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-------------------------------------------------------------------------------
Readme for Linux device driver for the OmniVision OV511 USB to camera bridge IC
-------------------------------------------------------------------------------
Author: Mark McClelland
Homepage: http://alpha.dyndns.org/ov511
INTRODUCTION:
This is a driver for the OV511, a USB-only chip used in many "webcam" devices.
Any camera using the OV511/OV511+ and the OV7610/20/20AE CCD should work. It
supports streaming and capture of color or monochrome video via the Video4Linux
API. Most V4L apps are compatible with it, but a few video-conferencing programs
do not work yet. The following resolutions are supported: 640x480, 448x336,
384x288, 352x288, and 320x240.
If you need more information, please visit the OV511 homepage at the above URL.
WHAT YOU NEED:
- If you want to help with the development, get the chip's specification docs at
http://www.ovt.com/omniusbp.html
- A Video4Linux compatible frame grabber program (I recommend vidcat and xawtv)
vidcat is part of the w3cam package: http://www.hdk-berlin.de/~rasca/w3cam/
xawtv is available at: http://www.in-berlin.de/User/kraxel/xawtv.html
HOW TO USE IT:
You must have first compiled USB support, support for your specific USB host
controller (UHCI or OHCI), and Video4Linux support for your kernel (I recommend
making them modules.)
Next, (as root) from your appropriate modules directory (lib/modules/2.3.XX):
insmod usb/usbcore.o
insmod usb/usb-uhci.o <OR> insmod usb/ohci-hcd.o
insmod misc/videodev.o
insmod usb/ov511.o
If it is not already there (it usually is), create the video device:
mknod /dev/video c 81 0
Sometimes /dev/video is a symlink to /dev/video0
You will have to set permissions on this device to allow you to read/write
from it:
chmod 666 /dev/video
chmod 666 /dev/video0 (if necessary)
Now you are ready to run a video app! Both vidcat and xawtv work well for me
at 640x480.
[Using vidcat:]
vidcat -s 640x480 > test.jpg
xview test.jpg
[Using xawtv:]
You must make some modifications to the source and compile it before you use it.
(Note: this may not be applicable to versions other than 3.06)
In src/Xawtv.ad, change xawtv.tv.width to 640 and xawtv.tv.height to 480. Next,
in src/grab-v4l.c, change SYNC_TIMEOUT from 1 to 2. Then, from the main xawtv
directory:
make clean
./configure
make
make install
Now you should be able to run xawtv. Right click for the options dialog. If
you get a scrambled image it is likely that you made a mistake in Xawtv.ad.
Try setting the size to 320x240 if all else fails.
MODULE PARAMETERS:
You can set these with: insmod ov511 NAME=VALUE
There is currently no way to set these on a per-camera basis.
NAME: autoadjust
TYPE: integer (boolean)
DEFAULT: 1
DESC: The camera normally adjusts exposure, gain, and hue automatically. This
can be set to 0 to disable this automatic adjustment. Note that there is
currently no way to set these parameters manually once autoadjust is
disabled.
NAME: debug
TYPE: integer (0-6)
DEFAULT: 3
DESC: Sets the threshold for printing debug messages. The higher the value,
the more is printed. The levels are cumulative, and are as follows:
0=no debug messages
1=init/detection/unload and other significant messages
2=some warning messages
3=config/control function calls
4=most function calls and data parsing messages
5=highly repetitive mesgs
NAME: fix_rgb_offset
TYPE: integer (boolean)
DEFAULT: 0
DESC: Some people have reported that the blue component of the image is one
or so lines higher than the red component. This is only apparent in
images with white objects on black backgrounds at 640x480. Setting this
to 1 will realign the color planes correctly. NOTE: This is still
experimental and very buggy. You will likely need a fast (500 MHz) CPU.
NAME: snapshot
TYPE: integer (boolean)
DEFAULT: 0
DESC: Set to 1 to enable snapshot mode. read() will block until the snapshot
button is pressed. Note that this does not yet work with most apps,
including xawtv and vidcat. NOTE: See the section "TODO" for more info.
NAME: sensor
TYPE: integer ([0, 1, 3])
DEFAULT: [varies]
DESC: If you know that your camera sensor is not detected correctly, set this
parameter. This is a global option for all attached OV511 cameras. You
will probably never need to set this, but if you do, valid values are:
0 for OV7620
1 for OV7620AE
3 for OV7610
NAME: i2c_detect_tries
TYPE: integer (don't set it insanely high!)
