Libdc1394 Library Support for IEEE 1394 Cameras HOWTO


Rohit Agarwal


<rohdimp_24@rediffmail.com>
            

Vikram B


<vickys_box@rediffmail.com>
            
2006-01-23

Revision History
Revision 1.2 2007-04-14 RA
Addition of DMA related section contributed by Ian Peikon <idp2@duke.edu>and
Tim Hanson <tim@hardcarve.com>
Revision 1.0 2006-01-23 TMM
Initial release, reviewed by TLDP
Revision 0.4 2005-12-18 TMM
Correction of markup
Revision 0.3 2005-11-27 TMM
Conversion to DocBook XML
Revision 0.2 2005-10-15 VB
Minor fixes.
Revision 0.1 2005-10-10 RA &amp; VB
Initial draft.

Abstract
This document discusses how to set up the libdc1394 library on Linux for
support of IEEE 1394 (FireWire) cameras.
-------------------------------------------------------------------------------
Table of Contents


  1._Introduction

  2._Requirements

  3._Installation

  4._Concepts_and_Basic_Programs


        4.1._Important_Data_Structures

        4.2._Types_of_functions

        4.3._Coriander:_A_GUI_for_the_libdc1394_library

        4.4._Example:_How_to_grab_image_from_the_IEEE1394_camera

        4.5._Example:_How_to_grab_image_from_the_IEEE1394_camera_using_DMA

        4.6._How_to_get_color_images:_Bayer_Pattern_Concepts

        4.7._Common_Problems_Faced_While_Working_With_IEEE1394_Cameras


  5._References

  A._Appendix_A


        1._License

        2._Disclaimer

        3._About_Authors

        4._Dedications



1. Introduction

We felt a HOWTO on this topic was required since very little documentation is
available for the libdc1394 library. Moreover, the IEEE1394 cameras are gaining
popularity, which will lead to many people using this library to develop
applications for cameras on Linux. This HOWTO is an outcome of our experience
working with the Point Grey Dragonfly IEEE1394 camera on Linux.
We have given the overview of the library in layman's terms, so anybody who has
some programming experience will easily understand the contents.

2. Requirements

Various libraries and modules required are:

* Library: libdc1394-1.1.0
* Supporting Library: libraw1394-1.2.0
* Supporting Modules: ieee1394, raw1394, ohci1394, video1394
* Linux Kernel: 2.6.10 or above


3. Installation

Prerequisite: Make sure that the kernel is compiled with IEEE1394 built-in
support. This is critical!
You can add support for the IEEE1394 devices by compiling the kernel again.
Don't panic! Here are the steps to compile the kernel:
Go to the directory where your kernel source code is present. Normally it is in
/usr/src. We suggest that you download a fresh copy of the kernel source code
(2.6.10) from www.kernel.org.
Thus, cd /usr/src/kernel-2.6.10 (kernel-2.6.10 is the name of the source code
directory. It can vary from system to system.)

  1. make menuconfig
  2. The menu will come up. Select Device Drivers
  3. The Device Drivers menu will come up. Select IEEE1394 (Firewire) Support
  4. Mark the following as <M> in the menu that is shown:

       a. OHCI-1394 support
       b. OHCI-1394 Video Support
       c. OHCI-1394 DVI/O Support
       d. RAW IEEE1394 I/O Support

  5. Press ESC to come out of the menu
  6. Save the configuration

Install libraw1394-1.2.0
The following steps are required to successfully install the library
(libdc1394). As a rule of thumb, the installation has to be done as the root
user.
We already had this library installed in our Linux, so we skipped this step. If
you do not have this library installed, make sure you install it before moving
further. Here are the steps for the installation:

  1. su root
  2. tar -xvzf libraw1394-1.2.0.tar.gz
  3. cd libraw1394-1.2.0
  4. ./configure
  5. make
  6. make install

Install libdc1394-1.1.0

  1. su root (if you haven't already)
  2. tar -xvzf libdc1394-1.1.0.tar.gz
  3. cd libdc1394-1.1.0
  4. ./configure
  5. cd libdc1394
  6. make
  7. make install

Install the modules

  1. modprobe ohci1394
  2. modprobe video 1394
  3. modprobe ieee1394
  4. modprobe raw1394
  5. lsmod to view that all the modules (ieee1394, raw1394, ohci1394 and
     video1394) are now installed.


Note on dependencies:

The modules have some dependencies:

* ohci1394 to video1394
* ieee1394 to video1394, ohci1394, and raw1394

So if you are installing modules with insmod, video1394 and raw1394 have to be
installed first, followed by ohci1394 and ieee1394.
Create proper 1394 devices

  1. cd /dev
  2. mknod raw1394 c 171 0
  3. chmod 666 /dev/raw1394
  4. mkdir video1394
  5. cd video1394
  6. mknod 0 c 171 16
  7. mknod 1 c 171 17
  8. chmod 666 /dev/video1394/*


Note on automating module start-up:

Every time the system is restarted, the nodes are destroyed and the modules are
removed automatically. So we wrote a script to automate this installation task
at start-up, to undo all the damage done during rebooting!
Set user paths

  1. su user
  2. Check for the LD_LIBRARY_PATH. It should contain /usr/local/lib. This is
     necessary to run the applications with the help of the shared
     libdc1394_cotrol.so.13 object file.


Note on setting path:

You can also set the path by adding /usr/local/lib in /etc/ld.so.conf.
This completes the installation phase.
In order to make sure the installation is correct, connect the camera to the
IEEE1394 card (assuming that the IEEE1394 card is already installed on the
system) and just run testlibraw:
$ testlibraw
This tests for the presence of the host card, camera and other related
parameters. Below is a typical output from testlibraw:

  Successfully got handle
  current generation number: 17
  1 card(s) found
  nodes on bus: 2, card name: ohci1394
  using first card found: 2 nodes on bus, local ID is 0, IRM is 1

  doing transactions with custom tag handler
  trying to send read request to node 0... completed with value 0x23127bac
  trying to send read request to node 1... completed with value 0x60217dac

  using standard tag handler and synchronous calls
  trying to read from node 0... completed with value 0x04477dac
  trying to read from node 1... completed with value 0xd37380ac

  testing FCP monitoring on local node
  got fcp command from node 0 of 8 bytes: 01 23 45 67 89 ab cd ef
  got fcp response from node 0 of 8 bytes: 01 23 45 67 89 ab cd ef

  polling for leftover messages

The libdc1394-1.1.0 library comes with some example programs which are very
helpful in understanding how the programs are to be written. There is a
Makefile available in the examples folder of the tar file. To compile and
execute the programs:
cd libdc1394-1.1.0/examples
make
You can get programs exclusively written for the Point Grey cameras at http://
www.ptgrey.com/support/kb/data/grabdma.tgz.
Fortunately, we have an open source graphical application developed for the
IEEE1394 cameras, known as Coriander that provides a nice Graphical User
Interface for libdc1394 to help the user work with the camera more efficiently.
Later we will discuss how Coriander helped us in debugging. Next, we briefly
explain how to install Coriander.
Installation of Coriander

  1. Make sure that you have libdc1394 and the Gnome libraries (Coriander uses
     gnome.h) installed on your Linux machine. For more details regarding the
     requirements, look into the user manual provided by Coriander: http://
     damien.douxchamps.net/ieee1394/coriander/manual.php.
  2. Download the following tar file from sourceforge.net: coriander-
     1.0.1.tar.gz, then proceed as shown below:

       a. su root
       b. tar -xvzf coriander-1.0.1.tar.gz
       c. cd coriander-1.0.1
       d. ./configure
       e. cd src
       f. make
       g. make install

  3. Run Coriander as follows:

       cd coriander-1.0.1/coriander-1.0.1/src
       ./coriander

     Fortunately, the installation of the libdc1394 and related modules is
     simple and does not pose any major problems. Some minor problems you may
     face are due to mistakes such as not installing it as root or not changing
     the permissions of the newly created IEEE1394 devices.


