[MPlayer-users] Re: Crop before deinterlacing OK?

[Matthias Wieser]

Am Dienstag, 26. Juli 2005 01:17 schrieb Rich Felker:
> On Mon, Jul 25, 2005 at 03:02:22PM +0200, Matthias Wieser wrote:
> > Am Montag, 25. Juli 2005 14:43 schrieb Rich Felker:
> > > > But as pp=lb by the very nature of the system introduces some
> > > > vertical blurring this sharpening might improve the overall
> > > > quality.
> > >
> > > If you weren't going to encode, yes. But a sharpening filter will
> > > just hurt compressibility and lower the psnr of the actual encode.
> >
> > Do you always apply an gaussian blur filter before encoding because
> > mencoder -lavcopts [...]:psnr will then show a higher psnr? ;-)
>
> No, obviously this is bogus reasoning,

That's what I wanted to show.

> but actually it will improve 
> quality at a fixed bitrate unless the bitrate is extremely high.

?? I don't use "extremely high" bitrate and I don't think -vf unsharp= 
will improve quality (at least if you don't omit postprocessing).

> > The PSNR between the original frame and a pp=l5 processed frame is
> > significantly higher than the PSNR between the original and a pp=lb
> > processed frame. So why not encode the frames which are nearer to the
> > original?
>
> Neither is anywhere near the original if your original is interlaced.

That stands for both.

> On the other hand, if the original is progressive, both will change
> the image,

Yes.

> and then pp=l5 will also result in worse psnr during 
> compression,

No, pp=l5 is nearer to the original, so psnr is higher.

For progressive content I just did the comparison. pp=l5 results in much 
higher psnr between the original frames and the frames from the resulting 
video.

> To me it sounds like nonsense. I agree this happens, but I don't think
> it's anywhere near enough to be the cause unless you have a really
> shitty TFT. I'll believe it when someone does some proper tests...

The shitty TFTs (TN) generally are the ones with low response times. The 
good ones (with large viewing angles) generally show higher response 
times. It's generally known that response time between shades of gray is 
higher than beween black/white.

regards,
  Matthias