v4l2 camera测试程序 保存成图片

v4l2 camera测试程序 保存成图片

标签： c语言linuxuvc_camera

2016-04-27 17:09 445人阅读 评论(0) 收藏 举报

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uvc（4）

作者同类文章 X

• •RGB565,RGB24,YUV
• •记录USB摄像头的几个问题
• •Linux UVC driver 独立交叉编译记录
• •linux 下USB 摄像头的使用说明

版权声明：本文为博主原创文章，转载请注明转载地址。

使用的usb camera 是 0ac8:3420，使用网上找到的代码改

保存在图片，中间的LCD部分可以删了，我还要用就没改。

[cpp] view plain copy

print ?

1. /* 
2.  * main.c 
3.  * 
4.  *  Created on: Apr 25, 2016 
5.  *      Author: anzyelay 
6.  */  
7. #include <unistd.h>  
8. #include <linux/fb.h>  
9. #include <stdio.h>  
10. #include <stdlib.h>  
11. #include <string.h>  
12. #include <assert.h>  
13. #include <getopt.h>  
14. #include <fcntl.h>  
15. #include <unistd.h>  
16. #include <errno.h>  
17. #include <malloc.h>  
18. #include <sys/stat.h>  
19. #include <sys/types.h>  
20. #include <sys/time.h>  
21. #include <sys/mman.h>  
22. #include <sys/ioctl.h>  
23.   
24. #include <asm/types.h>  
25. #include <linux/videodev2.h>  
26.   
27. #include "bmp.h"  
28.   
29. #define CAMERA_DEVICE "/dev/video0"  
30. #define FB_DEVICE "/dev/fb0"  
31.   
32. #define VIDEO_WIDTH 640  
33. #define VIDEO_HEIGHT 480  
34. #define BUFFER_COUNT 4  
35.   
36. typedef struct VideoBuffer {  
37.     void   *start;  
38.     size_t  length;  
39. } VideoBuffer;  
40.   
41. VideoBuffer framebuf[BUFFER_COUNT];  
42.   
43. //查表法，把YUV422转换为RGB32  
44. void process(unsigned long *rgb_buf, unsigned char *v_buf)  
45. {  
46.     int r,g,b;  
47.     int u,v;  
48.     int y[2];  
49.     int rv,guv,bu,i;  
50.     unsigned int *fb_buf = (unsigned int *)rgb_buf;  
51.     y[0]=(int)*v_buf;  
52.     v=(int)*(v_buf+1);  
53.     y[1]=(int)*(v_buf+2);  
54.     u=(int)*(v_buf+3);  
55.     rv=rvarrxyp[v];  
56.     guv=guarrxyp[u]+gvarrxyp[v];  
57.     bu=buarrxyp[u];  
58.   
59.     for(i=0;i<2;i++){  
60.         r=y[i]+rv;  
61.         g=y[i]-guv;  
62.         b=y[i]+bu;  
63.         if (r>255) r=255;  
64.         if (r<0) r=0;  
65.         if (g>255) g=255;  
66.         if (g<0) g=0;  
67.         if (b>255) b=255;  
68.         if (b<0) b=0;  
69.         *(fb_buf+i)=(b<<16)+(g<<8)+r;  
70.     }  
71. }  
72.   
73. int main()  
74. {  
75.     int i, ret;  
76.     // 打开摄像头设备  
77.     int fd;  
78.     fd = open(CAMERA_DEVICE, O_RDWR, 0);  
79.     if (fd < 0) {  
80.         printf("Open %s failed\n", CAMERA_DEVICE);  
81.         return -1;  
82.     }  
83.   
84.     // 获取驱动信息  
85.     struct v4l2_capability cap;  
86.     ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);  
87.     if (ret < 0) {  
88.         printf("VIDIOC_QUERYCAP failed (%d)\n", ret);  
89.         goto __error1;  
90.     }  
91.   
92.     printf("Capability Informations:\n");  
93.     printf(" driver: %s\n", cap.driver);  
94.     printf(" card: %s\n", cap.card);  
95.     printf(" bus_info: %s\n", cap.bus_info);  
96.     printf(" version: %u.%u.%u\n", (cap.version>>16)&0XFF, (cap.version>>8)&0XFF,cap.version&0XFF);  
97.     printf(" capabilities: %08X\n", cap.capabilities);  
98.   
99.     // 设置视频格式  
100.     struct v4l2_format fmt;  
101.     memset(&fmt, 0, sizeof(fmt));  
102.     fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
103.     fmt.fmt.pix.width       = VIDEO_WIDTH;  
104.     fmt.fmt.pix.height      = VIDEO_HEIGHT;  
105.     fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;  
