[FFmpeg-user] decomb versus deinterlace

Jim DeLaHunt list+ffmpeg-user at jdlh.com
Sun Apr 19 00:35:57 EEST 2020

On 2020-04-18 13:06, Mark Filipak wrote:
> 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.

I like this as an attempt to explain terms simply but clearly and 
unambiguously. Thank you!

It would be even better if you would define "frame" and "field" as part 
of this, or point to definitions. Also, is part of the definition of 
"field" that it has half the visual information of a "frame", in the 
form of every other scan line of the frame?

(And what is a "scan line"? etc.  Wouldn't it be nice to have a book 
which explained all these concepts clearly and unambiguously?)

Best regards,
       —Jim DeLaHunt, software engineer, Vancouver, Canada

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