4. Concepts and Basic Programs

At present, the documents that are available for understanding libdc1394 are
very few. Among the available documents are a FAQ, which only talks about the
general concept of the camera and a few forums where people have posted their
queries.
We had to read the libdc1394 source code to understand how to grab a frame from
the camera. The extreme need for a complete explanation on this topic
encouraged us to write this HOWTO.
On the basis of what we understood by exploring the source code of the camera,
we are presenting our insights on the library.
We encourage you to keep referring following files while reading through the
next section:

  1. dc1394_control.h
  2. dc1394_control.c
  3. dc1394_capture.c
  4. dc1394_format7.c

The dc1394_control.h file is the most important, as it contains the declaration
of various functions and data structures. It should be read to understand the
features supported by IEEE1394 cameras and the functions which access and
control various features of camera.
The dc1394 library works closely with raw1394 since all the functions make use
of functions of raw1394 (raw1394_read() and raw1394_write()) in order to
retrieve or modify the values of various parameters of the camera. This is one
of the reasons why raw1394 must be installed before installing libdc1394.
To understand how the functions provided by the library work, we need to
understand few technical aspects of the IEEE1394 camera:

  1. There can be more than one camera connected to the host card at any time,
     hence one need to uniquely identify the camera node.
  2. The camera has some control registers to set camera features.
  3. According to IEEE specifications, the camera can grab images in different
     formats. The image formats are defined by two parameters: format and mode.
     Five modes are defined:

       a. Format_0 contains low resolution mode up to 640x480
       b. Format_1 contains medium resolution modes: 800x600 and 1024x768
       c. Format_2 contains mega pixel modes: 1280x960 and 1600x1200
       d. Format_7 is the scalable image format. With this, you can change the
          image size, color coding and other parameters

     It may be possible that a camera does not support some modes, so we need
     to be careful during the setup. You use setup to set various parameters
     like data speed, image mode, framerate that are necessary to make the
     camera ready to grab the image. We will shortly discuss setup functions.
  4. In order to set or get the values of the parameters/features of the
     camera, the library functions will modify or read the register values.
  5. The camera can work with or without DMA. We are greatful to Ian Peikon and
     Tim Hanson for contributing a section on IEEE1394 camera using DMA support

With the above background, we begin our discussion about the various functions,
data structures and other miscellaneous features available in the
dc1394_control.h file.
We would like to mention one important aspect of the dc1394_control.h file,
which is that it lists out the values that can be set for the data speeds,
frame rates, camera modes and image formats. All the values are in the form of
enumerations to help you write readable code. For example, enumeration for
speed indicates that the data speed can be set only as 100, 200, 400, 800, 1600
or 3200.
The dc1394_control.h also lists the features (brightness, hue, sharpness,
saturation, etc.) supported for your camera.

4.1. Important Data Structures

The library provides some structures which are useful in storing camera and
image related information. They have been declared in the dc1394_control.h
file.
 _____________________________________________________________________________
|Structure___________|Use_____________________________________________________|
|                    |Helps in accessing the information about the camera     |
|dc1394_camerainfo   |model, vendor, ccr_offset (used to access the           |
|____________________|registers)._____________________________________________|
|                    |Contains various parameters that are to be manipulated  |
|dc1394_cameracapture|while the camera setup. It also declares a buffer of int|
|____________________|type_that_will_be_used_to_store_the_grabbed_frame.______|
|dc1394_misc_info    |Contains the information about the ISO channel id, iso- |
|____________________|channel_speed,_memory_channel_number.___________________|
|                    |Contains the information about a particular feature     |
|dc1394_feature_info |(brightness, hue, gamma, white balance, etc.,) for      |
|____________________|example_the_availability_and_values_for_it._____________|

We will be largely concerned with the dc1394_cameracapture structure.

4.2. Types of functions

We have categorized the functions provided by the library into 6 types. (The
categorization is purely done on our own for the ease of discussion). Each of
these functions has been declared in dc1394_control.h. We suggest you to keep a
copy of the file on hand while going through the subsequent section.

  1. Get/Query Functions
  2. Set Functions
  3. Print Functions
  4. Setup Functions
  5. Format7 Functions
  6. Release Functions


4.2.1. Get/Query Functions

These functions are used to get the value of various features of the camera,
the information about the ISO channel, trigger mode, frame rate, format and
mode. The functions contain get or query in their names.
For example,

  int dc1394_get_gamma (raw1394handle_t handle, node_t node, unsigned
  int *gamma)

gets the value of the gamma attribute for the camera.
Most of the get functions take a minimum of three parameters:

  1. Both the raw1394handle_t and node_t nodes: these two together identify the
     camera
  2. A pointer to obtain the value, for example, int * gamma

If we try to trace the flow of the function call, we can understand what
actually happens:
Figure 1. Flow of get function call
 Get Function Call

In case the get function you called is meant to retrieve the value of a camera
feature (the value for the parameters listed in feature enumeration), that get
function will call another get function (GetFeatureValue), which takes the
enumeration value of the feature as input. For example, in the case of gamma
value, the function passes 422 as the value (this value can be calculated from
the enumeration given in the dc1394_control.h file).
Ultimately, the GetCameraControlRegister function, whose task is to get the
value from the appropriate control registers, is called. This functions takes
the offset value (octlet_t offset), which is the offset from the base register
as the input to its call. The function prototype is declared in
dc1394_internal.h.

  GetCameraControlRegister (raw1394handle_t handle, nodeid_t node,
                           octlet_t offset, quadlet_t *value)

The above will store the final result in the value.

Note on data types:

The library makes use of typedefed data types octlet_t and quadlet_t very
frequently . These are defined in dc1394_internal.h and stand for 8-byte and 4-
byte data types.
The GetCameraControlRegister function will in turn call dc1394_get_camera_info
() to get the address of the base register:

  camera->ccr_base = CONFIG_ROM_BASE + info->ccr_offset;

Once the base register and the offset is known, raw1394_read() is called by
GetCameraControlRegister to read the actual values.
Now the get function (dc1394_get_gamma) uses the value returned by the
GetCameraControlRegister to modify the parameter gamma.

  int dc1394_get_gamma (raw1394handle_t handle, node_t node , unsigned int
  *gamma )

In this way, the user obtains the value of the camera parameter he queried for.

4.2.2. Set Functions

These functions are used to set the values of various camera features. There is
a corresponding set function for almost each get function. You can recognize
these functions by searching for set string.
For example,

  dc1394_set_gamma (raw1394handle_t handle, nodeid_t node, int
  gamma)

Like the get function, this function needs raw1394handle_t and nodeid_t for
camera identification.
The other parameter, gamma, is the user-specified value for the gamma
parameter.
The flow of the function call is quite helpful in understanding what is
actually happening. The flow is exactly same as that of the get function. The
only difference is this time all the intermediate functions are also set
functions, and instead of raw1394_read(), it uses raw1394_write() to write the
value of the camera parameter on to the registers.
Figure 2. Flow of set function call
 Flow of set function call


4.2.3. Print Functions

There are three print functions available:

  1. dc1394_print_camera_info: This function is used to print the values stored
     in the dc1394camera_info structure. The print function is usually called
     after dc1394_get_camera_info() to ensure that the dc1394camera_info
     structure is not NULL.
  2. dc1394_print_feature: This function is used to print the value of any
     feature. It takes as an input the pointer to dc1394_feature_info
     structure.
  3. dc1394_print_feature_set: This function is used to print the values of all
     features present in the camera. It takes as an input the pointer to
     dc1394_feature_set structure. The function call basically calls
     dc1394_print_feature repeatedly in a for loop.


