Hi,
I noticed that AEC (Automatic Exposure Control, or
V4L2_CID_EXPOSURE_AUTO) does not work in the ov534 gspca driver, either
from guvcview or qv4l2.
From what I can see (but I do not have a deep knowledge of v4l2) this
happens because:
- V4L2_CID_EXPOSURE_AUTO is of class V4L2_CTRL_CLASS_CAMERA which is
greater than V4L2_CTRL_CLASS_USER
- some programs use VIDIOC_G_EXT_CTRLS with this class of controls;
for instance v4l2-ctrl does more or less this:
if (V4L2_CTRL_ID2CLASS(qctrl.id) != V4L2_CTRL_CLASS_USER)
test_ioctl(fd, VIDIOC_G_EXT_CTRLS, &ctrls)
else
test_ioctl(fd, VIDIOC_G_CTRL, &ctrl)
- gspca does not handle the _EXT_CTRLS ioclts
So in ov534, but I think in m5602 too, V4L2_CID_EXPOSURE_AUTO does not
work from guvcview, qv4l2, or v4l2-ctrl, for instance the latter fails
with the message:
error 25 getting ext_ctrl Auto Exposure
I tried adding an hackish implementation of vidioc_g_ext_ctrls and
vidioc_s_ext_ctrls to gspca, and with these V4L2_CID_EXPOSURE_AUTO seems
to work, but I need to learn more about this kind of controls before
I can propose a decent implementation for mainline inclusion myself, so
if anyone wants to anticipate me I'd be glad to test :)
Unrelated, but maybe worth mentioning is that V4L2_CID_EXPOSURE_AUTO is
of type MENU, while some drivers are treating it as a boolean, I think
I can fix this one if needed.
Thanks,
Antonio
--
Antonio Ospite
http://ao2.it
A: Because it messes up the order in which people normally read text.
See http://en.wikipedia.org/wiki/Posting_style
Q: Why is top-posting such a bad thing?
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