Frank de Jong wrote:
> Hi,
>
> For our project of soccer-playing robots, we use off-the-shelf WinTV
> frame grabber cards to import from our Jai CVS3300 PAL cameras. We
> noticed that the colors as displayed on our Philips PAL monitors were
> different from the results from the grabber, using the Linux BTTV
> driver. This is no big surprise in itself, but it led us to look into
> the driver source code, and we noticed that a different gain is used
> for U and for V in bt848_sat():
>
> /* 0-511 for the color */
> val_u = color >> 7;
> val_v = ((color>>7)*201L)/237;
>
> We looked in the BT878 PDF document (127 pages), and found no reason
> for this factor. Can anyone explain what this factor is for?
The ranges for u and v are different.
u is 0 ... 201%, with 0xfe (100%) as power-on default.
v is 0 ... 283%, with 0xb4 (100%) as power-on default.
pages 113/114 in my copy of the pdf file.
I'd say the 237 is a tyops, should be 283.
Gerd
--
Damn lot people confuse usability and eye-candy.
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