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+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
+~~~~~~~~~~~~~~
+
+============== ========================================================
+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.