[MPlayer-dev-eng] Re: ccache
Billy Biggs
vektor at dumbterm.net
Mon Jan 6 05:29:31 CET 2003
Tobias Diedrich (td at sim.uni-hannover.de):
> Billy Biggs wrote:
>
> > I don't really think this is valid, since depending on your standard
> > for 4:2:0 the chroma samples are located in different places.
> > Sometimes the chroma samples are from the middle of the four Y'
> > samples, sometimes it's between the two left samples.
>
> Huh? Why should the be in different places according to the above ?
In MPEG2:
Y1 Y2
C
Y3 Y4
In MPEG1, H.261, H.263, and most JPEG images:
Y1 Y2
C
Y3 Y4
And you want to output this:
[Y1,C1] [Y2,C2]
[Y3,C3] [Y4,C4]
And so you interpolate differently to get these values depending on
where the chroma sample is positioned. These are both 4:2:0 but the
chroma value is in a different location for interpolation.
This article shows using Catmull-Rom interpolation for the MPEG2 case
of 4:2:0 to 4:2:2.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnwmt/html/YUVFormats.asp
Note that you have to convert interlaced MPEG2 images differently than
progressive MPEG2 images, as the chroma is also interlaced.
--
Billy Biggs
vektor at dumbterm.net
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