4.2.4. Setup Functions

As the name suggests, these functions are used to prepare the camera to start
grabbing the images. In order to setup the camera, some parameters must be
passed to the function. The number and the type of parameters are specific to
the setup function, but essentially three parameters must be passed in all the
setup functions: raw1394handle_t, nodeid_t and the pointer to the
dc1394_cameracapture structure (this is to provide the buffer for grabbed
images and keep attributes, like height and width of frame).
As mentioned previously, raw1394handle_t and nodeid_t uniquely define the
camera, while the pointer to dc1394_cameracapture provides the buffer for the
image frame to be grabbed. It also stores information about the width and
height of the frame which is useful at the time of image processing.
Other parameters that are passed are data speed, frame rate, image format,
image mode and ISO channel number.
In case the camera uses DMA, the number of DMA buffers and drop frames is to be
provided. In most applications you will want to set the number of DMA buffers
relatively low(i.e. 1) this ensures that you are viewing frames in near real
time. Drop frames is also important for real time as it causes the capture
function to throw away the frames buffered in the DMA ring buffer except fot
the last. We will discuss about DMA functions in the later part of this HowTo
The various setup functions are:

  1. dc1394_dma_setup_capture
  2. dc1394_setup_capture
  3. dc1394_setup_format7_capture
  4. dc1394_dma_setup_format7_capture

These setup functions have been defined in dc1394_capture.c.
You have a choice while passing the values for the parameters, like data-speed,
format, mode, and channel. Instead of providing the value yourself, you may
instruct the function to take the value from the camera. This can be done by
passing QUERY_FROM_CAMERA in place of the actual value for that function
parameter.
The basic flow of control is easy to understand:
Figure 3. Flow of the setup function call
 Flow of the setup function call

As shown in Figure 3, the Setup function in turn calls various set functions to
set the parameter values to the camera registers. In the case of DMA setup,
after the set functions have been called the ioctl system call is called to
allocate memory for the DMA buffers and returns a pointer capture_buffer in
user space.
The ioctl system calls will fail if the DMA is not setup correctly
The setup functions also allocate memory for the camera _capture buffer:

  camera->capture_buffer=(int*)malloc(camera->quadlets_per_frame*4);


4.2.5. Format7 Functions

These functions are used only if the camera is set for Format7. This format is
preferred since this allows the user to define the size of the image to be
captured according to his need. By default the size is 1024x768; you can set it
to different dimensions, say 960x720.
All Format7 functions have format7 in their function names, and the functions
have been defined in a separate file, dc1394_format7.c.
The setup function for Format7 has a minor difference from the normal setup
since it also asks for the size of the frame, while you don't have to pass the
format parameter as the setup function, as it is meant only for a particular
format, for example Format7. The function call flow remains the same as
discussed in the previous section.
The Format7 get functions are called query functions. The mechanism is
different from the normal get/query functions: they don't call
GetCameraControlRegister; instead, they call GetCameraFormat7Register().
The following flowchart will make the differences evident:
Figure 4. Flow of the Format7 query function call
 Flow of the Format7 query function call

The Format7 query function will call GetCameraFormat7Register, which is
supposed to read the values from the control and status registers of the
camera. This function in turn will call the QueryFormat and CSROffset to know
the offset for the particular information that has been queried. After getting
the offset, raw1394_read is used to actually read the values.
The Format7 set functions also follow the same logic with the obvious
difference that the reading functions are replaced by writing functions, for
example, SetCameraFormat7Register and raw1394_write().

4.2.6. Release Functions

These are the final set of functions identified by us. The basic job of these
functions is to release the memory allocated to the capture buffer by the setup
routine. This is essential to save the system from memory leaks.
These functions are defined in dc1394_capture.c:

  dc1394_release_camera()

This function in turn calls free (camera -> capture_buffer), which frees the
memory.
Similarly, the release function is available for DMA setup.

4.3. Coriander: A GUI for the libdc1394 library

Coriander helps in easy handling of the IEEE1394 cameras. It uses the above
discussed functions and libraries and provides a GUI for them. The main
advantage of Coriander is that it saves time that is normally wasted in camera
setup. Also, Coriander shows only those features and attributes that are
present on the camera and hence you can judge how useful the camera will be for
your application development. The most important feature of Coriander is its
ability to display the captured image at run-time.
Coriander also allows the user to convert a BGGR image to RGB. We will discuss
the meaning of these types of images in detail in later sections. Some files
that can be useful in understanding the functionality of Coriander are:

  1. thread_iso.c
  2. Camera.c
  3. main.c

The Coriander homepage contains an excellent user manual which can be useful in
case of any difficulty: http://damien.douxchamps.net/ieee1394/coriander/
manual.php.
Our use of Coriander was limited only to checking that the camera was working
properly and confirming the focus was correct. We will give some more usage
information for Coriander in later sections.

4.4. Example: How to grab image from the IEEE1394 camera

In this section we will demonstrate how to write a small program to grab an
image from the camera. We have taken the program (grab_gray_image.c) given in
the examples in the library tar file. We have removed some lines to increase
the readability of the code. We have provided the explanation for this code
below. In order to provide you with a clear picture of which section of the
code does what, we grouped the code lines together by task below.

    #include <stdio.h>
    #include <libraw1394/raw1394.h>
    #include <libdc1394/dc1394_control.h>
    #include <stdlib.h>
    #define IMAGE_FILE_NAME "Image.pgm"

    int main(int argc, char *argv[])
    {

      FILE* imagefile;
      dc1394_cameracapture camera;
      int numNodes;
      int numCameras;
      raw1394handle_t handle;
      nodeid_t * camera_nodes;

           /* Open ohci and asign handle to it */

           handle = dc1394_create_handle(0);
      if (handle==NULL)
      {
           fprintf( stderr, "Unable to aquire a raw1394 handle\n\n"
                      );
           exit(1);
      }

           /* get the camera nodes and describe them as we find them */

      numNodes = raw1394_get_nodecount(handle);
      camera_nodes = dc1394_get_camera_nodes(handle,&amp;numCameras,1);
      fflush(stdout);
      if (numCameras<1)
      {
        fprintf( stderr, "no cameras found :(\n");
        dc1394_destroy_handle(handle);
        exit(1);
      }
      printf("working with the first camera on the bus\n");

      if( camera_nodes[0] == numNodes-1)
      {
        fprintf( stderr, "\n"
           "Sorry, your camera is the highest numbered node\n");
        dc1394_destroy_handle(handle);
        dc1394_free_camera_nodes(camera_nodes);
        exit( 1);
      }

      /*setup capture */

      if (dc1394_setup_capture(handle,camera_nodes[0],
                               0, /* channel */

                               FORMAT_VGA_NONCOMPRESSED,
                               MODE_640x480_MONO,
                               SPEED_400,
                               FRAMERATE_7_5,
                               &amp;camera)!=DC1394_SUCCESS)
      {
        fprintf( stderr,"unable to setup camera-\n"
           "check line %d of %s to make sure\n"
           "that the video mode,framerate and format are\n"
           "supported by your camera\n",
           __LINE__,__FILE__);
        dc1394_release_camera(handle,&amp;camera);
        dc1394_destroy_handle(handle);
        dc1394_free_camera_nodes(camera_nodes);
        exit(1);
      }
      dc1394_free_camera_nodes(camera_nodes);

      /* set trigger mode */

      if( dc1394_set_trigger_mode(handle, camera.node, TRIGGER_MODE_0)
          != DC1394_SUCCESS)
      {
        fprintf( stderr, "unable to set camera trigger mode\n");
  #if 0
        dc1394_release_camera(handle,&amp;camera);
        dc1394_destroy_handle(handle);
        exit(1);
  #endif
      }

      /* have the camera start sending us data*/

      if (dc1394_start_iso_transmission(handle,camera.node)
          !=DC1394_SUCCESS)
      {
        fprintf( stderr, "unable to start camera iso transmission\n");
        dc1394_release_camera(handle,&amp;camera);
        dc1394_destroy_handle(handle);
        exit(1);
      }

