linux系统V4L2架构OV3640摄像头视频捕获保存图片jpg格式

大家好，我aiku，最近在做一个linux摄像头的应用程序，主要功能是：arm板子210跑linux系统，进行摄像头视频采集，捕获一帧视频然后保存成图片。功能很简单，但是我确搞了很久，过程中遇到了很多问题，在此写下点滴记录以备忘，还有很多问题待决解……

硬件平台：arm cotex-A8（s5pv210开发板） + ov3640 CMOS摄像头

软件平台： (1)开发平台：xp系统上装的virtualbox-2.6.8虚拟机 + ubuntu12.04

(2)arm板子系统：linux 2.6.35 内核 + qtopia文件系统

一、摄像头程序：

1、源代码：camera3640.c

#include "classroom.h"

/*******************************************************************************************************************************************************************/

extern char * chpt_lcd_mmap_addr; //lcd的缓存指针
extern unsigned int int_lcd_width; //lcd的宽度
extern unsigned  int int_lcd_height; //lcd的高度
extern unsigned int int_lcd_pixel; //lcd的像素

extern unsigned int cameratimes; //Camera采集的次数控制变量
extern const unsigned int camMaxtime; //Camera最多采集的次数

struct buffer  // 每个缓冲帧的数据结构
{
void * start;
size_t length;
}*buffers;

const char * CameraName = "/dev/video0"; //摄像头设备名
int cam_fd = -1; //摄像头打开文件

static int n_buffers = 0;

unsigned int times = 0;
unsigned int bufferLenth = 0;

/*******************************************************************************************************************************************************************/

void cameraOpen(void)
{
cam_fd = open( CameraName, O_RDWR | O_NONBLOCK, 0 );  //阻塞方式打开摄像头
if(cam_fd < 0)
{
printf("Open fimc0 error.\n");
exit(1);
}
}

void cameraInit(void)
{
struct v4l2_capability cap;
int ret = 0;
unsigned int min;
struct v4l2_input input;

ret = ioctl( cam_fd, VIDIOC_QUERYCAP, &cap );
if( ret < 0 )
{
printf("set VIDIOC_QUERYCAP error.\n");
exit(1);
}

if( !(cap.capabilities & V4L2_CAP_STREAMING) )
{
printf("%s can not streaming.\n");
exit(1);
}

input.index = 0;

if ((ioctl(cam_fd, VIDIOC_S_INPUT, &input)) < 0) //单输入模式
{
printf("set s_input error.\n");
exit(1);
}

//设置视频的格式
struct v4l2_format fmt;

CLEAR(fmt);

fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; //数据流类型，永远是：V4L2_BUF_TYPE_VIDEO_CAPTURE
fmt.fmt.pix.width = int_lcd_width; //800 宽，必须是16的倍数
fmt.fmt.pix.height = int_lcd_height; //400 高，必须是16的倍数
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB32;  //视频数据存储类型，例如是YUV4：2：2还是RGB
fmt.fmt.pix.field = V4L2_FIELD_ANY;

if ( ioctl(cam_fd, VIDIOC_S_FMT, &fmt) == -1 )
{
printf("set format error\n");
}
//如果该视频设备驱动不支持你所设定的图像格式，视频驱动会重新修改struct v4l2_format结构体变量的值为该视频设备所支持的图像格式，
//所以在程序设计中，设定完所有的视频格式后，要获取实际的视频格式，要重新读取struct v4l2_format结构体变量。
if(ioctl(cam_fd, VIDIOC_G_FMT, &fmt) == -1)
{
printf("Unable to get format\n");
exit(1);
}
{
printf("fmt.type:\t\t%d\n",fmt.type);
printf("pix.pixelformat:\t%c%c%c%c\n",fmt.fmt.pix.pixelformat & 0xFF, (fmt.fmt.pix.pixelformat >> 8) & 0xFF,
(fmt.fmt.pix.pixelformat >> 16) & 0xFF, (fmt.fmt.pix.pixelformat >> 24) & 0xFF);
printf("pix.height:\t\t%d\n",fmt.fmt.pix.height);
printf("pix.width:\t\t%d\n",fmt.fmt.pix.width);
printf("pix.field:\t\t%d\n",fmt.fmt.pix.field);
}

//printf("real format is %d X %d,pixel is %d!\n",fmt.fmt.pix.width,fmt.fmt.pix.height,fmt.fmt.pix.pixelformat);

if( int_lcd_width != fmt.fmt.pix.width )
{
int_lcd_width = fmt.fmt.pix.width;
fprintf(stderr,"Image width set to %i by device %s.\n", int_lcd_width, CameraName );
}
if( int_lcd_height != fmt.fmt.pix.height )
{
int_lcd_height = fmt.fmt.pix.height;
fprintf(stderr, "Image height set to %i by device %s.\n", int_lcd_height, CameraName );
}

min = fmt.fmt.pix.width * 2;
if( fmt.fmt.pix.bytesperline < min )
{
fmt.fmt.pix.bytesperline = min;
}

min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
if( fmt.fmt.pix.sizeimage < min )
{
fmt.fmt.pix.sizeimage = min;
}

mmapInit();

