[XviD-devel] stereo video streams

[Luca Piccarreta]

You could think of rectifying images before interlacing them.
Rectification is a homography (projection) of both images
in such a way that corresponding points on both images
share the same y-coord.
(I'm assuming that you're talking about a calibrated stereo
camera)
This *might* give you some improvement in coding efficiency.
Luca Piccarreta.

----- Original Message ----- 
From: "Christoph Lampert" <chl at math.uni-bonn.de>
To: <xvid-devel at xvid.org>
Sent: Wednesday, March 23, 2005 9:23 AM
Subject: Re: [XviD-devel] stereo video streams


> Hi,
> 
> 
> sage weil wrote:
> 
> > Hi,
> >
> > I'm looking for a way to efficiently encode a pair of video streams 
> > from a stereo camera.  A few obvious possibilities present themselves 
> > but are not entirely ideal:
> >
> > - Put frames side by side and encode as usual.  Macroblock searches 
> > won't find similar blocks from the other camera with a localized 
> > search...
> 
> This will not make a significant difference to encoding both 
> independently, you are right.
> 
> > - Interleave left and right frames.  If xvid searches more than one 
> > frame back then this would work reasonably well, but I'm pretty sure 
> > it doesn't? And if it did the motion prediction would end up way off, 
> > resulting in suboptimal performance...
> 
> This might indeed work well with codecs that support more than 1 
> reference frame (e.g. H.264 aka H.26L aka AVC aka MPEG4v10), but XviD is 
> MPEG4v2 and there it's not possible. I would also strongly advise 
> against hacking the format to support this, because it would need quite 
> some new syntax elements and would be completely incompatible, causing 
> major confusion.
> 
> > Does anybody have any thoughts about what might be necessary in terms 
> > of code changes to make this work well?
> 
> My idea was to interleave left and right row by row and test encoding 
> with or without interlaced DCT. You can still access them independently 
> by using a twice as high stride value, and in areas where the 
> displacement is low, it might be beneficial to
> have both views as close to each other as possible.
> 
> 
> gruel
> 
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