[V4L2+RTP] FireWRT远程视频监控-2 - Firefly开源社区

struct buffer{
void *start;
size_t length;
};
struct camera{
char *device_name;//设备名字 /dev/videoX
int fd;//摄像头句柄
int width;//输出的视频宽度
int height;//高度
int display_depth;
int image_size;//一帧数据大小
int frame_number;
int support_fmt;//摄像头支持的格式如果支持Jpeg就以此获得数据，如果只支持yuyv就输出yuyv在用程序转化为jpeg
unsigned int n_buffers;//缓冲区个数
struct v4l2_capability v4l2_cap;
struct v4l2_cropcap v4l2_cropcap;
struct v4l2_format v4l2_fmt;
struct v4l2_crop v4l2_crop;
struct v4l2_fmtdesc v4l2_fmtdesc;
struct v4l2_streamparm v4l2_setfps;
struct buffer *buffers;
};
/*上面参数fmt_select选择*/
#define FMT_JPEG 0x101
#define FMT_YUYV422 0x102
#define FMT_YUYV420 0x104

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/*外界接口*/
void v4l2_init(struct camera *cam)
{
open_camera(cam);
init_camera(cam);
start_capturing(cam);
}

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/*摄像头操作函数*/
static void open_camera(struct camera *cam)
{
struct stat st;
if (-1 == stat(cam->device_name, &st)) {
fprintf(stderr, "Cannot identify '%s': %d, %s\n", cam->device_name,errno, strerror(errno));
exit(EXIT_FAILURE);
}
if (!S_ISCHR(st.st_mode)) {
fprintf(stderr, "%s is no device\n", cam->device_name);
exit(EXIT_FAILURE);
}
cam->fd = open(cam->device_name, O_RDWR, 0); // | O_NONBLOCK 打开摄像头记录fd
if (-1 == cam->fd) {
fprintf(stderr, "Cannot open '%s': %d, %s\n", cam->device_name, errno,strerror(errno));
exit(EXIT_FAILURE);
}
}

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static void init_camera(struct camera*cam)
{
struct v4l2_capability *cap = &(cam->v4l2_cap);
struct v4l2_cropcap *cropcap = &(cam->v4l2_cropcap);
struct v4l2_crop *crop = &(cam->v4l2_crop);
struct v4l2_format *fmt = &(cam->v4l2_fmt);
struct v4l2_fmtdesc *fmtdesc = &(cam->v4l2_fmtdesc);
struct v4l2_streamparm *streamparm = &(cam->v4l2_setfps);
struct v4l2_requestbuffers req;
unsigned int min;
int pos = -1;
/*1.查询设备属性*/
if (-1 == xioctl(cam->fd, VIDIOC_QUERYCAP, cap)) {
if (EINVAL == errno) {
fprintf(stderr, "%s is no V4L2 device\n", cam->device_name);
exit(EXIT_FAILURE);
}else
errno_exit("VIDIOC_QUERYCAP");
}
/*2.是否支持图像获取*/
if (!(cap->capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf(stderr, "%s is no video capture device\n", cam->device_name);
exit(EXIT_FAILURE);
}
/*3.查询设备是否支持流输出*/
if (!(cap->capabilities & V4L2_CAP_STREAMING)) {
fprintf(stderr, "%s does not support streaming i/o\n",cam->device_name);
exit(EXIT_FAILURE);
}
#ifdef OUTPUT_CAMINFO
printf("VIDOOC_QUERYCAP\n");
printf("driver:\t\t%s\n",cap->driver);
printf("card:\t\t%s\n",cap->card);
printf("bus_info:\t%s\n",cap->bus_info);
printf("version:\t%d\n",cap->version);
printf("capabilities:\t%x\n",cap->capabilities);
#endif
/*打印摄像头支持的格式*/
fmtdesc->index = 0;
fmtdesc->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
#ifdef OUTPUT_CAMINFO
printf("support format:\n");
#endif
while(ioctl(cam->fd,VIDIOC_ENUM_FMT,fmtdesc) != -1){
#ifdef OUTPUT_CAMINFO
printf("\t%d,%s\n",fmtdesc->index+1,fmtdesc->description);
#endif
/*4.查看摄像头输出的视频格式 jpeg yuyv420 yuyv422*/
pos = find_string(fmtdesc->description,"JPEG");
if(pos != -1){
cam->support_fmt |= FMT_JPEG;
goto CON;
}
pos = find_string(fmtdesc->description,"4:2:2");
if(pos!=-1){
cam->support_fmt |= FMT_YUYV422;
goto CON;
}
pos = find_string(fmtdesc->description,"4:2:0");
if(pos!=-1){
cam->support_fmt |= FMT_YUYV420;
goto CON;
}
CON:
fmtdesc->index++;
}
/*5.设置输出格式*/
CLEAR(*cropcap);
cropcap->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
/*v4l2_cropcap 结构体用来设置摄像头的捕捉能力，在捕捉上视频时应先先设置v4l2_cropcap 的 type 域，再通过 VIDIO_CROPCAP 操作命令获取设备捕捉能力的参数，保存于 v4l2_cropcap 结构体中，包括 bounds（最大捕捉方框的左上角坐标和宽高），defrect（默认捕捉方框的左上角坐标和宽高）等。v4l2_format 结构体用来设置摄像头的视频制式、帧格式等，在设置这个参数时应先填好 v4l2_format 的各个域，如 type（传输流类型），fmt.pix.width(宽)，fmt.pix.heigth(高)，fmt.pix.field(采样区域，如隔行采样)，fmt.pix.pixelformat(采
样类型，如 YUV4:2:2)，然后通过 VIDIO_S_FMT 操作命令设置视频捕捉格式*/
crop->c.width = cam->width;
crop->c.height = cam->height;
crop->c.left = 0;
crop->c.top = 0;
crop->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
CLEAR(*fmt);
fmt->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt->fmt.pix.width = cam->width;
fmt->fmt.pix.height = cam->height;
if( (cam->support_fmt & FMT_JPEG) == FMT_JPEG){
fmt->fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
cam->support_fmt = FMT_JPEG;/*记录设备输出的图像格式*/
}
else if((cam->support_fmt & FMT_YUYV422) == FMT_YUYV422){
fmt->fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
cam->support_fmt = FMT_YUYV422;
}
else if( (cam->support_fmt & FMT_YUYV420 ) == FMT_YUYV420 ){
fmt->fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;
cam->support_fmt = FMT_YUYV420;
}
else
errno_exit("no support fmt");
fmt->fmt.pix.field = V4L2_FIELD_INTERLACED;
if (-1 == xioctl(cam->fd,VIDIOC_S_FMT,fmt))
errno_exit("VIDIOC_S_FMT fail");
#if 1
CLEAR(*streamparm);
streamparm->type=V4L2_BUF_TYPE_VIDEO_CAPTURE;
streamparm->parm.capture.timeperframe.numerator = 1;
streamparm->parm.capture.timeperframe.denominator = 25;
if(-1==xioctl(cam->fd,VIDIOC_S_PARM,streamparm))
errno_exit("VIDIOC_S_PARM");
#endif
min = fmt->fmt.pix.width * 2;/*YUYV 每个像素占用2个字节*/
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;
/*6.分配内存，映射内存*/
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)) {
if (EINVAL == errno) {
fprintf(stderr, "%s does not support "
"memory mapping\n", cam->device_name);
exit(EXIT_FAILURE);
} else
errno_exit("VIDIOC_REQBUFS");
}
if (req.count < 2) {
fprintf(stderr, "Insufficient buffer memory on %s\n", cam->device_name);
exit(EXIT_FAILURE);
}
cam->buffers = calloc(req.count, sizeof(*(cam->buffers)));
if (!cam->buffers) {
fprintf(stderr, "Out of memory\n");
exit(EXIT_FAILURE);
}
for(cam->n_buffers = 0;cam->n_buffers < req.count;cam->n_buffers++){
struct v4l2_buffer buf;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = cam->n_buffers;
if (-1 == xioctl(cam->fd, VIDIOC_QUERYBUF, &buf))
errno_exit("VIDIOC_QUERYBUF");
cam->buffers[cam->n_buffers].length = buf.length;
/*映射内存*/
cam->buffers[cam->n_buffers].start = mmap(NULL /* start anywhere */,buf.length, PROT_READ | PROT_WRITE /* required */,MAP_SHARED /* recommended */, cam->fd, buf.m.offset);
if (MAP_FAILED == cam->buffers[cam->n_buffers].start)
errno_exit("mmap");
}
}

