194 lines
8 KiB
ReStructuredText
Executable file
194 lines
8 KiB
ReStructuredText
Executable file
The cpia2 driver
|
|
================
|
|
|
|
Authors: 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.
|
|
|
|
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.
|
|
|
|
Making and installing the stv672 driver modules
|
|
-----------------------------------------------
|
|
|
|
Requirements
|
|
~~~~~~~~~~~~
|
|
|
|
Video4Linux must be either compiled into the kernel or
|
|
available as a module. Video4Linux2 is automatically detected and made
|
|
available at compile time.
|
|
|
|
Setup
|
|
~~~~~
|
|
|
|
Use 'modprobe cpia2' to load and 'modprobe -r cpia2' to unload. This
|
|
may be done automatically by your distribution.
|
|
|
|
Driver options
|
|
~~~~~~~~~~~~~~
|
|
|
|
.. tabularcolumns:: |p{13ex}|L|
|
|
|
|
|
|
============== ========================================================
|
|
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:
|
|
|
|
.. code-block:: none
|
|
|
|
options cpia2 num_buffers=3 buffer_size=65535
|
|
|
|
If the driver is compiled into the kernel, at boot time specify them
|
|
like this:
|
|
|
|
.. code-block:: none
|
|
|
|
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.
|
|
|
|
========== ========== ======== =====
|
|
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
|
|
========== ========== ======== =====
|
|
|
|
Table: Image size(bytes)
|
|
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
Programmer's overview of cpia2 driver
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a
|
|
division of ST Microelectronics). There are two versions. The first is the
|
|
STV0672, which is capable of up to 30 frames per second (fps) in frame sizes
|
|
up to CIF, and 15 fps for VGA frames. The STV0676 is an improved version,
|
|
which can handle up to 30 fps VGA. Both coprocessors can be attached to two
|
|
CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor. These will
|
|
be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors.
|
|
|
|
The two chipsets operate almost identically. The core is an 8051 processor,
|
|
running two different versions of firmware. The 672 runs the VP4 video
|
|
processor code, the 676 runs VP5. There are a few differences in register
|
|
mappings for the two chips. In these cases, the symbols defined in the
|
|
header files are marked with VP4 or VP5 as part of the symbol name.
|
|
|
|
The cameras appear externally as three sets of registers. Setting register
|
|
values is the only way to control the camera. Some settings are
|
|
interdependant, such as the sequence required to power up the camera. I will
|
|
try to make note of all of these cases.
|
|
|
|
The register sets are called blocks. Block 0 is the system block. This
|
|
section is always powered on when the camera is plugged in. It contains
|
|
registers that control housekeeping functions such as powering up the video
|
|
processor. The video processor is the VP block. These registers control
|
|
how the video from the sensor is processed. Examples are timing registers,
|
|
user mode (vga, qvga), scaling, cropping, framerates, and so on. The last
|
|
block is the video compressor (VC). The video stream sent from the camera is
|
|
compressed as Motion JPEG (JPEGA). The VC controls all of the compression
|
|
parameters. Looking at the file cpia2_registers.h, you can get a full view
|
|
of these registers and the possible values for most of them.
|
|
|
|
One or more registers can be set or read by sending a usb control message to
|
|
the camera. There are three modes for this. Block mode requests a number
|
|
of contiguous registers. Random mode reads or writes random registers with
|
|
a tuple structure containing address/value pairs. The repeat mode is only
|
|
used by VP4 to load a firmware patch. It contains a starting address and
|
|
a sequence of bytes to be written into a gpio port.
|