Re: [PATCH 2/3] libv4lconvert: pac7302-devices: remove unneeded flag V4LCONTROL_WANTS_WB

["Frank Schäfer" <fschaefer.oss@googlemail.com>]

Am 10.09.2012 20:33, schrieb Hans de Goede:
> Hi,
>
> On 09/10/2012 05:41 PM, Frank Schäfer wrote:
>> Am 09.09.2012 23:24, schrieb Hans de Goede:
>>> Hi,
>>>
>>> On 09/09/2012 08:36 PM, Frank Schäfer wrote:
>>>> The gspca_pac7302 driver already provides this control.
>>>>
>>>> Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
>>>> ---
>>>>    lib/libv4lconvert/control/libv4lcontrol.c |   12 ++++--------
>>>>    1 files changed, 4 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/lib/libv4lconvert/control/libv4lcontrol.c
>>>> b/lib/libv4lconvert/control/libv4lcontrol.c
>>>> index 1272256..3d7a816 100644
>>>> --- a/lib/libv4lconvert/control/libv4lcontrol.c
>>>> +++ b/lib/libv4lconvert/control/libv4lcontrol.c
>>>> @@ -202,14 +202,10 @@ static const struct v4lcontrol_flags_info
>>>> v4lcontrol_flags[] = {
>>>>        { 0x145f, 0x013a, 0,    NULL, NULL, V4LCONTROL_WANTS_WB,
>>>> 1500 },
>>>>        { 0x2001, 0xf115, 0,    NULL, NULL, V4LCONTROL_WANTS_WB,
>>>> 1500 },
>>>>        /* Pac7302 based devices */
>>>> -    { 0x093a, 0x2620, 0x0f, NULL, NULL,
>>>> -        V4LCONTROL_ROTATED_90_JPEG | V4LCONTROL_WANTS_WB, 1500 },
>>>> -    { 0x06f8, 0x3009, 0,    NULL, NULL,
>>>> -        V4LCONTROL_ROTATED_90_JPEG | V4LCONTROL_WANTS_WB, 1500 },
>>>> -    { 0x06f8, 0x301b, 0,    NULL, NULL,
>>>> -        V4LCONTROL_ROTATED_90_JPEG | V4LCONTROL_WANTS_WB, 1500 },
>>>> -    { 0x145f, 0x013c, 0,    NULL, NULL,
>>>> -        V4LCONTROL_ROTATED_90_JPEG | V4LCONTROL_WANTS_WB, 1500 },
>>>> +    { 0x093a, 0x2620, 0x0f, NULL, NULL, V4LCONTROL_ROTATED_90_JPEG },
>>>> +    { 0x06f8, 0x3009, 0,    NULL, NULL, V4LCONTROL_ROTATED_90_JPEG },
>>>> +    { 0x06f8, 0x301b, 0,    NULL, NULL, V4LCONTROL_ROTATED_90_JPEG },
>>>> +    { 0x145f, 0x013c, 0,    NULL, NULL, V4LCONTROL_ROTATED_90_JPEG },
>>>>        /* Pac7311 based devices */
>>>>        { 0x093a, 0x2600, 0x0f, NULL, NULL, V4LCONTROL_WANTS_WB },
>>>>        /* sq905 devices */
>>>>
>>>
>>> WANTS_WB does not add a whitebalance control, which these cameras
>>> indeed
>>> already have, it adds a (software) autowhitebalance control, which
>>> enables
>>> libv4lconvert doing software whitebalance correction. Although your
>>> kernel patch for the pac7302 driver to pick a better default
>>> whitebalance
>>> value, probably helps a lot to get the colors less screwed up, in
>>> the end
>>> we still need some sort of awb to adjust to changing lightning
>>> conditions,
>>> that is what this flag adds, as the pac7302 driver lacks awb.
>>
>> Ok, so WANTS_WB is actually WANTS_AUTOWB. ;)
>> But... IIRC... the software AWB control is always there, even without
>> this flag !?
>> Or is it just about switching AWB on by default ?
>
> Correct, also note that the awb control will only show up for devices
> which
> have non standard formats, since those need to always go through
> libv4lconvert
> anyways, it does not get added to standard cams unless specifically
> enabled
> through a quirk list entry.

Good to know that, thanks !

>
>> And if AWB is on, the WB control should be disabled, right ?
>
> No, the software AWB works by applying software rgb gains, so the
> hardware
> control is still useful, as the better the color balance of the input,
> the better the end-result will be.

Hmm... auto-whitebalance should compensate the setting made with the
manual hardware controlled whitebalance.
But I guess they are working too differenty.

Regards,
Frank

>
> Regards,
>
> Hans