1The cpia2 driver 2================ 3 4Authors: Peter Pregler <Peter_Pregler@email.com>, 5Scott J. Bertin <scottbertin@yahoo.com>, and 6Jarl Totland <Jarl.Totland@bdc.no> for the original cpia driver, which 7this one was modelled from. 8 9Introduction 10------------ 11 12This is a driver for STMicroelectronics's CPiA2 (second generation 13Colour Processor Interface ASIC) based cameras. This camera outputs an MJPEG 14stream at up to vga size. It implements the Video4Linux interface as much as 15possible. Since the V4L interface does not support compressed formats, only 16an mjpeg enabled application can be used with the camera. We have modified the 17gqcam application to view this stream. 18 19The driver is implemented as two kernel modules. The cpia2 module 20contains the camera functions and the V4L interface. The cpia2_usb module 21contains usb specific functions. The main reason for this was the size of the 22module was getting out of hand, so I separated them. It is not likely that 23there will be a parallel port version. 24 25Features 26-------- 27 28- Supports cameras with the Vision stv6410 (CIF) and stv6500 (VGA) cmos 29 sensors. I only have the vga sensor, so can't test the other. 30- Image formats: VGA, QVGA, CIF, QCIF, and a number of sizes in between. 31 VGA and QVGA are the native image sizes for the VGA camera. CIF is done 32 in the coprocessor by scaling QVGA. All other sizes are done by clipping. 33- Palette: YCrCb, compressed with MJPEG. 34- Some compression parameters are settable. 35- Sensor framerate is adjustable (up to 30 fps CIF, 15 fps VGA). 36- Adjust brightness, color, contrast while streaming. 37- Flicker control settable for 50 or 60 Hz mains frequency. 38 39Making and installing the stv672 driver modules 40----------------------------------------------- 41 42Requirements 43~~~~~~~~~~~~ 44 45Video4Linux must be either compiled into the kernel or 46available as a module. Video4Linux2 is automatically detected and made 47available at compile time. 48 49Setup 50~~~~~ 51 52Use 'modprobe cpia2' to load and 'modprobe -r cpia2' to unload. This 53may be done automatically by your distribution. 54 55Driver options 56~~~~~~~~~~~~~~ 57 58.. tabularcolumns:: |p{13ex}|L| 59 60 61============== ======================================================== 62Option Description 63============== ======================================================== 64video_nr video device to register (0=/dev/video0, etc) 65 range -1 to 64. default is -1 (first available) 66 If you have more than 1 camera, this MUST be -1. 67buffer_size Size for each frame buffer in bytes (default 68k) 68num_buffers Number of frame buffers (1-32, default 3) 69alternate USB Alternate (2-7, default 7) 70flicker_freq Frequency for flicker reduction(50 or 60, default 60) 71flicker_mode 0 to disable, or 1 to enable flicker reduction. 72 (default 0). This is only effective if the camera 73 uses a stv0672 coprocessor. 74============== ======================================================== 75 76Setting the options 77~~~~~~~~~~~~~~~~~~~ 78 79If you are using modules, edit /etc/modules.conf and add an options 80line like this: 81 82.. code-block:: none 83 84 options cpia2 num_buffers=3 buffer_size=65535 85 86If the driver is compiled into the kernel, at boot time specify them 87like this: 88 89.. code-block:: none 90 91 cpia2.num_buffers=3 cpia2.buffer_size=65535 92 93What buffer size should I use? 94~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 95 96The maximum image size depends on the alternate you choose, and the 97frame rate achieved by the camera. If the compression engine is able to 98keep up with the frame rate, the maximum image size is given by the table 99below. 100 101The compression engine starts out at maximum compression, and will 102increase image quality until it is close to the size in the table. As long 103as the compression engine can keep up with the frame rate, after a short time 104the images will all be about the size in the table, regardless of resolution. 105 106At low alternate settings, the compression engine may not be able to 107compress the image enough and will reduce the frame rate by producing larger 108images. 109 110The default of 68k should be good for most users. This will handle 111any alternate at frame rates down to 15fps. For lower frame rates, it may 112be necessary to increase the buffer size to avoid having frames dropped due 113to insufficient space. 114 115========== ========== ======== ===== 116Alternate bytes/ms 15fps 30fps 117========== ========== ======== ===== 118 2 128 8533 4267 119 3 384 25600 12800 120 4 640 42667 21333 121 5 768 51200 25600 122 6 896 59733 29867 123 7 1023 68200 34100 124========== ========== ======== ===== 125 126Table: Image size(bytes) 127 128 129How many buffers should I use? 130~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 131 132For normal streaming, 3 should give the best results. With only 2, 133it is possible for the camera to finish sending one image just after a 134program has started reading the other. If this happens, the driver must drop 135a frame. The exception to this is if you have a heavily loaded machine. In 136this case use 2 buffers. You are probably not reading at the full frame rate. 137If the camera can send multiple images before a read finishes, it could 138overwrite the third buffer before the read finishes, leading to a corrupt 139image. Single and double buffering have extra checks to avoid overwriting. 140 141Using the camera 142~~~~~~~~~~~~~~~~ 143 144We are providing a modified gqcam application to view the output. In 145order to avoid confusion, here it is called mview. There is also the qx5view 146program which can also control the lights on the qx5 microscope. MJPEG Tools 147(http://mjpeg.sourceforge.net) can also be used to record from the camera. 148 149Notes to developers 150~~~~~~~~~~~~~~~~~~~ 151 152 - This is a driver version stripped of the 2.4 back compatibility 153 and old MJPEG ioctl API. See cpia2.sf.net for 2.4 support. 154 155Programmer's overview of cpia2 driver 156~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 157 158Cpia2 is the second generation video coprocessor from VLSI Vision Ltd (now a 159division of ST Microelectronics). There are two versions. The first is the 160STV0672, which is capable of up to 30 frames per second (fps) in frame sizes 161up to CIF, and 15 fps for VGA frames. The STV0676 is an improved version, 162which can handle up to 30 fps VGA. Both coprocessors can be attached to two 163CMOS sensors - the vvl6410 CIF sensor and the vvl6500 VGA sensor. These will 164be referred to as the 410 and the 500 sensors, or the CIF and VGA sensors. 165 166The two chipsets operate almost identically. The core is an 8051 processor, 167running two different versions of firmware. The 672 runs the VP4 video 168processor code, the 676 runs VP5. There are a few differences in register 169mappings for the two chips. In these cases, the symbols defined in the 170header files are marked with VP4 or VP5 as part of the symbol name. 171 172The cameras appear externally as three sets of registers. Setting register 173values is the only way to control the camera. Some settings are 174interdependant, such as the sequence required to power up the camera. I will 175try to make note of all of these cases. 176 177The register sets are called blocks. Block 0 is the system block. This 178section is always powered on when the camera is plugged in. It contains 179registers that control housekeeping functions such as powering up the video 180processor. The video processor is the VP block. These registers control 181how the video from the sensor is processed. Examples are timing registers, 182user mode (vga, qvga), scaling, cropping, framerates, and so on. The last 183block is the video compressor (VC). The video stream sent from the camera is 184compressed as Motion JPEG (JPEGA). The VC controls all of the compression 185parameters. Looking at the file cpia2_registers.h, you can get a full view 186of these registers and the possible values for most of them. 187 188One or more registers can be set or read by sending a usb control message to 189the camera. There are three modes for this. Block mode requests a number 190of contiguous registers. Random mode reads or writes random registers with 191a tuple structure containing address/value pairs. The repeat mode is only 192used by VP4 to load a firmware patch. It contains a starting address and 193a sequence of bytes to be written into a gpio port. 194