}

void mmapInit(void) //内存映射
{
struct v4l2_requestbuffers req;

CLEAR (req);

req.count = 4;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;

if (-1 == xioctl(cam_fd, VIDIOC_REQBUFS, &req))//申请缓存，count是申请的数量
{

if (EINVAL == errno)
{
fprintf(stderr, "%s does not support memory mapping\n", CameraName);
exit(EXIT_FAILURE);
}
else
{
errno_exit("VIDIOC_REQBUFS");
}
}

if (req.count < 2)
{
fprintf(stderr, "Insufficient buffer memory on %s\n", CameraName);
exit(EXIT_FAILURE);
}

buffers = (struct buffer*)calloc(req.count, sizeof(*buffers));//内存中建立对应的空间

if (!buffers)
{
fprintf(stderr, "Out of memory\n");
exit(EXIT_FAILURE);
}

for (n_buffers = 0; n_buffers < req.count; ++n_buffers)//申请4帧缓存
{
struct v4l2_buffer buf;  //驱动中的一帧

CLEAR (buf);

buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;

if (-1 == xioctl(cam_fd, VIDIOC_QUERYBUF, &buf))//映射用户空间
{
errno_exit("VIDIOC_QUERYBUF");
}

buffers[n_buffers].length = buf.length;

//通过mmap()建立映射关系
buffers[n_buffers].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, cam_fd, buf.m.offset);

if (MAP_FAILED == buffers[n_buffers].start)
{
errno_exit("mmap");
}
}
}

void captureStart(void)
{
unsigned int i;
enum v4l2_buf_type type;

for ( i = 0; i < n_buffers; ++i )
{
struct v4l2_buffer buf;

CLEAR (buf);

buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;

if (-1 == xioctl(cam_fd, VIDIOC_QBUF, &buf))//申请到的缓存进入队列
{
errno_exit("VIDIOC_QBUF");
}
}

type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

if ( -1 == xioctl(cam_fd, VIDIOC_STREAMON, &type) )//开始捕获图像数据
{
errno_exit("VIDIOC_STREAMON");
}

}

void mainLoop(void)
{
unsigned int count;

count = 1;

while (count-- > 0)
{
for ( ; ; )
{
fd_set fds;
struct timeval tv;
int r;

FD_ZERO(&fds); //将指定的文件描述符集清空
FD_SET(cam_fd, &fds); //在文件描述符集中增加一个新的文件描述符

tv.tv_sec = 2;
tv.tv_usec = 0;

r = select(cam_fd + 1, &fds, NULL, NULL, &tv); //判断是否可读（即摄像头是否准备好），tv是等待的时间

if (-1 == r)
{
if (EINTR == errno)
continue;
errno_exit("select");
}

if (0 == r)
{
fprintf (stderr, "select timeout\n");
exit(EXIT_FAILURE);
}

if ( frameRead() )//如果可读则执行frameRead()并跳出循环
{
break;
}
}
}
}

unsigned char* frameRead(void)
{

struct v4l2_buffer buf;

CLEAR (buf);

buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;

if (-1 == xioctl(cam_fd, VIDIOC_DQBUF, &buf)) //列出采集的帧缓存
{
switch (errno)
{
case EAGAIN:
return 0;

case EIO:
default:
errno_exit("VIDIOC_DQBUF");
}
}

assert (buf.index < n_buffers);

imageProcess(buffers[buf.index].start); //拷贝视频到lcd

bufferLenth = buffers[buf.index].length;

if (-1 == xioctl(cam_fd, VIDIOC_QBUF, &buf))//再将其入列
{
errno_exit("VIDIOC_QBUF");
}

return (unsigned  char*)buffers[buf.index].start;
}

void imageProcess(const void* p)
{
unsigned char* src = (unsigned  char*)p;//摄像头采集的图像数据

cameratimes++;
printf("\n--------- this is %d times.\n",cameratimes);
printf("========= bufferLenth = %d.\n",bufferLenth);
printf("+++++++++ string length = %d.\n",strlen(src));
if(cameratimes >= camMaxtime)
{
//productBmp(src); //生成bmp图片
jpgImageProduct(src); //生成jpg图片
memcpy( chpt_lcd_mmap_addr, src, int_lcd_width*int_lcd_height*4 );  //在LCD液晶屏显示
}

}

void errno_exit(const char * s)
{
fprintf( stderr, "%s error %d, %s\n", s, errno, strerror(errno) );
exit(EXIT_FAILURE);
}

int xioctl(  int ffd, int request,  void * argp)
{
int r;

do
{
r = ioctl( ffd, request, argp );
}
while( r == -1 && EINTR == errno );

return r;
}

2、执行流程：

(1)打开设备：cameraOpen()

(2)设备初始化：cameraInit()

(3)建立内存映射：mmapInit()

(4)开始视频采集并捕获图像数据：captureStart()

(5)循环采集：mainLoop()

(6)读取数据：frameRead()

