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linux v4l 编程(2) V4L 查询操作

分类： 嵌入式

2011-06-16 01:33:45

Andrew Huang 转载请注明作者及网址

1.设备性能查询

v4l设备里中,使用ioctl的VIDIOCGCAP来查询设备的,这里v4l规定必须实现的操作.

struct video_capability  cap; 
 memset(&cap,0,sizeof(cap));
ret = ioctl(fd, VIDIOCGCAP, &cap);

其中struct video_capability定义在linux/videodevice.h.定义如下

struct video_capability
{
    char name[32];
    int type;
    int channels;    /* Num channels */
    int audios;    /* Num audio devices */
    int maxwidth;    /* Supported width */
    int maxheight;    /* And height */
    int minwidth;    /* Supported width */
    int minheight;    /* And height */
};


另外查询设备输入/输出通道,也是基本要求,用VIDIOCGCHAN命令


struct video_channel channel;
   int i;

   PRINT_V4L("channels\n");
       

   for(i=0; i<count;i++)
       {
        memset(&channel,0,sizeof(channel));
        channel.channel = i;
        if (-1 == ioctl(fd,VIDIOCGCHAN,&channel)) {
            
            continue;
        }
}

其中数据结构定义如下:
  

struct video_channel
{
    int channel;
    char name[32];
    int tuners;
    __u32 flags;
#define VIDEO_VC_TUNER        1    /* Channel has a tuner */
#define VIDEO_VC_AUDIO        2    /* Channel has audio */
    __u16 type;
#define VIDEO_TYPE_TV        1
#define VIDEO_TYPE_CAMERA    2
    __u16 norm;            /* Norm set by channel */
};


2.实现代码
  v4l设备里中,使用ioctl的VIDIOCGPICT来查询设备的支持视频格式
   struct video_picture pic;
   memset(&pic,0,sizeof(pic));
 
   ret = ioctl(fd, VIDIOCGPICT, &pic);

  其中video_picture的定义如下,plalette定义就是视频格式。
  1. struct video_picture
  2. {
  3.     __u16    brightness;
  4.     __u16    hue;
  5.     __u16    colour;
  6.     __u16    contrast;
  7.     __u16    whiteness;    /* Black and white only */
  8.     __u16    depth;        /* Capture depth */
  9.     __u16 palette;    /* Palette in use */
  10. #define VIDEO_PALETTE_GREY    1    /* Linear greyscale */
  11. #define VIDEO_PALETTE_HI240    2    /* High 240 cube (BT848) */
  12. #define VIDEO_PALETTE_RGB565    3    /* 565 16 bit RGB */
  13. #define VIDEO_PALETTE_RGB24    4    /* 24bit RGB */
  14. #define VIDEO_PALETTE_RGB32    5    /* 32bit RGB */
  15. #define VIDEO_PALETTE_RGB555    6    /* 555 15bit RGB */
  16. #define VIDEO_PALETTE_YUV422    7    /* YUV422 capture */
  17. #define VIDEO_PALETTE_YUYV    8
  18. #define VIDEO_PALETTE_UYVY    9    /* The great thing about standards is ... */
  19. #define VIDEO_PALETTE_YUV420    10
  20. #define VIDEO_PALETTE_YUV411    11    /* YUV411 capture */
  21. #define VIDEO_PALETTE_RAW    12    /* RAW capture (BT848) */
  22. #define VIDEO_PALETTE_YUV422P    13    /* YUV 4:2:2 Planar */
  23. #define VIDEO_PALETTE_YUV411P    14    /* YUV 4:1:1 Planar */
  24. #define VIDEO_PALETTE_YUV420P    15    /* YUV 4:2:0 Planar */
  25. #define VIDEO_PALETTE_YUV410P    16    /* YUV 4:1:0 Planar */
  26. #define VIDEO_PALETTE_PLANAR    13    /* start of planar entries */
  27. #define VIDEO_PALETTE_COMPONENT 7    /* start of component entries */
  28. };



3.实现代码
  1. /*
  2.  * Author: Andrew Huang <bluedrum@163.com>
  3.  * query v4l1 device capabilities
  4.  * date: 2010/06/16
  5.  */
  6. #include <stdio.h>
  7. #include <string.h>
  8. #include <errno.h>

