131 lines
5.6 KiB
Plaintext
131 lines
5.6 KiB
Plaintext
$Id: README,v 1.7 2005/08/29 23:39:57 sbertin Exp $
|
|
|
|
1. Introduction
|
|
|
|
This is a driver for STMicroelectronics's CPiA2 (second generation
|
|
Colour Processor Interface ASIC) based cameras. This camera outputs an MJPEG
|
|
stream at up to vga size. It implements the Video4Linux interface as much as
|
|
possible. Since the V4L interface does not support compressed formats, only
|
|
an mjpeg enabled application can be used with the camera. We have modified the
|
|
gqcam application to view this stream.
|
|
|
|
The driver is implemented as two kernel modules. The cpia2 module
|
|
contains the camera functions and the V4L interface. The cpia2_usb module
|
|
contains usb specific functions. The main reason for this was the size of the
|
|
module was getting out of hand, so I separated them. It is not likely that
|
|
there will be a parallel port version.
|
|
|
|
FEATURES:
|
|
- Supports cameras with the Vision stv6410 (CIF) and stv6500 (VGA) cmos
|
|
sensors. I only have the vga sensor, so can't test the other.
|
|
- Image formats: VGA, QVGA, CIF, QCIF, and a number of sizes in between.
|
|
VGA and QVGA are the native image sizes for the VGA camera. CIF is done
|
|
in the coprocessor by scaling QVGA. All other sizes are done by clipping.
|
|
- Palette: YCrCb, compressed with MJPEG.
|
|
- Some compression parameters are settable.
|
|
- Sensor framerate is adjustable (up to 30 fps CIF, 15 fps VGA).
|
|
- Adjust brightness, color, contrast while streaming.
|
|
- Flicker control settable for 50 or 60 Hz mains frequency.
|
|
|
|
2. Making and installing the stv672 driver modules:
|
|
|
|
Requirements:
|
|
-------------
|
|
This should work with 2.4 (2.4.23 and later) and 2.6 kernels, but has
|
|
only been tested on 2.6. Video4Linux must be either compiled into the kernel or
|
|
available as a module. Video4Linux2 is automatically detected and made
|
|
available at compile time.
|
|
|
|
Compiling:
|
|
----------
|
|
As root, do a make install. This will compile and install the modules
|
|
into the media/video directory in the module tree. For 2.4 kernels, use
|
|
Makefile_2.4 (aka do make -f Makefile_2.4 install).
|
|
|
|
Setup:
|
|
------
|
|
Use 'modprobe cpia2' to load and 'modprobe -r cpia2' to unload. This
|
|
may be done automatically by your distribution.
|
|
|
|
3. Driver options
|
|
|
|
Option Description
|
|
------ -----------
|
|
video_nr video device to register (0=/dev/video0, etc)
|
|
range -1 to 64. default is -1 (first available)
|
|
If you have more than 1 camera, this MUST be -1.
|
|
buffer_size Size for each frame buffer in bytes (default 68k)
|
|
num_buffers Number of frame buffers (1-32, default 3)
|
|
alternate USB Alternate (2-7, default 7)
|
|
flicker_freq Frequency for flicker reduction(50 or 60, default 60)
|
|
flicker_mode 0 to disable, or 1 to enable flicker reduction.
|
|
(default 0). This is only effective if the camera
|
|
uses a stv0672 coprocessor.
|
|
|
|
Setting the options:
|
|
--------------------
|
|
If you are using modules, edit /etc/modules.conf and add an options
|
|
line like this:
|
|
options cpia2 num_buffers=3 buffer_size=65535
|
|
|
|
If the driver is compiled into the kernel, at boot time specify them
|
|
like this:
|
|
cpia2.num_buffers=3 cpia2.buffer_size=65535
|
|
|
|
What buffer size should I use?
|
|
------------------------------
|
|
The maximum image size depends on the alternate you choose, and the
|
|
frame rate achieved by the camera. If the compression engine is able to
|
|
keep up with the frame rate, the maximum image size is given by the table
|
|
below.
|
|
The compression engine starts out at maximum compression, and will
|
|
increase image quality until it is close to the size in the table. As long
|
|
as the compression engine can keep up with the frame rate, after a short time
|
|
the images will all be about the size in the table, regardless of resolution.
|
|
At low alternate settings, the compression engine may not be able to
|
|
compress the image enough and will reduce the frame rate by producing larger
|
|
images.
|
|
The default of 68k should be good for most users. This will handle
|
|
any alternate at frame rates down to 15fps. For lower frame rates, it may
|
|
be necessary to increase the buffer size to avoid having frames dropped due
|
|
to insufficient space.
|
|
|
|
Image size(bytes)
|
|
Alternate bytes/ms 15fps 30fps
|
|
2 128 8533 4267
|
|
3 384 25600 12800
|
|
4 640 42667 21333
|
|
5 768 51200 25600
|
|
6 896 59733 29867
|
|
7 1023 68200 34100
|
|
|
|
How many buffers should I use?
|
|
------------------------------
|
|
For normal streaming, 3 should give the best results. With only 2,
|
|
it is possible for the camera to finish sending one image just after a
|
|
program has started reading the other. If this happens, the driver must drop
|
|
a frame. The exception to this is if you have a heavily loaded machine. In
|
|
this case use 2 buffers. You are probably not reading at the full frame rate.
|
|
If the camera can send multiple images before a read finishes, it could
|
|
overwrite the third buffer before the read finishes, leading to a corrupt
|
|
image. Single and double buffering have extra checks to avoid overwriting.
|
|
|
|
4. Using the camera
|
|
|
|
We are providing a modified gqcam application to view the output. In
|
|
order to avoid confusion, here it is called mview. There is also the qx5view
|
|
program which can also control the lights on the qx5 microscope. MJPEG Tools
|
|
(http://mjpeg.sourceforge.net) can also be used to record from the camera.
|
|
|
|
5. Notes to developers:
|
|
|
|
- This is a driver version stripped of the 2.4 back compatibility
|
|
and old MJPEG ioctl API. See cpia2.sf.net for 2.4 support.
|
|
|
|
6. Thanks:
|
|
|
|
- Peter Pregler <Peter_Pregler@email.com>,
|
|
Scott J. Bertin <scottbertin@yahoo.com>, and
|
|
Jarl Totland <Jarl.Totland@bdc.no> for the original cpia driver, which
|
|
this one was modelled from.
|