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luvcview分析--3.用SDL显示camera的图像

分类： LINUX

2015-08-10 17:42:21

一. 用SDL显示camera图像
1. SDL
虽然把图像写到文件中去己经很好很强大了,但进一步实时的显示图片是不是更好？
这就需要用到SDL了
2. 源码
2.1 display.c
  1. cong@msi:/work/test/uvcview/3display$ cat display.c
  2. #include "utils.h"
  3. #include <sys/types.h>
  4. #include <sys/stat.h>
  5. #include <fcntl.h>
  6. #include <linux/videodev2.h>
  7. #include <sys/mman.h>
  8. #include <SDL/SDL.h>
  9. #define VIDEO_DEVICE "/dev/video0"
  10. #define NB_BUFFER 4
  11. int fd;
  12. int ret = 0;
  13. struct v4l2_capability cap;
  14. struct v4l2_format fmt;
  15. struct v4l2_requestbuffers rb;
  16. struct v4l2_buffer vbuf;
  17. void* vmem[NB_BUFFER];
  18. unsigned char* tempbuffer;
  19. unsigned char* framebuffer;
  20. int type;
  21. int framesize;
  22. int width = 640; //1280; //640;
  23. int height= 480; // 720; // 480;
  24. float fps = 30.0;
  25. int format = V4L2_PIX_FMT_YUYV;

  27. init_camera()
  28. {
  29.     int i;
  30.     if( (fd = v4l2_open(VIDEO_DEVICE,O_RDWR)) == -1)
  31.     {
  32.         dbmsg("error: %s", strerror(errno));
  33.         return 0;
  34.     }
  35.     //check format is valid
  36.     //fix me

  38.     //set format and frame size
  39.     memset(&fmt, 0, sizeof(struct v4l2_fmtdesc));
  40.     fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  41.     fmt.fmt.pix.width = width;
  42.     fmt.fmt.pix.height = height;
  43.     fmt.fmt.pix.field = V4L2_FIELD_ANY;
  44.     if( (ret = v4l2_ioctl(fd, VIDIOC_S_FMT, &fmt)) < 0)
  45.     {
  46.         dbmsg("error: %s", strerror(errno));
  47.         return 0;
  48.     }

  50.     //mmap buffer: reqbufs-> querybuf -> mmap -> QBUF
  51.     memset(&rb, 0, sizeof(struct v4l2_requestbuffers));
  52.     rb.count = NB_BUFFER;
  53.     rb.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  54.     rb.memory = V4L2_MEMORY_MMAP;
  55.     if( (ret = v4l2_ioctl(fd, VIDIOC_REQBUFS, &rb)) < 0 )
  56.     {
  57.         dbmsg("error: %s", strerror(errno));
  58.         return 0;
  59.     }
  60.     for(i=0; i<NB_BUFFER; i++)
  61.     {
  62.         memset(&vbuf, 0, sizeof(struct v4l2_buffer));
  63.         vbuf.index = i;
  64.         vbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  65.         vbuf.memory = V4L2_MEMORY_MMAP;
  66.         if( (ret = v4l2_ioctl(fd, VIDIOC_QUERYBUF, &vbuf)) < 0)
  67.         {
  68.             dbmsg("error: %s", strerror(errno));
  69.             return 0;
  70.         }
  71.         dbmsg("len=%d, offset=%d", vbuf.length, vbuf.m.offset);
  72.         //if( (vmem[i] = v4l2_mmap(0, vbuf.length, PROT_READ, MAP_SHARED, fd, vbuf.m.offset)) == MAP_FAILED)
  73.         if( (vmem[i] = mmap(0, vbuf.length, PROT_READ, MAP_SHARED, fd, vbuf.m.offset)) == MAP_FAILED)    
  74.         {
  75.             dbmsg("error: %s", strerror(errno));
  76.             return 0;
  77.         }
  78.         dbmsg("Buffer mapped at address %p", vmem[i]);
  79.     }
  80.     for(i=0; i<NB_BUFFER; i++)
  81.     {
  82.         memset(&vbuf, 0, sizeof(struct v4l2_buffer));
  83.         vbuf.index = i;
  84.         vbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  85.         vbuf.memory = V4L2_MEMORY_MMAP;
  86.         if( (ret = v4l2_ioctl(fd, VIDIOC_QBUF, &vbuf)) < 0)
  87.         {
  88.             dbmsg("error: %s", strerror(errno));
  89.             return 0;
  90.         }
  91.     }

