Re: [Linux-uvc-devel] Motorola ROKR E6 'webcam' and resolution issues

[Laurent P. <lau...@id...>]

Hi Michał,

On Monday 15 February 2010 18:50:10 Michał Górny wrote:
> Hello,
> 
> I am using an Motorola ROKR E6 cell phone as a webcam and although it is
> listed on 'Supported devices' list as working, I am unable to get it fully
> working.

Sorry for that. The report I got 2 years and a half ago was thus inaccurate, 
the reporter had probably tested 640x480 only (or your device is broken and 
his wasn't :-)).

> The driver reports five different modes (resolutions) for the device,
> which are (output of guvcview):
> 
> { pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' }
> { discrete: width = 352, height = 288 }
> 	Time interval between frame: 1/20,
> { discrete: width = 176, height = 144 }
> 	Time interval between frame: 1/20,
> { discrete: width = 640, height = 480 }
> 	Time interval between frame: 1/15,
> { discrete: width = 320, height = 240 }
> 	Time interval between frame: 1/20,
> { discrete: width = 160, height = 120 }
> 	Time interval between frame: 1/20,
> 
> But in fact only 640x480 works correctly. 320x240 shows only quarter of
> the image which three other quarters lightly overlaying on it, and 160x120
> works on similar manner. The 352x288 and 176x144 modes show only junk.
> This makes the webcam unusable for applications such as Skype which
> request one of the smaller modes.

Ouch.

> I was able to workaround the issue through hardcoding the 640x480 mode in
> the driver (applications used software scaling then) but that's only an
> ugly workaround. I would appreciate if you could give me further tips on
> diagnosing the issue or simply implement a quirk allowing to drop unusable
> video modes (or even leave only the one with largest resolution).

Would you be able to test the device in Windows ? If it works there we could 
try to capture USB traffic to find out how the Windows driver initializes it.

I've seen similar problems with Ricoh webcams. It was caused by the uvcvideo 
driver selecting an alternate setting with a too high bandwidth (which is 
allowed, but not very optimum). Your device has a single alternate setting for 
the streaming interface, so it doesn't seem to be the same issue.

-- 
Regards,

Laurent Pinchart