—WebCam网络摄像头7 cmos–yuv rgb , Format…………:V4L2_PIX_FMT_YUYV

Y = 0.299R + 0.587G + 0.114B
U = -0.147R - 0.289G + 0.436B
V = 0.615R - 0.515G - 0.100B

R = Y + 1.14V
G = Y - 0.39U - 0.58V
B = Y + 2.03U
/*******************************************************************************************************/

[root@localhost input_cmoscamera]# pwd
/opt/FriendlyArm/mini2440/WebCam/mjpg-streamer/mjpg-streamer/plugins/input_cmoscamera
[root@localhost input_cmoscamera]# tree
.
|-- Makefile
|-- Makefile~
|-- dynctrl.c
|-- dynctrl.h
|-- dynctrl.lo
|-- huffman.h
|-- input_cmoscamera.so
|-- input_uvc.c
|-- jpeg_utils.c
|-- jpeg_utils.h
|-- jpeg_utils.lo
|-- uvc_compat.h
|-- uvcvideo.h
|-- v4l2uvc.c
|-- v4l2uvc.c~
|-- v4l2uvc.h
`-- v4l2uvc.lo

0 directories, 17 files

http://blog.csdn.net/songqqnew/article/details/7012927
cmos摄像头数据的读取方法和这个类似,此处的
input_uvc.c对应那里的input_s3c2410.c--调用v4l2uvc.c里函数的部分
v4l2uvc.c对应那里的s3c2410.c--与驱动亲密接触的部分

几点说明：
mjpg-streamer/plugins/input_cmoscamera/input_uvc.c

int input_init(input_parameter *param) 
{
  char *argv[MAX_ARGUMENTS]={NULL}, *dev = "/dev/camera", *s;
  int argc=1, width=640, height=512, fps=5, format=V4L2_PIX_FMT_YUYV, i;
  in_cmd_type led = IN_CMD_LED_AUTO;

  /* initialize the mutes variable */
  if( pthread_mutex_init(&controls_mutex, NULL) != 0 ) {
    IPRINT("could not initialize mutex variable\n");
    exit(EXIT_FAILURE);
  }

  /* convert the single parameter-string to an array of strings */
  argv[0] = INPUT_PLUGIN_NAME;
  if ( param->parameter_string != NULL && strlen(param->parameter_string) != 0 ) {
    char *arg=NULL, *saveptr=NULL, *token=NULL;

    arg=(char *)strdup(param->parameter_string);

    if ( strchr(arg, ' ') != NULL ) {
      token=strtok_r(arg, " ", &saveptr);
      if ( token != NULL ) {
        argv[argc] = strdup(token);
        argc++;
        while ( (token=strtok_r(NULL, " ", &saveptr)) != NULL ) {
          argv[argc] = strdup(token);
          argc++;
          if (argc >= MAX_ARGUMENTS) {
            IPRINT("ERROR: too many arguments to input plugin\n");
            return 1;
          }
        }
      }
    }
  }

  /* show all parameters for DBG purposes */
  for (i=0; i<argc; i++) {
    DBG("argv[%d]=%s\n", i, argv[i]);
  }

  /* parse the parameters */
  reset_getopt();
  while(1) {
    int option_index = 0, c=0;
    static struct option long_options[] = \
    {
      {"h", no_argument, 0, 0},
      {"help", no_argument, 0, 0},
      {"d", required_argument, 0, 0},
      {"device", required_argument, 0, 0},
      {"r", required_argument, 0, 0},
      {"resolution", required_argument, 0, 0},
      {"f", required_argument, 0, 0},
      {"fps", required_argument, 0, 0},
      {"y", no_argument, 0, 0},
      {"yuv", no_argument, 0, 0},
      {"q", required_argument, 0, 0},
      {"quality", required_argument, 0, 0},
      {"m", required_argument, 0, 0},
      {"minimum_size", required_argument, 0, 0},
      {"n", no_argument, 0, 0},
      {"no_dynctrl", no_argument, 0, 0},
      {"l", required_argument, 0, 0},
      {"led", required_argument, 0, 0},
      {0, 0, 0, 0}
    };

    /* parsing all parameters according to the list above is sufficent */
    c = getopt_long_only(argc, argv, "", long_options, &option_index);

