diff options
Diffstat (limited to 'Documentation/video4linux/README.cpia2')
| -rw-r--r-- | Documentation/video4linux/README.cpia2 | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/Documentation/video4linux/README.cpia2 b/Documentation/video4linux/README.cpia2 new file mode 100644 index 000000000000..f3bd3439ad91 --- /dev/null +++ b/Documentation/video4linux/README.cpia2 @@ -0,0 +1,130 @@ +$Id: README,v 1.7 2005/08/29 23:39:57 sbertin Exp $ + +1. 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 separted 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. + +2. Making and installing the stv672 driver modules: + + Requirements: + ------------- + This should work with 2.4 (2.4.23 and later) and 2.6 kernels, but has +only been tested on 2.6. Video4Linux must be either compiled into the kernel or +available as a module. Video4Linux2 is automatically detected and made +available at compile time. + + Compiling: + ---------- + As root, do a make install. This will compile and install the modules +into the media/video directory in the module tree. For 2.4 kernels, use +Makefile_2.4 (aka do make -f Makefile_2.4 install). + + Setup: + ------ + Use 'modprobe cpia2' to load and 'modprobe -r cpia2' to unload. This +may be done automatically by your distribution. + +3. 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: + 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,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. + + Image size(bytes) + 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 + + 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. + +4. 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. + +5. 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. + +6. Thanks: + + - 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. |