  10. #include <sys/types.h>
  11. #include <sys/stat.h>
  12. #include <fcntl.h>

  14. #include <linux/videodev.h>

  16. #define PRINT_V4L printf

  18. #define PRINT_IOCTL_CMD(cmd) printf(" %15s = (0x%x)\n",#cmd,cmd)
  19. #define PRINT_IOCTL_CMD2(cmd,n) printf(" %-20s(%d) = (0x%x)\n",#cmd,n,cmd)

  21. #define PRINT_V4L_MEMBER(m) printf(" %-20s:",#m);
  22. #define PRINT_V4L_STRING(m) printf(" %-20s:\"%s\"\n",#m,m)
  23. #define PRINT_V4L_INT(m) printf(" %-20s:%d\n",#m,m)
  24. #define PRINT_V4L_INTX(m) printf(" %-20s:0x%x\n",#m,m)

  26. /* 显示enum 值的之一*/
  27. #define TEST_V4L_FLAG0(m,f) printf("%s",((m & f)==f)?#f:"")

  29. /* 显示一个组合值的所有内容 */
  30. #define PRINT_V4L_FLAGS(m) printf(" %-20s:0x%x [",#m,m) /* 组合值开始*/
  31. #define TEST_V4L_FLAG(m,f) printf("%s",((m & f)==f)?#f",":"") /* 组合值中间值,可以有多个*/
  32. #define PRINT_V4L_FLAGS2(m) printf("]\n") /* 组合值结束*/


  35. #define PRINT_INT(e) printf("%s=%d\n",#e,e)


  38. int v4l_get_channels(int fd,int count)
  39. {
  40.    struct video_channel channel;
  41.    int i;

  43.    PRINT_V4L("channels\n");
  44.        

  46.    for(i=0; i<count;i++)
  47.        {
  48.         memset(&channel,0,sizeof(channel));
  49.         channel.channel = i;
  50.         if (-1 == ioctl(fd,VIDIOCGCHAN,&channel)) {
  51.             
  52.             continue;
  53.         }

  55.          PRINT_IOCTL_CMD2(VIDIOCGCAP,i);
  56.   
  57.      PRINT_V4L_INT(channel.channel);    
  58.         PRINT_V4L_STRING(channel.name);
  59.          PRINT_V4L_INT(channel.tuners);
  60.         

  62.          PRINT_V4L_FLAGS(channel.flags);    
  63.         TEST_V4L_FLAG(channel.flags,VIDEO_VC_TUNER);
  64.         TEST_V4L_FLAG(channel.flags,VIDEO_VC_AUDIO);        
  65.         PRINT_V4L_FLAGS2(channel.flags);


  68.          PRINT_V4L_FLAGS(channel.type);    
  69.         TEST_V4L_FLAG(channel.type,VIDEO_TYPE_TV);
  70.         TEST_V4L_FLAG(channel.type,VIDEO_TYPE_CAMERA);        
  71.         PRINT_V4L_FLAGS2(channel.type);

  73.         PRINT_V4L_INT(channel.norm);
  74.         
  75.        }
  76.     
  77.    
  78.    
  79. }

  81. int v4l_query_video_cap(int fd)
  82. {
  83.  int ret;
  84. struct video_capability cap;
  85.  memset(&cap,0,sizeof(cap));
  86. ret = ioctl(fd, VIDIOCGCAP, &cap);
  87. if(ret < 0)
  88.     {
  89.      printf("get vidieo capability error,error code: %d \n", errno);
  90.      return ret;
  91.     }
  92.     PRINT_V4L("general info\n");
  93.     PRINT_IOCTL_CMD(VIDIOCGCAP);

