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diff --git a/Documentation/admin-guide/media/cpia2.rst b/Documentation/admin-guide/media/cpia2.rst new file mode 100644 index 000000000000..f6ffef686462 --- /dev/null +++ b/Documentation/admin-guide/media/cpia2.rst @@ -0,0 +1,145 @@ +.. SPDX-License-Identifier: GPL-2.0 + +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:: + + 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. + +========== ========== ======== ===== +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. |