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static void start_capturing(struct camera *cam)
{
unsigned int i;
enum v4l2_buf_type type;
for (i = 0; i < cam->n_buffers; ++i) {
struct v4l2_buffer buf;
CLEAR(buf);
/*1.将内存放入缓冲区*/
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (-1 == xioctl(cam->fd, VIDIOC_QBUF, &buf))
errno_exit("VIDIOC_QBUF");
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
/*2.开始传输采集图像*/
if (-1 == xioctl(cam->fd, VIDIOC_STREAMON, &type))
errno_exit("VIDIOC_STREAMON");
}

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int read_frame(struct camera *cam,unsigned char *buffer,int *len/*数据大小*/)
{
fd_set fds;
struct timeval tv;
int r;
struct v4l2_buffer buf;
FD_ZERO(&fds);
FD_SET(cam->fd,&fds);
tv.tv_sec = 2;
tv.tv_usec = 0;
r = select(cam->fd+1,&fds,NULL,NULL,&tv);/*查询是否有数据*/
if(-1 == r){
if(EINTR == errno)
return 1;//表示应该继续读
errno_exit("select");
}
if(0 == r){
fprintf(stderr,"select timeout");
exit(EXIT_FAILURE);
}
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (-1 == xioctl(cam->fd, VIDIOC_DQBUF, &buf)) {/*从内核环形缓冲区取出一帧数据*/
switch (errno) {
case EAGAIN:
return -1;
case EIO:
default:
errno_exit("VIDIOC_DQBUF");
}
}
memcpy(buffer,(unsigned char *)cam->buffers[buf.index].start,buf.bytesused);/*将采集的一帧数据放到自定义的buffer中*/
//printf("cam->n_buffers=%d\nbuf.index=%d\nbuf.bytesused=%d\n",cam->n_buffers,buf.index,buf.bytesused);
*len = buf.bytesused;
if (-1 == xioctl(cam->fd, VIDIOC_QBUF, &buf))/*放回环形缓冲区*/
errno_exit("VIDIOC_QBUF");
dbug("video QBUF");
return 0;//成功
}

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