Hello Laurie,
On Sat, 8 Aug 2020 21:56:08 +0100
Laurence Tratt <lau...@tratt.net> wrote:
> On Sat, Aug 08, 2020 at 09:30:18PM +0200, Marcus Glocker wrote:
>
> Hello Marcus,
>
> >> I like your patch, which is better than my original! My only very
> >> minor comment is whether we might want to document that it's safe
> >> to put "0" in a "V4L2_CID_AUTO" settings, since the lowest value
> >> one of those can be is 0x900 (judging by videoio.h)? At least, I
> >> had to look to make sure it was safe :)
> > Sorry, I lost you. Which control value exactly can be lowest
> > 0x900?
>
> In this bit of your diff:
>
> #define CTRL_SHARPNESS 6
> - { "sharpness", 0, V4L2_CID_SHARPNESS, 0, 0, 0, 0, 0 },
> + { "sharpness", 0, V4L2_CID_SHARPNESS, 0, 0, 0, 0, 0, 0 },
> #define CTRL_WHITE_BALANCE_TEMPERATURE 7
> { "white_balance_temperature",
> - 0, V4L2_CID_WHITE_BALANCE_TEMPERATURE, 0, 0,
> 0, 0, 0 },
> + 0, V4L2_CID_WHITE_BALANCE_TEMPERATURE,
> + V4L2_CID_AUTO_WHITE_BALANCE, 0, 0, 0, 0, 0
> },
>
> it wasn't immediately obvious to me that the first "0" after
> V4L2_CID_SHARPNESS wouldn't conflict with some other V4L2 setting.
> But it turns out that all the V4L2_CID values are defined relative to
> this:
>
> #define V4L2_CID_BASE (V4L2_CTRL_CLASS_USER
> | 0x900)
>
> so "0" can't accidentally clash with anything. It's not a big deal :)
Oh right, got it now :-)
Yes, we should be safe by using '0' to indicate that a control has no
auto control available without conflicting.
> >> One other thing has occurred to me -- but can be done in a future
> >> patch -- is that we probably want to be able to do:
> >>
> >> $ video white_balance_temperature=auto
> > I was thinking about that as well but just not decided yet if we
> > should introduce this or for now be compliant with the GUI where
> > you would require to reset all settings to get back to auto.
>
> In a sense the command-line is already more expressive (you can, for
> example, express arbitrary white balance temperatures when in the GUI
> you have to use increments of 10), so I'm inclined to think that
> allowing them to be more separate is no bad thing.
Well yes, true.
> [I personally think the GUI controls are very hard to use in
> practise: they change so slowly that I find it almost impossible to
> A/B anything. So I'm a bit biased against them!]
I see your point. Lets add this to our backlog, as we say in Agile :-|
>
> Laurie
>
Marcus