    /* no more options to parse */
    if (c == -1) break;

    /* unrecognized option */
    if (c == '?'){
      help();
      return 1;
    }

    /* dispatch the given options */
    switch (option_index) {
      /* h, help */
      case 0:
      case 1:
        DBG("case 0,1\n");
        help();
        return 1;
        break;

      /* d, device */
      case 2:
      case 3:
        DBG("case 2,3\n");
        dev = strdup(optarg);
        break;

      /* r, resolution */
      case 4:
      case 5:
        DBG("case 4,5\n");
        width = -1;
        height = -1;

        /* try to find the resolution in lookup table "resolutions" */
        for ( i=0; i < LENGTH_OF(resolutions); i++ ) {
          if ( strcmp(resolutions[i].string, optarg) == 0 ) {
            width  = resolutions[i].width;
            height = resolutions[i].height;
          }
        }
        /* done if width and height were set */
        if(width != -1 && height != -1)
          break;
        /* parse value as decimal value */
        width  = strtol(optarg, &s, 10);
        height = strtol(s+1, NULL, 10);
        break;

      /* f, fps */
      case 6:
      case 7:
        DBG("case 6,7\n");
        fps=atoi(optarg);
        break;

      /* y, yuv */
      case 8:
      case 9:
        DBG("case 8,9\n");
        format = V4L2_PIX_FMT_YUYV;
        break;

      /* q, quality */
      case 10:
      case 11:
        DBG("case 10,11\n");
        format = V4L2_PIX_FMT_YUYV;
        gquality = MIN(MAX(atoi(optarg), 0), 100);
        break;

      /* m, minimum_size */
      case 12:
      case 13:
        DBG("case 12,13\n");
        minimum_size = MAX(atoi(optarg), 0);
        break;

      /* n, no_dynctrl */
      case 14:
      case 15:
        DBG("case 14,15\n");
        dynctrls = 0;
        break;

      /* l, led */
      case 16:
      case 17:
        DBG("case 16,17\n");
        if ( strcmp("on", optarg) == 0 ) {
          led = IN_CMD_LED_ON;
        } else if ( strcmp("off", optarg) == 0 ) {
          led = IN_CMD_LED_OFF;
        } else if ( strcmp("auto", optarg) == 0 ) {
          led = IN_CMD_LED_AUTO;
        } else if ( strcmp("blink", optarg) == 0 ) {
          led = IN_CMD_LED_BLINK;
        }
        break;

      default:
        DBG("default case\n");
        help();
        return 1;
    }
  }

  /* keep a pointer to the global variables */
  pglobal = param->global;

  /* allocate webcam datastructure */
  videoIn = malloc(sizeof(struct vdIn));
  if ( videoIn == NULL ) {
    IPRINT("not enough memory for videoIn\n");
    exit(EXIT_FAILURE);
  }
  memset(videoIn, 0, sizeof(struct vdIn));

  /* display the parsed values */
  IPRINT("Using CMOS Camera device.: %s\n", dev);
  IPRINT("Desired Resolution: %i x %i\n", width, height);
  IPRINT("Frames Per Second.: %i\n", fps);
  IPRINT("Format............: %s\n", (format==V4L2_PIX_FMT_YUYV)?"YUV":"MJPEG");
  if ( format == V4L2_PIX_FMT_YUYV )
    IPRINT("JPEG Quality......: %d\n", gquality);

  /* open video device and prepare data structure */
  if (init_videoIn(videoIn, dev, width, height, fps, format, 1) < 0) {
    IPRINT("init_VideoIn failed\n");
    closelog();
    exit(EXIT_FAILURE);
  }

  /*
   * recent linux-uvc driver (revision > ~#125) requires to use dynctrls
   * for pan/tilt/focus/...
   * dynctrls must get initialized
   */
  if (dynctrls)
    initDynCtrls(videoIn->fd);