  93.     //alloc framebuffer
  94.     framesize = ((width*height)<<1);
  95.     if( !(tempbuffer = malloc(framesize)))
  96.     {
  97.         dbmsg("error: %s", strerror(errno));
  98.         return 0;
  99.     }
  100.     if( !(framebuffer = malloc(width*height*8)))
  101.     {
  102.         dbmsg("error: %s", strerror(errno));
  103.         return 0;
  104.     }
  105.     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  106.     if( (ret = v4l2_ioctl(fd, VIDIOC_STREAMON, &type)) < 0)
  107.     {
  108.         dbmsg("error: %s", strerror(errno));
  109.         return 0;
  110.     }
  111. }

  113. int main ( int argc, char *argv[] )
  114. {
  115.     int i;
  116.     SDL_Surface* psscreen;
  117.     SDL_Overlay* overlay;
  118.     SDL_Rect drect;
  119.     unsigned char* p;
  120.     SDL_Init(SDL_INIT_EVERYTHING);
  121.     psscreen = SDL_SetVideoMode(width, height, 0, SDL_SWSURFACE);
  122.     SDL_WM_SetCaption( "YUV Window", NULL);
  123.     /* Create a YUV overlay */
  124.     overlay = SDL_CreateYUVOverlay(width, height, SDL_YUY2_OVERLAY, psscreen);
  125.     p = (unsigned char*) overlay->pixels[0];
  126.     drect.x = 0;
  127.     drect.y = 0;
  128.     drect.w = width;
  129.     drect.h = height;

  131.     init_camera();

  133.     while(1)
  134.     {
  135.         memset(&vbuf, 0, sizeof(struct v4l2_buffer));
  136.         vbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  137.         vbuf.memory = V4L2_MEMORY_MMAP;
  138.         if( (ret = v4l2_ioctl(fd, VIDIOC_DQBUF, &vbuf)) < 0)
  139.         {
  140.             dbmsg("error: %s", strerror(errno));
  141.             return 0;
  142.         }
  143.         if(vbuf.bytesused > framesize)
  144.         {
  145.             memcpy(framebuffer, vmem[vbuf.index], (size_t)framesize);
  146.         }else {
  147.             memcpy(framebuffer, vmem[vbuf.index], (size_t)vbuf.bytesused);
  148.             if( (ret=v4l2_ioctl(fd, VIDIOC_QBUF, &vbuf)) < 0)
  149.             {
  150.                 dbmsg("error: %s", strerror(errno));
  151.                 return 0;
  152.             }
  153.         }
  154.         SDL_LockYUVOverlay(overlay);
  155.         memcpy(p, framebuffer, width*height*2);
  156.         SDL_UnlockYUVOverlay(overlay);
  157.         SDL_DisplayYUVOverlay(overlay, &drect);
  158.         SDL_Delay(10);
  159.     }

  161.     return EXIT_SUCCESS;
  162. }
2.2 Makefile
  1. cong@msi:/work/test/uvcview/3display$ cat Makefile
  2. EXE=display
  3. CC=gcc
  4. SRC=$(wildcard *.c)
  5. #OBJ=$(SRC:.c=.o)
  6. OBJ=$(patsubst %.c,%.o,$(SRC))
  7. DEP=$(patsubst %.c,.%.d,$(SRC))
  8. CFLAGS=-g -O0 -I/work/test/uvcview/libv4l2/libv4l-0.6.1/include -DUSE_SDL -O2 -DLINUX -DVERSION=\"0.2.6\" -D_GNU_SOURCE=1 -D_REENTRANT
  9. #V4L2LIBS = $(shell pkg-config --libs libv4l2) -lSDL
  10. V4L2LIBS = -L/work/test/uvcview/libv4l2/libv4l-0.6.1/libv4l2 -lv4l2 \
  11.          -L/work/test/uvcview/libv4l2/libv4l-0.6.1/libv4lconvert/ -lv4lconvert \
  12.             -lrt -lm -lSDL                       -->链接库中加入了SDL
  13. $(EXE):$(OBJ)
  14.     $(CC) $(CFLAGS) $^ -o $@ $(V4L2LIBS)

  16. $(DEP):.%.d:%.c
  17.     @set -e; rm -f $@; \
  18.     $(CC) -MM $< > $@.$$$$; \
  19.     sed 's,/($*/)/.o[ :]*,/1.o $@ : ,g' < $@.$$$$ > $@; \
  20.     rm -f $@.$$$$

