基于S3C2440的Linux-3.6.6移植——基于UVC的USB摄像头移植及视频显示



基于UVC的USB摄像头的移植很简单，只需要在menuconfig中进行适当的配置即可，如下所示：

Device Drivers --->

     <*> Multimedia support --->

               [*] Video capture adapters--->

                            [*] V4L USBdevices --->

                                        <*> USB Video Class (UVC)

                                        [*]    UVC input events devicesupport

                                        <*> GSPCA based webcams --->

      [*] USB support --->

               [*] USB announce newdevices

                            <*> USB Gadget Support--->

                                       <*>    USB Webcam Gadget

 

经过上述配置以后的系统就能够正确识别出UVC的USB摄像头。把我的罗技C525摄像头插到开发板上，就会显示下列信息：

usb 1-1: new full-speed USB device number 2using s3c2410-ohci

usb 1-1: New USB device found,idVendor=046d, idProduct=0826

usb 1-1: New USB device strings: Mfr=0,Product=2, SerialNumber=1

usb 1-1: Product: HD Webcam C525

usb 1-1: SerialNumber: 19E19A50

uvcvideo: Found UVC 1.00 device HD WebcamC525 (046d:0826)

input: HD Webcam C525 as/devices/platform/s3c2410-ohci/usb1/1-1/1-1:1.2/input/input3

并且在/dev目录下，会自动创建video0设备节点，这就说明该摄像头可以正常使用了。

 

下面就介绍对摄像头的测试，在这里我们是利用摄像头采集视频信号并在LCD上实时显示。要完成上述工作，需要解决三个关键问题。一是V4L2编程；二是LCD的显示；三是彩色空间的转换。

V4L2是内核提供给应用程序访问音、视频驱动的统一接口。它的基本工作流程为：

打开设备文件--->查询设备属性--->设置视频格式--->请求分配内存，并映射到用户空间--->申请到的内存入队列，开始视频采集--->内存出队列，得到原始数据，这时就可以对原始数据进行适当处理--->内存重新入队列，以便循环--->停止采集--->关闭设备。

LCD的显示较简单，主要就是把framebuffer映射到用户空间，对该空间进行操作即可。

摄像头输出的主要格式是YUV422，该格式不能直接用于LCD的显示，所以需要彩色空间的转换，即把它转换为RGB格式。转换的公式其实很简单，但考虑到用于嵌入式系统，因此需要一些优化处理。

 

