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-$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 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.
-
-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 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.
-
- 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.