 
smoothing the resulting p30 (or p25) frames.

Combing is fields that are temporally offset by 1/24th second (or 1/25th second) resulting from 
telecine up-conversion of p24 to p30 (or p25).

Decombing is smoothing combed frames.

My video sources are generally:
p24 movies from blu-ray, or
p24 movies from DVD (i.e., soft telecine), or
i30 movies from DVD (i.e., hard telecine).

Should I ever encounter a i30-telecast video on a blu-ray or DVD, I might (but probably won't) 
deinterlace.

It seems to me that some people call combing that results from telecine, interlace. Though they are 
superficially similar, they're different.

Regards,
Mark.