下面就给出一段完整的视频显示的程序，我的开发板的LCD分辨率为320×240，彩色空间为RGB32，摄像头输出设置为176×144。

#include <unistd.h>#include <linux/fb.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <assert.h>#include <getopt.h>           #include <fcntl.h>            #include <unistd.h>#include <errno.h>#include <malloc.h>#include <sys/stat.h>#include <sys/types.h>#include <sys/time.h>#include <sys/mman.h>#include <sys/ioctl.h>#include <asm/types.h>        #include <linux/videodev2.h>#define CAMERA_DEVICE "/dev/video0"#define FB_DEVICE "/dev/fb0"#define VIDEO_WIDTH 176#define VIDEO_HEIGHT 144#define BUFFER_COUNT 4const int rvarrxyp[]={-180,-179,-177,-176,-175,-173,-172,-170,-169,-167,-166,-165,-163,-162,-160,-159,-158,-156,-155,-153,-152,-151,-149,-148,-146,-145,-144,-142,-141,-139,-138,-137,-135,-134,-132,-131,-129,-128,-127,-125,-124,-122,-121,-120,-118,-117,-115,-114,-113,-111,-110,-108,-107,-106,-104,-103,-101,-100,-99,-97,-96,-94,-93,-91,-90,-89,-87,-86,-84,-83,-82,-80,-79,-77,-76,-75,-73,-72,-70,-69,-68,-66,-65,-63,-62,-61,-59,-58,-56,-55,-53,-52,-51,-49,-48,-46,-45,-44,-42,-41,-39,-38,-37,-35,-34,-32,-31,-30,-28,-27,-25,-24,-23,-21,-20,-18,-17,-15,-14,-13,-11,-10,-8,-7,-6,-4,-3,-1,0,1,3,4,6,7,8,10,11,13,14,15,17,18,20,21,23,24,25,27,28,30,31,32,34,35,37,38,39,41,42,44,45,46,48,49,51,52,53,55,56,58,59,61,62,63,65,66,68,69,70,72,73,75,76,77,79,80,82,83,84,86,87,89,90,91,93,94,96,97,99,100,101,103,104,106,107,108,110,111,113,114,115,117,118,120,121,122,124,125,127,128,129,131,132,134,135,137,138,139,141,142,144,145,146,148,149,151,152,153,155,156,158,159,160,162,163,165,166,167,169,170,172,173,175,176,177,179};const int guarrxyp[]={-44,-44,-44,-43,-43,-42,-42,-42,-41,-41,-41,-40,-40,-40,-39,-39,-39,-38,-38,-38,-37,-37,-37,-36,-36,-36,-35,-35,-35,-34,-34,-34,-33,-33,-32,-32,-32,-31,-31,-31,-30,-30,-30,-29,-29,-29,-28,-28,-28,-27,-27,-27,-26,-26,-26,-25,-25,-25,-24,-24,-23,-23,-23,-22,-22,-22,-21,-21,-21,-20,-20,-20,-19,-19,-19,-18,-18,-18,-17,-17,-17,-16,-16,-16,-15,-15,-15,-14,-14,-13,-13,-13,-12,-12,-12,-11,-11,-11,-10,-10,-10,-9,-9,-9,-8,-8,-8,-7,-7,-7,-6,-6,-6,-5,-5,-4,-4,-4,-3,-3,-3,-2,-2,-2,-1,-1,-1,0,0,0,1,1,1,2,2,2,3,3,3,4,4,4,5,5,6,6,6,7,7,7,8,8,8,9,9,9,10,10,10,11,11,11,12,12,12,13,13,13,14,14,15,15,15,16,16,16,17,17,17,18,18,18,19,19,19,20,20,20,21,21,21,22,22,22,23,23,23,24,24,25,25,25,26,26,26,27,27,27,28,28,28,29,29,29,30,30,30,31,31,31,32,32,32,33,33,34,34,34,35,35,35,36,36,36,37,37,37,38,38,38,39,39,39,40,40,40,41,41,41,42,42,42,43,43,44,44};const int gvarrxyp[]={-92,-91,-90,-90,-89,-88,-87,-87,-86,-85,-85,-84,-83,-82,-82,-81,-80,-80,-79,-78,-77,-77,-76,-75,-75,-74,-73,-72,-72,-71,-70,-70,-69,-68,-67,-67,-66,-65,-65,-64,-63,-62,-62,-61,-60,-60,-59,-58,-57,-57,-56,-55,-54,-54,-53,-52,-52,-51,-50,-49,-49,-48,-47,-47,-46,-45,-44,-44,-43,-42,-42,-41,-40,-39,-39,-38,-37,-37,-36,-35,-34,-34,-33,-32,-32,-31,-30,-29,-29,-28,-27,-27,-26,-25,-24,-24,-23,-22,-22,-21,-20,-19,-19,-18,-17,-16,-16,-15,-14,-14,-13,-12,-11,-11,-10,-9,-9,-8,-7,-6,-6,-5,-4,-4,-3,-2,-1,-1,0,1,1,2,3,4,4,5,6,6,7,8,9,9,10,11,11,12,13,14,14,15,16,16,17,18,19,19,20,21,22,22,23,24,24,25,26,27,27,28,29,29,30,31,32,32,33,34,34,35,36,37,37,38,39,39,40,41,42,42,43,44,44,45,46,47,47,48,49,49,50,51,52,52,53,54,54,55,56,57,57,58,59,60,60,61,62,62,63,64,65,65,66,67,67,68,69,70,70,71,72,72,73,74,75,75,76,77,77,78,79,80,80,81,82,82,83,84,85,85,86,87,87,88,89,90,90,91};const int