      /* capture one frame */

      if (dc1394_single_capture(handle,&amp;camera)!=DC1394_SUCCESS)
      {
        fprintf( stderr, "unable to capture a frame\n");
        dc1394_release_camera(handle,&amp;camera);
        dc1394_destroy_handle(handle);
        exit(1);
      }

      /* Stop data transmission */

      if (dc1394_stop_iso_transmission(handle,camera.node)!=DC1394_SUCCESS)
      {
        printf("couldn't stop the camera?\n");
      }

      /* save image as 'Image.pgm' */

      imagefile=fopen(IMAGE_FILE_NAME, "w");

      if( imagefile == NULL)
      {
        perror( "Can't create '" IMAGE_FILE_NAME "'");
        dc1394_release_camera(handle,&amp;camera);
        dc1394_destroy_handle(handle);
        exit( 1);
      }

      /* Adding the pgm file header */

      fprintf(imagefile,"P5\n%u %u 255\n", camera.frame_width,
           camera.frame_height );

      /* Writing to the file */

      fwrite((const char *)camera.capture_buffer, 1,
           camera.frame_height*camera.frame_width, imagefile);
      fclose(imagefile);
      printf("wrote: " IMAGE_FILE_NAME "\n");

      /* Close camera */

      dc1394_release_camera(handle,&amp;camera);
      dc1394_destroy_handle(handle);
      return 0;
  }


 1   Include the header files, which means include:

     * libraw1394/raw1394.h
     * libdc1394/dc1394_control.h

     These are necessary in order to access functions of the library.
 2   Declare three variables of the following data types:

     * dc1394_cameracapture
     * raw1394handle_t
     * nodeid_t *

     The raw1394handle_t and nodeid_t * are required to uniquely identify the
     camera. Moreover, raw1394handle_t is used to hold the handle that is
     created for the OHCI-compliant host card.
 3   Open ohci and assign a handle to it.
     This is done by:
     handle=dc1394_create_handle(0)
     Where handle is of the raw1394handle_ttype> type. The parameter 0 refers
     to the position of the camera on host card (there may be more than one
     slot on the host card; 0 means that the camera is on the first slot ).
     If the wrong number is passed, the handle will not be created.
 4   Get camera nodes:
     There can be more than one camera node, since IEEE1394 supports multiple
     devices on a single port. But for our discussion we will assume that only
     a single camera is present. Here is how to get nodes:

       int numNodes = raw1394_get_nodecount(raw1394handle_t handle)
       camera_nodes=dc1394_getcamera_nodes(handle,&amp;numCameras,1)

     If the number of cameras returned is numCameras <1, this means no camera
     has been detected.
     1 in the function signifies that a printed description of the camera node
     found will be shown on the console.
 5   Check the condition of camera_nodes[0]==numNodes -1. It must be false. The
     explanation for this is outside the scope of this document.
 6   Call the setup function and pass the various parameters. For example, let
     us examine the setup function of the above example:

            dc1394_setup_capture(

       /* handle and camera_nodes[0] uniquely identifies the camera */
            handle,
           camera_nodes[0],
           0, /* channel */

       /*format of the Image */
           FORMAT_VGA_NONCOMPRESSED, MODE_640x480_MONO, /* mode of the image */
           SPEED_400, /* data speed */
           FRAMERATE_7_5, /*Frame rate */
           &amp;camera /*dc1394_cameracapture type pointer *./
           )!=DC1394_SUCCESS)

     Our suggestion is that the various parameters should be first queried from
     the camera and then passed. This is helpful in a successful setup since
     often the user does not know actual values of the various parameters that
     have to be passed in the setup function call, and ends up passing the
     wrong values. In such situations the setup is not done correctly and the
     camera doesn't get initialized.
     We are listing the appropriate get functions that should be called first
     in order to obtain the correct values of the setup parameters:

       1. dc1394_get_iso_channel_and_speed(handle,camera_nodes[0],
          &amp;channel,&amp;speed); /* to get the channel and the data speed */
       2. dc1394_get_video_format(handle,camera_nodes[0],&amp;format); /*to get
          the format */
       3. dc1394_get_video_framerate(handle,camera_nodes[0],&amp;framerate); /
          * to get the framerate*/
       4. dc1394_get_video_mode(handle,camera_nodes[0],&amp;mode); /* to get
          the mode */

     So the above dc1394_setup_capture function call will look like this:

            dc1394_setup_capture(

       /* handle and camera_nodes[0] uniquely identifies the camera */
            handle,
            camera_nodes[0],

          /*we pass the variables instead of actual values */
            channel ,
            format,
            mode,
            speed,
            framerate,
            &amp;camera /*dc1394_cameracapture type pointer *./
            )!=DC1394_SUCCESS)

 7   Setting the trigger mode. This is generally not required. This is just
     like brightness:
     dc1394_set_trigger_mode(handle,camera.node,TRIGGER_MODE_0) sets the
     trigger mode to 0.

     Note on nodes:

     We have passed camera.node which indicates that the dc1394_cameracapture
     structure is being used and only the particular node for which the camera
     has been setup is being referred to, but we can also use camera_nodes[0].
 8   Have the camera start sending the data to the user. This is done by
     starting the ISO transmission. The following function is used:
     dc1394_start_iso_transmission(handle,camera.node)
 9   Capture one frame by calling the function:
     dc1394_single_capture(handle,&amp;camera)
     Where camera is a pointer to the structure dc1394_cameracapture. This
     function will grab the image and store it in the buffer (capture_buffer)
     provided by the structure.
     In order to capture more than one frame use a for loop and place the
     function inside it:

       for( i=0;i<100 ;i++)/* to capture 100 images*/
       dc1394_single_capture(handle,&amp;camera)

 10  After the image has been grabbed, stop the data transmission by calling
     the following function:
     dc1394_stop_iso_transmission(handle,camera.node)
 11  Add a PGM file header to the captured buffer to see the image using gimp.
 12  Use fwrite to save the captured image, by writing the buffer
     (camera.capture_buffer) to a file. The other parameters like height and
     width of the image can be extracted from the same structure:
     camera.frame_width, camera.frame_height.
 13  Close the camera. This step is necessary to prevent a memory leak:

       dc1394_release_camera(handle,&amp;camera);
       dc1394_destroy_handle(handle);

     In order to compile the program, use: gcc -o grabImage grabImage.c -
     ldc1394_control -lraw1394, where grabImage.c is your program.

We hope that after going through this algorithmic way explanation you can
comfortably understand the example code.
If we used the Format7 image format, we would have to change only the
setup_capture function. Let us look at the setup function:

        dc1394_setup_format7_capture(
    /* handle and camera_nodes[0] uniquely identifies the camera */
              handle,
              camera_nodes[0],
              channel, /* channel */
              mode , /*mode */
              bytes_per_packet ,
              left ,/*area of interest start column */
              right, /*area of interest start row */
              width,/* area of interest width */
              height /* area of interest height */
             &amp;camera /* dc1394_cameracapture type pointer *./
              )!=DC1394_SUCCESS)

where the values of the parameters for channel, speed, bytes_per_packet, speed,
mode are found using the following functions:

  1. dc1394_get_iso_channel_and_speed(handle,camera_nodes[0],
     &amp;channel,&amp;speed) /* to get the channel and the data speed */
  2. dc1394_get_video_mode(handle,camera_nodes[0] &amp;mode); /* to get the
     mode */
  3. dc1394_query_format7_byte_per_packet(handle, camera_nodes[0], mode
     ,&amp;bytes_per_packet); /* to get the bytes per packet which depends on
     the mode*/
  4. The value of left, top can be set to QUERY_FROM_CAMERA, or can be
     specified directly by the user.
  5. The value of the width and height depends on the size of frame the user
     wants, for example, if one wants 960x720 then pass 960 as width and 720 as
     height.


