只是最后图像不清晰，尚不清楚原因
1.要用jpeg库编译，所以要先编译jpegsrc.v6b.tar.gz，
$ cd jpeg-6b
$ ./configure --prefix=/work/tools/gcc-3.4.5-glibc-2.3.6/arm-linux
$ make
$ make install
2.然后编译video2_jpeg.c
>arm-linux-gcc -o video2_jpeg video2_jpeg.c -I/work/tools/gcc -I/work/tools/gcc-3.4.5-glibc-2.3.6/arm-linux/include -L//work/tools/gcc-3.4.5-glibc-2.3.6/arm-linux/lib -ljpeg
源码video2_jpeg.c如下：
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define OUTPUT_BUF_SIZE 4096
#define CLEAR(x) memset(&(x), 0, sizeof(x))
#define WIDTH 320
#define HEIGHT 240
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 char * dev_name= "/dev/video0";
static int fd= -1;
struct buffer * buffers = NULL;
static unsigned int n_buffers = 0;
FILE *file_fd;
static unsigned long file_length;
static unsigned char *file_name;
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;
}
//......YUYV.....JPEG..
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;
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);
}
//读取一帧的内容
static int read_frame(void)
{
struct v4l2_buffer buf;
int ret;
unsigned int i;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
int ff = ioctl(fd, VIDIOC_DQBUF, &buf); ///出列采集的帧缓冲
if(ff<0)
printf("failture\n");
unsigned char src[buf.length+1];
unsigned char dest[buf.length+1];
assert(buf.index < n_buffers);
printf("buf.index dq is %d,\n",buf.index);
memcpy(src, buffers[buf.index].start, buf.length);
ret = compress_yuyv_to_jpeg(src, dest,(WIDTH * HEIGHT), 80);//....
fwrite(dest, ret, 1, file_fd);//........
ff=ioctl(fd, VIDIOC_QBUF, &buf); //....
if(ff<0)
printf("failture VIDIOC_QBUF\n");
return 1;
}
//上面四个函数都是给下面get_picture用的
//get_picture->read_frame->compress_yuyv_to_jpeg->dest_buffer
//在dest_buffer（）函数中：设置
//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;
int get_picture()
{
struct v4l2_capability cap;
struct v4l2_format fmt;
unsigned int i;
enum v4l2_buf_type type;
file_fd = fopen("test-mmap.jpg", "w");
fd = open(dev_name, O_RDWR | O_NONBLOCK, 0);
int ff=ioctl(fd, VIDIOC_QUERYCAP, &cap);//.......
if(ff<0)
printf("failture VIDIOC_QUERYCAP\n");
struct v4l2_fmtdesc fmt1;
int ret;
memset(&fmt1, 0, sizeof(fmt1));
fmt1.index = 0;
fmt1.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
while((ret = ioctl(fd, VIDIOC_ENUM_FMT, &fmt1)) == 0) //...........
{
fmt1.index++;
printf("{ pixelformat = '%c%c%c%c', description = '%s' }\n",
fmt1.pixelformat & 0xFF,(fmt1.pixelformat >> 8) & 0xFF,
(fmt1.pixelformat >> 16) & 0xFF,(fmt1.pixelformat >> 24) & 0xFF,
fmt1.description);
}
CLEAR(fmt);
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 640;
fmt.fmt.pix.height= 480;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
ff = ioctl(fd, VIDIOC_S_FMT, &fmt); //......
if(ff<0)
printf("failture VIDIOC_S_FMT\n");
file_length = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height; //......
struct v4l2_requestbuffers req;
CLEAR(req);
req.count = 1;
req.type= V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory= V4L2_MEMORY_MMAP;
ioctl(fd, VIDIOC_REQBUFS, &req);//.....count......
if(ff<0)
printf("failture VIDIOC_REQBUFS\n");
if(req.count < 1)
printf("Insufficient buffer memory\n");
buffers = calloc(req.count, sizeof(*buffers));
for(n_buffers = 0; n_buffers < req.count; ++n_buffers)
{
struct v4l2_buffer buf;
CLEAR(buf);
buf.type= V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory= V4L2_MEMORY_MMAP;
buf.index = n_buffers;
if(-1 == ioctl(fd, VIDIOC_QUERYBUF, &buf)) //......
printf("VIDIOC_QUERYBUF error\n");
buffers[n_buffers].length = buf.length;
buffers[n_buffers].start=mmap(NULL,buf.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,buf.m.offset); //..mmap......
if(MAP_FAILED == buffers[n_buffers].start)
printf("mmap failed\n");
}
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 == ioctl(fd, VIDIOC_QBUF, &buf))//..........
printf("VIDIOC_QBUF failed\n");
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if(-1 == ioctl(fd, VIDIOC_STREAMON, &type)) //........
printf("VIDIOC_STREAMON failed\n");
for(;;) //........IO
{
fd_set fds;
struct timeval tv;
int r;
FD_ZERO(&fds);//............
FD_SET(fd, &fds);//....................
/* Timeout. */
tv.tv_sec = 2;
tv.tv_usec = 0;
r = select(fd + 1, &fds, NULL, NULL, &tv);//......(...........tv...
if(-1 == r)
{
if(EINTR == errno)
continue;
printf("select err\n");
}
if(0 == r)
{
fprintf(stderr, "select timeout\n");
return -1;
}
if(read_frame())//.......read_frame..
break;
}
for(i = 0; i < n_buffers; ++i)
if(-1 == munmap(buffers[i].start, buffers[i].length))
printf("munmap error");
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if(-1 == ioctl(fd, VIDIOC_STREAMOFF, &type))
printf("VIDIOC_STREAMOFF");
close(fd);
fclose(file_fd);
return 0;
}
//main函数中调用这个函数就可以了
int main(){
get_picture();
return 0;
}
