从YUYV转换成MJPEG

Linux下摄像头采集图像的帧格式从YUYV转换成MJPEG

在做网络视频监控系统时，摄像头有的不支持v4l2_pix_fmt_mjpeg格式，只能支持v4l2_pix_fmt_yuyv格式，这样的话，不适合于在网络上的传输。为了将YUYV转换成MJPEG,我借助于jpeg库。

)jpeg源码包通过下面这个网址下载
                http://www.ijg.org/files/jpegsrc.v8b.tar.gz
                2)解压源码包

                $ tar xzvf jpegsrc.v8b.tar.gz

                $ cd jpeg-8b

                $ ./configure --prefix=/usr/local/jpeg

                $ make

                $ make install

2)具体用法：

 #include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.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 <memory.h>

#include <sys/mman.h>

#include <sys/ioctl.h>

#include <linux/videodev2.h>

#include <jpeglib.h>

#include "print.h"

#define OUTPUT_BUF_SIZE  4096

#define WIDTH 640

#define HEIGHT 480

struct buffer {

        void *                  start;

        size_t                  length;

};

typedef struct {

  struct jpeg_destination_mgr pub;

  JOCTET * buffer; 

  unsigned char *outbuffer;

  int outbuffer_size;

  unsigned char *outbuffer_cursor;

  int *written; 

}mjpg_destination_mgr;

typedef mjpg_destination_mgr *mjpg_dest_ptr;

static int  fd= -1;

struct buffer *buffers= NULL;

static unsigned int     n_buffers= 0;

char *temp_buffer      =NULL;

METHODDEF(void) init_destination(j_compress_ptr cinfo) {

  mjpg_dest_ptr dest = (mjpg_dest_ptr) cinfo->dest;

  dest->buffer = (JOCTET *)(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, OUTPUT_BUF_SIZE * sizeof(JOCTET));

  *(dest->written) = 0;

  dest->pub.next_output_byte = dest->buffer;

  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;

}

METHODDEF(boolean) empty_output_buffer(j_compress_ptr cinfo) {

  mjpg_dest_ptr dest = (mjpg_dest_ptr) cinfo->dest;

  memcpy(dest->outbuffer_cursor, dest->buffer, OUTPUT_BUF_SIZE);

  dest->outbuffer_cursor += OUTPUT_BUF_SIZE;

  *(dest->written) += OUTPUT_BUF_SIZE;

  dest->pub.next_output_byte = dest->buffer;

  dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;

  return TRUE;

}

METHODDEF(void) term_destination(j_compress_ptr cinfo) {

  mjpg_dest_ptr dest = (mjpg_dest_ptr) cinfo->dest;

  size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;

  /* Write any data remaining in the buffer */

  memcpy(dest->outbuffer_cursor, dest->buffer, datacount);

  dest->outbuffer_cursor += datacount;

  *(dest->written) += datacount;

}

void dest_buffer(j_compress_ptr cinfo, unsigned char *buffer, int size, int *written) {

  mjpg_dest_ptr dest;

  if (cinfo->dest == NULL) {

    cinfo->dest = (struct jpeg_destination_mgr *)(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof(mjpg_destination_mgr));

  }

  dest = (mjpg_dest_ptr)cinfo->dest;

  dest->pub.init_destination = init_destination;

  dest->pub.empty_output_buffer = empty_output_buffer;

  dest->pub.term_destination = term_destination;

  dest->outbuffer = buffer;

  dest->outbuffer_size = size;

  dest->outbuffer_cursor = buffer;

  dest->written = written;

}

//摄像头采集帧图像的YUYV格式转换为JPEG格式

int compress_yuyv_to_jpeg(unsigned char *buf, unsigned char *buffer, int size, int quality) {

  struct jpeg_compress_struct cinfo;

  struct jpeg_error_mgr jerr;

  JSAMPROW row_pointer[1];

  unsigned char *line_buffer, *yuyv;

  int z;

  static int written;

  //int count = 0;

  //printf("%s\n", buf);

  line_buffer = calloc (WIDTH * 3, 1);

  yuyv = buf;//将YUYV格式的图片数据赋给YUYV指针

  printf("compress start...\n");

  cinfo.err = jpeg_std_error (&jerr);

  jpeg_create_compress (&cinfo);

  /* jpeg_stdio_dest (&cinfo, file); */

  dest_buffer(&cinfo, buffer, size, &written);

  cinfo.image_width = WIDTH;

  cinfo.image_height = HEIGHT;

  cinfo.input_components = 3;

  cinfo.in_color_space = JCS_RGB;

  jpeg_set_defaults (&cinfo);

  jpeg_set_quality (&cinfo, quality, TRUE);

  jpeg_start_compress (&cinfo, TRUE);

  z = 0;

  while (cinfo.next_scanline < HEIGHT) {

    int x;

    unsigned char *ptr = line_buffer;

    for (x = 0; x < WIDTH; x++) {

      int r, g, b;

      int y, u, v;

      if (!z)

        y = yuyv[0] << 8;

      else

        y = yuyv[2] << 8;

      u = yuyv[1] - 128;

      v = yuyv[3] - 128;

      r = (y + (359 * v)) >> 8;

      g = (y - (88 * u) - (183 * v)) >> 8;

      b = (y + (454 * u)) >> 8;

      *(ptr++) = (r > 255) ? 255 : ((r < 0) ? 0 : r);

      *(ptr++) = (g > 255) ? 255 : ((g < 0) ? 0 : g);

      *(ptr++) = (b > 255) ? 255 : ((b < 0) ? 0 : b);

      if (z++) {

        z = 0;

        yuyv += 4;

      }

    } 

    row_pointer[0] = line_buffer;

    jpeg_write_scanlines (&cinfo, row_pointer, 1);

  }

  jpeg_finish_compress (&cinfo);

  jpeg_destroy_compress (&cinfo);

  free (line_buffer);

  return (written);

}

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