4.5. Example: How to grab image from the IEEE1394 camera using DMA

This section has been contributed by Ian Peikon <idp2@duke.edu>and Tim Hanson
<tim@hardcarve.com> We will now present an example of how to grab a frame by
the camera using DMA calls. The example is simple to understand as the logic
remains the same as the previous example. We will later compare the function
calls used in the previous example (without dma) and this example (with dma)
for better understanding.

  #include <stdio.h>
  #include <libraw1394/raw1394.h>
  #include <libdc1394/dc1394_control.h>
  #include <stdlib.h>
  #include <iostream>
  #define IMAGE_FILE_NAME "Image.pgm"
  using namespace std;

  int main(int arc, char *argv[]){
          FILE * imagefile;
          dc1394_cameracapture camera;
          int numNodes;
          int numCameras;
          raw1394handle_t handle;
          nodeid_t * camera_nodes;
          unsigned int channel, speed, format, framerate, mode;

          /*Step 1: Open ohci and assign a handle to it.*/
  	/*=======================================================*/
  	handle = dc1394_create_handle(0);
          if(handle==NULL){
                  fprintf(stderr, "Unable to acquire a handle. \n\n");
          }
          else{
  		 cout <<"dma1394: Handle aquired successfully-" <<handle<<"\n";
          }

  /*Step 2: Get the camera nodes and describe them as we find them.*/
  	/
  *=========================================================================*/
  	numNodes = raw1394_get_nodecount(handle);
          camera_nodes = dc1394_get_camera_nodes(handle, &amp;numCameras, 1);
          fflush(stdout);
          if (numCameras<1){
                  fprintf(stderr, "No cameras found :( \n");
                  dc1394_destroy_handle(handle);
                  return -1;
          }
          else{
                  cout<<"dma1394:"<< numCameras<<" cameras found. \n";
          }
          printf("dma1394: Working with the first camera on the bus.\n");
          if(camera_nodes[0] == numNodes-1){
                  fprintf(stderr, "\n" "dma1394: Sorry, your camera is the
  highest numbered node.\n");
                  dc1394_destroy_handle(handle);
                  dc1394_free_camera_nodes(camera_nodes);
                  return -1;
          }

  /*Step 3: Setup Capture*/
  	/*=====================================================================*/
  	/*Using camera functions to get the params by querying them*/
  	cout<<"INFO FOR DEBUG: \n"
                          "num_dma_buffers: "<< camera.num_dma_buffers<<"\n";
          dc1394_get_iso_channel_and_speed(handle, camera_nodes[0],
  &amp;channel, &amp;speed); /*get channel and speed*/
  	dc1394_get_video_format(handle, camera_nodes[0], &amp;format); /*get
  format*/
  	dc1394_get_video_framerate(handle, camera_nodes[0], &amp;framerate); /*get
  framerate*/
  	dc1394_get_video_mode(handle, camera_nodes[0], &amp;mode); /*get mode*/
  	cout<<"dc1394: Got parameters from the camera.\n"
                  "=======================================\n"
                  "Channel: "<< channel<< " \n"
                  "Speed: " <<speed <<" \n"
                  "Format: "<< format <<" \n"
                  "Framerate: " <<framerate<< "\n"
                  "Mode: "<< mode <<"\n";
          camera.num_dma_buffers = 8; /* set the dma buffers */
          camera.drop_frames = 1; /* set the number of drop frames */
          camera.dma_device_file = NULL;
          if(dc1394_dma_setup_capture(handle, camera_nodes[0], channel, format,
  mode, speed, framerate, camera.num_dma_buffers, camera.drop_frames,
  camera.dma_device_file, &amp;camera) !=DC1394_SUCCESS){
                  fprintf(stderr, "dma1394: Unable to setup camera.\n"
                                          "Check line %d of %s to ensure that
  the options set are supported by your camera.\n", __LINE__, __FILE__);
                  dc1394_destroy_handle(handle);
                  dc1394_free_camera_nodes(camera_nodes);
                  return -1;
          }
          else{
                  printf("dma1394: Capture has been setup.\n");
          }
          dc1394_free_camera_nodes(camera_nodes);

          //Set Trigger Mode -- Generally not required thus I will comment it
  out.
  	/*if(dc1394_set_trigger_mode(handle, camera.node, TRIGGER_MODE_0) !=
  DC1394_SUCCESS){
                  fprintf(stderr, "dma1394: Unable to set the camera trigger
  mode. Refer to line %d in %s.\n", __LINE__, __FILE__);
                  dc1394_release_camera(handle, &amp;camera);
                  dc1394_destroy_handle(handle);
          }
          else{
                  printf("dma1394: Successfully set trigger mode.\n");
          }*/

          /*Step 4: Start sending data */
  	/*=======================================================*/
  	if(dc1394_start_iso_transmission(handle, camera.node) != DC1394_SUCCESS){
                  fprintf(stderr, "dma1394: Unable to start the data
  transmission.\n");
                  dc1394_dma_done_with_buffer(&amp;camera);
  				dc1394_dma_release_camera(handle, &amp;camera);
                  dc1394_destroy_handle(handle);
                  return -1;
          }
          else{
                  printf("dma1394: Success.  Data Transmission started.\n");
          }

          /*Step 5: Capture Something...Anything...PLEASE*/
  	/*===============================================================*/
  	if(dc1394_dma_single_capture(&amp;camera) != DC1394_SUCCESS){
                  fprintf(stderr, "dma1394; DAIM, can't capture a single
  frame.\n");
  				dc1394_dma_done_with_buffer(&amp;camera); /*important step */
                  dc1394_dma_release_camera(handle, &amp;camera);
                  dc1394_destroy_handle(handle);
                  return -1;
          }
          else{
                  printf("dma1394: GREAT SUCCESS! Captured a single frame.\n");
          }

          /*Step 6: Stop sending data*/
  	/*==================================================*/
  	if(dc1394_dma_unlisten(handle, &amp;camera) != DC1394_SUCCESS){
          		fprintf(stderr, "Can't unlisten iso channel! \n");
          }
          else{
                  printf("dma1394: DMA unlistened. \n");
          }

  	if(dc1394_stop_iso_transmission(handle, camera.node) != DC1394_SUCCESS){
                  fprintf(stderr, " Can't stop the camera!! \n");
          }
          else{
                  printf("dma1394: Data transmission terminated. \n");
          }

          /*Step 7: Save our image*/
  	/*===============================================================*/
  	imagefile=fopen(IMAGE_FILE_NAME, "w");
          if(imagefile==NULL){
                  perror("dma1394: Can't create' "IMAGE_FILE_NAME" ' ");
                  dc1394_dma_done_with_buffer(&amp;camera);
  				dc1394_dma_release_camera(handle, &amp;camera);
                  dc1394_destroy_handle(handle);
                  return -1;
          }
          else{
                  cout<<"dma1394: Saved image in "<<IMAGE_FILE_NAME<<".\n";
          }
           /*Add pgm file header*/
  	fprintf(imagefile, "P5\n%u %u 255\n", camera.frame_width,
  camera.frame_height);

  		/*write to file*/
  	fwrite((const char *)camera.capture_buffer, 1,
  camera.frame_height*camera.frame_width, imagefile);
          fclose(imagefile);
          printf("dma1394: wrote: " IMAGE_FILE_NAME "\n");

          /*Step 8: Close camera*/
  	/*=============================================================*/
  	dc1394_dma_done_with_buffer(&amp;camera);
  	dc1394_dma_release_camera(handle, &amp;camera);
          dc1394_destroy_handle(handle);
          printf("dma1394: Camera released.  Exiting. \n");

          //Step END
  	return 0;

  }

Just like the previous example (Section 4.4,_“Example:_How_to_grab_image_from
the_IEEE1394_camera”) the program includes the necessary header files
(libraw1394/raw1394.h and libdc1394/dc1394_control.h) and then declare the
three variables of the following data type