  22. -include $(DEP)
  23. clean:
  24.     @rm $(EXE) $(OBJ) $(DEP) -f
  25. cong@msi:/work/test/uvcview/3display$
3.源码打包
3display.rar (下载后改名为3display.tar.gz)
二. 改进
1. 有图像显示出来了,但是还有几个问题
a. 程序结束不了,只能用kill强制杀死,
    这样做后,下次必需插拔usb摄像头才能正常使用
b. 关于v4l2_mmap这一直有个疑问
    为什么在luvcview的源码中没有问题,而我这儿一用就segment fault呢?
2.1 代码
  1. cong@msi:/work/test/uvcview/3display_1$ cat display.c
  2. #include "utils.h"
  3. #include <sys/types.h>
  4. #include <sys/stat.h>
  5. #include <fcntl.h>
  6. #include <linux/videodev2.h>
  7. #include <sys/mman.h>
  8. #include <SDL/SDL.h>
  9. #include <libv4l2.h>                      //少了一个头文件,带来的问题看下面
  10. #define VIDEO_DEVICE "/dev/video0"
  11. #define NB_BUFFER 4
  12. int fd;
  13. int ret = 0;
  14. struct v4l2_capability cap;
  15. struct v4l2_format fmt;
  16. struct v4l2_requestbuffers rb;
  17. struct v4l2_buffer vbuf;
  18. void* vmem[NB_BUFFER];
  19. unsigned char* tempbuffer;
  20. unsigned char* framebuffer;
  21. int type;
  22. int framesize;
  23. int width = 640; //1280; //640;
  24. int height= 480; // 720; // 480;
  25. float fps = 30.0;
  26. //int format = V4L2_PIX_FMT_MJPEG;
  27. int format = V4L2_PIX_FMT_YUYV;

  29. SDL_mutex *affmutex;
  30. SDL_Event sdlevent;
  31. int signal_quit = 1;

  33. static int eventThread(void* data)               //b.SDL的线程,用来检测事件
  34. {                                                //b.当有退出事件时,把signal_quit置空
  35.     while(signal_quit)                           //b.这时主线程监测到signal_quit为空就退出主线程
  36.     {
  37.         SDL_LockMutex(affmutex);
  38.         while(SDL_PollEvent(&sdlevent))
  39.         {
  40.             switch(sdlevent.type)
  41.             {
  42.                 case SDL_QUIT:
  43.                     {
  44.                         dbmsg("recv quit");
  45.                         signal_quit = 0;
  46.                     }
  47.                     break;
  48.                 default:
  49.                     dbmsg("sdl event");
  50.                     break;

  52.             }
  53.         }
  54.         SDL_UnlockMutex(affmutex);
  55.     }
  56. }
  57. init_camera()
  58. {
  59.     int i;
  60.     if( (fd = v4l2_open(VIDEO_DEVICE,O_RDWR)) == -1)
  61.     {
  62.         dbmsg("error: %s", strerror(errno));
  63.         return 0;
  64.     }
  65.     //check format is valid
  66.     //fix me

  68.     //set format and frame size
  69.     memset(&fmt, 0, sizeof(struct v4l2_fmtdesc));
  70.     fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  71.     fmt.fmt.pix.width = width;
  72.     fmt.fmt.pix.height = height;
  73.     fmt.fmt.pix.field = V4L2_FIELD_ANY;
  74.     if( (ret = v4l2_ioctl(fd, VIDIOC_S_FMT, &fmt)) < 0)
  75.     {
  76.         dbmsg("error: %s", strerror(errno));
  77.         return 0;
  78.     }

  80.     //mmap buffer: reqbufs-> querybuf -> mmap -> QBUF
  81.     memset(&rb, 0, sizeof(struct v4l2_requestbuffers));
  82.     rb.count = NB_BUFFER;
  83.     rb.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  84.     rb.memory = V4L2_MEMORY_MMAP;
  85.     if( (ret = v4l2_ioctl(fd, VIDIOC_REQBUFS, &rb)) < 0 )
  86.     {
  87.         dbmsg("error: %s", strerror(errno));
  88.         return 0;
  89.     }
  90.     for(i=0; i<NB_BUFFER; i++)
  91.     {
  92.         memset(&vbuf, 0, sizeof(struct v4l2_buffer));
  93.         vbuf.index = i;
  94.         vbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  95.         vbuf.memory = V4L2_MEMORY_MMAP;
  96.         if( (ret = v4l2_ioctl(fd, VIDIOC_QUERYBUF, &vbuf)) < 0)
  97.         {
  98.             dbmsg("error: %s", strerror(errno));
  99.             return 0;
  100.         }
  101.         dbmsg("len=%d, offset=%d", vbuf.length, vbuf.m.offset);
  102.         if( (vmem[i] = v4l2_mmap(0, vbuf.length, PROT_READ, MAP_SHARED, fd, vbuf.m.offset)) == MAP_FAILED)
  103.         {
  104.             dbmsg("error: %s", strerror(errno));
  105.             return 0;
  106.         }
  107.         dbmsg("Buffer mapped at address %p", vmem[i]);
  108.     }
  109.     for(i=0; i<NB_BUFFER; i++)
  110.     {
  111.         memset(&vbuf, 0, sizeof(struct v4l2_buffer));
  112.         vbuf.index = i;
  113.         vbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  114.         vbuf.memory = V4L2_MEMORY_MMAP;
  115.         if( (ret = v4l2_ioctl(fd, VIDIOC_QBUF, &vbuf)) < 0)
  116.         {
  117.             dbmsg("error: %s", strerror(errno));
  118.             return 0;
  119.         }
  120.     }

