[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH v1 2/3] v4l: Add AUTO option for the V4L2_CID_POWER_LINE_FREQUENCY control



On Tue, Sep 20, 2011 at 11:25:31PM +0200, Sylwester Nawrocki wrote:
> Hi Sakari,

Hi,

> On 09/20/2011 10:57 PM, Sakari Ailus wrote:
> > Hi Sylwester,
> > 
> > On Tue, Sep 20, 2011 at 01:58:58PM +0200, Sylwester Nawrocki wrote:
> >> V4L2_CID_POWER_LINE_FREQUENCY control allows applications to instruct
> >> a driver what is the power line frequency so an appropriate filter
> >> can be used by the device to cancel flicker by compensating the light
> >> intensity ripple and thus. Currently in the menu we have entries for
> >> 50 and 60 Hz and for entirely disabling the anti-flicker filter.
> >> However some devices are capable of automatically detecting the
> >> frequency, so add V4L2_CID_POWER_LINE_FREQUENCY_AUTO entry for them.
> >>
> >> Signed-off-by: Sylwester Nawrocki<s.nawrocki@xxxxxxxxxxx>
> >> Signed-off-by: Kyungmin Park<kyungmin.park@xxxxxxxxxxx>
> >> Acked-by: Laurent Pinchart<laurent.pinchart@xxxxxxxxxxxxxxxx>
> >> ---
> >>   Documentation/DocBook/media/v4l/controls.xml |    5 +++--
> >>   drivers/media/video/v4l2-ctrls.c             |    1 +
> >>   include/linux/videodev2.h                    |    1 +
> >>   3 files changed, 5 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml
> >> index 2420e4a..c6b3c46 100644
> >> --- a/Documentation/DocBook/media/v4l/controls.xml
> >> +++ b/Documentation/DocBook/media/v4l/controls.xml
> >> @@ -232,8 +232,9 @@ control is deprecated. New drivers and applications should use the
> >>   	<entry>Enables a power line frequency filter to avoid
> >>   flicker. Possible values for<constant>enum v4l2_power_line_frequency</constant>  are:
> >>   <constant>V4L2_CID_POWER_LINE_FREQUENCY_DISABLED</constant>  (0),
> >> -<constant>V4L2_CID_POWER_LINE_FREQUENCY_50HZ</constant>  (1) and
> >> -<constant>V4L2_CID_POWER_LINE_FREQUENCY_60HZ</constant>  (2).</entry>
> >> +<constant>V4L2_CID_POWER_LINE_FREQUENCY_50HZ</constant>  (1),
> >> +<constant>V4L2_CID_POWER_LINE_FREQUENCY_60HZ</constant>  (2) and
> >> +<constant>V4L2_CID_POWER_LINE_FREQUENCY_AUTO</constant>  (3).</entry>
> > 
> > A stupid question: wouldn't this be a case for a new control for automatic
> > power line frequency, in other words enabling or disabling it?
> 
> IMO this would complicate things in kernel and user land, without any reasonable
> positive effects. AUTO seems to fit well here, it's just another mode of operation
> of a power line noise filter. Why make things more complicated than they need to be ? 

The advantage would be to be able to get the power line frquency if that's
supported by the hardware. This implementation excludes that. Such
information might be interesting to add e.g. to the image's exif data.

Not sure if that's important, though.

> > 
> >>   	</row>
> >>   	<row>
> >>   	<entry><constant>V4L2_CID_HUE_AUTO</constant></entry>
> >> diff --git a/drivers/media/video/v4l2-ctrls.c b/drivers/media/video/v4l2-ctrls.c
> >> index 06b6014..20abe5d 100644
> >> --- a/drivers/media/video/v4l2-ctrls.c
> >> +++ b/drivers/media/video/v4l2-ctrls.c
> >> @@ -210,6 +210,7 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> >>   		"Disabled",
> >>   		"50 Hz",
> >>   		"60 Hz",
> >> +		"Auto",
> >>   		NULL
> >>   	};
> >>   	static const char * const camera_exposure_auto[] = {
> >> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> >> index c33f462..87210f1 100644
> >> --- a/include/linux/videodev2.h
> >> +++ b/include/linux/videodev2.h
> >> @@ -1125,6 +1125,7 @@ enum v4l2_power_line_frequency {
> >>   	V4L2_CID_POWER_LINE_FREQUENCY_DISABLED	= 0,
> >>   	V4L2_CID_POWER_LINE_FREQUENCY_50HZ	= 1,
> >>   	V4L2_CID_POWER_LINE_FREQUENCY_60HZ	= 2,
> >> +	V4L2_CID_POWER_LINE_FREQUENCY_AUTO	= 3,
> >>   };
> >>   #define V4L2_CID_HUE_AUTO			(V4L2_CID_BASE+25)
> >>   #define V4L2_CID_WHITE_BALANCE_TEMPERATURE	(V4L2_CID_BASE+26)
> >> -- 
> >> 1.7.6.3
> >>
> > 
> 
> --
> Thanks,
> Sylwester

-- 
Sakari Ailus
e-mail: sakari.ailus@xxxxxx	jabber/XMPP/Gmail: sailus@xxxxxxxxxxxxxx
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Linux Input]     [Video for Linux]     [Mplayer Users]     [Linux USB Devel]     [Linux Audio Users]     [Photos]     [Yosemite Photos]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Devices]     [Yosemite Backpacking]

Add to Google Powered by Linux