r200 xvideo gamma curve

[Alex Deucher]

On 10/14/06, Edgar Toernig <froese at gmx.de> wrote:
> Hi,
>
> I wasn't satisfied with the quality of the xvideo overlay.
> Dark areas had a very low color resolution giving large
> patches of the same color without any details.  At 6.9
> release time a looked at radeon_video and noticed that
> the gamma curve seems to be non-linear at gamma 1.0.  I
> changed it[1] and IMO the picture is much better now - dark
> areas have much more details.
>
> Is the gamma curve supposed to be non-linear or is it just
> some kind of "make dark areas black" hack?
>

The values for the various gamma setting were given to me by ati.  As
you can see the entire curve can be adjusted, I just picked the preset
values ati offers in their windows driver.  If your changes make a
good improvement, I'm happy to apply the patch.  If you have ideas any
further enhancements let me know and we can discsuss the hardware
capabilities in detail.

Thanks,

Alex

> Anyway, I would prefer the gamme curve produced by this
> patch at any time:
>
> --- a/src/radeon_video.c
> +++ b/src/radeon_video.c
> @@ -547,9 +547,9 @@ static GAMMA_CURVE_R100 gamma_curve_r100
>  static GAMMA_CURVE_R200 gamma_curve_r200[8] =
>   {
>         /* Gamma 1.0 */
> -      {0x00000040, 0x00000000,
> -       0x00000040, 0x00000020,
> -       0x00000080, 0x00000040,
> +      {0x00000100, 0x00000000,
> +       0x00000100, 0x00000020,
> +       0x00000100, 0x00000040,
>         0x00000100, 0x00000080,
>         0x00000100, 0x00000100,
>         0x00000100, 0x00000100,
>
> Ciao, ET.
>
> [1] As I have no docs, I've no idea what these values
> really mean so I simply tried some settings.
>