[mythtv-users] contrast/brightness/colour/hue in capturecard versus channel table

Noah Beck noah.b.beck at gmail.com
Mon Dec 1 00:38:01 UTC 2008


After poking around the source, the answers to my own questions:

> How do the channel and capturecard contrast/brightness/colour/hue values interact?

They are added together, and only the least significant 16 bits of the
result are used.

> How do the range of values allowed in the SQL tables map to the range of values
> allowed by my particular card (a PVR-150 using the ivtv driver)?

For my particular case (a Hauppauge PVR-150 using ivtv driver), it
seems to work like this for a given picture attribute:

ch.val: the channel table value
card.val: the capturecard value
ivtv.val: the value shown by v4l2-ctl
ivtv.min: the min value shown by v4l2-ctl
ivtv.max: the max value showsn by v4l2-ctl

ivtv.val = ivtv.min + ( (ivtv.max - ivtv.min) / 65536) * (ch.val + card.val)

Noah

On Wed, Nov 26, 2008 at 4:19 PM, Noah Beck <noah.b.beck at gmail.com> wrote:
> I have a Hauppauge WinTV PVR-150 (actually two; I haven't set the
> second one up yet) and have just installed mythtv-0.21 from atrpms on
> a Fedora 9 install.  My root drive died; I had a fedora 6 +
> mythtv-0.20 install before.  I've gotten everything back up and
> working and noticed that my color settings are back to the default
> again.  This makes sense since I had stored the color settings in the
> channel table before, and when I did the re-install, I had it delete
> the channel lineup and re-download it from schedulesdirect.
>
> According to ivtv, I have these settings available on the card:
>
>                     brightness (int)  : min=0 max=255 step=1
> default=128 value=128 flags=slider
>                       contrast (int)  : min=0 max=127 step=1
> default=64 value=64 flags=slider
>                     saturation (int)  : min=0 max=127 step=1
> default=64 value=64 flags=slider
>                            hue (int)  : min=-128 max=127 step=1
> default=0 value=0 flags=slider
>
> I have notes from before my drive crash that say that I would like to
> adjust this to:
>
>  brightness=240
>  contrast=120
>  saturation=64
>  hue=-15
>
> As mentioned in the subject line, there are _two_ tables that have
> contrast/brightness/colour/hue columns: channel and capturecard.  In
> table channel, the default values for all 4 columns are 32768.  In
> table capturecard, the default values for all 4 columns are 0.
>
> It seems logical that I should be adjusting the values in the
> capturecard table, since my second capture card will possibly want
> different values.  But how do the two tables' values interact with
> each other?  Is the channel value added to the card value and the
> result applied when a recording begins?  And how do the range of
> values allowed in the SQL tables (presumably -2^31 through +2^31) map
> to the range of values allowed by my particular card (listed above)?
>
> Thanks,
> Noah
>


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