[XviD-devel] stereo video streams

[Dirk Knop]

Hi,

wouldn't it be safer and equally efficient to just vertically stack the 
images and strip the images again after decoding? You could use any 
codec with such a solution then.

Cheers
Koepi

Luca Piccarreta wrote:

>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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>>    
>>
>
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>