Re: NTSC/PAL resolution support for "EasyCap" device

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Bastien,

On Friday 03 Jun 2016 12:53:31 Bastien Nocera wrote:
> On Fri, 2016-06-03 at 01:37 +0300, Laurent Pinchart wrote:
> > On Tuesday 31 May 2016 12:38:49 Bastien Nocera wrote:
> >> Hey,
> >> 
> >> I saw your commits to add quirks for Arkmicro "webcams". I recently
> >> bought a dirt cheap "EasyCap" device on eBay, but it only seems to
> >> support 640x480 instead of the native "NRSC" resolution as
> >> mentioned on the device's box.
> >> 
> >> $ v4l2-ctl --list-formats-ext -d /dev/video0 
> >> ioctl: VIDIOC_ENUM_FMT
> >> 
> >> 	Index       : 0
> >> 	Type        : Video Capture
> >> 	Pixel Format: 'MJPG' (compressed)
> >> 	Name        : Motion-JPEG
> >> 	
> >> 		Size: Discrete 640x480
> >> 		
> >> 			Interval: Discrete 0.017s (60.000 fps)
> >> 			Interval: Discrete 0.033s (30.000 fps)
> >> 			Interval: Discrete 0.067s (15.000 fps)
> >> 			Interval: Discrete 0.200s (5.000 fps)
> >> 		
> >> 		Size: Discrete 352x288
> >> 		
> >> 			Interval: Discrete 0.017s (60.000 fps)
> >> 			Interval: Discrete 0.033s (30.000 fps)
> >> 			Interval: Discrete 0.067s (15.000 fps)
> >> 			Interval: Discrete 0.200s (5.000 fps)
> >> 
> >> Device is:
> >> Bus 003 Device 066: ID 18ec:5850 Arkmicro Technologies Inc. 
> >> 
> >> In your professional opinion, should I try using
> >> UVC_QUIRK_PROBE_DEF or UVC_QUIRK_PROBE_MINMAX as a quirk for this device?
> >> Is there a stand-alone driver somewhere that I can use for testing
> >> (rather than recompiling a whole kernel)?
> > 
> > Those quirks will not affect the available resolutions.
> 
> OK. I also made my own testing tree to copy/paste those devices.
> 
> > UVC devices expose a list of resolutions they support through the USB 
> > descriptors, and the uvcvideo device merely uses that list to expose
> > supported  resolutions to userspace.
> 
> Full lsusb below.

Thanks. The device only advertises two resolutions, 640x480 and 352x288.

> > If the device doesn't expose resolutions other than the above two, the
> > box could be lying, or the device could use non-standard extensions to UVC
> > to support additional resolutions. The first step would be to try the
> > camera in a  Windows machine to see if additional resolutions are
> > available (without installing any additional device-specific software).
> 
> I should be able to find a Windows somewhere, but which application
> should I use to see if those resolutions are indeed available?

My (lack of) Windows knowledge doesn't allow me to answer that question, but 
I'm sure searching online will give you answers.

> BTW, given the price of the device, I'd be fine getting one for you to
> test (6€ from eBay, shipping included).

Thanks, but I'm already overwhelmed with work, I'd rather have you performing 
the tests. Beside, I have no Windows machine :-)

-- 
Regards,

Laurent Pinchart