106.     fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;  
107.     ret = ioctl(fd, VIDIOC_S_FMT, &fmt);  
108.     if (ret < 0) {  
109.         printf("VIDIOC_S_FMT failed (%d)\n", ret);  
110.         goto __error1;  
111.     }  
112.   
113.     //获取视频格式(原因是设置视频格式时如果有错误，VIDIOC_S_FMT时会自动转换成合作的格式，所以再获取一次)  
114.     ret = ioctl(fd, VIDIOC_G_FMT, &fmt);  
115.     if (ret < 0) {  
116.         printf("VIDIOC_G_FMT failed (%d)\n", ret);  
117.         goto __error1;  
118.     }  
119.     // Print Stream Format  
120.     printf("Stream Format Informations:\n");  
121.     printf(" type: %d\n", fmt.type);  
122.     printf(" width: %d\n", fmt.fmt.pix.width);  
123.     printf(" height: %d\n", fmt.fmt.pix.height);  
124.     char fmtstr[8];  
125.     memset(fmtstr, 0, 8);  
126.     memcpy(fmtstr, &fmt.fmt.pix.pixelformat, 4);  
127.     printf(" pixelformat: %s\n", fmtstr);  
128.     printf(" field: %d\n", fmt.fmt.pix.field);  
129.     printf(" bytesperline: %d\n", fmt.fmt.pix.bytesperline);  
130.     printf(" sizeimage: %d\n", fmt.fmt.pix.sizeimage);  
131.     printf(" colorspace: %d\n", fmt.fmt.pix.colorspace);  
132.     printf(" priv: %d\n", fmt.fmt.pix.priv);  
133.     printf(" raw_date: %s\n", fmt.fmt.raw_data);  
134.   
135. //-----------------------------------------------  
136.     //请求分配内存  
137.     struct v4l2_requestbuffers reqbuf;  
138.     reqbuf.count = BUFFER_COUNT;  
139.     reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
140.     reqbuf.memory = V4L2_MEMORY_MMAP;  
141.   
142.     ret = ioctl(fd , VIDIOC_REQBUFS, &reqbuf);//在内核虚拟地址空间中申请reqbuf.count个连续的内存  
143.     if(ret < 0) {  
144.         printf("VIDIOC_REQBUFS failed (%d)\n", ret);  
145.         goto __error1;  
146.     }  
147.   
148.     struct v4l2_buffer buf;  
149.     for (i = 0; i < reqbuf.count; i++)  
150.     {  
151.         buf.index = i;  
152.         buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
153.         buf.memory = V4L2_MEMORY_MMAP;  
154.         //根据buf.index询访内存为后面的映射做准备（本质就是设置buf.m.offset+=buf.length偏移）  
155.         ret = ioctl(fd , VIDIOC_QUERYBUF, &buf);  
156.         if(ret < 0) {  
157.             printf("VIDIOC_QUERYBUF (%d) failed (%d)\n", i, ret);  
158.             goto __error1;  
159.         }  
160.         //映射到用户空间  
161.         //就是将之前内核分配的视频缓冲（VIDIOC_REQBUFS）映射到用户空间，这样用户空间就可以直接读取内核扑获的视频数据  
162.         //buf.m.offset表示要对内核中的哪个video buffer进行映射操作  
163.         framebuf[i].length = buf.length;  
164.         framebuf[i].start = (char *) mmap(0, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset);  
165.         if (framebuf[i].start == MAP_FAILED) {  
166.             printf("mmap (%d) failed: %s\n", i, strerror(errno));  
167.             ret = -1;  
168.             goto __error1;  
169.         }  
170.   
171.         //内存入队列  
172.         ret = ioctl(fd , VIDIOC_QBUF, &buf);  
173.         if (ret < 0) {  
174.             printf("VIDIOC_QBUF (%d) failed (%d)\n", i, ret);  
175.             goto __error2;  
176.         }  
177.   
178.         printf("Frame buffer %d: address=0x%x, length=%d\n", i,  
179.                 (unsigned long)framebuf[i].start,  
180.                 (unsigned int)framebuf[i].length);  
181.     }  
182. //--------------------------------------  
183.   
184.     // 启动视频流  
185.     enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