  95.     PRINT_V4L_STRING(cap.name);
  96.     PRINT_V4L_INT(cap.channels);
  97.     PRINT_V4L_INT(cap.audios);
  98.     PRINT_V4L_INT(cap.maxwidth);
  99.     PRINT_V4L_INT(cap.maxheight);
  100.     PRINT_V4L_INT(cap.minwidth);
  101.     PRINT_V4L_INT(cap.minheight);
  102.     
  103.     
  104.     
  105.     PRINT_V4L_FLAGS(cap.type);    
  106.     TEST_V4L_FLAG(cap.type,VID_TYPE_CAPTURE);
  107.     TEST_V4L_FLAG(cap.type,VID_TYPE_TUNER);
  108.     TEST_V4L_FLAG(cap.type,VID_TYPE_TELETEXT);
  109.     TEST_V4L_FLAG(cap.type,VID_TYPE_OVERLAY);
  110.     TEST_V4L_FLAG(cap.type,VID_TYPE_CHROMAKEY);
  111.     TEST_V4L_FLAG(cap.type,VID_TYPE_CLIPPING);
  112.     TEST_V4L_FLAG(cap.type,VID_TYPE_FRAMERAM);
  113.     TEST_V4L_FLAG(cap.type,VID_TYPE_SCALES);
  114.     TEST_V4L_FLAG(cap.type,VID_TYPE_MONOCHROME);
  115.     TEST_V4L_FLAG(cap.type,VID_TYPE_SUBCAPTURE);
  116.     TEST_V4L_FLAG(cap.type,VID_TYPE_MPEG_DECODER);
  117.     TEST_V4L_FLAG(cap.type,VID_TYPE_MPEG_ENCODER);
  118.     TEST_V4L_FLAG(cap.type,VID_TYPE_MJPEG_DECODER);
  119.     TEST_V4L_FLAG(cap.type,VID_TYPE_MJPEG_ENCODER);


  122.     PRINT_V4L_FLAGS2(cap.type);

  124.     v4l_get_channels(fd,cap.channels);
  125.    return 0;

  127. }



  131. int v4l_query_video_picture(int fd)
  132. {

  134.  int ret;
  135.  struct video_picture pic;
  136.  memset(&pic,0,sizeof(pic));
  137.  
  138. ret = ioctl(fd, VIDIOCGPICT, &pic);
  139. if(ret < 0)
  140.     {
  141.      printf("get vidieo picture error,error code: %d \n", errno);
  142.      return ret;
  143.     }

  145.    
  146.     PRINT_IOCTL_CMD(VIDIOCGPICT);
  147.     PRINT_V4L_INT(pic.brightness);
  148.     PRINT_V4L_INT(pic.hue);
  149.     PRINT_V4L_INT(pic.colour);
  150.     PRINT_V4L_INT(pic.contrast);
  151.     PRINT_V4L_INT(pic.whiteness);
  152.     PRINT_V4L_INT(pic.depth);

  154.      PRINT_V4L_MEMBER(pic.palette);
  155.       TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_GREY);
  156.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_HI240);
  157.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_RGB565);
  158.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_RGB24);
  159.     TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_RGB32);
  160.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_RGB555);
  161.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV422);;
  162.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUYV);
  163.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_UYVY);
  164.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV420);
  165.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV411);
  166.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_RAW);
  167.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV422P);
  168.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV411P);
  169.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV420P);
  170.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_YUV410P);
  171.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_PLANAR);
  172.      TEST_V4L_FLAG0(pic.palette,VIDEO_PALETTE_COMPONENT);
  173.     
  174.      PRINT_V4L("\n");

  176.     return 0;
  177. }
  178. int main(int argc,char * argv[])
  179. {
  180.    char dev_name[64] = "/dev/video2";
  181.    int cam_fd =-1;

  183.    if(argc>1)
  184.        {
  185.         strncpy(dev_name,argv[1],sizeof(dev_name)-1);
  186.        }

  188.    
  189.     cam_fd = open(dev_name,O_RDWR|O_NONBLOCK);

  191.     if(cam_fd == -1)
  192.         {
  193.          printf("open failure \n");
  194.          return -1;
  195.         }


  198.     printf("### v4l device info [%s] ###\n",dev_name);

  200.     
  201.    v4l_query_video_cap(cam_fd);
  202.    
  203.    v4l_query_video_picture(cam_fd);
  204.    // get_supported_video_formats(cam_fd);
  205.     close(cam_fd);

