[MEncoder-users] RGB => YV12 conversion

[Rich Felker]

On Wed, Sep 28, 2005 at 11:00:11PM +0400, Vladimir Mosgalin wrote:
> Hi Rich Felker!
> 
>  On 2005.09.28 at 11:25:41 -0400, Rich Felker wrote next:
> 
> > > staircases and moir patterns are exactly what I was talking about.
> > 
> > These are common symptoms to identify it by, not definitions.
> 
> Where can I find exact definition? You know, aliasing is a generic word,
> and when talking about picture on computer screen, it usually means just
> what I said. If you know more specific definition, related strictly to
> video, please tell it.

Look up sampling theory, shannon's theorem, nyquist frequency, or
other related terms. Wikipedia probably has good info.

Essentially, aliasing is what happens when you try to reproduce a
signal based on too few samples, and the higher frequencies (above the
maximal frequency representable by your sampling, i.e. half the
sampling rate aka the nyquist frequency) wrap down into the lower
frequency bands.

> > > No, it looks a bit worse. And aliasing effect is stronger with it (but
> > > when downscaling with bicubic scaler it appears _too_). But I don't
> > > really understand what do you want to say, that phrase of mine wasn't
> > > related to the rest of mail. Just an objection to your "nothing can be
> > > worse than <something you don't like much>".
> > 
> > I think if you understood sampling theory my statement would make
> > sense and not be so unbelievable..
> 
> What should I agree to, that downscaling by throwing away half of the
> lines is bad and makes this effect stronger? Yes, that's right. But I
> know a man who doesn't hesitate to do this and they don't really worry
> about this. I also know some people who capture video from tv tuner at
> full resolution and then "deinterlace", as they say, by downscaling
> height by two. They are completely satisfied with results.
> 
> (As for me, I don't downscale, so I don't really care - and if I do, any
> effect is about equally bad)
> 
> So if YOU think that nothing can be worse and everyone thinks so, let me
> assure you, you are completely wrong.

Well I won't continue to argue with you, but I think these people are
both being rather ridiculous and stubborn in their preferences...

Rich