186.     ret = ioctl(fd, VIDIOC_STREAMON, &type);  
187.     if (ret < 0) {  
188.         printf("VIDIOC_STREAMON failed (%d)\n", ret);  
189.         goto __error2;  
190.     }  
191.   
192.     struct fb_var_screeninfo vinfo;  
193.     struct fb_fix_screeninfo finfo;  
194.     int x,y;  
195.     int fd_fb;  
196.     long int screen_size = 0;  
197.     unsigned long  *fbp32 = NULL;  
198.     //打开LCD设备  
199.     fd_fb = open(FB_DEVICE, O_RDWR);  
200.     if (fd_fb < 0)  
201.     {  
202.         printf("Error: cannot open framebuffer device.\n");  
203.         goto __error2;  
204.     }  
205.     if (ioctl(fd_fb, FBIOGET_FSCREENINFO, &finfo))  
206.     {  
207.         printf("Error reading fixed information.\n");  
208.         goto __error3;  
209.     }  
210.     //获取LCD属性信息  
211.     if (ioctl(fd_fb, FBIOGET_VSCREENINFO, &vinfo))  
212.     {  
213.         printf("Error 2 reading variable information.\n");  
214.         goto __error3;  
215.     }  
216.   
217.     //一屏的字节数  
218.     screen_size = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;  
219.     printf("LCD:  %dx%d, %dbpp, screen_size = %ld\n",  
220.             vinfo.xres,  
221.             vinfo.yres,  
222.             vinfo.bits_per_pixel,  
223.             screen_size );  
224.   
225.     //映射framebuffer到用户空间  
226.     fbp32 = (unsigned long *)mmap(0, screen_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_fb, 0);  
227.     if (fbp32 == MAP_FAILED)  
228.     {  
229.         printf("Error: failed to map framebuffer device to memory.\n");  
230.         goto __error3;  
231.     }  
232.   
233.     printf("start camera testing...\n");  
234.     //开始视频显示  
235. //    while(1)  
236.     unsigned long *picdata = (unsigned long *)malloc(fmt.fmt.pix.height*fmt.fmt.pix.width*4);  
237.     memset(picdata,0,fmt.fmt.pix.height*fmt.fmt.pix.width*4);  
238.     for(i=0;i<1;i++)  
239.     {  
240.         memset(&buf,0,sizeof(buf));  
241.         buf.index = 0;  
242.         buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
243.         buf.memory = V4L2_MEMORY_MMAP;  
244.         //内存空间出队列  
245.        ret = ioctl(fd, VIDIOC_DQBUF, &buf);  
246.        if (ret < 0)  
247.        {  
248.            printf("VIDIOC_DQBUF failed (%d)\n", ret);  
249.            break;  
250.        }  
251.        if(vinfo.bits_per_pixel == 32)  
252.        {  
253.            //yuv422 两个像素占4个字节（Y0，V，Y1，U），两个像素共用一个UV对，总字节数为W*H*2，  
254.            //而RGB32则正好两个像素是一个LONG型对齐，以LONG为单位一次可计算两个像素点，之后framebuf自增4个字节地址指向一两个像素点  
255.            for(y = 0; y < fmt.fmt.pix.height;  y++)  
256.            {  
257.                for(x = 0; x < fmt.fmt.pix.width/2; x++)  
258.                {  
259.                    //YUV422转换为RGB32  
260. //                   process(fbp32 + y*vinfo.xres + x,  
261. //                         (U8 *)framebuf[buf.index].start + (y*fmt.fmt.pix.width+x)*2);  
262.                    //由于是以long为基数自增，所以一行long数为：width(long)=width(int)/2  
263.                    process((picdata + y*fmt.fmt.pix.width/2 + x),  
264.                            (U8 *)framebuf[buf.index].start + y*fmt.fmt.pix.width*2+x*4);  
265.                }  
266.             }  
267.   
268.         }  
269.   
270.         // 内存重新入队列  
271.         ret = ioctl(fd, VIDIOC_QBUF, &buf);  
272.         if (ret < 0)  
