Theodore,
Aside from detect measurment of the power line, isn't a camera the best sort of sensor for this measurment anyway?
Just compute the average image luminosity over several frames and look for (10 Hz ?) periodic variation (beats), indicating a mismatch.
Sure you could just ask the user, but where's the challenge in that. ;)
Regards,
Andy
Theodore Kilgore <kilgota@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
>On Sun, 19 Dec 2010, Paulo Assis wrote:
>
>> Hi,
>>
>> 2010/12/18 Theodore Kilgore <kilgota@xxxxxxxxxxxxxxxxxxxxxx>:
>> >
>> > Does anyone know whether, somewhere in the kernel, there exists a scheme
>> > for detecting whether the external power supply of the computer is using
>> > 50hz or 60hz?
>> >
>> > The reason I ask:
>> >
>> > A certain camera is marketed with Windows software which requests the user
>> > to set up the option of 50hz or 60hz power during the setup.
>> >
>> > Judging by what exists in videodev2.h, for example, it is evidently
>> > possible to set up this as a control setting in a Linux driver. I am not
>> > aware of any streaming app which knows how to access such an option.
>> >
>>
>> Most uvc cameras present this as a control, so any v4l2 control app
>> should let you access it.
>> If your camera driver also supports this control then this shouldn't
>> be a problem for any generci v4l2 app.
>> here are a couple of ones:
>>
>> v4l2ucp (control panel)
>> guvcview ("guvcview --control_only" will work along side other apps
>> just like v4l2ucp)
>> uvcdynctrl from libwebcam for command line control utility .
>>
>> Regards,
>> Paulo
>
>Thank you.
>
>I still think that it would be even more clever to detect the line
>frequency automatically and then just to set the proper setting, if needed
>or desirable. That was one of the parts of my question about it, after
>all. But if nobody has ever had a reason to do such detection already it
>would perhaps be much more trouble than it is worth just do support a
>cheap camera.
>
>Theodore Kilgore
>--
>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
ÿô.nlj·Ÿ®‰†+%ŠË±é¥Šwÿº{.nlj·¥Š{±þg‰¯â^n‡r¡öë¨è&£ûz¹Þúzf£¢·hšˆ§~††Ûÿÿïÿ‘ê_èæ+v‰¨þ)ßø
