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All Documentation files outside the uAPI are all licensed with, at least, GPL 2.0. So, mark them as such. The ondes at media/uapi are at least GFDL 1.1+. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
196 lines
8.0 KiB
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196 lines
8.0 KiB
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.. SPDX-License-Identifier: GPL-2.0
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The cpia2 driver
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================
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Authors: Peter Pregler <Peter_Pregler@email.com>,
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Scott J. Bertin <scottbertin@yahoo.com>, and
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Jarl Totland <Jarl.Totland@bdc.no> for the original cpia driver, which
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this one was modelled from.
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Introduction
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------------
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This is a driver for STMicroelectronics's CPiA2 (second generation
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Colour Processor Interface ASIC) based cameras. This camera outputs an MJPEG
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stream at up to vga size. It implements the Video4Linux interface as much as
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possible. Since the V4L interface does not support compressed formats, only
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an mjpeg enabled application can be used with the camera. We have modified the
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gqcam application to view this stream.
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The driver is implemented as two kernel modules. The cpia2 module
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contains the camera functions and the V4L interface. The cpia2_usb module
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contains usb specific functions. The main reason for this was the size of the
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module was getting out of hand, so I separated them. It is not likely that
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there will be a parallel port version.
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Features
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--------
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- Supports cameras with the Vision stv6410 (CIF) and stv6500 (VGA) cmos
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sensors. I only have the vga sensor, so can't test the other.
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- Image formats: VGA, QVGA, CIF, QCIF, and a number of sizes in between.
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VGA and QVGA are the native image sizes for the VGA camera. CIF is done
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in the coprocessor by scaling QVGA. All other sizes are done by clipping.
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- Palette: YCrCb, compressed with MJPEG.
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- Some compression parameters are settable.
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- Sensor framerate is adjustable (up to 30 fps CIF, 15 fps VGA).
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- Adjust brightness, color, contrast while streaming.
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- Flicker control settable for 50 or 60 Hz mains frequency.
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Making and installing the stv672 driver modules
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-----------------------------------------------
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Requirements
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~~~~~~~~~~~~
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Video4Linux must be either compiled into the kernel or
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available as a module. Video4Linux2 is automatically detected and made
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available at compile time.
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Setup
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~~~~~
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Use 'modprobe cpia2' to load and 'modprobe -r cpia2' to unload. This
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may be done automatically by your distribution.
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Driver options
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~~~~~~~~~~~~~~
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.. tabularcolumns:: |p{13ex}|L|
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============== ========================================================
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Option Description
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============== ========================================================
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video_nr video device to register (0=/dev/video0, etc)
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range -1 to 64. default is -1 (first available)
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If you have more than 1 camera, this MUST be -1.
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buffer_size Size for each frame buffer in bytes (default 68k)
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num_buffers Number of frame buffers (1-32, default 3)
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alternate USB Alternate (2-7, default 7)
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flicker_freq Frequency for flicker reduction(50 or 60, default 60)
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flicker_mode 0 to disable, or 1 to enable flicker reduction.
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(default 0). This is only effective if the camera
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uses a stv0672 coprocessor.
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============== ========================================================
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Setting the options
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~~~~~~~~~~~~~~~~~~~
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If you are using modules, edit /etc/modules.conf and add an options
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line like this:
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.. code-block:: none
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options cpia2 num_buffers=3 buffer_size=65535
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If the driver is compiled into the kernel, at boot time specify them
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like this:
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.. code-block:: none
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cpia2.num_buffers=3 cpia2.buffer_size=65535
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What buffer size should I use?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The maximum image size depends on the alternate you choose, and the
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frame rate achieved by the camera. If the compression engine is able to
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keep up with the frame rate, the maximum image size is given by the table
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below.
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The compression engine starts out at maximum compression, and will
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increase image quality until it is close to the size in the table. As long
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as the compression engine can keep up with the frame rate, after a short time
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the images will all be about the size in the table, regardless of resolution.
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At low alternate settings, the compression engine may not be able to
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compress the image enough and will reduce the frame rate by producing larger
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images.
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The default of 68k should be good for most users. This will handle
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any alternate at frame rates down to 15fps. For lower frame rates, it may
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be necessary to increase the buffer size to avoid having frames dropped due
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to insufficient space.
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========== ========== ======== =====
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Alternate bytes/ms 15fps 30fps
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========== ========== ======== =====
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2 128 8533 4267
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3 384 25600 12800
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4 640 42667 21333
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5 768 51200 25600
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6 896 59733 29867
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7 1023 68200 34100
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========== ========== ======== =====
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Table: Image size(bytes)
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How many buffers should I use?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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For normal streaming, 3 should give the best results. With only 2,
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it is possible for the camera to finish sending one image just after a
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program has started reading the other. If this happens, the driver must drop
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a frame. The exception to this is if you have a heavily loaded machine. In
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this case use 2 buffers. You are probably not reading at the full frame rate.
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If the camera can send multiple images before a read finishes, it could
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overwrite the third buffer before the read finishes, leading to a corrupt
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image. Single and double buffering have extra checks to avoid overwriting.
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Using the camera
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~~~~~~~~~~~~~~~~
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We are providing a modified gqcam application to view the output. In
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order to avoid confusion, here it is called mview. There is also the qx5view
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program which can also control the lights on the qx5 microscope. MJPEG Tools
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(http://mjpeg.sourceforge.net) can also be used to record from the camera.
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Notes to developers
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~~~~~~~~~~~~~~~~~~~
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- This is a driver version stripped of the 2.4 back compatibility
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and old MJPEG ioctl API. See cpia2.sf.net for 2.4 support.
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Programmer's overview of cpia2 driver
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a
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division of ST Microelectronics). There are two versions. The first is the
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STV0672, which is capable of up to 30 frames per second (fps) in frame sizes
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up to CIF, and 15 fps for VGA frames. The STV0676 is an improved version,
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which can handle up to 30 fps VGA. Both coprocessors can be attached to two
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CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor. These will
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be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors.
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The two chipsets operate almost identically. The core is an 8051 processor,
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running two different versions of firmware. The 672 runs the VP4 video
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processor code, the 676 runs VP5. There are a few differences in register
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mappings for the two chips. In these cases, the symbols defined in the
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header files are marked with VP4 or VP5 as part of the symbol name.
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The cameras appear externally as three sets of registers. Setting register
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values is the only way to control the camera. Some settings are
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interdependant, such as the sequence required to power up the camera. I will
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try to make note of all of these cases.
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The register sets are called blocks. Block 0 is the system block. This
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section is always powered on when the camera is plugged in. It contains
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registers that control housekeeping functions such as powering up the video
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processor. The video processor is the VP block. These registers control
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how the video from the sensor is processed. Examples are timing registers,
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user mode (vga, qvga), scaling, cropping, framerates, and so on. The last
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block is the video compressor (VC). The video stream sent from the camera is
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compressed as Motion JPEG (JPEGA). The VC controls all of the compression
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parameters. Looking at the file cpia2_registers.h, you can get a full view
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of these registers and the possible values for most of them.
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One or more registers can be set or read by sending a usb control message to
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the camera. There are three modes for this. Block mode requests a number
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of contiguous registers. Random mode reads or writes random registers with
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a tuple structure containing address/value pairs. The repeat mode is only
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used by VP4 to load a firmware patch. It contains a starting address and
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a sequence of bytes to be written into a gpio port.
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