273.           {  
274.             printf("VIDIOC_QBUF failed (%d)\n", ret);  
275.             break;  
276.           }  
277.   
278.     }//while(1)  
279.   
280.     /*save image picture captured*/  
281.     char picname[100];  
282.     sprintf(picname,"./niu_%d*%d.bmp",fmt.fmt.pix.width,fmt.fmt.pix.height);  
283.     GenBmpFile((U8 *)picdata,32,fmt.fmt.pix.width,fmt.fmt.pix.height,picname);  
284.   
285.     //释放fbp32资源  
286.     munmap(fbp32, screen_size);  
287.  __error3://关闭fd_fb设备  
288.     close(fd_fb);  
289.  __error2://释放framebuf资源  
290.     for (i=0; i< 4; i++)  
291.     {  
292.         munmap(framebuf[i].start, framebuf[i].length);  
293.     }  
294.  __error1://关闭fd设备  
295.     close(fd);  
296.     return ret;  
297. }  
298.   
299.   
300. //------------save image picture captured--------///  
301. int GenBmpFile(U8 *pData, U8 bitCountPerPix, U32 width, U32 height, const char *filename)  
302. {  
303.     FILE *fp = fopen(filename, "wb");  
304.     if(!fp)  
305.     {  
306.         printf("fopen failed : %s, %d\n", __FILE__, __LINE__);  
307.         return 0;  
308.     }  
309.     U32 bmppitch = ((width*bitCountPerPix + 31) >> 5) << 2;  
310.     U32 filesize = bmppitch*height;  
311.   
312.     BITMAPFILE bmpfile;  
313.     bmpfile.bfHeader.bfType = 0x4D42;  
314.     bmpfile.bfHeader.bfSize = filesize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);  
315.     bmpfile.bfHeader.bfReserved1 = 0;  
316.     bmpfile.bfHeader.bfReserved2 = 0;  
317.     bmpfile.bfHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);  
318.   
319.     bmpfile.biInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);  
320.     bmpfile.biInfo.bmiHeader.biWidth = width;  
321.     bmpfile.biInfo.bmiHeader.biHeight = height;  
322.     bmpfile.biInfo.bmiHeader.biPlanes = 1;  
323.     bmpfile.biInfo.bmiHeader.biBitCount = bitCountPerPix;  
324.     bmpfile.biInfo.bmiHeader.biCompression = 0;  
325.     bmpfile.biInfo.bmiHeader.biSizeImage = filesize;  
326.     bmpfile.biInfo.bmiHeader.biXPelsPerMeter = 0;  
327.     bmpfile.biInfo.bmiHeader.biYPelsPerMeter = 0;  
328.     bmpfile.biInfo.bmiHeader.biClrUsed = 0;  
329.     bmpfile.biInfo.bmiHeader.biClrImportant = 0;  
330.   
331.     fwrite(&(bmpfile.bfHeader), sizeof(BITMAPFILEHEADER), 1, fp);  
332.     fwrite(&(bmpfile.biInfo.bmiHeader), sizeof(BITMAPINFOHEADER), 1, fp);  
333.     fwrite(pData,filesize,1, fp);  
334. //    U8 *pEachLinBuf = (U8*)malloc(bmppitch);  
335. //    memset(pEachLinBuf, 0, bmppitch);  
336. //    U8 BytePerPix = bitCountPerPix >> 3;  
337. //    U32 pitch = width * BytePerPix;  
338. //    if(pEachLinBuf)  
339. //    {  
340. //        int h,w;  
341. //        for(h = height-1; h >= 0; h--)  
342. //        {  
343. //            for(w = 0; w < width; w++)  
344. //            {  
345. //                //copy by a pixel  
346. //                pEachLinBuf[w*BytePerPix+0] = pData[h*pitch + w*BytePerPix + 0];  
347. //                pEachLinBuf[w*BytePerPix+1] = pData[h*pitch + w*BytePerPix + 1];  
348. //                pEachLinBuf[w*BytePerPix+2] = pData[h*pitch + w*BytePerPix + 2];  
349. //            }  
350. //            fwrite(pEachLinBuf, bmppitch, 1, fp);  
351. //  
352. //        }  
353. //        free(pEachLinBuf);  
354. //    }  
355.   
356.     fclose(fp);  
357.   
358.     return 1;  
359. }  