  /*
   * switch the LED according to the command line parameters (if any)
   */
  input_cmd(led, 0);

  return 0;
}

从 
char *argv[MAX_ARGUMENTS]={NULL}, *dev = "/dev/camera", *s;
  int argc=1, width=640, height=512, fps=5, format=V4L2_PIX_FMT_YUYV, i;
可知默认设备/dev/camera,默认格式V4L2_PIX_FMT_YUYV
并且从
      /* y, yuv */
      case 8:
      case 9:
        DBG("case 8,9\n");
        format = V4L2_PIX_FMT_YUYV;
        break;
可知指定 -y后格式也是V4L2_PIX_FMT_YUYV

其中init_videoIn()在mjpg-streamer/plugins/input_cmoscamera/v4l2uvc.c

int init_videoIn(struct vdIn *vd, char *device, int width, int height, int fps, int format, int grabmethod)
{


  if (vd == NULL || device == NULL)
    return -1;
  if (width == 0 || height == 0)
    return -1;
  if (grabmethod < 0 || grabmethod > 1)
    grabmethod = 1;		//mmap by default;
  vd->videodevice = NULL;
  vd->status = NULL;
  vd->pictName = NULL;
  vd->videodevice = (char *) calloc (1, 16 * sizeof (char));
  vd->status = (char *) calloc (1, 100 * sizeof (char));
  vd->pictName = (char *) calloc (1, 80 * sizeof (char));
  snprintf (vd->videodevice, 12, "%s", device);
  vd->toggleAvi = 0;
  vd->getPict = 0;
  vd->signalquit = 1;
  vd->width = width;
  vd->height = height;
  vd->fps = fps;
  vd->formatIn = format;
  vd->grabmethod = grabmethod;

 
  if (init_v4l2 (vd) < 0) {
    fprintf (stderr, " Init Camera interface failed !! exit fatal \n");
    goto error;;
  }
  
  // alloc a temp buffer to reconstruct the pict 
  vd->framesizeIn = (vd->width * vd->height << 1);
  vd->framebuffer =  (unsigned char *) calloc(1, (size_t) vd->framesizeIn);
  if (!vd->framebuffer)
    goto error;
  return 0;
error:
  free(vd->videodevice);
  free(vd->status);
  free(vd->pictName);
  close(vd->fd);
  return -1;
}

同文件下的init_v4l2()

static int init_v4l2(struct vdIn *vd)
{
	int fd = open(vd->videodevice, O_RDONLY);
	if (fd > 0)
	{
		// Set preview width,height
		ioctl(fd, 0x0000, vd->width);
		ioctl(fd, 0x0001, vd->height);
	    	close(fd);
	}
	else
	{
		goto fatal;
	}
	// Open camera
	fdcamera = fopen(vd->videodevice,"rb");

	if (fdcamera == NULL)
	{
		printf("Could not open camera\n");
		goto fatal;
	}

	
  return 0;
fatal:
  return -1;

}

line7 line8的2行
        ioctl(fd, 0x0000, vd->width);
        ioctl(fd, 0x0001, vd->height);
返回值 < 0.只是没有打印,原因同前面的那篇一样,由于驱动没有实现ioctl。这两行注释掉即可。

数据获取同
http://blog.csdn.net/songqqnew/article/details/7012927
类似，均用read方式，因为是由ov9650驱动实现决定的。搜索“见下面”
mjpg-streamer/plugins/input_cmoscamera/input_uvc.c

/******************************************************************************
Description.: this thread worker grabs a frame and copies it to the global buffer
Input Value.: unused
Return Value: unused, always NULL
******************************************************************************/
void *cam_thread( void *arg ) {
  /* set cleanup handler to cleanup allocated ressources */
  pthread_cleanup_push(cam_cleanup, NULL);

  while( !pglobal->stop ) {

    /* grab a frame */
    if( uvcGrab(videoIn) < 0 ) {//见下面
      IPRINT("Error grabbing frames\n");
      exit(EXIT_FAILURE);
    }
  
    DBG("received frame of size: %d\n", videoIn->buf.bytesused);

    /*
     * Workaround for broken, corrupted frames:
     * Under low light conditions corrupted frames may get captured.
     * The good thing is such frames are quite small compared to the regular pictures.
     * For example a VGA (640x480) webcam picture is normally >= 8kByte large,
     * corrupted frames are smaller.
     */
    //if ( videoIn->buf.bytesused < minimum_size ) {
    //  DBG("dropping too small frame, assuming it as broken\n");
    //  continue;
    //}