DEFAULT: 5
DESC: This is the number of times the driver will try to sync and detect the
internal i2c bus (which connects the OV511 and sensor). If you are
getting intermittent detection failures ("Failed to read sensor ID...")
you should increase this by a modest amount. If setting it to 20 or so
doesn't fix things, look elsewhere for the cause of the problem.
NAME: aperture
TYPE: integer (0 - 15)
DEFAULT: [varies by sensor]
DESC: For legal values, see the OV7610/7620 specs under register Common F.
This setting affects the upper nybble of that reg (bits 4-7). This is
for if you want to play with the camera's pixel saturation.
NAME: force_rgb
TYPE: integer (boolean)
DEFAULT: 0
DESC: Force image to be read in RGB instead of BGR. This option allow
programs that expect RGB data (e.g. gqcam) to work with this driver. If
your colors look VERY wrong, you may want to change this.
NAME: buf_timeout
TYPE: integer
DEFAULT: 5 (seconds)
DESC: Number of seconds before unused frame buffers are deallocated.
Previously, memory was allocated upon open() and deallocated upon
close(). Deallocation now occurs only if the driver is closed and this
timeout is reached. If you are capturing frames less frequently than
the default timeout, increase this. This will not make any difference
with programs that capture multiple frames during an open/close cycle.
NAME: cams
TYPE: integer (1-4 for OV511, 1-31 for OV511+)
DEFAULT: 1
DESC: Number of cameras allowed to stream simultaneously on a single bus.
Values higher than 1 reduce the data rate of each camera, allowing two
or more to be used at once. If you have a complicated setup involving
both OV511 and OV511+ cameras, trial-and-error may be necessary for
finding the optimum setting.
NAME: retry_sync
TYPE: boolean
DEFAULT: 0
DESC: Prevent apps from timing out if frame is not done in time. This is
useful if you are having problems with Xawtv getting "stuck" on a frame
when your system is under heavy load.
NAME: sensor_gbr
TYPE: boolean
DEFAULT: 0
DESC: This makes the sensor output GBR422 instead of YUV420. This saves the
driver the trouble of converting YUV to RGB, but it currently does not
work very well (the colors are not quite right)
WORKING FEATURES:
o Color streaming/capture at 640x480, 448x336, 384x288, 352x288, and 320x240
o RGB24, RGB565, YUV420, YUV422, YUYV, and YUV422P color
o Monochrome
o Setting/getting of saturation, contrast, brightness, and hue (only some of
them work the OV7620 and OV7620AE)
o /proc status reporting
EXPERIMENTAL FEATURES:
o fix_rgb_offset: Sometimes works, but other times causes errors with xawtv and
corrupted frames. If you have a very fast CPU, you can try it.
o Snapshot mode (only works with some read() based apps; see below for more)
o OV6620 sensor support
o GBR422 parsing
o 160x120
TODO:
o Fix the noise / grainy image problem.
o Get compression working. It would be a nice addition as it improves
frame rate quite a bit. OmniVision wouldn't tell me how the algorithm works,
so we can't really work on that yet. Please kindly inform OmniVision that you
would like them to release their specifications to the Linux community.
o YUV422
o Fix fixFrameRGBoffset(). It is not stable yet with streaming video.
o V4L2 support (Probably not until it goes into the kernel)
o Get rid of the memory management functions (put them in videodev.c??)
o Setting of contrast and brightness not working with 7620/7620AE
o Driver/camera state save/restore for when USB supports suspend/resume
o Unstable on SMP systems
o OV7620/OV6620 experience frame corruption with moving objects
o OV6620 is too dark
o 176x144 support
o Driver sometimes hangs upon close() with OHCI
o The image should always be written properly to the mmap'ed buffer as long as
the requested image size is at least the minimum size. This will likely
require a rewrite of all the parsing code.
HOW TO CONTACT ME:
You can email me at mwm@i.am . Please prefix the subject line
with "OV511: " so that I am certain to notice your message.
CREDITS:
The code is based in no small part on the CPiA driver by Johannes Erdfelt,
Randy Dunlap, and others. Big thanks to them for their pioneering work on that
and the USB stack. Thanks to Bret Wallach for getting camera reg IO, ISOC, and
image capture working. Thanks to Orion Sky Lawlor, Kevin Moore, and Claudio
Matsuoka for their work as well.
|