/*
 * main.c
 *
 *  Created on: Apr 25, 2016
 *      Author: anzyelay
 */
#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>

#include "bmp.h"

#define CAMERA_DEVICE "/dev/video0"
#define FB_DEVICE "/dev/fb0"

#define VIDEO_WIDTH 640
#define VIDEO_HEIGHT 480
#define BUFFER_COUNT 4

typedef struct VideoBuffer {
    void   *start;
    size_t  length;
} VideoBuffer;

VideoBuffer framebuf[BUFFER_COUNT];

//查表法，把YUV422转换为RGB32
void process(unsigned long *rgb_buf, unsigned char *v_buf)
{
    int r,g,b;
    int u,v;
    int y[2];
    int rv,guv,bu,i;
    unsigned int *fb_buf = (unsigned int *)rgb_buf;
    y[0]=(int)*v_buf;
    v=(int)*(v_buf+1);
    y[1]=(int)*(v_buf+2);
    u=(int)*(v_buf+3);
    rv=rvarrxyp[v];
    guv=guarrxyp[u]+gvarrxyp[v];
    bu=buarrxyp[u];

    for(i=0;i<2;i++){
        r=y[i]+rv;
        g=y[i]-guv;
        b=y[i]+bu;
        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+i)=(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);
        goto __error1;
    }

    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);
        goto __error1;
    }

    //获取视频格式(原因是设置视频格式时如果有错误，VIDIOC_S_FMT时会自动转换成合作的格式，所以再获取一次)
    ret = ioctl(fd, VIDIOC_G_FMT, &fmt);
    if (ret < 0) {
        printf("VIDIOC_G_FMT failed (%d)\n", ret);
        goto __error1;
    }
    // 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);//在内核虚拟地址空间中申请reqbuf.count个连续的内存
    if(ret < 0) {
        printf("VIDIOC_REQBUFS failed (%d)\n", ret);
        goto __error1;
    }

    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;
        //根据buf.index询访内存为后面的映射做准备（本质就是设置buf.m.offset+=buf.length偏移）
        ret = ioctl(fd , VIDIOC_QUERYBUF, &buf);
        if(ret < 0) {
            printf("VIDIOC_QUERYBUF (%d) failed (%d)\n", i, ret);
            goto __error1;
        }
        //映射到用户空间
        //就是将之前内核分配的视频缓冲（VIDIOC_REQBUFS）映射到用户空间，这样用户空间就可以直接读取内核扑获的视频数据
        //buf.m.offset表示要对内核中的哪个video buffer进行映射操作
        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));
            ret = -1;
            goto __error1;
        }

        //内存入队列
        ret = ioctl(fd , VIDIOC_QBUF, &buf);
        if (ret < 0) {
            printf("VIDIOC_QBUF (%d) failed (%d)\n", i, ret);
            goto __error2;
        }

        printf("Frame buffer %d: address=0x%x, length=%d\n", i,
        		(unsigned long)framebuf[i].start,
        		(unsigned int)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);
        goto __error2;
    }

    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 < 0)
    {
        printf("Error: cannot open framebuffer device.\n");
        goto __error2;
    }
    if (ioctl(fd_fb, FBIOGET_FSCREENINFO, &finfo))
    {
        printf("Error reading fixed information.\n");
        goto __error3;
    }
    //获取LCD属性信息
    if (ioctl(fd_fb, FBIOGET_VSCREENINFO, &vinfo))
    {
        printf("Error 2 reading variable information.\n");
        goto __error3;
    }

    //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 (fbp32 == MAP_FAILED)
    {
        printf("Error: failed to map framebuffer device to memory.\n");
        goto __error3;
    }

    printf("start camera testing...\n");
    //开始视频显示
//    while(1)
    unsigned long *picdata = (unsigned long *)malloc(fmt.fmt.pix.height*fmt.fmt.pix.width*4);
    memset(picdata,0,fmt.fmt.pix.height*fmt.fmt.pix.width*4);
    for(i=0;i<1;i++)
    {
    	memset(&buf,0,sizeof(buf));
        buf.index = 0;
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
    	//内存空间出队列
       ret = ioctl(fd, VIDIOC_DQBUF, &buf);
       if (ret < 0)
       {
           printf("VIDIOC_DQBUF failed (%d)\n", ret);
           break;
       }
       if(vinfo.bits_per_pixel == 32)
       {
    	   //yuv422 两个像素占4个字节（Y0，V，Y1，U），两个像素共用一个UV对，总字节数为W*H*2，
    	   //而RGB32则正好两个像素是一个LONG型对齐，以LONG为单位一次可计算两个像素点，之后framebuf自增4个字节地址指向一两个像素点
    	   for(y = 0; y < fmt.fmt.pix.height;  y++)
           {
               for(x = 0; x < fmt.fmt.pix.width/2; x++)
               {
                   //YUV422转换为RGB32
//                   process(fbp32 + y*vinfo.xres + x,
//                		   (U8 *)framebuf[buf.index].start + (y*fmt.fmt.pix.width+x)*2);
            	   //由于是以long为基数自增，所以一行long数为：width(long)=width(int)/2
            	   process((picdata + y*fmt.fmt.pix.width/2 + x),
            			   (U8 *)framebuf[buf.index].start + y*fmt.fmt.pix.width*2+x*4);
               }
            }