* dc1394_cameracapture
* raw1394handle_t
* nodeid_t *

After this the following steps are followed which are very similar to the
previous example (Section 4.4,_“Example:_How_to_grab_image_from_the_IEEE1394
camera”)

  1. Open ohci and assign handle to it using the function dc1394_create_handle
     (0)
  2. Get the camera nodes using the function dc1394_get_camera_nodes
  3. Find out various parameters need to be passed during the camera setup.
     This is done by querying the camera using the following functions

     o dc1394_get_iso_channel_and_speed(): To get the channel and speed
       information
     o dc1394_get_video_format(): To get the camera format
     o dc1394_get_video_framerate(): To get the framerate information
     o dc1394_get_video_mode(): To get the camera mode

     Also we are required to set the dma buffers to 8 and number of drop frames
     to 1. Once the values of the parameter have been obtained
     (framerate,format,mode,channel,speed etc), they are passed in
     dc1394_dma_setup_capture which then sets up the camera and enables it for
     capturing video. For DMA you must pass the number of dma buffers and drop
     frames parameter.
  4. After the camera is set, dc1394_start_iso_transmission() is called. This
     function starts data transactions from the camera to the bus.
  5. Now capture one frame using dc1394_dma_single_capture(). This function
     will capture a frame into the dma buffer
     After the frame has been grabbed release the dma buffer using
     dc1394_dma_done_with_buffer(). This is required so that the memory can be
     reused. It is imperative that dc1394_dma_done_with_buffer() always follows
     a dma_capture function call
     So in order to capture more than one frame the code will be

       for( i=0;i<100 ;i++)/* to capture 100 images*/
       	{
       	dc1394_dma_single_capture(&amp;camera);
       	dc1394_dma_done_with_buffer(&amp;camera);
       	}

  6. Stop listening to the iso channel by calling dc1394_dma_unlisten()
     Terminate the data transmission by calling dc1394_stop_iso_transmission()
  7. Save the image in a file and add a PGM header for viewing using gimp.
  8. Finally call dc1394_release_camera to release the camera

If DMA is not setup correctly you will get the following error message:
VIDEO1394_IOC_LISTEN_CHANNEL ioctl failed
There are various reasons for this error which will be further explained in the
Problems section (Section 4.7,_“Common_Problems_Faced_While_Working_With
IEEE1394_Cameras”)
Thus we can see that the image capture using DMA is not much different from non
DMA method. We have compared the functions used in two approaches in the
following table.
 _____________________________________________________________________________
|Non_DMA_steps________________|DMA_steps____________________|Comments_________|
|dc1394_create_handle_________|dc1394_create_handle_________|Create_handle____|
|dc1394_get_camera_nodes______|dc1394_get_camera_nodes______|Get_camera_nodes_|
|                             |                             |Call setup       |
|                             |                             |functions to set |
|dc1394_setup_capture         |dc1394_dma_setup_capture     |various          |
|                             |                             |parameters of    |
|_____________________________|_____________________________|camera___________|
|                             |                             |Start sending the|
|dc1394_start_iso_transmission|dc1394_start_iso_transmission|data from camera |
|_____________________________|_____________________________|to_the_bus_______|
|dc1394_single_capture        |dc1394_dma_single_capture,   |Capture one frame|
|_____________________________|dc1394_dma_done_with_buffer__|_________________|
|                             |dc1394_dma_unlisten,         |Stop sending the |
|dc1394_stop_iso_transmission |dc1394_stop_iso_transmission |data from camera |
|_____________________________|_____________________________|to_the_bus_______|
|dc1394_release_camera,       |dc1394_dma_done_with_buffer, |                 |
|dc1394_destroy_handle        |dc1394_dma_release_camera,   |Close the camera |
|_____________________________|dc1394_destroy_handle________|_________________|


4.6. How to get color images: Bayer Pattern Concepts

The image grabbed by the sample code in the previous section is not colored (we
have intentionally used the words “not colored,” since the image is not gray-
scale either). It is actually a Bayer Pattern. We will give an overview of
Bayer Patterns and how they are used to get a colored image in this section.
Digital cameras use a solid-state device called an image sensor. These
fingernail-sized silicon chips contain millions of photosensitive diodes called
photosites. When you take a picture with a digital camera, the intensity of
light hitting each photo site on the sensor is recorded as a signal. Depending
on the camera, either 12 or 14 bits of data are recorded. At 12 bits, the
camera can record 4,096 levels of brightness. At 14 bits, the camera can record
16,384 levels of brightness. This is referred to as bit depth. The higher the
bit depth, the finer is the detail, the smoother the transition between tones,
and the higher the dynamic range (the ability of the camera to hold detail in
both highlighted and shadowed areas). But at capture, digital images are
grayscale, not color. To record color information, each pixel on the sensor is
covered with a red, green, or blue filter, with the colors alternating. A
common arrangement of color filters is the Bayer Pattern array that alternates
colors, but that also uses twice as many green filters as red and blue. Twice
as many green filters are used because our eyes are more sensitive to green.
This pattern, or sequence, of filters can vary, but the widely adopted Bayer
Pattern, which was invented at Kodak, is a repeating 2x2 arrangement. Each
pixel has been made sensitive only to one color (one spectral band).
A Typical Bayer Pattern will look like this:
Figure 5. Bayer Pattern
 Bayer Pattern

The tile or square (pixel) labeled B means this particular tile is sensitive
only to Blue light, and so on.
The Bayer Patterns may be classified into 4 types, depending on how we have
arranged the colors. The naming of the Bayer Pattern is done by taking a 2x2
matrix from the top most corner of the pattern and the colors being read in
(0,0),(0,1),(1,0),(1,1) order. So for the above Bayer Pattern, if we take the
2x2 matrix as:
Figure 6. BGGR Pattern
 BGGR Pattern

The pattern is therefore known as BGGR
The other possible patterns are:
Figure 7. Other Patterns
 Other Patterns

The image we obtained in the previous example was a Bayer Pattern image also
known as a RAW image. This was stored in camera.capture_buffer. In order to
view what we have captured we convert this RAW image to .PGM by adding a header
(look at the explanation in Section 4.4,_“Example:_How_to_grab_image_from_the
IEEE1394_camera”).
In order to get a colored image, the Bayer Pattern image is converted to a RGB
image. A RGB image is an enhanced version of the Bayer Pattern image; we try to
find the value of the two missing colors at each pixel (remember that each
pixel of the sensor is covered by Bayer Pattern filter so we get a single color
at any pixel by default). This is done by using different algorithms like
Nearest Neighbor,Edge Sense, and so on:
Figure 8. RAW to RGB
 RAW to RGB

where the shaded values are to be calculated by the algorithm. Subscript
denotes the tile on the Bayer Pattern to which the value of R, G, and B
belongs. Note that the image size will become 3 times the Bayer Pattern. In
order to view the RGB image we convert it to a Bit Map, or .BMP image, by
adding a bitmap header.
To get a clear picture of what's happening, we have provided the following
diagram:
Figure 9. Bayer to Bitmap conversion
 Bayer to Bitmap conversion

Let's understand how the RAW to RGB conversion algorithms work. We will look
into the Nearest Neighbor algorithm in detail. Other Algorithms are thoroughly
explained at the following web link: http://www-ise.stanford.edu/~tingchen/
main.htm.
Most of these algorithms make use of some kind of interpolations.

