[FFmpeg-user] Best way to scale interlaced video

[Francois Visagie]

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of Nicholas Robbins
> Sent: 26 February 2014 00:36
> To: FFmpeg user questions
> Subject: Re: [FFmpeg-user] Best way to scale interlaced video
> 
> > On Tuesday, February 25, 2014 3:11 PM, Andrey Aleksandrovich
> <andrey.aleksandrovich at googlemail.com> wrote:
> 
> > > On 2/25/14, Massimo Battistel <battistel at gmail.com> wrote:
> >>  hello,
> >>  I have to scale 16:9 interlaced 1080i video down to PAL 576i 4:3
> >> with black  bars.
> >
> > Do you really need 4:3 aspect?
> >
> > If so, you can do something like that chain:
> > 1920x1080 at 50i -> (lossless codec) 1920x540 at 50p -> (lossless codec)
> > 720x576 at 50p -> 720x576 at 50i
> 
> I think this is actually a terrible idea. Rescaling the interlaced fields
will
> introduce artifacts. I see that the scale filter has an "interlaced aware
scaling"
> option that seems to be what he should use.

That's correct; it's the 'interl' option to '-vf scale'.

> With that in mind, I think his
> question of "how does interlaced aware scaling work" is the real
questions.
> 
> > It is the best way to save time resolution (frame fields - fine motion
> > scenes), while the static scenes will be little worse, cause of
> > upscale fields from 540 to 576. However, you can to do not upscale and
> > replace those 36 lines with black borders. Aspect ratio will be lost
> > corrupt.
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