  122.     //alloc framebuffer
  123.     framesize = ((width*height)<<1);
  124.     if( !(tempbuffer = malloc(framesize)))
  125.     {
  126.         dbmsg("error: %s", strerror(errno));
  127.         return 0;
  128.     }
  129.     if( !(framebuffer = malloc(width*height*8)))
  130.     {
  131.         dbmsg("error: %s", strerror(errno));
  132.         return 0;
  133.     }
  134.     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  135.     if( (ret = v4l2_ioctl(fd, VIDIOC_STREAMON, &type)) < 0)
  136.     {
  137.         dbmsg("error: %s", strerror(errno));
  138.         return 0;
  139.     }
  140. }


  143. int main ( int argc, char *argv[] )
  144. {
  145.     int i;
  146.     SDL_Surface* psscreen;
  147.     SDL_Overlay* overlay;
  148.     SDL_Rect drect;
  149.     SDL_Thread* sdl_thread;
  150.     unsigned char* p;
  151.     SDL_Init(SDL_INIT_EVERYTHING);
  152.     psscreen = SDL_SetVideoMode(width, height, 0, SDL_SWSURFACE);
  153.     SDL_WM_SetCaption( "YUV Window", NULL);
  154.     /* Create a YUV overlay */
  155.     overlay = SDL_CreateYUVOverlay(width, height, SDL_YUY2_OVERLAY, psscreen);
  156.     p = (unsigned char*) overlay->pixels[0];
  157.     drect.x = 0;
  158.     drect.y = 0;
  159.     drect.w = width;
  160.     drect.h = height;

  162.     init_camera();

  164.     //sdl get signal quit
  165.     affmutex = SDL_CreateMutex();
  166.     sdl_thread = SDL_CreateThread(eventThread, NULL);            //a.SDL创建线程

  168.     while(signal_quit)                                           //c.当主线程监测到signal_quit为空时,就退出主线程
  169.     {
  170.         memset(&vbuf, 0, sizeof(struct v4l2_buffer));
  171.         vbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  172.         vbuf.memory = V4L2_MEMORY_MMAP;
  173.         if( (ret = v4l2_ioctl(fd, VIDIOC_DQBUF, &vbuf)) < 0)
  174.         {
  175.             dbmsg("error: %s", strerror(errno));
  176.             return 0;
  177.         }
  178.         if(vbuf.bytesused > framesize)
  179.         {
  180.             memcpy(framebuffer, vmem[vbuf.index], (size_t)framesize);
  181.         }else {
  182.             memcpy(framebuffer, vmem[vbuf.index], (size_t)vbuf.bytesused);
  183.             if( (ret=v4l2_ioctl(fd, VIDIOC_QBUF, &vbuf)) < 0)
  184.             {
  185.                 dbmsg("error: %s", strerror(errno));
  186.                 return 0;
  187.             }
  188.         }
  189.         SDL_LockYUVOverlay(overlay);
  190.         memcpy(p, framebuffer, width*height*2);
  191.         SDL_UnlockYUVOverlay(overlay);
  192.         SDL_DisplayYUVOverlay(overlay, &drect);
  193.         SDL_Delay(10);
  194.     }
  195.     SDL_WaitThread(sdl_thread, &ret);                          //d.当线程退出时干清理的事
  196.     SDL_DestroyMutex(affmutex);
  197.     //close_v4l2
  198.     type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  199.     if( (ret=v4l2_ioctl(fd, VIDIOC_STREAMOFF, &type)) < 0)     //d.将STREAM关闭,这样下次还可以打开
  200.     {
  201.         dbmsg("error: %s", strerror(errno));
  202.         return 0;
  203.     }
  204.     if(NULL != framebuffer)
  205.         free(framebuffer);
  206.     framebuffer = NULL;

  208.     return EXIT_SUCCESS;
  209. }
  210. cong@msi:/work/test/uvcview/3display_1$
3. 代码打包
3display_1.rar (下载后改名为3display_1.tar.gz)
4. 说明
a. 为了让程序退出,这儿加入了SDL线程来监听退出事件,有退出事件触发时就通知主while退出
b. 在主while退出时需要把camera的视频关闭,这样下次才可以打开
c.关于为什么老是会出现下面的warning?
  1. display.c:102:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  2.          if( (vmem[i] = v4l2_mmap(0, vbuf.length, PROT_READ, MAP_SHARED, fd, vbuf.m.offset)) == MAP_FAILED)
最后发现原来是#include <libv4l2.h>没有加入头文件,我说这个warning怎么提示v4l2_mmap返回的是integer呢?
看来有些warning也是需要重视的.



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