On Sun, Mar 25, 2007 at 08:09:19PM +0200, Laurent Pinchart wrote:
> The Linux UVC driver doesn't support reading directly from the device
> (yet). Only the streaming I/O method (using mmap) is supported. You can
> test your webcam with luvcview.
Hi Laurent,
Thanks for the feedback. I had tried a few other utilities to read from
/dev/vide0, but they were giving me errors as well. I thought that cat(1)
would be the simplest way to demonstrate the problem, but I guess not :-)
When I try using the luvcview utility, the error messages I'm seeing are:
[EMAIL PROTECTED] ~/luvcview-20060920]$ ./luvcview
uvcview version 0.1.7
Video driver: x11
A window manager is available
video /dev/video0
Unable to set format: 5.
Init v4L2 failed !! exit fatal
And in dmesg, I see:
[17357520.848000] uvcvideo: Trying format 0x47504a4d (MJPG): 320x240.
[17357520.848000] uvcvideo: Using default frame interval 66666.6 us
(15.0 fps).
[17357521.148000] uvcvideo: Failed to query (1) UVC control 1 (unit 0)
: -110 (exp. 26).
Looking at the luvcview-20060920/v4l2uvc.c file, the codepath that
generates the "Unable to set format" error is:
/* set format in */
memset(&vd->fmt, 0, sizeof(struct v4l2_format));
vd->fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
vd->fmt.fmt.pix.width = vd->width;
vd->fmt.fmt.pix.height = vd->height;
vd->fmt.fmt.pix.pixelformat = vd->formatIn;
vd->fmt.fmt.pix.field = V4L2_FIELD_ANY;
ret = ioctl(vd->fd, VIDIOC_S_FMT, &vd->fmt);
if (ret < 0) {
printf("Unable to set format: %d.\n", errno);
goto fatal;
}
Which I thought that may be an indication that I needed to use the "-f"
or "-s" command line arguments to change the requested format or size to
something that may be better supported by my camera, so I tried a number
of different permutations with:
for f in yuv jpg; do
for s in 1024x576 1280x960 160x120 176x144 320x240 352x288 432x240 \
480x360 512x288 640x360 640x480 704x576 864x480 960x720; do
./luvcview -f $f -s $s -o ~/foo
done
done
However, none of them appeared to be successful.
Searching around for the "Failed to query" error message that appeared in
dmesg seems to suggest that I may be hitting a Logitech hardware bug :-(
Bleh.
-mct
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