Video Signal Type in V4L

Video Signal Type in V4L

[Abhishek Bansal]

Hi All,

Is there any way by which I can know Input signal type (in terms of
DVI/Composite/USB/SDI) and refresh rate from a V4L video capture device.
Any available V4L Structure/Flag from which I can deduce this information. 
Please help !

Thank You
Abhishek Bansal

Re: Video Signal Type in V4L

[Devin Heitmueller]

> Is there any way by which I can know Input signal type (in terms of
> DVI/Composite/USB/SDI) and refresh rate from a V4L video capture device.
> Any available V4L Structure/Flag from which I can deduce this information.
> Please help !

The extent to which the data is available is the name field in the G_FMT call:

http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-enuminput.html

For most devices, the driver developer names the individual inputs
"Composite", "S-Video", "Tuner", etc.

The only level of distinction other than the name is the type field,
which today is V4L2_INPUT_TYPE_TUNER for an RF tuner and
V4L2_INPUT_TYPE_CAMERA for everything else.

To my knowledge there aren't any current drivers in the main tree that
support DVI or SDI capture, so nobody has really cared to make the API
more flexible to extend the "type" field with other values (which
would both be easier to machine parse, localize, and be consistent
across boards).

Devin

--
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com

Re: Video Signal Type in V4L

[Mauro Carvalho Chehab]

Em Fri, 26 Apr 2013 02:15:03 +0530
"Abhishek Bansal" <abhishek@vizexperts.com> escreveu:

> Hi All,
> 
> Is there any way by which I can know Input signal type (in terms of
> DVI/Composite/USB/SDI) 

As input "type", currently no. However, by looking at the video input 'name'
field, it is possible to know if it is a composite, S-video, ... input entry.
The input name is a string, and the naming convention depends on the driver.

see field 'name' at
http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-enuminput.html

And this ioctl for retrieving it for the current input:
	http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-g-input.html

> and refresh rate from a V4L video capture device.

Yes, via VIDIOC_G_PARM. see timeperframe field there:
	http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-g-parm.html

Not all drivers implement it through.

> Any available V4L Structure/Flag from which I can deduce this information. 


> Please help !
> 
> Thank You
> Abhishek Bansal
> 
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-- 

Cheers,
Mauro