Trent Piepho (xyzzy@xxxxxxxxxxxxx): > > Looking at the datasheet, I'm unclear as to whether we can change > > the behavior of the bttv driver to output correct chroma. If we > > can, I > > Seems like it should be possible in the planar mode. I don't think > the bt848 can do 4:2:0 in pack mode? The vertical subsampling is done > by the DMA program just SKIPing every other line. No, I don't think it can output 4:2:0 packed. So, you're saying we can just edit the DMA program to not SKIP every other line (which is pretty wrong if the image is composed of two fields)? That would be nice, if you can also have it perform some averaging of chroma. Ideally I think of it like this: Let o == chroma + luma sample, x == luma sample. So, for 4:2:0 encoding, we get this: 1: o x o x o x o x 2: o x o x o x o x 3: o x o x o x o x 4: o x o x o x o x The bttv driver currently outputs 4:2:0 planar like this: 1: o x o x o x o x 2: x x x x x x x x 3: o x o x o x o x 4: x x x x x x x x But that sucks, since scanlines 2 and 4 are from another field, and now I have no chroma samples from it. I want it like this: 1: o x o x o x o x 2: o x o x o x o x 3: x x x x x x x x 4: x x x x x x x x Where the chroma samples on lines 1 and 2 are actually filtered to represent 1-3 and 2-4 respectively. This is how MPEG defines 4:2:0. -- Billy Biggs bbiggs@xxxxxxxxxxxx http://www.billybiggs.com/ wbiggs@xxxxxxxxxxxx
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