        }

        // 内存重新入队列
        ret = ioctl(fd, VIDIOC_QBUF, &buf);
        if (ret < 0)
          {
            printf("VIDIOC_QBUF failed (%d)\n", ret);
            break;
          }

    }//while(1)

    /*save image picture captured*/
    char picname[100];
    sprintf(picname,"./niu_%d*%d.bmp",fmt.fmt.pix.width,fmt.fmt.pix.height);
    GenBmpFile((U8 *)picdata,32,fmt.fmt.pix.width,fmt.fmt.pix.height,picname);

    //释放fbp32资源
    munmap(fbp32, screen_size);
 __error3://关闭fd_fb设备
 	close(fd_fb);
 __error2://释放framebuf资源
    for (i=0; i< 4; i++)
    {
        munmap(framebuf[i].start, framebuf[i].length);
    }
 __error1://关闭fd设备
    close(fd);
    return ret;
}


//------------save image picture captured--------///
int GenBmpFile(U8 *pData, U8 bitCountPerPix, U32 width, U32 height, const char *filename)
{
    FILE *fp = fopen(filename, "wb");
    if(!fp)
    {
        printf("fopen failed : %s, %d\n", __FILE__, __LINE__);
        return 0;
    }
    U32 bmppitch = ((width*bitCountPerPix + 31) >> 5) << 2;
    U32 filesize = bmppitch*height;

    BITMAPFILE bmpfile;
    bmpfile.bfHeader.bfType = 0x4D42;
    bmpfile.bfHeader.bfSize = filesize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmpfile.bfHeader.bfReserved1 = 0;
    bmpfile.bfHeader.bfReserved2 = 0;
    bmpfile.bfHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    bmpfile.biInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpfile.biInfo.bmiHeader.biWidth = width;
    bmpfile.biInfo.bmiHeader.biHeight = height;
    bmpfile.biInfo.bmiHeader.biPlanes = 1;
    bmpfile.biInfo.bmiHeader.biBitCount = bitCountPerPix;
    bmpfile.biInfo.bmiHeader.biCompression = 0;
    bmpfile.biInfo.bmiHeader.biSizeImage = filesize;
    bmpfile.biInfo.bmiHeader.biXPelsPerMeter = 0;
    bmpfile.biInfo.bmiHeader.biYPelsPerMeter = 0;
    bmpfile.biInfo.bmiHeader.biClrUsed = 0;
    bmpfile.biInfo.bmiHeader.biClrImportant = 0;

    fwrite(&(bmpfile.bfHeader), sizeof(BITMAPFILEHEADER), 1, fp);
    fwrite(&(bmpfile.biInfo.bmiHeader), sizeof(BITMAPINFOHEADER), 1, fp);
    fwrite(pData,filesize,1, fp);
//    U8 *pEachLinBuf = (U8*)malloc(bmppitch);
//    memset(pEachLinBuf, 0, bmppitch);
//    U8 BytePerPix = bitCountPerPix >> 3;
//    U32 pitch = width * BytePerPix;
//    if(pEachLinBuf)
//    {
//        int h,w;
//        for(h = height-1; h >= 0; h--)
//        {
//            for(w = 0; w < width; w++)
//            {
//                //copy by a pixel
//                pEachLinBuf[w*BytePerPix+0] = pData[h*pitch + w*BytePerPix + 0];
//                pEachLinBuf[w*BytePerPix+1] = pData[h*pitch + w*BytePerPix + 1];
//                pEachLinBuf[w*BytePerPix+2] = pData[h*pitch + w*BytePerPix + 2];
//            }
//            fwrite(pEachLinBuf, bmppitch, 1, fp);
//
//        }
//        free(pEachLinBuf);
//    }

    fclose(fp);