(7)数据处理：imageProcess()

3、常见错误及解决方法：

(1) No capture device info

VIDIOC_REQBUFS error 19, No such device

这个错误纠结了很久很久，在网上搜了很久，在群里问了很多人，都没解决，最后求助出售此试验箱设备公司的工程师，他也没给出原因，只是给了我一个可以运行的例程，我就自己对照了下，然后调试，查出来，原因在与，没有设置

二、保存jpg图片程序：

1、源代码：jpg.c

/*
* jpg.c
*
*/

#include "classroom.h"

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#define jpgImageName "test.jpg"

extern char * chpt_lcd_mmap_addr;
extern unsigned  int int_lcd_height;
extern unsigned int int_lcd_width;
extern unsigned  int int_lcd_pixel;

static unsigned  int width;
static unsigned int height;
static unsigned  int channel;

static unsigned  char jpegQuality = 100;

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

static void jpegWrite(unsigned char* img)
{
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr jerr;

JSAMPROW row_pointer[1];
FILE *outfile = fopen( jpgImageName, "w");

// try to open file for saving
if (!outfile) {
errno_exit("jpeg");
}

// create jpeg data
cinfo.err = jpeg_std_error( &jerr );
jpeg_create_compress(&cinfo);
jpeg_stdio_dest(&cinfo, outfile);

// set image parameters
cinfo.image_width = width;
cinfo.image_height = height;
cinfo.input_components = 3;
cinfo.in_color_space = JCS_RGB;

// set jpeg compression parameters to default
jpeg_set_defaults(&cinfo);
// and then adjust quality setting
jpeg_set_quality(&cinfo, jpegQuality, TRUE);

// start compress
jpeg_start_compress(&cinfo, TRUE);

// feed data
while (cinfo.next_scanline < cinfo.image_height)
{
row_pointer[0] = &img[(cinfo.image_height - cinfo.next_scanline - 1) * cinfo.image_width*3];
jpeg_write_scanlines(&cinfo, row_pointer, 1);
}

// finish compression
jpeg_finish_compress(&cinfo);

// destroy jpeg data
jpeg_destroy_compress(&cinfo);

// close output file
fclose(outfile);
}


void jpgImageProduct(const void* p)
{
usleep(500000);

unsigned char* dst;
unsigned char* src = (unsigned  char*)p;
unsigned int j;
unsigned int i;

width = int_lcd_width;
height = int_lcd_height;

dst = (unsigned char*)malloc (width*height*3+66);

for (i=0; i< height; i++)
{
for(j=0;j
{
memcpy(dst+(i*width+j)*3, src+(i*width+j)*4+2,1);
memcpy(dst+(i*width+j)*3+1, src+(i*width+j)*4+1,1);
memcpy(dst+(i*width+j)*3+2, src+(i*width+j)*4,1);
}
}
jpegWrite(dst);
free(dst);
}

/*
 *     jpg.c
 *
 */

#include "classroom.h"

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#define jpgImageName "test.jpg"

extern char * chpt_lcd_mmap_addr;
extern unsigned int int_lcd_height;
extern unsigned int int_lcd_width;
extern unsigned int int_lcd_pixel;

static unsigned int width;
static unsigned int height;
static unsigned int channel;

static unsigned char jpegQuality = 100;

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

static void jpegWrite(unsigned char* img)
{
  struct jpeg_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
	
  JSAMPROW row_pointer[1];
  FILE *outfile = fopen( jpgImageName, "w");

  // try to open file for saving
  if (!outfile) {
    errno_exit("jpeg");
  }

  // create jpeg data
  cinfo.err = jpeg_std_error( &jerr );
  jpeg_create_compress(&cinfo);
  jpeg_stdio_dest(&cinfo, outfile);

  // set image parameters
  cinfo.image_width = width;	
  cinfo.image_height = height;
  cinfo.input_components = 3;
  cinfo.in_color_space = JCS_RGB;

  // set jpeg compression parameters to default
  jpeg_set_defaults(&cinfo);
  // and then adjust quality setting
  jpeg_set_quality(&cinfo, jpegQuality, TRUE);

  // start compress 
  jpeg_start_compress(&cinfo, TRUE);

  // feed data
  while (cinfo.next_scanline < cinfo.image_height) 
  {
	row_pointer[0] = &img[(cinfo.image_height - cinfo.next_scanline - 1) * cinfo.image_width*3];
    jpeg_write_scanlines(&cinfo, row_pointer, 1);
  }

  // finish compression
  jpeg_finish_compress(&cinfo);

  // destroy jpeg data
  jpeg_destroy_compress(&cinfo);

  // close output file
  fclose(outfile);
}


void jpgImageProduct(const void* p)
{
	usleep(500000);

	unsigned char* dst;
	unsigned char* src = (unsigned char*)p;
	unsigned int j;
	unsigned int i;

	width = int_lcd_width;
    height = int_lcd_height;

	dst = (unsigned char*)malloc (width*height*3+66);

	for (i=0; i< height; i++)
	{
		for(j=0;j

•