v4lif.c

基于V4L开发的一个运动监测的程序

/*
 * v4lif.c
 * This file contains routines for reading an image from a v4l device
 *
 * Derived from work by:
 * Copyright (C) 1998 Rasca, Berlin
 * EMail: [e-mail]
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/types.h>
#include <linux/videodev.h>

#include "v4lif.h"

/*
 * read rgb image from v4l device
 * return: mmap'ed buffer and size
 *
 * sample call:
 *	int size;
 *	char *image;
 *  int dev = v4l_open(VIDEO_DEV, IN_DEFAULT);
 *	image = get_image (dev, width, height, input, norm, palette, &size);
 *	// process rgb image buffer as required here
 *	// then dont forget to release buffers
 *	if (size)
 *		munmap(image, size);
 *	else if (image)
 *		free(image);
 *  v4l_close(dev);
*/
char *get_image(int dev, int width, int height, int input,int norm,int fmt,int *size)
{
	struct video_capability vid_caps;
	struct video_mbuf vid_buf;
	struct video_mmap vid_mmap;
	struct video_channel vid_chnl;
	char *map = NULL;
	int len;
	
	*size = 0;		// keep caller happy on error returns
	                // setting input = 1 gets some users going
	if (ioctl (dev, VIDIOCGCAP, &vid_caps) == -1) 
	{
		printf("ioctl (VIDIOCGCAP) failed\n");
		return (NULL);
	}
	if (input != IN_DEFAULT) 
	{
		vid_chnl.channel = -1;
		if (ioctl (dev, VIDIOCGCHAN, &vid_chnl) == -1) 
		{
			printf("ioctl (VIDIOCGCHAN) failed\n");
		} 
		else 
		{
			vid_chnl.channel = input;
			vid_chnl.norm    = norm;
			if (ioctl (dev, VIDIOCSCHAN, &vid_chnl) == -1) 
			{
				printf("ioctl (VIDIOCSCHAN) failed");
				return (NULL);
			}
		}
	}
	
	// if no video buffer set, then set it
	//printf("before VIDIOCGMBUF vidbuf size=%d bytes\n",vid_buf.size);	
	if (ioctl (dev, VIDIOCGMBUF, &vid_buf) == -1) 
	{
		//printf("after VIDIOCGMBUF vidbuf size=%d bytes\n",vid_buf.size);		
		// to do a normal read()
		map = malloc (width * height * 3);
		len = read (dev, map, width * height * 3);
		if (len <=  0) 
		{
			free (map);
			return (NULL);
		}
		*size = 0;
		return (map);
	}

	map = mmap (0, vid_buf.size, PROT_READ|PROT_WRITE,MAP_SHARED,dev,0);
	if ((unsigned char *)-1 == (unsigned char *)map) 
	{
		printf("mmap() failed \n");
		return (NULL);
	}

	vid_mmap.format = fmt;
	vid_mmap.frame = 0;
	vid_mmap.width = width;
	vid_mmap.height =height;
//printf("VIDIOCMCAPTURE started\n");
	if (ioctl (dev, VIDIOCMCAPTURE, &vid_mmap) == -1) 
	{
		printf("VIDIOCMCAPTURE failed\n");
		munmap (map, vid_buf.size);
		return (NULL);
	}
//printf("VIDIOCSYNC started\n");
	if (ioctl (dev, VIDIOCSYNC, &vid_mmap) == -1) 
	{
		printf("VIDIOCSYNC failed \n");
		munmap (map, vid_buf.size);
		return (NULL);
	}
//printf("VIDIOCSYNC finished %d bytes\n",vid_buf.size);	
	// vid_buf.size is actually the size of 2 frame buffers in the driver
	*size = vid_buf.size;
	return (map);
}


/*
 *  int v4l_open(char *device)
 *	example call  int dev = v4l_open(VIDEO_DEV);
 *
 *
 */
int v4l_open(char *device)
{
	int dev = -1;
	int max_try = 5;	/* we try 5 seconds/times to open the device */
	/* open the video4linux device */
	while (max_try) 
	{
		dev = open (device, O_RDWR);
		if (dev == -1) 
		{
			if (!--max_try) 
			{
				fprintf (stderr, "Can't open device %s\n", device);
				exit (0);
			}
			sleep (1);
		} 
		else 
		{
			break;
		}
	}
	
	return dev;
}

/*
 *  void v4l_close(int dev)
 *	example call  v4l_close(dev);
 *
 */
void v4l_close(int dev)
{
	if (dev > 0)
		close(dev);
}