readme.stv680

这是stv0680的usb摄像头在linux下的驱动程序

February 1, 2002. Version 0.25 of the STV0680 webcam driver.

* Ver 0.25. Fixed a bug in checking the allowed sizes versus supported 
  modes. Driver was trying to set to size not supported in that mode.  
  The fix allows QVGA cameras to work with gnomemeeting, which wants QCIF.  
  Also fixed typo in proc_stv680_destroy, thanks to Reinhard Max. Update
  for MOD_COUNT for 2.4 series from Oliver Neukum.

* Ver 0.24. Several small bug fixes: webcam no longer crashes after two 
  frames, a swapRGB override switch has been added, the green line around 
  the frame is no longer there, and the brightness does not revert to 
  default when changing sizes.

* The driver is now in the kernel code (2.4.17 and above). This brings 
  the tarball version into sync with that, except for two items which 
  are only in kernels 2.4.12 (?) and above. These are the module_license 
  and the FILL_BULK.. macro, which is now fill_bulk.. inline. Also there 
  is a fix for the problem with webcam crashing after two pictures. The 
  shapen filter was taken out, for various reasons.

* I have included the gamma correction-white balance filter from pencam 
  (it is set for incandescent light) and the sharpen filter, set to a 
  default value of 66%. This may make the images a little grainy, but 
  they are much sharper. The sharpen_percent value is defined at the 
  beginning of stv680.c and can be reduced if you feel that it is making 
  the images look grainy. The filter type can also be changed, but you have 
  to set it in the values.c program, compile and run it to generate the 
  values, and paste them into stv680.h. The top of the values.c files 
  tells you how.
  
* I have made some changes in the way the camera is initialized that 
  should make the driver more stable. If you have debug set to 2, you 
  should see fewer "STV: Lost data in camera transfer" messages, and 
  fewer usb bulk transfer timeouts.

  * The driver should automatically detect whether swapRGB needs to 
    be set. You shoyld not have to use that option when you load the 
    driver.
    
  * I have implimented a simple brightness function, that should work 
    with the brightness control of the application. I have done nothing 
    with hue, contrast, or color. These must be handled in software and 
    I want to get the driver more stable before working on these functions. 
    Several people have sent me code for dealing with color balance but 
    I had some trouble implimenting the code, so I have skipped that for 
    the time being.
    
  * You should be able to change the picture size to half and back again. 
    I believe the CIF should work (if your camera supports it), but have 
    not tested this setting yet.        

***********************************************************
 Special thanks to Steve Miller and STMicrolectronics, for 
  providing me with information about the usb commands, and 
  especially to Steve for his encouragement while I was 
  struggling to write the driver.
***********************************************************

Some notes on the compiling, installing, using the stv680 driver:

* You need to be root to compile, load and unload the module.

* Make: just do "make". You should have a recent 2.4 kernel; I've been 
  using Mandrake 2.4.8-26mdk. I was also able to compile and run the 
  driver on a stock Mandrake 8.0, kernel 2.4.3, but I had to fix a few 
  things. The only one that might be of concern to you is the 
  "#define KERNEL_VER 243" near the top of stv680.c. I have commented 
  it out; if you get a compile error about too many parameters in 
  video_register_device, uncomment the #define KERNEL_VER 243 line. 
  I would recommend you upgrade to a more recent kernel; the usb 
  system has changed a lot from 2.4.3 to 2.4.7 or .8, and is more stable 
  now.
    
  I got a lot of errors when I tried to compile for a 2.2.17 kernel, and 
  I don't think I will try to backport the driver to a 2.2 kernel. The 
  video system also changed a lot between 2.2 and 2.4.

* Early on, I had some problems with the usb-uhci controller. The 
  problems were mainly kernel opps or usb bulk message timeouts. I 
  did not have these problems with an ohci controller, but I also 
  changed the software quite a bit, and I have not had these problems 
  for some time. If you encounter them, check whether you have an ohci 
  or uhci controller (look at the output of lsmod), and DON'T try to 
  load the driver again. In extreme cases it can cause system corruption. 
  Email me with the details.
  