    return 1;
}

bmp.h

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1. /* 
2.  * bmp.h 
3.  * 
4.  *  Created on: Apr 26, 2016 
5.  *      Author: anzyelay 
6.  */  
7.   
8. #ifndef BMP_H_  
9. #define BMP_H_  
10.   
11. #pragma pack(push, 1)  
12. typedef unsigned char  U8;  
13. typedef unsigned short U16;  
14. typedef unsigned int   U32;  
15.   
16. typedef struct tagBITMAPFILEHEADER  
17. {  
18.  U16 bfType;  
19.  U32 bfSize;  
20.  U16 bfReserved1;  
21.  U16 bfReserved2;  
22.  U32 bfOffBits;  
23. } BITMAPFILEHEADER;  
24.   
25. typedef struct tagBITMAPINFOHEADER  
26. {  
27.  U32 biSize;  
28.  U32 biWidth;  
29.  U32 biHeight;  
30.  U16 biPlanes;  
31.  U16 biBitCount;  
32.  U32 biCompression;  
33.  U32 biSizeImage;  
34.  U32 biXPelsPerMeter;  
35.  U32 biYPelsPerMeter;  
36.  U32 biClrUsed;  
37.  U32 biClrImportant;  
38. } BITMAPINFOHEADER;  
39.   
40. typedef struct tagRGBQUAD  
41. {  
42.  U8 rgbBlue;  
43.  U8 rgbGreen;  
44.  U8 rgbRed;  
45.  U8 rgbReserved;  
46. } RGBQUAD;  
47.   
48. typedef struct tagBITMAPINFO  
49. {  
50.  BITMAPINFOHEADER bmiHeader;  
51.  RGBQUAD bmiColors[1];  
52. } BITMAPINFO;  
53.   
54.   
55. typedef struct tagBITMAP  
56. {  
57.  BITMAPFILEHEADER bfHeader;  
58.  BITMAPINFO biInfo;  
59. }BITMAPFILE;  
60.   
61. #pragma pack(pop)  
62.   
63. int GenBmpFile(U8 *pData, U8 bitCountPerPix, U32 width, U32 height, const char *filename);  
64.   
65. //YUV422转换为RGB32表  
66. const int rvarrxyp[]={  
67. -180,-179,-177,-176,-175,-173,-172,-170,-169,-167,-166,-165,-163,-162,-160,-159,-158,-156,-155,-153,-152,-151,  
68. -149,-148,-146,-145,-144,-142,-141,-139,-138,-137,-135,-134,-132,-131,-129,-128,-127,-125,-124,-122,-121,-120,  
69. -118,-117,-115,-114,-113,-111,-110,-108,-107,-106,-104,-103,-101,-100,-99,-97,-96,-94,-93,-91,-90,-89,-87,-86,  
70. -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,  
71. -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,  
72. -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,  
73. 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,  
74. 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,  
75. 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,  
76. 176,177,179};  
77.   
78. const int guarrxyp[]={  
79. -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,  
80. -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,  
81. -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,  
82. -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,  
83. -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,  
84. 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,  
85. 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,  
86. 39,39,39,40,40,40,41,41,41,42,42,42,43,43,44,44};  
87.   
88. const int gvarrxyp[]={  
89. -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,  
90. -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,  
91. -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,  
92. -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,  
93. -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,  
94. 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,  
95. 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,  
96. 77,78,79,80,80,81,82,82,83,84,85,85,86,87,87,88,89,90,90,91};  
97.   
98. const int buarrxyp[]={  
99. -228,-226,-224,-222,-221,-219,-217,-215,-213,-212,-210,-208,-206,-205,-203,-201,-199,-197,-196,-194,-192,-190,-189,  
100. -187,-185,-183,-181,-180,-178,-176,-174,-173,-171,-169,-167,-165,-164,-162,-160,-158,-157,-155,-153,-151,-149,-148,  
101. -146,-144,-142,-141,-139,-137,-135,-133,-132,-130,-128,-126,-125,-123,-121,-119,-117,-116,-114,-112,-110,-109,-107,  
102. -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,  
103. -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,  
104. -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,  
105. 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,  
106. 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,  
107. 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};  
108.   
109.   
110. #endif /* BMP_H_ */  