  207.    return 0;
  208.     
  209. }





4.测试结果
   使用mini6410,Linux 2.6.28.6,注意这里/dev/video0 ,/dev/video1,是CMOS摄像头,它们的驱动对于 V4l1,并且一运行某些V4L1的ioctl命令的就产生oops.
  关于修正这一些BUG，可以参见我的博文
     <信息的分析>>
     http://blog.chinaunix.net/space.php?uid=20587912&do=blog&id=2163944

使用用USB摄像头,我使用的是ZC301摄像头.设备结点是/dev/video2
 三种测试结果如下:
 

./test_v4l /dev/video2
### v4l device info [/dev/video2] ###
general info
      VIDIOCGCAP = (0x803c7601)
  cap.name            :"PC Camera"
  cap.channels        :1
  cap.audios          :0
  cap.maxwidth        :640
  cap.maxheight       :480
  cap.minwidth        :48
  cap.minheight       :32
  cap.type            :0x1 [VID_TYPE_CAPTURE,]
channels
 VIDIOCGCAP          (0) = (0x803c7601)
  channel.channel     :0
  channel.name        :"zc3xx"
  channel.tuners      :0
  channel.flags       :0x0 []
  channel.type        :0x2 [VIDEO_TYPE_CAMERA,]
  channel.norm        :0
     VIDIOCGPICT = (0x800e7606)
  pic.brightness      :32896
  pic.hue             :0
  pic.colour          :0
  pic.contrast        :32768
  pic.whiteness       :39321
  pic.depth           :8
  pic.palette         :
-----------------------------------------------------------------------

./test_v4l /dev/video0
### v4l device info [/dev/video0] ###

general info
      VIDIOCGCAP = (0x803c7601)
  cap.name            :"s3c-fimc0"
  cap.channels        :2
  cap.audios          :0
  cap.maxwidth        :0
  cap.maxheight       :0
  cap.minwidth        :48
  cap.minheight       :32
  cap.type            :0x29 [VID_TYPE_CAPTURE,VID_TYPE_OVERLAY,VID_TYPE_CLIPPING,]
channels
 VIDIOCGCAP          (0) = (0x803c7601)
  channel.channel     :0
  channel.name        :"External Camera Input"
  channel.tuners      :0
  channel.flags       :0x0 []
  channel.type        :0x2 [VIDEO_TYPE_CAMERA,]
  channel.norm        :0
 VIDIOCGCAP          (1) = (0x803c7601)
  channel.channel     :1
  channel.name        :"Memory Input"
  channel.tuners      :0
  channel.flags       :0x0 []
  channel.type        :0x2 [VIDEO_TYPE_CAMERA,]
  channel.norm        :0
     VIDIOCGPICT = (0x800e7606)
  pic.brightness      :0
  pic.hue             :0
  pic.colour          :0
  pic.contrast        :0
  pic.whiteness       :0
  pic.depth           :32
  pic.palette         :
[root@FriendlyARM 2]#

--------------------------------------------------------------------------------------------------------------------------

./test_v4l /dev/video1
### v4l device info [/dev/video1] ###

general info
      VIDIOCGCAP = (0x803c7601)
  cap.name            :"s3c-fimc1"
  cap.channels        :2
  cap.audios          :0
  cap.maxwidth        :0
  cap.maxheight       :0
  cap.minwidth        :48
  cap.minheight       :32
  cap.type            :0x29 [VID_TYPE_CAPTURE,VID_TYPE_OVERLAY,VID_TYPE_CLIPPING,]
channels
 VIDIOCGCAP          (0) = (0x803c7601)
  channel.channel     :0
  channel.name        :"External Camera Input"
  channel.tuners      :0
  channel.flags       :0x0 []
  channel.type        :0x2 [VIDEO_TYPE_CAMERA,]
  channel.norm        :0
 VIDIOCGCAP          (1) = (0x803c7601)
  channel.channel     :1
  channel.name        :"Memory Input"
  channel.tuners      :0
  channel.flags       :0x0 []
  channel.type        :0x2 [VIDEO_TYPE_CAMERA,]
  channel.norm        :0
     VIDIOCGPICT = (0x800e7606)
  pic.brightness      :0
  pic.hue             :0
  pic.colour          :0
  pic.contrast        :0
  pic.whiteness       :0
  pic.depth           :32
  pic.palette         :
[root@FriendlyARM 2]#



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