4.6.1. Nearest Neighbor Algorithm

In this interpolation method, each interpolated output pixel is assigned the
value of the nearest pixel in the input image. The nearest neighbor can be any
one of the upper, lower, left or right pixels.
An example will make the logic clear. We try to find the G values for the R, B
tiles for a 3x3 block (shown as shaded region. The blank squares either bear R
value or B value. We have not shown them just to make the figure easy to
understand). Here we assume the left neighboring pixel value is used to fill
the missing ones.
Figure 10. Nearest Neighbour
 Nearest Neighbour

The table on the left shows the G values for the Bayer Pattern image. In order
to find out the missing G values for the other squares that originally contains
only R or B we use the following approach:
Find the nearest G value square and copy the G value of that square onto the R
(B) square. This has been illustrated in the above figure. The square next to
G7 had a value of either R or B. So to get G8 (a G value for square 8) we
copied the G value of square 7, since it was the nearest so G8 = G7. Similarly
we filled the other non G value squares.
The same logic is applied when finding R and B values for the green squares.

4.6.2. Example program to understand how the colored image is grabbed using
IEEE1394 Camera

Now that we have presented the basic concept of the RAW, RGB and the conversion
algorithm, we feel that you can understand an example program that gives us a
colored image.
We have chosen the format as Format7 because the camera we used responds to
this format only. We will make use of another example code which provides the
implementation of the algorithms. The program is conversions.cpp, in the
grabdma folder, available for download at http://www.ptgrey.com/support/kb/
data/grabdma.tgz.
To run the code, make sure that you have the following files:

* conversions.h
* conversions.cpp
* grabcolor.cpp - also from the grabdma folder. We have modified the code
  according to our requirements and removed some of the lines. Since most of
  the code is same as the previously discussed code, we have explained only the
  portions that are different. These portions have been emphasized.


  #include <stdio.h>
  #include <libraw1394/raw1394.h>
  #include <libdc1394/dc1394_control.h>
  #include <stdlib.h>
  #include <onversions.h>

  #define IMAGE "Image.rgb"

  int main(int argc, char *argv[])
  {
    FILE* imagefile;
    dc1394_cameracapture camera;
    int numNodes;
    int numCameras;
    raw1394handle_t handle;
    nodeid_t * camera_nodes;
    int channel,speed,mode,bytes_per_packet;

     /* Open ohci and asign handle to it */

      handle = dc1394_create_handle(0);
    if (handle==NULL)
    {
      fprintf( stderr, "Unable to aquire a raw1394 handle\n\n"
         "Please check \n"
           " - if the kernel modules `ieee1394',`raw1394' and `ohci1394' are
  loaded \n"
           " - if you have read/write access to /dev/raw1394\n\n");
  exit(1);
    }

    /* get the camera nodes and describe them as we find them */

    numNodes = raw1394_get_nodecount(handle);
    camera_nodes = dc1394_get_camera_nodes(handle,&amp;numCameras,1);
    fflush(stdout);
    if (numCameras<1)
    {
      fprintf( stderr, "no cameras found :(\n");
      dc1394_destroy_handle(handle);
      exit(1);
    }
    printf("working with the first camera on the bus\n");

    if( camera_nodes[0] == numNodes-1)
    {
      fprintf( stderr, "\n"
             "Sorry, your camera is the highest numbered node\n");
      dc1394_destroy_handle(handle);
      dc1394_free_camera_nodes(camera_nodes);
      exit( 1);
    }

    /*obtain the values of the parameter from the camera */

  dc1394_get_video_mode(handle,camera_nodes[0],(unsigned int *)&amp;mode);

  dc1394_get_iso_channel_and_speed(handle,camera_nodes[0],
  (unsigned int *)&amp;channel, (unsigned int *)&amp;speed);

  dc1394_query_format7_byte_per_packet(handle,camera_nodes[0],(unsigned)
  mode,&amp;bytes_per_packet);

    /*setup capture */

  if (dc1394_setup_format7_capture(handle,
             camera_nodes[0],
           channel , /* channel */
           mode,
           speed,
           bytes_per_packet,
           0,
           0,
           960,
           720,
           &amp;camera)!=DC1394_SUCCESS)
    {
      fprintf( stderr,"unable to setup camera-\n"
           "check line %d of %s to make sure\n"
           "that the video mode,framerate and format are\n"
           "supported by your camera\n",
           __LINE__,__FILE__);
      dc1394_release_camera(handle,&amp;camera);
      dc1394_destroy_handle(handle);
      dc1394_free_camera_nodes(camera_nodes);
      exit(1);
    }
    dc1394_free_camera_nodes(camera_nodes);

    /* have the camera start sending us data*/

    if (dc1394_start_iso_transmission(handle,camera.node)
        !=DC1394_SUCCESS)
    {
      fprintf( stderr, "unable to start camera iso transmission\n");
      dc1394_release_camera(handle,&amp;camera);
      dc1394_destroy_handle(handle);
      exit(1);
    }

    /* capture one frame */

    if (dc1394_single_capture(handle,&amp;camera)!=DC1394_SUCCESS)
    {
      fprintf( stderr, "unable to capture a frame\n");
      dc1394_release_camera(handle,&amp;camera);
      dc1394_destroy_handle(handle);
      exit(1);
    }

    /*query the camera to determine the Bayer pattern*/

  quadlet_t qValue;
     GetCameraControlRegister( handle,
                Camera_nodes[0],
                0x1040,/* Bayer Tile Mapping register */
                &amp;qValue );

     bayer_pattern_t pattern = BAYER_PATTERN_BGGR;
     switch( qValue )
     {
        case 0x42474752:/* BGGR */
         pattern = BAYER_PATTERN_BGGR;
         break;
        case 0x47524247:/* GRBG */
         pattern = BAYER_PATTERN_GRBG;
         break;
        case 0x52474742: /* RGGB */
         pattern = BAYER_PATTERN_RGGB;
         break;
        case 0x47425247:/* GBRG */
         pattern = BAYER_PATTERN_GBRG;
         break;
        case 0x59595959:/* YYYY = BW */
         fprintf( stderr, "Camera is black and white\n" );
         cleanup();
         return 1;
        default:
        fprintf(stderr,
            "Camera BAYER_TILE_MAPPING register has an unexpected value:\n"
            "\t0x%x\n", qValue );

        return 1;
     }

     int bufferSize = camera.frame_width*camera.frame_height;

     /* assign a buffer of size three time the original image */

     unsigned char* rgbBuffer = new unsigned char[3 * bufferSize];

     unsigned char* src = (unsigned char*)camera.capture_buffer;

     unsigned char* captureBuffer=
              (unsigned char*)camera.capture_buffer;
     for ( int i = 0; i < bufferSize; i++ )
     {
         src[i] = captureBuffer[ i * bytesPerPixel ];
     }

     /* convert to color image */

     BayerNearestNeighbor (src,
               rgbBuffer,
               camera.frame_width,
               camera.frame_height,
               pattern );


     /* Stop data transmission */

    if (dc1394_stop_iso_transmission(handle,camera.node)!=DC1394_SUCCESS)
    {
    printf("couldn't stop the camera?\n");
    }

    /* save image as 'Image.rgb' without adding any pgm header */

    printf( "Saving the image...\n" );
    imagefile = fopen( IMAGE, "w" );

    fwrite( rgbBuffer, 3,
           bufferSize, imagefile );

    fclose( imagefile );

    /* Close camera */

    dc1394_release_camera(handle,&amp;camera);
    dc1394_destroy_handle(handle);
    return 0;
  }

As we have already discussed the use of GetCameraControlRegister, you can
understand that it has been used to find out the value contained at 0x1040.
Libdc1394 does not provide any function to query this address, so we explicitly
used this call to get the value.
It is important to understand the utility of the above function call. Refer to
our discussion about the Bayer Pattern filters in the previous section. We know
that the pattern can be BGGR, RGGB, GRBG, and GRBG. The algorithm that we use
for converting the Bayer Pattern to RGB requires to know about the type of
pattern the camera filter has got so that it can carry out some initialization
(refer to conversions.cpp for details). The fourth parameter in the function
call:

