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diff --git a/Documentation/media/v4l-drivers/cpia2.rst b/Documentation/media/v4l-drivers/cpia2.rst new file mode 100644 index 000000000000..763705c1f50f --- /dev/null +++ b/Documentation/media/v4l-drivers/cpia2.rst @@ -0,0 +1,190 @@ +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. |