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Doubts in converting Ycbcr422 interlaced to Ycbcr420 non-interlaced CIF on DM642 EVM

Started by kcl_008 December 27, 2004
I use the following Parameters in the evmdm642_vcapparms.c file

VPORTCAP_Params.fldOp = VPORT_FLDOP_FRAME
SAA7115_ConfParams.inmode = SAA7115_MODE_NTSC720
SAA7115_ConfParams.outemode = SAA7115_MODE_CIF

I detected that capture frame buffer,both the iFrm.cb1 and iFrm.cr1 has a
size of 50688 (176 x 288). 

What should I do to downsample the capture frame to 4:2:0 , CIF standard
(chroma 176 x144) and non-interlace?

If I use the following method will i get the CIF standard.
1) Drop the even lines ( get 4:2:0 )
2) Average out every pair of vertical lines (get 176x144)

Is my method correct? 

Hope someone can clear my doubts. Thanks

>I use the following Parameters in the evmdm642_vcapparms.c file > >VPORTCAP_Params.fldOp = VPORT_FLDOP_FRAME >SAA7115_ConfParams.inmode = SAA7115_MODE_NTSC720 >SAA7115_ConfParams.outemode = SAA7115_MODE_CIF > >I detected that capture frame buffer,both the iFrm.cb1 and iFrm.cr1 has
a
>size of 50688 (176 x 288). > >What should I do to downsample the capture frame to 4:2:0 , CIF standard >(chroma 176 x144) and non-interlace? > >If I use the following method will i get the CIF standard. >1) Drop the even lines ( get 4:2:0 ) >2) Average out every pair of vertical lines (get 176x144) > >Is my method correct? > >Hope someone can clear my doubts. Thanks > >
Both 1 & 2 above will get you a chroma frame with size 176x144 with different degrees perceived image of quality. Since the original data was in 4:2:2 format, the downsampled chroma frames essentially simulate a 4:2:0 color subsampling scheme. I believe DM642 EVM video port has an option for hardware resampling of captured 4:2:2 frames to 4:2:0. So check if you can use set and use this option with the video driver. That'll save you a lot of cycles. This message was sent using the Comp.DSP web interface on www.DSPRelated.com