Kevin Ruland wrote:
> Hi all,
>
> I'd like to try to tune my pvr 500 to make it appear more like my tv's
> tuner. I am no video expert and don't know the proper terms, but it
> looks like bright portions of the image "bloom" and drown out other
> regions. Can somebody provide me with information (in layman's terms)
> about each of the parameters exposed by ivtv-tune and how they will
> qualitatively affect video performance.
>
> If it makes any difference my card has the Philips tuner and cx25843
> decoder.
>
> I will return the gift by writing this up on the wiki.
>
> Thanks much.
>
> Kevin
>
>
>
Kevin,
It sounds to me like your contrast or brightness is too high. You
can change it in Mythtv by press the G key while in liveTV mode. It will
toggle between
brightness, contrast, color, hue. Use the left/right arrow keys to
adjust the value. This is stored in the database individual per channel.
If you're not using mythtv, use ivtvctl -Y to view the current settings,
and ivtvctl -y brightness=xxx to set it, where xxx is a number between 0
and 256 with 127 being the default
I will try to explain the settings further, without getting to technical
Brightness
This controls how bright the whole picture is. If this control is too
low, dark-grey shadow areas will be forced to black, and any detail in
between is lost.
if the brightness is too high, white areas will become washed out, and
the same thing happens to highlight details. This might be part of your
problem.
Contrast
This controls the difference between black and white. If Contrast is set
to high, both shadows and bright highlights are squished. something like
having the brightness too high
and too low at the same time. If the contrast is too low, white becomes
grey, black becomes grey, and the pictures look washed out.
Ideally, the brightness control should set the black level, and the
contrast control should adjust only the white level, but the contrast
control (at least on my pvr250) adjust both
it lowers the white level and raises the black level. So, set the
brightness first, then adjust the contrast, then go back and adjust the
brightness again
Color
This is the amount of color applied to the greyscale picture, if you set
this to zero, you get a greyscale picture. If it is set too high, bright
colors will bleed around their
borders.
Hue
This is the tint adjustment. If this is set incorrect, colors in the
picture will be the captured wrong. People's facing may look green or
purple.
I hope this helps a bit.
Richard
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