/*
 * bmp.h
 *
 *  Created on: Apr 26, 2016
 *      Author: anzyelay
 */

#ifndef BMP_H_
#define BMP_H_

#pragma pack(push, 1)
typedef unsigned char  U8;
typedef unsigned short U16;
typedef unsigned int   U32;

typedef struct tagBITMAPFILEHEADER
{
 U16 bfType;
 U32 bfSize;
 U16 bfReserved1;
 U16 bfReserved2;
 U32 bfOffBits;
} BITMAPFILEHEADER;

typedef struct tagBITMAPINFOHEADER
{
 U32 biSize;
 U32 biWidth;
 U32 biHeight;
 U16 biPlanes;
 U16 biBitCount;
 U32 biCompression;
 U32 biSizeImage;
 U32 biXPelsPerMeter;
 U32 biYPelsPerMeter;
 U32 biClrUsed;
 U32 biClrImportant;
} BITMAPINFOHEADER;

typedef struct tagRGBQUAD
{
 U8 rgbBlue;
 U8 rgbGreen;
 U8 rgbRed;
 U8 rgbReserved;
} RGBQUAD;

typedef struct tagBITMAPINFO
{
 BITMAPINFOHEADER bmiHeader;
 RGBQUAD bmiColors[1];
} BITMAPINFO;


typedef struct tagBITMAP
{
 BITMAPFILEHEADER bfHeader;
 BITMAPINFO biInfo;
}BITMAPFILE;

#pragma pack(pop)

int GenBmpFile(U8 *pData, U8 bitCountPerPix, U32 width, U32 height, const char *filename);

//YUV422转换为RGB32表
const 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};


#endif /* BMP_H_ */

此代码在PC机上可以正常显示，但下到开发板老是出现

[cpp] view plain copy

print ?

1. VIDIOC_S_FMT failed -1  

VIDIOC_S_FMT failed -1

此错误，

检查 发现是 设置格式错误，百度各种说法，有说是pixelformat格式不对的，但在PC机上却是正常的，不管了，先换换，把VIDIOC_S_FMT 和 VIDIOC_G_FMT 反下，先查询支持什么格式再设置，

更改如下

[cpp] view plain copy

print ?

1. // 设置视频格式  
2.     struct v4l2_format <span style="color:#FF0000;">fmt1</span>,fmt;    //fmt1临时查询格式使用  
3.     memset(&fmt1, 0, sizeof(fmt1));  
4.     memset(&fmt, 0, sizeof(fmt));  
5.     fmt1.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;</span>  
6.     //先获取视频格式  
7.     ret = ioctl(fd, VIDIOC_G_FMT, &fmt1);  
8.     if (ret < 0) {  
9.         printf("VIDIOC_G_FMT failed (%d)\n", ret);  
10.         goto __error1;  
11.     }  
12.     fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;  
13.     fmt.fmt.pix.width       = VIDEO_WIDTH;  
14.     fmt.fmt.pix.height      = VIDEO_HEIGHT;  
15.     fmt.fmt.pix.pixelformat = fmt1.fmt.pix.pixelformat;   //把上面查询到地格式赋给要设置的变量  
16.     fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;  
17.     ret = ioctl(fd, VIDIOC_S_FMT, &fmt);  
18.     if (ret < 0) {  
19.         printf("VIDIOC_S_FMT failed (%d)\n", ret);  
20.         goto __error1;  
21.     }  

// 设置视频格式
    struct v4l2_format <span style="color:#FF0000;">fmt1</span>,fmt;    //fmt1临时查询格式使用
    memset(&fmt1, 0, sizeof(fmt1));
    memset(&fmt, 0, sizeof(fmt));
    fmt1.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;</span>
    //先获取视频格式
    ret = ioctl(fd, VIDIOC_G_FMT, &fmt1);
    if (ret < 0) {
        printf("VIDIOC_G_FMT failed (%d)\n", ret);
        goto __error1;
    }
    fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width       = VIDEO_WIDTH;
    fmt.fmt.pix.height      = VIDEO_HEIGHT;
    fmt.fmt.pix.pixelformat = fmt1.fmt.pix.pixelformat;   //把上面查询到地格式赋给要设置的变量
    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);
        goto __error1;
    }

编译在PC上可正常能过，调试信息时： pixelformat: YUYV

下到板子上也能正常运行下去了，调试信息：pixelformat: MJPG

输出格式居然不一样。。。。。。

终于知道错误原因了，应该是开发板和电脑上的UVC驱动版本不一样导致输出的支持格式不一。优化下代码，转MJPG格式输出，MJPG保存图片函数：

//保存为图片  test.jpg
int GenJpgFile(VideoBuffer *buffers,const char *filename){
    FILE *fp = NULL;
    fp = fopen(filename, "w");
    if(fp != NULL){
        fwrite(buffers->start, 1,buffers->length, fp);
        sync();
        fclose(fp);
        return 1;
    }
    return 0;
}

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