buarrxyp[]={-228,-226,-224,-222,-221,-219,-217,-215,-213,-212,-210,-208,-206,-205,-203,-201,-199,-197,-196,-194,-192,-190,-189,-187,-185,-183,-181,-180,-178,-176,-174,-173,-171,-169,-167,-165,-164,-162,-160,-158,-157,-155,-153,-151,-149,-148,-146,-144,-142,-141,-139,-137,-135,-133,-132,-130,-128,-126,-125,-123,-121,-119,-117,-116,-114,-112,-110,-109,-107,-105,-103,-101,-100,-98,-96,-94,-93,-91,-89,-87,-85,-84,-82,-80,-78,-76,-75,-73,-71,-69,-68,-66,-64,-62,-60,-59,-57,-55,-53,-52,-50,-48,-46,-44,-43,-41,-39,-37,-36,-34,-32,-30,-28,-27,-25,-23,-21,-20,-18,-16,-14,-12,-11,-9,-7,-5,-4,-2,0,2,4,5,7,9,11,12,14,16,18,20,21,23,25,27,28,30,32,34,36,37,39,41,43,44,46,48,50,52,53,55,57,59,60,62,64,66,68,69,71,73,75,76,78,80,82,84,85,87,89,91,93,94,96,98,100,101,103,105,107,109,110,112,114,116,117,119,121,123,125,126,128,130,132,133,135,137,139,141,142,144,146,148,149,151,153,155,157,158,160,162,164,165,167,169,171,173,174,176,178,180,181,183,185,187,189,190,192,194,196,197,199,201,203,205,206,208,210,212,213,215,217,219,221,222,224,226};typedef struct VideoBuffer {    void   *start;    size_t  length;} VideoBuffer;VideoBuffer framebuf[BUFFER_COUNT];//查表法，把YUV422转换为RGB32void process(unsigned long  *fb_buf, unsigned char *v_buf){    int r,g,b;    int y0,u,y1,v;    y0=(int)*v_buf;    v=(int)*(v_buf+1);    y1=(int)*(v_buf+2);    u=(int)*(v_buf+3);    r=y0+rvarrxyp[v];    g=y0-guarrxyp[u]-gvarrxyp[v];    b=y0+buarrxyp[u];    if (r>255) r=255;    if (r<0) r=0;    if (g>255) g=255;    if (g<0) g=0;    if (b>255) b=255;    if (b<0) b=0;    *fb_buf=(b<<16)+(g<<8)+r;    r=y1+rvarrxyp[v];    g=y1-guarrxyp[u]-gvarrxyp[v];    b=y1+buarrxyp[u];    if (r>255) r=255;    if (r<0) r=0;    if (g>255) g=255;    if (g<0) g=0;    if (b>255) b=255;    if (b<0) b=0;    *(fb_buf+1)=(b<<16)+(g<<8)+r;}int main(){    int i, ret;      // 打开摄像头设备    int fd;    fd = open(CAMERA_DEVICE, O_RDWR, 0);    if (fd < 0) {        printf("Open %s failed\n", CAMERA_DEVICE);        return -1;    }    // 获取驱动信息    struct v4l2_capability cap;    ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);    if (ret < 0) {        printf("VIDIOC_QUERYCAP failed (%d)\n", ret);        return ret;    }    printf("Capability Informations:\n");    printf(" driver: %s\n", cap.driver);    printf(" card: %s\n", cap.card);    printf(" bus_info: %s\n", cap.bus_info);    printf(" version: %u.%u.%u\n", (cap.version>>16)&0XFF, (cap.version>>8)&0XFF,cap.version&0XFF);    printf(" capabilities: %08X\n", cap.capabilities);    // 设置视频格式    struct v4l2_format fmt;    memset(&fmt, 0, sizeof(fmt));    fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;    fmt.fmt.pix.width       = VIDEO_WIDTH;    fmt.fmt.pix.height      = VIDEO_HEIGHT;    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;    fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;    ret = ioctl(fd, VIDIOC_S_FMT, &fmt);    if (ret < 0) {        printf("VIDIOC_S_FMT failed (%d)\n", ret);        return ret;    }    //获取视频格式    ret = ioctl(fd, VIDIOC_G_FMT, &fmt);    if (ret < 0) {        printf("VIDIOC_G_FMT failed (%d)\n", ret);        return ret;    }    // Print Stream Format    printf("Stream Format Informations:\n");    printf(" type: %d\n", fmt.type);    printf(" width: %d\n", fmt.fmt.pix.width);    printf(" height: %d\n", fmt.fmt.pix.height);    char fmtstr[8];    memset(fmtstr, 0, 8);    memcpy(fmtstr, &fmt.fmt.pix.pixelformat, 4);    printf(" pixelformat: %s\n", fmtstr);    printf(" field: %d\n", fmt.fmt.pix.field);    printf(" bytesperline: %d\n", fmt.fmt.pix.bytesperline);    printf(" sizeimage: %d\n", fmt.fmt.pix.sizeimage);    printf(" colorspace: %d\n", fmt.fmt.pix.colorspace);    printf(" priv: %d\n", fmt.fmt.pix.priv);    printf(" raw_date: %s\n", fmt.fmt.raw_data);    //请求分配内存    struct v4l2_requestbuffers reqbuf;        reqbuf.count = BUFFER_COUNT;    reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;    reqbuf.memory = V4L2_MEMORY_MMAP;        ret = ioctl(fd , VIDIOC_REQBUFS, &reqbuf);    if(ret < 0) {        printf("VIDIOC_REQBUFS failed (%d)\n", ret);        return ret;    }    VideoBuffer*  buffers = calloc( reqbuf.count, sizeof(*buffers) );    struct v4l2_buffer buf;    for (i = 0; i < reqbuf.count; i++)     {        buf.index = i;        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;        buf.memory = V4L2_MEMORY_MMAP;        //获取内存空间        ret = ioctl(fd , VIDIOC_QUERYBUF, &buf);        if(ret < 0) {            printf("VIDIOC_QUERYBUF (%d) failed (%d)\n", i, ret);            return ret;        }        //映射到用户空间        framebuf[i].length = buf.length;        framebuf[i].start = (char *) mmap(0, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset);        if (framebuf[i].start == MAP_FAILED) {            printf("mmap (%d) failed: %s\n", i, strerror(errno));            return -1;        }            //内存入队列        ret = ioctl(fd , VIDIOC_QBUF, &buf);        if (ret < 0) {            printf("VIDIOC_QBUF (%d) failed (%d)\n", i, ret);            return -1;        }        printf("Frame buffer %d: address=0x%x, length=%d\n", i, (unsigned int)framebuf[i].start, framebuf[i].length);    }    // 启动视频流    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;    ret = ioctl(fd, VIDIOC_STREAMON, &type);    if (ret < 0) {        printf("VIDIOC_STREAMON failed (%d)\n", ret);        return ret;    }    struct fb_var_screeninfo vinfo;    struct fb_fix_screeninfo finfo;    int x,y;    int fd_fb;    long int screen_size = 0;    unsigned long  *fbp32 = NULL;    //打开LCD设备    fd_fb = open(FB_DEVICE, O_RDWR);    if (!fd_fb)    {        printf("Error: cannot open framebuffer device.\n");        return(1);    }    if (ioctl(fd_fb, FBIOGET_FSCREENINFO, &finfo))    {        printf("Error reading fixed information.\n");        return(2);    }    //获取LCD属性信息    if (ioctl(fd_fb, FBIOGET_VSCREENINFO, &vinfo))    {        printf("Error 2 reading variable information.\n");        return(3);    }    //一屏的字节数    screen_size = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;    printf("LCD:  %dx%d, %dbpp, screen_size = %ld\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel, screen_size );    //映射framebuffer到用户空间    fbp32 = (unsigned long *)mmap(0, screen_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_fb, 0);    if ((int)fbp32 == -1)    {        printf("Error: failed to map framebuffer device to memory.\n");        return(4);    }    printf("start camera testing...\n");    //开始视频显示    while(1)    {        //内存空间出队列        ret = ioctl(fd, VIDIOC_DQBUF, &buf);        if (ret < 0)          {            printf("VIDIOC_DQBUF failed (%d)\n", ret);            return ret;         }       if(vinfo.bits_per_pixel == 32)         {           for(y = 0; y < fmt.fmt.pix.height;  y++)              {               for(x = 0; x < fmt.fmt.pix.width; x++)                   {                   //YUV422转换为RGB32                   process(fbp32+y * vinfo.xres + x, framebuf[buf.index].start+y * fmt.fmt.pix.width*2+x*2);                   x++;                   }               }          }         // 内存重新入队列        ret = ioctl(fd, VIDIOC_QBUF, &buf);        if (ret < 0)           {            printf("VIDIOC_QBUF failed (%d)\n", ret);            return ret;          }    }//while(1)    //释放资源    for (i=0; i< 4; i++)     {        munmap(framebuf[i].start, framebuf[i].length);    }    munmap(fbp32, screen_size);    //关闭设备    close(fd);    close(fd_fb);    return 0;}

这里有一个问题，我的摄像头是支持320×240，但无法实现该格式的视频输出，也不能设置更高的视频分辨率，不知何故？