[XviD-devel] Fades

[Michael Militzer]

Hi,

----- Original Message -----
From: "Christoph Lampert" <chl@math.uni-bonn.de>
To: <xvid-devel@xvid.org>
Sent: Monday, November 18, 2002 10:33 AM
Subject: Re: [XviD-devel] Fades


> On Mon, 18 Nov 2002, daniel smith wrote:
>
> > i worked a while back on adapting ME to fully match epzs.  during
playing with subsets i figured why not add a "subset d" which is just the
0,0 vector checked with a mean-removed SAD, only to be performed if subsets
a,b,c all fail to meet a threshold.
> >
> > it wouldn't catch every fade, but would certainly help (and not be all
> > that expensive).  might even help with some strobe effects.
>
> I guess normal SAD won't catch even the simplest fades, because there's a
> bias in luminance between current and reference. But we could use mrSAD
> for this last check, if we find some constants to compare SAD-values to
> mrSAD-values. Somehow I'd guess both would be very comparable, because
> only DC coefficient is missing, but my old tests showed that mrSAD values
> are much lower.
> Range of values for SAD and mrSAD should be comparable, because
> otherwise we'd have to modify mode decision etc.

hm, couldn't SysKin's chroma ME be helpful for fades? I'd suppose that
chroma SAD should be very small for (0,0) during fades, only luma is
changing. So if chroma SAD is also considered during the MV search, (0,0)
vector should be favorized over any other vector during fades (well, at
least more than with luma search only) and ME performance should improve at
fades - right?

> Is anyone willing to test this? I'll be too busy with my PhD for the next
> 4 weeks, but I just did a 2CD Rip of "Forrest Gump" and image was perfect
> except for the very first and the very last 5 seconds, which were simple
> fade and so extremely blocky, I had to cut them out :-(

well, I'm currently already way too busy with my studies, so unfortunately I
don't have time to play around with fades...

bye,
Michael