[x264-devel] Regarding horizontal and vertical range of motion vectors.

[mahesh k]

Ok thanks for your reply.
But can you please tell me is  that must that chroma motion vectors are to
be determined from luma motion vectors.
As far as my thinking For baseline profile (YUV 4:2:0) the chroma motion
vectors are half to that of luma motion vectors. Am i correct? IF not how to
get them?

Best regards,
Mahesh.


On 11/16/07, Panagiotis Issaris <takis.issaris at uhasselt.be> wrote:
>
> Hi Mahesh,
>
> mahesh k schreef:
> > Hi all,
> >
> > Can any one please tell me whats the need of having different horizontal
> and
> > vertical ranges for motion vector components in H.264 . Also the
> horizontal
> > ranges are independent of levels but the vertical ranges depend on level
> of
> > the decoder ?
> >
> > I am working on H.264 decoder (Constrained to only baseline profile).
> > Please tell me how to handle the motion vectors if they point to a
> > Macroblock outside the frame boundary.?
>
> AFAIK, if they point left or right of the frame boundary, you have to
> replicate the pixels on the border, so, if this would be a block at the
> extreme right of the frame, right at the border:
> 45 34 37 40 |
> 34 33 45 46 |
> 12 13 34 35 |
> 43 44 46 59 |
>
> This would become something like this:
> 45 34 37 40 | 40 40 40 ...
> 34 33 45 46 | 46 46 46 ...
> 12 13 34 35 | 35 35 35 ...
> 43 44 46 59 | 59 59 59 ...
>
> Similar for a motion vector pointing above or below the frame boundary.
>
> I'm pretty sure about this for luma, less sure for chroma...
>
> And, unfortunately, I'm not sure yet what happens for motion vectors
> pointing outside the corners of the frame.
>
>
> And just as it might help you in the future: There's two mailinglist
> which are not about a specific H.264 encoder but are more about
> MPEG-4/H.264 in general: mp4-tech[1] and jvt-experts[2].
>
> With friendly regards,
> Takis
> --
> vCard: http://issaris.org/pi.vcf
> PGP key: http://issaris.org/pi.key
>
>
>
> [1] http://lists.mpegif.org/mailman/listinfo/mp4-tech
> [2] http://mailman.rwth-aachen.de/mailman/listinfo/jvt-experts
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