[FFmpeg-user] -pix_fmt yuv420p and deinterlacing

[Katherine Frances]

On Mon, Feb 27, 2017 at 12:19 AM, Carl Eugen Hoyos <ceffmpeg at gmail.com>
wrote:

> 2017-02-26 12:11 GMT+01:00 Katherine Frances <knfrances at gmail.com>:
> > Thanks again, Andy.
> > So if I understand correctly:
> >
> >    1.  *-vf scale=interl=1* registers to libx264 that the input is
> >    interlaced and to be 'aware' of that in future operations.
>
> No, the option is meant to tell the scale filter that it has to
> adapt its operations for interlaced content.
>
> > *yadif*, of course, does the actual deinterlacing.
>
> Yes.
>
> >    2. If used in the same script, *scale* must precede *yadif. *Although
> it
> >    seems rather redundant.
>
> I would suggest the opposite since giving yadif more information could
> help. There may be a performance trade-off though.
>
> >    3. If deinterlacing with *yadif*, *yadif* should precede chroma
> >    downsampling
>
> Same reasoning as above.
>
> > (via *-pix_fmt yuv420p*)
>
> You should not use a (non-trivial) filter-chain and -pix_fmt since
> iirc, the output (the filter order) is not defined. (But it is a bad idea
> anyway.)
>
> "Scaling" and "Chroma-downsampling" are the same insofar as
> they are both done by the scale filter.
>
> Did you already tell us if the content you see is actually interlaced?
>
> As said, please find out what top-posting means and avoid it
> here.
>
> Carl Eugen


Hi Carl,

Thank you for your answer.

Here I'm confused:

>    2. If used in the same script, *scale* must precede *yadif. *Although
> it
> >    seems rather redundant.
> I would suggest the opposite since giving yadif more information could
> help. There may be a performance trade-off though.


If the order is yadif -> scale, how is yadif getting more information?
Sorry, I think I'm missing something here.

You should not use a (non-trivial) filter-chain and -pix_fmt since iirc,
> the output (the filter order) is not defined. (But it is a bad idea anyway.)


I'm not clear on your meaning here. It's not possible to do both of these
operations (deinterlace + chroma-downsample to 4:2:0) in one script?

"Scaling" and "Chroma-downsampling" are the same insofar as they are both
> done by the scale filter.


I didn't realize that scale also takes care of the 4:2:2 -> 4:2:0 change.
Thank you for telling me.

Did you already tell us if the content you see is actually interlaced?
>

Yes, the source file is definitely interlaced.

I hope this post is formatted correctly. Thank you for your help,

Best, K.