    /* copy JPG picture to global buffer */
    pthread_mutex_lock( &pglobal->db );

    /*
     * If capturing in YUV mode convert to JPEG now.
     * This compression requires many CPU cycles, so try to avoid YUV format.
     * Getting JPEGs straight from the webcam, is one of the major advantages of
     * Linux-UVC compatible devices.
     */
    if (videoIn->formatIn == V4L2_PIX_FMT_YUYV) {
      DBG("compressing frame\n");
      pglobal->size = compress_yuyv_to_jpeg(videoIn, pglobal->buf, videoIn->framesizeIn, gquality);
    }
    else {
      DBG("copying frame\n");
      pglobal->size = memcpy_picture(pglobal->buf, videoIn->tmpbuffer, videoIn->buf.bytesused);
    }

#if 0
    /* motion detection can be done just by comparing the picture size, but it is not very accurate!! */
    if ( (prev_size - global->size)*(prev_size - global->size) > 4*1024*1024 ) {
        DBG("motion detected (delta: %d kB)\n", (prev_size - global->size) / 1024);
    }
    prev_size = global->size;
#endif

    /* signal fresh_frame */
    pthread_cond_broadcast(&pglobal->db_update);
    pthread_mutex_unlock( &pglobal->db );

    DBG("waiting for next frame\n");

    /* only use usleep if the fps is below 5, otherwise the overhead is too long */
    if ( videoIn->fps < 5 ) {
      usleep(1000*1000/videoIn->fps);
    }
  }

  DBG("leaving input thread, calling cleanup function now\n");
  pthread_cleanup_pop(1);

  return NULL;
}

mjpg-streamer/plugins/input_cmoscamera/v4l2uvc.c

int uvcGrab(struct vdIn *vd)
{
#define HEADERFRAME1 0xaf
  int ret;
  int nSize = 0;
  
  //if (!vd->isstreaming)
  //  if (video_enable(vd))
  //    goto err;

  //memset(&vd->buf, 0, sizeof(struct v4l2_buffer));
  //vd->buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  //vd->buf.memory = V4L2_MEMORY_MMAP;

  nSize = fread(vd->framebuffer,1,vd->framesizeIn,fdcamera);//原始数据塞进vd->framebuffer
  vd->buf.bytesused = nSize;//原始数据大小塞进vd->buf.bytesused
  
  //ret = ioctl(vd->fd, VIDIOC_DQBUF, &vd->buf);
  if (nSize !=  vd->framesizeIn) {
    perror("Read size small than requested");
    goto err;
  }


//  ret = ioctl(vd->fd, VIDIOC_QBUF, &vd->buf);
//  if (ret < 0) {
//    perror("Unable to requeue buffer");
//    goto err;
//  }

  return 0;

err:
  vd->signalquit = 0;
  return -1;
}

线程函数cam_thread中有调用如下图像格式转换函数

    /*
     * If capturing in YUV mode convert to JPEG now.
     * This compression requires many CPU cycles, so try to avoid YUV format.
     * Getting JPEGs straight from the webcam, is one of the major advantages of
     * Linux-UVC compatible devices.
     */
    if (videoIn->formatIn == V4L2_PIX_FMT_YUYV) {
      DBG("compressing frame\n");
      pglobal->size = compress_yuyv_to_jpeg(videoIn, pglobal->buf, videoIn->framesizeIn, gquality);//格式化图像数据塞进pglobal->buf
    }
    else {
      DBG("copying frame\n");
      pglobal->size = memcpy_picture(pglobal->buf, videoIn->tmpbuffer, videoIn->buf.bytesused);//图像数据塞进pglobal->buf
    }

由于cmos指定格式是YUV,所以从驱动中获取到的数据是YUV格式,所以需要转换成MJPEG格式以便显示,所以此处实际上调用compress_yuyv_to_jpeg()
一般要避免使用YUV格式，因为这个转换函数浪费时间。从浏览器中观察cmos的动态表现也可以看出来，比较慢。
可以直接从WebCam中获取MJPEG的格式就不需要转换了---但ov9650不支持---http://blog.csdn.net/songqqnew/article/details/7013054
zc0301pl支持，见下文。