---------- Forwarded message ----------
From: Hans Verkuil <hverkuil@xxxxxxxxx>
Date: 2011/2/13
Subject: Re: v4l2 lost frame when use with epoll
To: xinglp <xinglp@xxxxxxxxx>
抄送： bill@xxxxxxxxxxxx
On Sunday, February 13, 2011 13:33:27 xinglp wrote:
> 2011/2/13 Hans Verkuil <hverkuil@xxxxxxxxx>:
> > On Sunday, February 13, 2011 09:18:41 xinglp wrote:
> >> It seems like that epoll_wait() do not return as soon as possible when one
> >> frame be captured, it only returns when 4(set by ioctl(..VIDIOC_REQBUFS..).)
> >> frames be captured.
> >> And v4l2_buffer::sequence indecates one lost per 4 frames.
> >
> > What hardware/driver are you using?
> I' using uvcvideo. I've tried two cheap usbcam at two PC.
>
> lsusb
> Bus 002 Device 002: ID 1871:01f0 Aveo Technology Corp.
>
> lsmod
> Module Size Used by
> uvcvideo 54924 -
> videodev 65184 -
>
> DG45ID mainboard and a hp2530p notebook.
A quick follow-up: I could reproduce this with uvc. It works fine with vivi
and gspca, so this seems to be a uvc bug.
Please post this bug report to the linux-media mailinglist with a CC to
Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> who is the uvc maintainer.
Regards,
Hans
>
> >> The source in attachment can reproducte it, run it with option --epoll
> >> to make it use epoll.
> >>
> >> The attachment is a modified version of the follow URL.
> >> http://v4l2spec.bytesex.org/v4l2spec/capture.c
> >>
> >
> > I can't reproduce this with the vivi driver. It's much more likely to be a
> > driver issue.
> On my machine, vivi even not work with epoll(). only capture one frame
> and stop.(epoll_wait() never return again.)
>
> >
> > BTW, it's much better to mail the linux-media mailinglist. Also note that Bill
> > is no longer involved in V4L.
> I can't subscribe any kernel maillist successfully.
>
> > Regards,
> >
> > Hans
> >
> > --
> > Hans Verkuil - video4linux developer - sponsored by Cisco
> >
>
>
--
Hans Verkuil - video4linux developer - sponsored by Cisco
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