     BayerNearestNeighbor (src,
               rgbBuffer,
               camera.frame_width,
               camera.frame_height,
               pattern )

refers to this value.
BayerNearestNeighbor is the function call for the interpolation algorithm we
discussed in the last section. This is implemented in conversions.cpp.
Having understood this, we move on to the switch-cases. The value that is
obtained for the Bayer Pattern (qvalue) is in the hex form which needs to be
decoded for setting the value of the variable pattern.
The case statements indicate the various hex values relating to the Bayer
Pattern that can be returned by the various cameras. The intimidating values
are actually quite easy to decode. Here's the trick:
The hex code for various colors is as follows:

* 42h -> B
* 47h -> G
* 52h -> R

Now if the qvalue contains 0x42474752, it means: B (42h) G (47h) G (47h) R
(52h) or BGGR. We can therefore decode all the case statements similarly.
Finally, we need to declare another image buffer that will contain the RGB
image. Remember that the size of the RGB is 3 times the size of the Bayer
Pattern image. rgbbuffer is therefore assigned 3 times the buffer size
(camera.capture_buffer). This buffer (rgbbuffer) will be passed as the
destination buffer (the second parameter in BayerNearestNeighbor).
After the buffer has been filled with the RGB values we write it in the file
image.rgb.
In order to view this image using gimp, we need to append a bitmap header. The
method we employed was as follows:

  1. Save the RGB image buffer in a file, say, image.rgb.
  2. Make a bitmap header and save it in a separate file, bmpheader. Refer to
     http://www.fortunecity.com/skyscraper/windows/364/bmpffrmt.html for header
     details.
  3. cat bmpheader image.rgb > bmpfile
  4. Open bmpfile using gimp.

In order to run the program, use the following steps:

  g++ -c conversions.cpp
  g++ -o grabcolor conversions.o grabcolor.cpp -lraw1394
  -ldc1394_control


Note on available algorithms:

There are many algorithms that are available in conversions.cpp, so depending
upon the requirements, you can call the necessary functions.
The Coriander application is useful in finding out how the RGB image will look
after undergoing different conversion algorithms. For example, it provides the
choice between Nearest Neighbor, Edge Sense and Down Sample conversion
algorithms. The difference can be observed on a mouse click.

4.7. Common Problems Faced While Working With IEEE1394 Cameras

We now look at some of the common problems faced while working with the camera,
however we have only listed those problems which we faced. These problems are
likely to be faced by anyone who uses the library and the camera. Some of the
problems were solved with a proper reasoning but some were just hit-and-miss
attempts. The problems and their solutions are listed below.

* Problem #1. After the installation of the library and the modules the camera
  did not respond
  Solution: We disconnected the camera and connected it again. May be this has
  to be repeated multiple times. We could not figure out an appropriate reason
  for this but it works.
* Problem #2. Program is not compiling
  Solution: If one forgets to link the executable with raw1394 and
  dc1394_control the program won't compile. The correct way is:

    gcc -o xx xx.c -lraw1394 -ldc1394_control /*for C files*/
    g++ -o xx xx.cpp -lraw1394 -ldc1394_control /* for Cpp files */

* Problem #3. Compilation failed, giving the error: libdc1394_control.so.13:
  cannot open the shared object file.
  Solution: Check for the environment variable LD_LIBRARY_PATH. This should
  contain the path of the shares library. On our system the path was /usr/
  local/lib. The path must be set accordingly.
* Problem #4. Program hangs when executed.
  Solution: This primarily happens if the values of parameters that are passed
  to the setup function are not supported by the camera. For e.g. setting the
  mode mode_640x480_MONO16 when it is not supported. Our suggestion is that one
  should always query for the values and then pass them to the function (as
  explained in the example code, located in Section 4.4,_“Example:_How_to_grab
  image_from_the_IEEE1394_camera”).
* Problem #5. IDEO1394_IOC_LISTEN_CHANNEL ioctl failed error message being
  displayed.
  Solution: (contributed by Ian and Tim). There are various reasons for this
  error message. Type dmesg in the command prompt to gain a better
  understanding of the problem. Here is a list of problem we ran into

  o Channel 0 is not being used- This means you are listening on the iso
    channel and then calling a capture function again. Make sure not to call
    dma_unlisten until you are ready to stop iso transmission.
  o Channel 0 is already being used- This means you have set two camera nodes
    to the same Channel. Fix your dma_setup_capture(). This could also mean
    that you have tried to call the setup function more than once without
    releasing the camera between the calls. This error is more likely to occur
    when you are working with more than one camera.
  o Buffer 0 is already being used- This means that you have not freed the DMA
    buffer before trying to write to it again. Make sure to alternate
    dma_done_with_buffer calls with dma_capture_calls

* Problem #6. Used CTRL+C to terminate the image grabbing program, but the next
  time the program is run, it just hangs.
  Solution: The error usually occurs because the camera functions like a pipe
  and experiences a broken pipe situation if terminated without flushing the
  memory channels. The trick is to disconnect the camera and connect it again.
  One can also try debugging the problem by reinstalling the ohci1394,
  video1394, raw1394, video1394 modules, which works occasionally.
* Problem #7. Every parameter is okay and the installation is also fine, but
  even then, when the program is executed the camera is still not detected.
  Solution: This is a strange problem which we also face frequently. The
  solution is based on trial and error, but it always works:

    1. Disconnect the camera first and then reconnect it.
    2. Now run Coriander (that's why we suggest that you install Coriander
       before you start working with the camera).
    3. Make all the necessary adjustments; for example, select the mode of the
       camera, the frame size, and so forth.
    4. Close Coriander.
    5. Execute your program.

  Bingo!!! It works.

  Note on first step above:

  The first step is critical since we experienced an error message from
  Coriander about not finding the camera if we did not disconnect and reconnect
  the camera before running Coriander.


5. References


  1. http://kauri.auck.irl.cri.nz/~johanns/libdc1394/libdc1394_FAQ.html,
     libdc1394 FAQ by Johann Schoonees.
  2. http://www.ptgrey.com/
  3. http://www-ise.stanford.edu/~tingchen
  4. http://damien.douxchamps.net/ieee1394/coriander/manual.php
  5. Point Grey Dragonfly Camera Technical Reference Manual, Version 2.1.2.1.3
  6. Raw Capture: A Second Chance to Get it Right, by Charlotte K. Lowrie,
     2005-09-01
  7. http://www.linuxfocus.org
  8. http://www.fortunecity.com/skyscraper/windows/364/bmpffrmt.html


A. Appendix A


1. License

This document, Libdc1394 Library support for IEEE 1394 Cameras HOWTO, is
copyrighted © 2005 by Rohit Agarwal &amp; Vikram B. Permission is granted to
copy, distribute and/or modify this document under the terms of the GNU Free
Documentation License, Version 1.2 or any later version published by the Free
Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and
with no Back-Cover Texts. A copy of the license is available at http://
www.gnu.org/copyleft/fdl.html.

2. Disclaimer

Although we have tried to do our best to bring out this HOWTO in a good form,
we are not responsible for any damage due to the actions taken based upon the
information contained in this document. It is impossible to test things under
all the configurations, so probably some of the hints given in this document
may be incorrect and may not work on your system. In case you find anything
wrong, let us know it first. We will rewrite the document as soon as possible.
This document is provided “as is”. We put great effort into writing it as
accurately as we could, but you are using the information contained herein at
your own risk. In no event shall we be liable for any damages resulting from
the use of this work.

3. About Authors

Rohit Agarwal and Vikram B are pursuing their Masters Degrees in IT from the
International Institute of Information Technology, Bangalore, India.
They can be contacted at:

* rohdimp_24@rediffmail.com <Rohit>
* vickys_box@rediffmail.com <Vikram>


4. Dedications

We are grateful to all our friends for their support. We would specially like
to thank Chinmay Narayan our batch mate for his valuable advices. We would like
to dedicate this document to our Professor, Mr. S. Nagrajan, for he is the one
who motivated us to contribute to the open source community.