Re: [Qemu-devel] Webcams under KVM and Linux

[Peter Baitz]

Hello Natalia and Andreas,

Thank you for the replies and suggestions.  I will lookup V4L. 

Natalia,

So your patch creates a generic webcam under KVM/Qemu to allow many webcams to work?

My only concern is the following:   I use specific Philips webcams, and one in particular has a long exposure modification that the PWC driver (Fedora 11 guest on Fedora 15 host) coupled with Qastrocam-G2 (v4.9) allows the "shutter" to remain open through USB control of the LED.  If the guest restorts to using a generic webcam driver, I think this would preclude functionality that the native driver supports ? 

Also, can you tell me - when KVM is running my guest, should the PWC webcam driver be loaded and/or the /dev/video0 on the HOST (F15), versus the guest (F11) ?   I am confused as to which components are supposed to be enabled or disabled while running the guest webcam.   What I see is when I enable the webcam USB device in KVM, it appears to disable the /dev/video0 on the host an brings it up in the guest.   And the pwc driver loads and remains on both host and guest. 

Peter


--- On Sun, 5/29/11, Natalia Portillo <address@hidden> wrote:

From: Natalia Portillo <address@hidden>
Subject: Re: [Qemu-devel] Webcams under KVM and Linux
To: "Andreas Färber" <address@hidden>
Cc: "Peter Baitz" <address@hidden>, "QEMU Developers" <address@hidden>
Date: Sunday, May 29, 2011, 1:53 PM

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More concretely search for patches sent by me.

Even when EHCI is finished still is the problem of isochronous transfer not working well because of timing issues on QEMU.

My patches overcome the need for ISO transfer and EHCI controllers completely, as well as providing an universal device to the guest that works with every Windows >XP, every Linux and even Mac OS X.

El 29/05/2011, a las 14:37, Andreas Färber escribió:

> Hello,
>
> Am 29.05.2011 um 15:01 schrieb Peter Baitz:
>
>>
>>> [...] You should notice that it is not just adding
>>> ISOC and USB 2.0 support, but also to prioritize the processing of isoc
>>> packets on a virtual environment, and to provide enough throughput for
>>> video streams
>>
>> [...] Please check the qemu-devel mailing list archive, specifically regarding recent discussions about EHCI (USB 2.0). Some of those threads address isochronous transfer as well.
>>
>> In the meantime, you could also try to assign a complete host controller to the guest to get a webcam working. I tried this a while ago, though the result was only moderately well working here.
>
>> [...] I would indeed like to hear more about what the project is adding to KVM - Qemu to allow video to work with webcams
> [...]
>> I was told I could try to add a complete host controller to the guest, but am not entirely sure I understand what that means?  Looking for specifics?  Is there a suggestion for doing this during install of the KVM guest, or can this be done while the guest is running, or otherwise?
>
> Independent of the ongoing EHCI work, I remember a patch specifically for webcams a while ago, try searching the archives for V4L.
>
> Andreas

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