* Install: "make install" should work. I normally load the module from 
  the current directory. You will need to "modprobe usbvideo" first. 
  Then "insmod ./stv680.o". I have been running a script when I test 
  the driver with apps, such as "stvtest"; this loads the driver, runs 
  xawtv with debug enables (xawtc -noxv debug 2 2>| stv.log), and then 
  rmmods the driver.

***************************  NOTE  ********************************
  
* xawtv seems to see the video output as BGR instead of RGB. Gqcam, on 
  the other hand, does see the output as RGB. When the output and the 
  application do not agree on the format, the image will be dim and 
  have a blue tint. I have made a parameter, swapRGB, to handle this. 
  It normally defaults to 0 (OFF), so gqcam is happy. If you are running 
  xawtv or some other app in which the image appears dim and bluish, try 
  loading the driver with swapRGB=1 ("insmod ./stv680.o swapRGB=1"). 
  
  Also, xawtv apparently uses a transfer method called mmap which gives 
  a higher frame rate (hence smoother motion) than gqcam, which uses the 
  standard read(). Try setting the frame rate to max for gqcam with the 
  -F option (see gqcam -h). Of course, video frame rates also depend upon 
  your CPU speed. Video is pretty smooth with an 800MHz Duron, less so 
  with a 400MHz K6-3. I also have to use the option "-noxv" with xawtv on 
  my system.

*******************************************************************  

* There is an interface to the /proc/video device. When the driver is 
  loaded and an application requests video data, you should find that 
  /proc/video/stv/videox exits, where x is 0, 1, .. (usually 0). If 
  you type "more /proc/video/stv680/videox" you will get information on 
  whether the driver is streaming, how many frames have been transferred 
  or lost, etc. 

* About the image sizes: my camera (Nisius Quickpix2) supports both VGA 
  (640x480), and QVGA (320x240). According to the documentation I have 
  seen, the STV0680 and the VV6500 sensor can support CIF (352x288). My 
  camera apparently does not support CIF, as attempts to set the mode to 
  CIF failed and the camera software reports it as not supported. 
  Nevertheless, I think I have seen some cameras baed on the STV0680 
  that do support CIF. I have therefore set the driver to try this mode 
  first. If that fails, it falls back to QVGA. I have not tried VGA; for 
  one thing, the frame rate would be about 3 frames/sec, and I would have 
  to change the memory allocation of a number of buffers, using the slower 
  vmalloc instead of kmalloc. I have been unable to test the CIF mode, but 
  I believe it should work. The dmesg output will tell you the modes 
  supported and the mode finally settled on. The original mode the camera 
  was in should be restored when the driver exits. Using the application 
  to resize the image should work; if your video mode is QVGA, sizes 
  320x240 and 160x120 should be available if the application 
  suppports it (for CIF, the sizes are 352x288 and 176x144). 
  
****************************  NOTE  **********************************

  All images stored in the camera are overwritten when video streaming 
  starts. That is a function of the hardware and there is nothing I can 
  do about it, except to automatically save the images to disk (but 
  where? using what name? and writing to disk from kernel space is not 
  easy). If you want to save pictures already in the camera, do it 
  using the pencam program before you load the driver and start a 
  video application.
  
**********************************************************************

* There are some pretty rough spots yet. I would plug the camera in first, 
  then load the driver. Unload the driver before unplugging the camera. 
  Information and error messages can be read with the dmesg command, or 
  in /var/log/messages or /var/log/syslog. I am have implimented a debug=x 
  option. 0 is the default; a few message are printed (in dmesg or the logs). 
  "debug=1" give more messages, and "debug=2" gives even more. Any condition 
  which causes the driver to quit (such as being unable to allocate memory 
  for a buffer) should print an error message regardless of the debug value.
  
  Sometimes an application seems to hang; wait a few minutes and it usually 
  starts. If it doesn't, kill it and unload and then reload the driver.  
  DO NOT unplug the camera while it is streaming video (look at the LCD 
  display on the back; the segments counter-rotate when streaming video). 
  Unplugging the camera while it is streaming video will probably hang 
  your system, and during the subsequent reboot and system check you risk 
  data loss and/or file system corruption. As usual, there are no guarantees 
  or warranties, implied or otherwise, when using this driver. If you download, 
  compile and run it, the risk is yours.