[MEncoder-users] Low res video playback in high res

[Reimar Döffinger]

On Sun, Apr 03, 2016 at 09:04:58PM +1000, Bill Crockett wrote:
> >>> Just wondering if it is possible to either re-encode or play back
> >>> a 1280x720 video in 1920x1080 resolution without losing sharpness, 
> >>> detail
> >>> ...etc?
> >>
> >> Sorry to have to say this, but it is impossible.  See for yourself:
> >>
> >> mplayer -vf scale=1920:1080 your_video
> >>
> >> It is like zooming in.  Quality goes out the window.
> >
> > There are better scaling windows (-sws) but if you consider that as 
> > quality
> > going out the window probably nothing will make you happy...
> > Though if sharpness, detail, .. is the only concern you can use
> > nearest-neighbour scaling.  It will not lose any, but it will likely look 
> > a bit
> > strange and bad since every other line/column becomes twice as
> > high/wide. Definitely no loss of sharpness or anything though.  As the 
> > scale
> > factor is 1.5 it should be possible to do better by not just duplicating 
> > every
> > other row/column but instead inserting the average.  But it will likely 
> > look
> > more blurry even though it is not.
> 
> I thought the -sws 9 (lanczos) was the best choice.   -sws 4 nearest 
> neighbour (bad quality)

There is no "best" without specifying the criteria.
Lanczos is considered on of the best looking by most people
in most cases. That doesn't change that e.g. I don't like
it compared to a smooth bicubic and that it e.g. fails
very badly at scaling content that was scaled before.
Also you specifically asked about preserving content.
For upscaling -sws 4 will 100% preserve the data, which
Lanczos cannot guarantee. To most people it will look
like crap if you upscale by around 2x or more though.

> Are you referring to -vf  ilpack=0 
> nearest-neighbour sampling?  Are these option the best?

No, I don't see what ilpack has to do with it.

> mencoder -sws 9 -vf scale=1920:1800 (encoding options) -o 
> 1920_1800_video.mpg 1280_720_video.mpg 

Also, what I said so far applied to viewing.
Presuming you are not using an extremely high, near-lossless
bitrate, Lanczos due to creating sharpening and ringing is
likely to vastly increase bitrate/decrease quality.
Upscaling, especially at a factor 1.5, before encoding will
cost you a lot and if in any way possible you should of
course avoid it, so under that aspect these clearly aren't
good options. But I assume you have a reason.
Also why 1800? Just typo I guess?